Terms Starting with "V"

521 terms

V

V abbreviation for verbal ability.

V1

V1 visual area 1, which in primates is coextensive with the striate cortex (primary visual cortex). Neurons in V1 have relatively simple stimulus requirements for maximum activation, unlike the visual areas to which V1 projects, which include V2, V4, and V5. V1 is the preferred name of this cortex for discussions of the functional differences between cortical regions; striate cortex, primary visual cortex, and area 17 are the preferred names for discussions of cortical anatomy.

V2

V2 visual area 2, which in primates is a band of cerebral cortex located adjacent and anterior to V1. It is coextensive with Brodmann’s area 18 (see prestriate cortex) and receives its major input from V1.

V3

V3 visual area 3, which in primates is located in the prestriate cortex anterior to V2, from which it receives signals. It is specialized for monochromatic pattern perception. The ventral region is also referred to as area VP (ventral posterior area), whereas the dorsal region is often divided into two regions, V3a and V3b. The relationship among these three aspects of V3 is not fully understood.

V4

V4 visual area 4, which in primates is located in the occipitotemporal cortex. Most neurons in V4 are sensitive to wavelength, and damage to a similar area in the human brain causes cerebral achromatopsia, a form of cortical color blindness (see achromatism).

V5

V5 visual area 5, which in primates is located in the temporal cortex. Most neurons in V5 are sensitive to the rate and direction of motion of a stimulus, and damage to a similar area in the human brain causes akinetopsia (motion agnosia). Also called MT (i.e., middle temporal, because V5 is located toward the back of the middle temporal gyrus); visual area MT.

VA

VA abbreviation for U.S. Department of Veterans Affairsus-department-of-veterans-affairs.

VABS

VABS abbreviation for Vineland Adaptive Behavior Scales.

vACC

vACC abbreviation for ventral anterior cingulate cortex.

vacuum activity

vacuum activity in classical ethology, the occurrence of a fixed action pattern in the absence of the usual external stimulus (the releaser, or sign stimulus) that triggers the pattern. This is believed to be caused by a build-up of action-specific or motivational energy that overrides the innate releasing mechanism. Also called vacuum response. [proposed by Konrad Lorenz]

vagabond neurosis

vagabond neurosis see dromomania.

vagal tone

vagal tone a measure of the variability of the heart rate associated with inhalation and exhalation (see respiratory sinus arrhythmia), which is thought to reflect parasympathetic influence via the vagus nerve.

vagina

vagina n. a tubelike structure in female mammals that leads from the cervix (neck) of the uterus to the exterior. The muscular walls of the vagina are lined with mucous membrane, and two pairs of vestibular glands around the vaginal opening secrete a fluid that facilitates penetration by the penis during coitus. —vaginal adj.

vagina dentata

vagina dentata in folklore, a vagina with teeth that can castrate the male partner. In the classical psychoanalytic theory of Sigmund Freud, for women, it is a fantasy believed to stem from intense penis envy and a desire to castrate the partner as an act of revenge; for men, it is believed to stem from castration anxiety.

vagina envy

vagina envy a psychological characteristic of men who desire the ability to become pregnant and bear children. See also femininity complex; womb envy.

vaginal administration

vaginal administration see administration.

vaginal orgasm

vaginal orgasm 1. female orgasm achieved through vaginal stimulation. 2. in early psychoanalytic theory, the “mature, feminine” orgasm, as opposed to “immature, masculine” orgasms produced from clitoral stimulation. This view has long since been refuted. Indeed, researchers have demonstrated that the clitoris is the focus of female sexual response and that vaginal orgasms are primarily related to indirect stimulation of the clitoris and labia during intercourse. See coital anorgasmia.

vaginal plethysmograph

vaginal plethysmograph see plethysmography.

vaginal sex

vaginal sex sexual intercourse by means of vaginal penetration. See coitus.

vaginismus

vaginismus n. a sexual dysfunction in which spasmic contractions of the muscles around the vagina occur during or immediately preceding sexual intercourse, causing the latter to be painful or impossible. See also functional vaginismus.

vagotomy

vagotomy n. surgical cutting or interruption of the vagus nerve, which has motor, sensory, and physiological functions.

vagus nerve

vagus nerve the tenth cranial nerve, a mixed nerve with both sensory and motor fibers that serves many functions. The sensory fibers innervate the external ear, vocal organs, and thoracic and abdominal viscera. The motor nerves innervate the tongue, vocal organs, and—through many ganglia of the parasympathetic nervous system—the thoracic and abdominal viscera. Also called cranial nerve X; pneumogastric nerve.

VAKT

VAKT abbreviation for visual, auditory, kinesthetic, and tactile (senses). See Fernald method.

valence

valence n. 1. in the field theory of Kurt Lewin, the subjective value of an event, object, person, or other entity in the life space of the individual. An entity that attracts the individual has positive valence, whereas one that repels has negative valence. 2. in certain theories of motivation, the anticipated satisfaction of attaining a particular goal or outcome.

valence–instrumentality–expectancy theory

valence–instrumentality–expectancy theory a theory of work motivation holding that the level of effort exerted by employees will depend on a combination of three variables: (a) the expectancy of employees that effort will lead to success in the job, (b) the belief of employees that success will lead to particular outcomes (see instrumentality theory), and (c) the value of these outcomes (see valence). A numerical value can be obtained for variable (a) using the subjective probability estimates of employees, for variable (b) by measuring the correlation of performance to rewards, and for variable (c) by asking employees to rate the desirability of the rewards. The motivational force, or the amount of effort employees will exert, can then be calculated. See also path–goal theory of leadership; Porter–Lawler model of motivation. [proposed in 1964 by Canadian organizational psychologist Victor H. Vroom (1932– )]

validating marriage

validating marriage a long-lasting marriage in which the partners express mutual respect even when they disagree.

validation

validation n. the process of establishing the truth or logical cogency of something. An example is determining the accuracy of a research instrument in measuring what it is designed to measure. In some forms of psychotherapy, validation may take the form of mirroring of the client’s judgment or experience by the therapist. —validate vb.

validity

validity n. 1. the characteristic of being founded on truth, accuracy, fact, or law. 2. the degree to which empirical evidence and theoretical rationales support the adequacy and appropriateness of conclusions drawn from some form of assessment. Validity has multiple forms, depending on the research question and on the particular type of inference being made. For example, the three major types of test validity are criterion validity, based on correlation with an accepted standard; construct validity, based on the conceptual variable underlying a test; and content validity, based on the subject matter of a test. Other forms of validity prominent in the social sciences include ecological validity, external validity, internal validity, and statistical conclusion validity. —valid adj.

validity check

validity check the process of verifying that a data set is free of errors and adheres to standard or intended rules. Performed manually or using software, a validity check may involve such things as verifying the accuracy of calculations and the legitimacy of included values (e.g., impossible values are not present), confirming that information is consistent across records, and confirming that no records are missing.

validity coefficient

validity coefficient an index, typically a correlation coefficient, that reflects how well an assessment instrument predicts a well-accepted indicator of a given concept or criterion. For example, if a measure of criminal behavior is valid, then it should be possible to use it to predict whether a person (a) will be arrested in the future for a criminal violation, (b) is currently breaking the law, and (c) has a previous criminal record. A validity coefficient could be used to relate scores on the measure to each of these criteria and thus determine how useful the measure actually is for behavioral forecasting.

validity criterion

validity criterion an external concept or standard of comparison that is used to define the attribute an instrument is purported to measure and that is applied in estimating how well the measurement instrument actually fulfills its intended purpose.

validity generalization

validity generalization the use of meta-analysis and other statistical procedures to assess the evidence of a test’s adequacy and appropriateness in multiple situations and settings. Validity generalization typically involves correcting all of the correlations being examined for methodological and statistical limitations and flaws and providing estimates of correlations or results that would have been obtained in the absence of such limitations.

validity tag

validity tag see metacognitive model of attitudes.

Valium

Valium n. a trade name for diazepam.

valor

valor n. see courage.

valproic acid

valproic acid a carboxylic acid (also formulated as valproate sodium; U.S. trade name: Depacon) used as an anticonvulsant and mood stabilizer. Although exact mechanisms of action remain unclear, valproic acid may exert its effects by reducing membrane sodium-channel activity (see ion channel), thereby slowing neuronal activity. It may also stimulate the synthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Valproic acid and valproate sodium are officially approved by the U.S. Food and Drug Administration for the management of seizures and of manic episodes associated with bipolar disorders. Although in general less toxic than lithium, these drugs have been associated with fatalities due to liver failure, particularly in children under 2 years of age, as well as pancreatitis; serum monitoring of drug levels and liver function is therefore required, particularly on starting treatment. Valproic acid and valproate sodium should not be taken during pregnancy due to risks of neural tube defects in the fetus; fetal exposure to valproic acid in the first trimester has also been linked to an increased risk of autism. U.S. trade name: Depakene.

VALS

VALS n. Values, Attitudes, and Lifestyles: a proprietary method of segmenting consumers according to their personal characteristics. Eight categories of consumers are identified on the basis of responses to proprietary questionnaires.

value

value n. 1. the mathematical magnitude or quantity of a variable. 2. a moral, social, or aesthetic principle accepted by an individual or society as a guide to what is good, desirable, or important. 3. the worth, usefulness, or importance attached to something.

value analysis

value analysis a type of content analysis of written material, consisting of a table or other systematic notation documenting the frequency of appearance in the material of all expressions referring to specified values.

value judgment

value judgment an assessment of individuals, objects, or events in terms of the values held by the observer rather than in terms of their intrinsic characteristics objectively considered. In some areas, such as aesthetics or morality, where there often are no objective right or wrong responses, value judgments are common, but in hard and social sciences they are frequently considered undesirable.

value system

value system the moral, social, aesthetic, economic, and religious concepts accepted either explicitly or implicitly by an individual or a particular society.

value-driven care

value-driven care a federally backed movement to improve quality and reduce costs in U.S. health care by increasing system transparency and encouraging consumer choice. Such an emphasis on quality contrasts with the current volume-driven model of care in which consumers are passive recipients of treatments and providers are reimbursed for the number of cases they handle, regardless of patient outcome or the standard of services rendered. The central premise underlying value-driven care is that informed consumers are active and discriminating decision makers who will examine their available service options and choose those that will be the most beneficial and cost effective, and that this in turn will foster competition among providers to provide better services at reduced costs (e.g., by eliminating waste, improving cooperation and coordination among providers, preventing foreseeable patient complications, etc.). For example, if a person needing an operation is able to review readily available statistics on outcome, price, and so forth, he or she will likely avoid choosing hospitals, procedures, or medical professionals having poor success rates or costing too much. According to the U.S. government, however, the success of value-driven care requires not only the consistent measurement and public reporting of provider quality and cost information, but also the nationwide adoption of standardized, interoperable health information technology and the use of incentives that motivate all parties within the system—payors, patients, providers, and health care facilities—to achieve better care for less money.

value-expressive function of an attitude

value-expressive function of an attitude the role an attitude can play in the expression of core values. For example, a person might adopt a positive attitude toward a religious symbol because that symbol is associated with important religious values. See also functional approach to attitudes.

value-free evaluation

value-free evaluation see goal-free evaluation.

Values and Preferences Scale (VPS)

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values clarification

values clarification any process intended to promote an individual’s awareness and understanding of his or her moral principles and ethical priorities and their relationships to behavior in daily life. Individuals may be asked to carry out a series of exercises to this effect in some forms of psychotherapy.

values education

values education 1. instruction that is focused on principles, moral standards, or ethical qualities that are considered desirable, in addition to academic instruction. 2. education focused on socially acceptable or correct living.

Values, Attitudes, and Lifestyles

Values, Attitudes, and Lifestyles see VALS.

vampirism

vampirism n. 1. in folk belief and literature, the practices associated with vampires (“undead” corpses supposed to drink the blood of living beings). In the portrayal of vampirism in literature, sexual pleasure is often associated with sucking blood from another person, a representation of the “love bite.” 2. a paraphilia whereby the drinking of blood elicits sexual arousal or pleasure. Also called Renfield’s syndrome. [first described by German psychiatrist Richard von Krafft-Ebing (1840–1902); named after the lawyer and later insane follower of Dracula in the 1897 novel by Bram Stoker] 3. a rare symptom of schizophrenia, characterized by vampiric or other delusions and the drinking of blood. Both of the last two senses are also called clinical vampirism.

van Buchem’s syndrome

van Buchem’s syndrome an autosomal aberration marked by thickening and osteosclerosis of bones of the face, skull, and trunk, resulting in facial paralysis and loss of hearing and vision. The symptoms usually begin around puberty. [Francis Steven Peter van Buchem (1897–1979), Dutch physician]

vandalism

vandalism n. willful defacement or destruction of property. A persistent pattern of vandalism is one symptom of conduct disorder.

Vandenbergh effect

Vandenbergh effect the effects of chemical communication in influencing age of puberty in rodent populations. Adult males produce an odor that can accelerate puberty in young females, leading to earlier reproduction. However, adult females produce odors that inhibit puberty in females. As a result, in low-density populations with more males than females, young females mature earlier, but in dense populations with many adult females, young females mature more slowly, leading to a regulation of population density. See also Whitten effect. [John G. Vandenbergh (1935– ), U.S. biologist]

vanishing cues methodology

vanishing cues methodology a computer-assisted training technique designed to teach new, complex knowledge to individuals with memory impairment. The technique takes advantage of the patient’s preserved ability to respond to partial cues. Initially, as much information is provided as is needed for the patient to make a correct response. Across learning trials, information is gradually withdrawn until the patient can respond correctly in the absence of any cues.

variability

variability n. 1. the quality of being subject to change or variation in behavior or emotion. 2. the degree to which members of a group or population differ from each other, as measured by statistics such as the range, standard deviation, and variance.

variable

variable n. a condition in an experiment or a characteristic of an entity, person, or object that can take on different categories, levels, or values and that can be quantified (measured). For example, test scores and ratings assigned by judges are variables. Numerous types of variables exist, including categorical variables, dependent variables, independent variables, mediators, moderators, and random variables. Compare constant.

variable error

variable error see random error.

variable rate theory

variable rate theory a group of theories that describe aging as resulting from individual differences that are affected by internal factors such as disease, genetic mutations, or metabolism, and by external factors such as environment, diet, or exercise. Compare genetic programming theory.

variable stimulus

variable stimulus in psychophysical research, any one of a set of experimental stimuli that are to be systematically compared to a constant stimulus.

variable-interval schedule (VI schedule)

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variable-ratio schedule (VR schedule)

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variable-time schedule (VT schedule)

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variance

variance (symbol: σ2) n. a measure of the spread, or dispersion, of scores within a sample or population, whereby a small variance indicates highly similar scores, all close to the sample mean, and a large variance indicates more scores at a greater distance from the mean and possibly spread over a larger range. See also standard deviation.

variance estimate

variance estimate an index of variation in a population that has been calculated using a sample of that population. For example, a sample standard deviation is an estimate of the deviation in the larger population.

variance-stabilizing transformation

variance-stabilizing transformation in regression analysis or analysis of variance, any of a class of mathematical processes that convert data showing heterogeneity of variance to a different form, so as to enable the application of specific analytical techniques or to simplify considerations.

variance–covariance matrix

variance–covariance matrix see covariance matrix.

variant

variant n. in a group of objects or events, one that differs from the others in some way while remaining essentially similar to them.

variate

variate n. 1. a specific value of a particular variable. 2. a random variable itself.

variation

variation n. 1. the existence of qualitative differences in form, structure, behavior, and physiology among the individuals of a population, whether due to heredity or to environment. Both artificial selection and natural selection operate on variations among organisms, but only genetic variation is transmitted to offspring. 2. in statistics, the degree of variance or dispersion of values that is obtained for a specific variable.

variation coefficient

variation coefficient see coefficient of variation.

variations of aging

variations of aging individual differences in the effects of aging caused either by intrinsic factors (e.g., disease, genetics) or by extrinsic factors (e.g., lifestyle, environment, culture).

varicella

varicella n. see chicken pox.

varicella-zoster

varicella-zoster n. see chicken pox; herpes infection.

varied mapping

varied mapping in a search task, a condition in which target and distractor stimuli change roles randomly over the course of an experiment, so that a stimulus may be a target in one trial and a distractor in the next. Compare consistent mapping.

variety

variety n. 1. in biological taxonomy, a subdivision of a species comprising those members of the species that are distinct with reference to particular minor characteristics that do not affect their ability to interbreed to produce fertile offspring. The various breeds of domestic animals are examples of varieties. 2. in linguistics, a version of a language that is phonologically or grammatically distinct from the standard language and may be associated with such categories as region, ethnicity, or social class. See also dialect; register.

variform universal

variform universal see psychological universal.

varimax rotation

varimax rotation a statistical procedure applied within factor analysis and principal components analysis to simplify solutions and enhance interpretation of the results. It is a type of orthogonal rotation intended to make each factor have a small number of large factor loadings and a large number of zero (or small) factor loadings. Thus, following a varimax rotation, each original variable tends to be associated with a small number of factors, and each factor represents only a small number of variables. See factor rotation.

vas deferens

vas deferens (pl. vasa deferentia) a duct that conveys spermatozoa from the epididymis and unites with the duct of the seminal vesicle to form the ejaculatory duct, which leads to the urethra. Also called ductus deferens; seminal duct; spermatic duct.

vas-

VA abbreviation for U.S. Department of Veterans Affairsus-department-of-veterans-affairs.

vascular dementia

vascular dementia severe loss of cognitive functioning as a result of cerebrovascular disease. It can be due to repeated strokes, a single large stroke, or chronic cerebral ischemia. It is one of the most common types of dementia. Also called multi-infarct dementia.

vascular depression

vascular depression a major depressive episode that occurs shortly after the onset or treatment of cardiovascular disease or that is assumed to be caused by cardiovascular disease. Often, this episode is characterized by anhedonia rather than depressed mood.

vascular insufficiency

vascular insufficiency failure of the cardiovascular system to deliver an adequate supply of blood to the body tissues. This may involve large regions of the body or a particular organ or area of an organ. Atherosclerosis, for example, can reduce the blood supply to the leg muscles, causing cramplike pains and limping; the heart, resulting in angina pectoris; or the brain, causing symptoms of stroke.

vascular sclerosis

vascular sclerosis thickening of the walls of the blood vessels, possibly related to hypertension. In audition, the condition can lead to hearing loss, often seen as a function of aging (see presbycusis).

vasculitis

vasculitis n. inflammation of a blood vessel.

vasectomy

vasectomy n. a surgical procedure for male sterilization in which the vas deferens, which carries sperm from the testes to the urethra, is removed, segmented, or cut and the resulting openings blocked. The procedure must be regarded as permanent as it cannot always be reversed.

vaso- (vas-)

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vasoconstriction

vasoconstriction n. narrowing of blood vessels, which is controlled by vasomotor nerves of the sympathetic nervous system or by such agents as vasopressin or sympathomimetic drugs. It has the effect of increasing blood pressure. See also ergot derivative.

vasoconstrictor

vasoconstrictor n. any drug or other agent (e.g., the hormone vasopressin) that causes constriction of blood vessels so that the diameter of the vessels is reduced. The vasomotor nerves of the sympathetic nervous system also serve as vasoconstrictors. Vasoconstrictor drugs are used to increase blood pressure that has fallen to dangerously low levels. Also called vasopressor.

vasodilation

vasodilation n. widening of blood vessels, as by the action of a vasomotor nerve or a drug, which has the effect of lowering blood pressure.

vasodilator

vasodilator n. any drug or other agent that serves to increase the diameter of blood vessels, generally by relaxing smooth muscle in arterial walls. Vasodilators are commonly used in the treatment of hypertension and angina pectoris.

vasomotor

vasomotor adj. describing or relating to nerve fibers, drugs, or other agents that can affect the diameter of blood vessels, especially small arteries, by causing contraction or relaxation of the smooth muscle of their walls. Fibers of the sympathetic and parasympathetic divisions of the autonomic nervous system have a vasomotor effect.

vasopressin

vasopressin n. a peptide hormone produced in the paraventricular nucleus and supraoptic nucleus of the hypothalamus and released by the posterior pituitary gland into the blood as controlled by osmoreceptors. It has two forms that differ by a single amino acid—lysine vasopressin (LVP) in pigs and arginine vasopressin (AVP) in humans and all other mammals—and that bind to one of three distinct receptors, called V1a, V1b, and V2. Both forms increase fluid retention in the body by signaling the kidneys to reabsorb water instead of excreting it in urine, and they raise blood pressure by signaling specific smooth muscle cells to contract and narrow small blood vessels. Beside these and other physiological functions, vasopressin modulates complex cognitive functions—such as attention, learning, and the formation and recall of memories—and may also modulate emotion. Additionally, vasopressin and the chemically related peptide hormone oxytocin have been implicated in a range of mammalian social behaviors, such as aggression, territoriality, maternal and paternal care, pair-bond formation and mating, social recognition, attachment, affiliation, and vocalization, as well as components of human-specific social behaviors and disorders (e.g., autism). Vasopressin itself may be involved in the pathophysiology of anxiety disorders, including posttraumatic stress disorder, and has been implicated in the pathophysiology of depression as well. AVP secretion appears to play a critical role in the stress response through activation of the hypothalamic–pituitary–adrenal axis (HPA axis): In times of stress, the HPA axis secretes corticotropin-releasing factor and AVP to stimulate the release of corticotropin from the anterior pituitary gland synergistically, culminating in a rise in circulating glucocorticoids. Vasopressin is produced synthetically (e.g., desmopressin) for such therapeutic purposes as helping the body conserve fluids (e.g., in the treatment of diabetes insipidus), restoring blood pressure (e.g., in the treatment of hypotension), and facilitating blood clotting (e.g., in the treatment of hemophilia). Also called antidiuretic hormone (ADH).

vasopressor

vasopressor 1. adj. causing constriction of blood vessels and thereby raising blood pressure. 2. n. see vasoconstrictor.

vasovagal syncope

vasovagal syncope see syncope.

Vater’s corpuscle

Vater’s corpuscle see Pacinian corpuscle. [Abraham Vater (1684–1751), German anatomist and botanist]

VCP

VCP abbreviation for visual comfort probability.

VD

VD abbreviation for venereal disease. See sexually transmitted disease.

vection

vection n. see induced movement.

vector

vector n. 1. a mathematical entity with magnitude and direction. Compare scalar. 2. in multivariate analysis, a one-dimensional arrangement in which the scores of n individuals on a particular measure are arrayed. 3. in matrix algebra, a column or row of a matrix. 4. an animal or other organism that carries and spreads disease. 5. see gene therapy.

Vedanta

Vedanta n. a collection of metaphysical theories and mental disciplines that emerged in India around the 6th century bce and derived from the sacred texts of Hinduism, the Upanishads. The sophistication of certain of these philosophies has influenced modern science, including the development of quantum theory. See object of consciousness; pure consciousness.

vegetative

vegetative adj. 1. pertaining to basic physiological functions, such as those involved in growth, respiration, sleep, digestion, excretion, and homeostasis, that are governed primarily by the autonomic nervous system, which is sometimes called the vegetative nervous system. 2. living without apparent cognitive neurological function or responsiveness, as in persistent vegetative state. 3. denoting asexual reproduction, especially in plants.

vegetative soul

vegetative soul in the thought of Aristotle, the type of soul possessed by plants. The vegetative soul has the capacity for growth and reproduction but does not have the capacity to receive and react to sense impressions or the capacity for rational thought. Compare rational soul; sensitive soul.

vegetative state

vegetative state a condition in which a person appears awake but lacks any self-awareness, environmental awareness, or basic or higher level cognitive functions (e.g., information processing, language comprehension and production, perception). The individual exhibits normal reflexes, circadian rhythms (including sleep–wake cycles), respiration, circulation, and other brainstem- and hypothalamus-governed functions but shows no voluntary behavior or other purposeful response to stimuli. Additionally, electroencephalography often reveals slowed electrical activity. Typically associated with destruction of vast areas of cerebral cortex or its integrating connections as a result of trauma, the condition is most often seen following coma but also occurs in those who have various degenerative disorders or severe congenital malformations of the nervous system. A persistent vegetative state (PVS, or persistent noncognitive state) is one lasting more than four weeks from which there is the possibility—however slim—of recovery, whereas a permanent vegetative state is one lasting more than three to 12 months (depending upon cause) from which there is no chance of regaining consciousness. The vegetative state is distinct from both brain death and the minimally conscious state but nonetheless is misdiagnosed as the latter nearly half the time. The assessment of residual cognitive abilities is extremely difficult, and uniform assessment protocols for the vegetative state have yet to be established. However, advanced functional neuroimaging techniques (e.g., event-related potentials, functional magnetic resonance imaging) are being investigated as a source of information beyond the traditional clinical method to aid diagnosis, and several recently developed measures using structured behavioral observations, such as the Sensory Modality Assessment and Rehabilitation Technique (SMART) and the Wessex Head Injury Matrix (WHIM), are now available. [defined in 1972 by British neurologist William Bryan Jennett (1926–2008) and U.S. neurologist Fred Plum (1924–2010)]

vegetotherapy

vegetotherapy n. see orgone therapy.

velar

velar 1. adj. of or relating to the soft palate. 2. adj. denoting a speech sound articulated by the soft palate, for example, the [hl] in Welsh Llandovery or the [kh] in Scottish loch or German Bach. 3. n. a speech sound made in this way.

velocity of conduction

velocity of conduction the speed at which nerve impulses travel along the axon of a neuron. Measurements by various techniques show that axons vary considerably in velocity of conduction, from 80 to 120 m/s for large, myelinated A fibers to 0.5 to 2 m/s for small, unmyelinated C fibers. Conduction velocity was first measured by Hermann von Helmholtz. See also peripheral nerve fiber classification.

Velten technique

Velten technique a mood-induction technique that is widely used to put people in a more positive frame of mind. Individuals are asked to read a series of 58 statements about their mood, energy level, achievements, and potential and to reflect on the truth of each one as it applies to their own experience. The statements, which are printed on separate cards, are carefully graded so that each one is slightly more positive than the previous ones: The series begins with the statement, “Today is neither better nor worse than any other day,” and ends with the statement, “Wow, I feel great!” The aim is to create an ideal performance state through positive self-talk. [Theodore Velten, U.S. psychologist]

velum

velum n. (pl. vela) 1. an anatomical structure resembling a veil, such as the velum medullare superior, a thin layer of white matter that forms the roof of the superior part of the fourth ventricle of the brain. 2. the soft palate.

velum palatinum

velum palatinum see soft palate.

venereal disease (VD)

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venesection

venesection n. see phlebotomy.

venire

venire n. a panel of prospective jurors drawn from the community. Typically, they are randomly selected from large lists, such as voter registration lists or lists of licensed drivers. Before individuals are included in the venire, they may be screened for factors such as age, citizenship, criminal history, and prior jury service. Also called jury pool.

venlafaxine

venlafaxine n. an antidepressant that works by inhibiting the reuptake of both serotonin and norepinephrine; it belongs to a class called the SNRIs (serotonin and norepinephrine reuptake inhibitors). Its mechanism of action therefore differs from that of the SSRIs, which some believe makes it a more effective treatment for depression. It is also appropriate for treatment of generalized anxiety disorder and social anxiety disorder. Like other antidepressants, it should not be administered concurrently with monoamine oxidase inhibitors. U.S. trade name: Effexor.

Venn diagram

Venn diagram a visual depiction of elements and relations. Circles represent the elements of a set, and the union and intersection between or among the circles represent relationships between the sets (i.e., the degree to which they are mutually inclusive or exclusive). [John Venn (1834–1923), British logician]

venous thrombosis

venous thrombosis see thrombosis.

ventilation

ventilation n. in psychotherapy and counseling, a client’s full and free expression of feelings or emotions, especially in session.

ventr-

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ventral

ventral adj. denoting the abdomen or the front surface of the body. In reference to the latter, this term sometimes is used interchangeably with anterior. Compare dorsal. —ventrally adv.

ventral amygdalofugal pathway

ventral amygdalofugal pathway the larger of the two efferent pathways from the amygdala in the brain (see also stria terminalis). It carries fibers from the basolateral group of nuclei and the central nucleus to the hypothalamus and various regions of the forebrain (including the cingulate cortex and orbitofrontal cortex) and brainstem (with which it has reciprocal connections).

ventral anterior cingulate cortex

ventral anterior cingulate cortex see anterior cingulate cortex.

ventral anterior nucleus

ventral anterior nucleus a nucleus of the anterior thalamus that receives inputs from the basal ganglia and sends connections to the precentral cerebral cortex.

ventral horn

ventral horn either of the bottom regions of the H-shaped pattern formed by the periaqueductal gray in the spinal cord. The ventral horns contain large motor neurons whose axons form the ventral roots. Also called anterior horn. Compare dorsal horn.

ventral lateral nucleus

ventral lateral nucleus see lateroventral nucleus.

ventral posterior cingulate cortex

ventral posterior cingulate cortex see posterior cingulate cortex.

ventral root

ventral root any of the spinal roots that carry motor nerve fibers and arise from the spinal cord on the front surface of each side. Also called anterior root; motor root. Compare dorsal root. See also Bell–Magendie law.

ventral stream

ventral stream a series of cortical maps of the visual field that flow from the occipital cortex to the temporal lobe. These maps represent nameable visual features of objects, such as color, size, texture, object identity, and the like. The ventral stream is known informally as the “what” pathway of perception. Compare dorsal stream.

ventral tegmental area

ventral tegmental area an area in the midbrain ventral to the periaqueductal gray and dorsal to the substantia nigra. It forms part of the limbic system, sending dopaminergic neurons to the mesocortical system and mesolimbic system.

ventral white commissure

ventral white commissure see white commissure.

ventricle

ventricle n. 1. an anatomical cavity in the body, such as any of the ventricles of the heart. 2. any of the four interconnected cavities inside the brain, which serve as reservoirs of cerebrospinal fluid. Each of the two lateral ventricles communicates with the third ventricle via the interventricular foramen; the third and fourth ventricles communicate with each other via the cerebral aqueduct, and with the central canal of the spinal cord and the subarachnoid space. Also called cerebral ventricle. —ventricular adj.

ventricular puncture

ventricular puncture a surgical procedure in which an opening from the outside is made to the lateral ventricle areas of the brain. The procedure may be performed in order to reduce intracranial pressure, to inject medications (e.g., antibiotics) directly into the brain, or to obtain cerebrospinal fluid.

ventricular system

ventricular system the network of ventricles and passageways in the brain, spinal cord, and subarachnoid space through which the cerebrospinal fluid circulates as a source of nutrients for tissues of the central nervous system.

ventricular zone

ventricular zone a region of actively dividing tissue cells lining the cerebral ventricles that provides neurons mainly in early development and in glial cells (see glia) throughout life. See subventricular zone.

ventriculoatrial shunt

ventriculoatrial shunt see shunt.

ventriculomegaly

ventriculomegaly n. abnormal enlargement of a ventricle.

ventriculostomy

ventriculostomy n. a treatment for hydrocephalus in which an opening is created between the floor of the third ventricle of the brain and the underlying cisterna to permit the free flow of cerebrospinal fluid.

ventriloquism effect

ventriloquism effect the tendency for sounds to appear to emanate from plausible visual objects, regardless of the actual source of the sound. For example, the voices of actors in a movie are localized to the images on the screen, rather than to the speakers that produce the sound. The ventriloquism effect stems from visual capture.

ventro- (ventr-)

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ventrodorsal

ventrodorsal adj. oriented or directed from the front (ventral) region of the body to the back (dorsal) region. Compare dorsoventral. —ventrodorsally adv.

ventromedial hypothalamic syndrome

ventromedial hypothalamic syndrome a set of symptoms caused by induced lesions in the ventromedial nucleus of the hypothalamus in the brain of an experimental animal (e.g., rat). The syndrome consists of two stages. The first (or dynamic) stage is characterized by hyperphagia (overeating) and subsequent weight gain, resulting in obesity. The second (or static) stage includes stabilization of body weight, resistance to food-getting behavior, and finickiness, such that the animal is willing to eat only easily obtainable and palatable foods. Also called hypothalamic hyperphagia. Compare lateral hypothalamic syndrome.

ventromedial hypothalamus (VMH)

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ventromedial nucleus

ventromedial nucleus a group of nuclei within the ventromedial hypothalamus that receives input from the amygdala and is associated particularly with eating and sexual behavior. The ventromedial nucleus traditionally has been referred to as the satiety center because of its presumed dominance over the cessation of eating (indeed, structural or functional damage results in excessive eating), but it is now known that other neural areas are involved in this function as well. See also ventromedial hypothalamic syndrome.

ventromedial pathway

ventromedial pathway any of four major descending groups of nerve fibers within the motor system, conveying information from diffuse areas of the cerebral cortex, midbrain, and cerebellum. These pathways include the anterior corticospinal tract, which descends directly from motor cortex to the anterior horn of the spinal cord; the vestibulospinal tract, which carries information from the vestibular nuclei for control of equilibratory responses; the tectospinal tract, for control of head and eye movements; and the reticulospinal tract, for maintaining posture.

ventroposterior nucleus

ventroposterior nucleus a nucleus of the thalamus in the brain that relays messages from the spinal cord to the primary somatosensory area in the anterior parietal cortex. It includes the medial and lateral ventroposterior subnuclei, representing the face and body respectively, and receives input from cutaneous receptors. The ventroposterior nucleus is part of the ventroposterior nuclear complex; this also includes the ventroposterior superior nucleus, which receives input from muscle spindles, and the ventroposterior inferior nucleus, which receives spinothalamic terminations related to touch, pain, and temperature. Also called posterior ventral lateral nucleus; postventral nucleus; ventral posterior lateral nucleus.

venue sampling

venue sampling see time–location sampling.

VEP

VEP abbreviation for visual evoked potential.

verapamil

verapamil n. see calcium-channel blocker.

veratrine

veratrine n. see hellebore.

verb

verb n. a word or phrase used to describe an action, occurrence, or state, forming the essential part of the predicate of a sentence. The verb is also identifiable as the element of the sentence that marks temporality (tense), mood, voice (see active voice; passive voice), and number agreement with the subject. See also actional verb; auxiliary verb; causative verb.

verbal ability (V)

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verbal abuse

verbal abuse extremely critical, threatening, or insulting words delivered in oral or written form and intended to demean, belittle, or frighten the recipient.

verbal alexia

verbal alexia a form of agnosia in which an individual may recognize single letters but not whole words or combinations of letters. See alexia.

verbal amnesia

verbal amnesia a loss of the ability to remember words due to neurological disorder or disease. See neurological amnesia.

verbal aphasia

verbal aphasia another name for expressive aphasia.

verbal apraxia

verbal apraxia see apraxia.

verbal behavior

verbal behavior all behavior that involves words, including speaking, listening, writing, and reading. The term is used by those who favor a behavioristic account of language (see behaviorism) in which human verbal behavior is thought to be explained by general laws of learning and behavior observable in other species; that is, its reinforcement is socially mediated by the responses of others. This contrasts with the cognitive approach dominant in psycholinguistics and specifically with the theory of the cognitive task specificity of language. [first described by B. F. Skinner in 1957]

verbal behavior therapy

verbal behavior therapy based on the principles of applied behavior analysis and B. F. Skinner’s concept of verbal behavior, a therapy that is primarily used to teach speech to nonverbal children with autism. The therapy uses various reinforcers (food, toys) first to prompt the child to vocalize sounds and then to imitate whole words and phrases. The therapy also aims to improve the child’s attentional ability and social and cognitive skills. Also called applied verbal behavior.

verbal communication

verbal communication see communication.

verbal comprehension

verbal comprehension an individual’s ability to understand the language used by others, as determined by his or her receptive vocabulary and receptive language skills.

Verbal Comprehension Index

Verbal Comprehension Index on the Wechsler Adult Intelligence Scale and other Wechsler tests, a subset of verbal tests thought to measure verbal knowledge and comprehension more purely than the other tests included in the verbal IQ.

verbal conditioning

verbal conditioning the conditioning of a verbal response (such as the use of a specific word) through reinforcement, usually given in the form of attention or praise. For instance, the experimenter might respond “Okay” whenever the participant uses the pronoun I but does not respond to the use of other pronouns. [introduced in 1955 by U.S. behaviorist Joel Greenspoon (1920–2004)]

verbal deprivation hypothesis

verbal deprivation hypothesis the hypothesis that children who are denied regular experience of an elaborated code of language—that is, a more formal use of language involving complex constructions and an unpredictable vocabulary—may develop an educational and even cognitive deficit. The concept is controversial as it has been associated with the view that nonstandard or vernacular forms of a language (e.g., Black English) are inherently inferior. The idea that nonstandard forms inhibit higher level cognitive processes (e.g., abstract reasoning) is now discredited, but concerns remain that lack of early exposure to the more formal codes of a language appears to correlate with educational underachievement. [proposed in 1973 by British sociologist Basil Bernstein (1924–2000)]

verbal factor

verbal factor a factor obtained by factor analysis that represents the latent trait underlying verbal abilities.

verbal fluency test

verbal fluency test any of a group of tests in which participants are required, within a limited period, to generate words that fit a specific category or have specific characteristics (e.g., they may all start with the same letter or be from the same semantic category). Compare design fluency test.

verbal intelligence

verbal intelligence the ability to use words and combinations of words effectively in communication and problem solving.

verbal IQ

verbal IQ a broad measure of verbal ability as obtained on standardized intelligence tests and affected by native verbal skills, experience, education, test taking skills, and test motivation. See IQ.

verbal leakage

verbal leakage slips of the tongue, verbal ambiguities, or other aspects of speech thought to reveal information about an individual’s motives and behavior that he or she has attempted to conceal. Body language that is similarly revealing is described by some psychologists as nonverbal leakage. See also Freudian slip; parapraxis; symptomatic act.

verbal learning

verbal learning the process of learning about verbal stimuli and responses, such as letters, digits, nonsense syllables, or words. The methods used include paired-associates learning and serial learning. Researchers in the verbal learning tradition, influenced by Hermann Ebbinghaus and by associationism, sought to uncover basic laws of learning by studying simple materials under controlled conditions. Compare nonverbal learning.

verbal masochism

verbal masochism a sexual disorder in which an individual enjoys hearing words that are humiliating and insulting and derives sexual excitement from the abuse. According to Theodor Reik, the sexual excitement may depend on the choice and emphasis of words or sentences used.

verbal memory

verbal memory the capacity to remember something written or spoken that was previously learned (e.g., a poem). Compare motor memory; visual memory.

verbal narrative

verbal narrative an oral recounting of an event, as when a person describes a recent date to a friend over the telephone. Such spoken-word narratives help provide an individual with a sense of self and of history and often include descriptions of mood, conflicts, stressors, and concerns. They contrast with visual narratives, which describe events through images, and textual narratives, which describe events in writing. Research has revealed that the ability to narrate life experiences is significant in understanding and treating certain disorders, particularly posttraumatic stress disorder. The use of such narratives as a specific therapeutic technique is known as narrative therapy.

verbal overshadowing

verbal overshadowing the tendency for the verbal description of a stimulus to impair later accurate memory of the stimulus. For instance, verbally describing a face that has just been seen may reduce later recognition or identification of that face in a picture lineup.

verbal paraphasia

verbal paraphasia a form of paraphasia characterized by the inclusion of inappropriate words and phrases in a person’s speech.

verbal protocol

verbal protocol a method of eliciting verbal reports of individuals’ thoughts as they perform a set of specified research tasks. Participants are asked to describe whatever they are seeing, thinking, doing, and feeling as it occurs during task performance. Rather than capturing mere summaries of a task’s results, the method provides the researcher with insight about the cognitive processes involved in task completion and the representations on which they operate.

verbal protocol analysis

verbal protocol analysis see protocol analysis.

verbal report

verbal report see reportability.

verbal satiation

verbal satiation see masturbatory satiation.

verbal test

verbal test any test or scale in which performance depends upon one’s ability to comprehend, use, or otherwise manipulate words.

verbal thought

verbal thought a reasoning process that requires language and thus represents the merging of language and thought. Children first use language to guide thought by speaking out loud; only later does speech go underground to become covert verbal thought. See egocentric speech; inner language. [proposed by Lev Vygotsky]

verbalization

verbalization n. 1. the expression of thoughts, feelings, and fantasies in words. Verbalization is a common feature of most forms of psychotherapy. Apart from the general communication that occurs between therapist and client as part of the psychotherapeutic process, a particularly striking form of verbalization occurs in the use of free association. 2. in psychiatry, a symptom involving excessive or uncontrolled speech, as in circumstantiality or pressured speech. —verbalize vb.

verbally governed behavior

verbally governed behavior see rule-governed behavior.

verbatim recall

verbatim recall recollection of the exact wording of verbal material (e.g., a conversation, poem, or quotation). See also rote recall.

verbatim trace

verbatim trace see fuzzy trace theory.

verbigeration

verbigeration n. apparently meaningless repetition of specific words or phrases. Also called catalogia; cataphasia.

vergence

vergence n. a turning movement of the eyes to focus on an item in the depth plane. If they turn toward each other, the movement is convergence; if they turn away from each other, it is divergence.

veridical

veridical adj. 1. truthful. 2. of mental phenomena, such as memories or beliefs, corresponding to external reality.

veridical hallucination

veridical hallucination in parapsychology, a hallucination depicting events later proven to be true.

veridical perception

veridical perception accurate perception of what is real.

verification

verification n. the process of establishing the truth or accuracy of something, especially the use of objective, empirical data to test or support the truth of a statement, conclusion, or hypothesis.

verification time

verification time in studies of cognition, a measure of the time taken by a participant to indicate whether a statement is true or to verify that a particular stimulus meets some prespecified condition.

verisimilitude

verisimilitude n. the appearance of being true. In scientific investigation, a theory or model is said to have verisimilitude if it can be shown to be more consistent with empirically verified fact than its predecessors or competitors.

vermis

vermis n. (pl. vermes) the median lobe of the cerebellum, which lies between the two cerebellar hemispheres. Also called vermis cerebelli. —vermicular adj.

vernacular

vernacular n. the indigenous or characteristic language or dialect spoken routinely by a particular group of people: everyday language. It usually coexists with an official formal language (see standard language) used in schools and government. See diglossia.

Versed

Versed n. a trade name for midazolam.

verstehende Psychologie

verstehende Psychologie understanding psychology (German): an approach to psychology advocated by German philosopher Wilhelm Dilthey (1833–1911). Dilthey argued that psychology belonged to the human sciences (Geisteswissenschaften) as opposed to the natural sciences (Naturwissenschaften) and that its goal was therefore understanding (Verstehen) rather than explanation in terms of natural laws. For psychology, the object of understanding is lived experience (Erlebnis), and the goal must be articulation of the meaning of the experience from the perspective of the person living it. This approach was influential in the development of phenomenology, modern hermeneutics, and existential psychology. See Geisteswissenschaftliche Psychologie; Naturwissenschaftliche Psychologie.

vertebral artery

vertebral artery a paired artery that runs upward alongside the vertebrae of the neck. Each vertebral artery enters the skull through the foramen magnum (see foramen) near the top of the spinal column, where it joins the vertebral artery from the other side to form the basilar artery.

vertebral column

vertebral column see spinal column.

vertex potential

vertex potential a brain potential recorded by electrodes placed at the vertex (top) of the skull. The vertex potential seems to be evoked by a variety of stimuli but is closely associated with attention.

vertical décalage

vertical décalage in Piagetian theory, the invariable sequence in which the different stages of development (sensorimotor, preoperational, concrete operational, formal operational) are attained. Compare horizontal décalage.

vertical group

vertical group a group composed of individuals who come from different social classes. Compare horizontal group.

vertical job enlargement

vertical job enlargement see job enlargement.

vertical loading

vertical loading see job enlargement.

vertical mobility

vertical mobility the movement or displacement of individuals or groups from one social class to another. This may take the form of upward mobility or downward mobility. Compare horizontal mobility. See social mobility.

vertical transmission

vertical transmission see horizontal transmission.

vertical–horizontal illusion

vertical–horizontal illusion see horizontal–vertical illusion.

vertigo

vertigo n. an unpleasant, illusory sensation of movement or spinning of oneself or one’s surroundings because of neurological disorders, psychological stress (e.g., anxiety), or activities that disturb the labyrinth (which contains the organs of balance) in the inner ear (as in a roller-coaster ride).

very low birth weight (VLBW)

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vesicle

vesicle n. a fluid-filled saclike structure, such as any of the synaptic vesicles in axon terminals that contain neurotransmitter molecules. —vesicular adj.

vested interest

vested interest the extent to which an attitude object is seen as being related to a person’s material self-interest. It is assumed to be a determinant of related constructs, such as the importance of an attitude and ego involvement. It is also a determinant of attitude strength.

vestibular adaptation

vestibular adaptation an effect of repeated stimulation that can result in suppression of the vestibular (balance) function and may be observed in individuals whose daily activities require frequent or repeated turning of the head (e.g., ballet dancers and figure skaters).

vestibular apparatus

vestibular apparatus the organ of balance and equilibrium, which is situated in the inner ear and contains receptors that detect the orientation and changes in the position of the head in space. It consists of the semicircular canals and vestibular sacs. See also vestibular system.

vestibular glands

vestibular glands two pairs of glands situated on either side of the vaginal orifice. Their secretions lubricate the vulva and vagina and assist penetration by the penis during coitus. The larger pair (the greater vestibular glands) are also called Bartholin’s glands.

vestibular illusion

vestibular illusion a spatial disorientation due to inaccurate vestibular (balance) information, for example, following adaptation of a vestibular receptor.

vestibular membrane

vestibular membrane see Reissner’s membrane.

vestibular nerve

vestibular nerve a division of the vestibulocochlear nerve that carries nerve fibers from the vestibular system in the inner ear; it is associated with the sense of balance and orientation in space. Fibers of the vestibular nerve terminate in the vestibular nuclei of the brainstem.

vestibular nuclei

vestibular nuclei nuclei in the dorsolateral part of the pons and the medulla oblongata in the brain that receive fibers from the vestibular nerve and serve the sense of balance and orientation in space. They send fibers to the cerebellum, reticular formation, thalamus, and the vestibulospinal tract (see ventromedial pathway).

vestibular nystagmus

vestibular nystagmus involuntary eye movements consisting of slow drift in one direction followed by a rapid movement in the opposite direction, caused by stimulation of the vestibular apparatus during rotation of the head. Also called rotational nystagmus. Compare physiological nystagmus.

vestibular receptors

vestibular receptors nerve cells associated with the sense of balance, located in the cristae of the semicircular canals and in the maculae of the utricle and saccule. They occur in two similar forms: a hair cell enclosed in a chalicelike nerve ending and a cylindrical hair cell that synapses at its base with a nerve ending.

vestibular sacs

vestibular sacs two sacs in the inner ear—the utricle and saccule—that, together with the semicircular canals, comprise the vestibular apparatus (see also vestibular system). The vestibular sacs respond both to gravity to encode information about the head’s orientation and to linear acceleration.

vestibular sense

vestibular sense see sense of equilibrium.

vestibular system

vestibular system a system in the body that is responsible for maintaining balance, posture, and the body’s orientation in space and plays an important role in regulating locomotion and other movements. It consists of the vestibular apparatus in the inner ear, the vestibular nerve, and the various cortical regions associated with the processing of vestibular (balance) information.

vestibule

vestibule n. a chamber that leads to a body cavity or that connects one cavity to another. The vestibule of the vagina is the cavity in the vulva, between the two labia minora, into which the vagina, urethra, and greater vestibular glands open. The vestibule of the inner ear is the cavity of the bony labyrinth that contains the utricle and saccule (the vestibular sacs) and is connected to the semicircular canals and cochlea. —vestibular adj.

vestibule training

vestibule training an approach to personnel training in which new employees, before starting their work duties, spend some time learning in a special section (vestibule), apart from the actual work environment that duplicates as precisely as possible the setting and conditions in which the employees will actually be working once their training is complete. See off-the-job training; on-the-job training.

vestibulo-ocular reflex (VOR)

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vestibulocochlear nerve

vestibulocochlear nerve the eighth cranial nerve: a sensory nerve containing tracts that innervate both the sense of hearing and the sense of balance. It has two divisions, the vestibular nerve, originating in the vestibule and the semicircular canals, and the auditory nerve (acoustic or cochlear nerve), originating in the cochlea. The vestibulocochlear nerve transmits impulses from the inner ear to the medulla oblongata and pons and has fibers that continue into the cerebrum and cerebellum. Also called cranial nerve VIII.

vestibulospinal tract

vestibulospinal tract a tract that sends impulses from the vestibular nucleus to the spinal cord. It is divided into lateral and medial branches and serves to control balance and orientation in space.

vestigial body image

vestigial body image the subjective or internal image of one’s appearance that is not necessarily modified by changes to one’s external features. For example, individuals who have lost large amounts of weight may continue to have a vestigial body image of themsleves as an overweight individual.

vestured genital apposition

vestured genital apposition sexual activity in which clothed participants place their genital regions together and thrust or rub against each other, simulating coitus. The activity may or may not be carried to the point of orgasm for one or both partners.

VFDT

VFDT abbreviation for Visual Form Discrimination Test. See visual form discrimination.

VI

VI abbreviation for variable interval. See variable-interval schedule.

vibration

vibration n. a periodic motion of an object, such as a tuning fork, with a frequency that is usually measured in hertz.

vibration disease

vibration disease an occupational health hazard resulting from acoustic or mechanical vibration and shock to the body. The extent of the damage depends on the frequencies of vibrations and the duration of exposure. See also hand–arm vibration syndrome.

vibration environment

vibration environment an environment in which the oscillations of an operational vehicle in motion are transmitted to humans by supporting seats, floors, walls, and handles. Such vibration can have mechanical effects on the human body that are similar to those caused by acceleration. The magnitude of the vibration effects depends on the frequency range of the vibration force and its relationship to the body’s dynamic response.

vibration experience

vibration experience a sensation produced by contact with a pulsating or rapidly vibrating object that stimulates receptors in the skin. The vibration sense can be measured with a mechanical vibrator that can be adjusted for threshold frequencies of the effect.

vibration receptor

vibration receptor a nerve ending that responds to various ranges of vibration frequencies. Vibration receptors have been identified through histological studies as Pacinian corpuscles, located at depths ranging from the skin surface to the connective tissue covering the surface of a bone. Some vibration receptors seem most sensitive to vibrations between 100 and 500 Hz, whereas others are most sensitive to those below 100 Hz.

vibration sense

vibration sense see vibration experience.

vibration white finger

vibration white finger see hand–arm vibration syndrome.

vibrator

vibrator n. an appliance containing a small electric motor that produces a vibrating action, used to stimulate the genitals and other sensitive areas during masturbation or sexual activity with a partner. The device may be powered by batteries or by household electric current. Some vibrators strap on the hand, making the fingers vibrate during sexual stimulation. Another type has a vibrating mechanism on which a number of attachments of different sizes, shapes, and textures can be placed, and these stimulate the body directly. Other vibrators are cylinders that can be used externally or inserted into the vagina or anus.

vibrotactile aid

vibrotactile aid see tactile sensory aid.

vibrotactile masking

vibrotactile masking the interference of one vibrotactile stimulus pattern with another that may occur if the two patterns are presented in close temporal proximity. Masking may be forward or backward.

vibrotactile threshold

vibrotactile threshold the minimum level of stimulation at which a vibration is perceived. Different types of mechanoreceptors are sensitive to different specific frequencies of vibration.

vicarious

vicarious adj. 1. substitutive or second-hand: applied, for example, to the satisfaction obtained by viewing the experiences of others in television programs. It is widely believed that human conditioning of fear responses can occur through vicarious means and that gratification of needs can be partially accomplished through watching the actions of others. See also observational learning. 2. occurring when one organ performs part of the functions normally performed by another.

vicarious brain process

vicarious brain process see vicarious function.

vicarious conditioning

vicarious conditioning see observational learning.

vicarious extinction

vicarious extinction a phenomenon in which behavioral inhibitions are eliminated by observational experiences alone, with accompanying generalized and enduring reductions in fear arousal and avoidance behavior. Vicarious extinction requires exposing observers to stimulus events in which a model repeatedly exhibits approach responses toward a feared object without incurring any aversive consequences. For example, vicarious extinction for a person who is afraid of dogs might involve watching as another individual engages with a series of different dogs in a pen and interacts with each one in a way that becomes progressively more involved (e.g., petting, then feeding, then leash walking, then picking up each animal) without being bitten or experiencing other negative consequences.

vicarious function

vicarious function a theory to explain the ability to recover from the effects of brain damage. It is based on evidence that many functions are not strictly localized in the brain and that many brain areas can assume a function previously performed by a brain area that has been damaged. Also called vicarious brain process.

vicarious learning

vicarious learning see observational learning.

vicarious reinforcement

vicarious reinforcement the process whereby a person becomes more likely to engage in a particular behavior (response) by observing another individual being reinforced for that behavior. An important concept in social learning theory, vicarious reinforcement often leads to imitation: for example, a student who hears the teacher praise a classmate for neat penmanship on an assignment and who then carefully handwrites his or her own assignment is considered to have received vicarious reinforcement. See also observational learning.

vicarious traumatization (VT)

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vicious circle

vicious circle a situation or behavioral pattern in which an individual’s or group’s problems become increasingly difficult because of a tendency to address or ignore them repetitively through unhealthy defensive reactions that, in fact, compound them.

vicious circularity

vicious circularity the logical problem that is presented by certain kinds of self-referring paradox, such as This sentence is a lie, and by certain related cruxes in set theory, notably those arising from the idea that a set can be the member of itself. See also circular reasoning.

Vicodin

Vicodin n. a trade name for a combination of hydrocodone and acetaminophen.

victim

victim n. 1. an individual who is the target of another person’s violent, discriminatory, harassing, or assaultive behaviors. 2. an individual who has experienced an accident or natural disaster. See victimization.

victim blaming

victim blaming see blaming the victim.

victim impact statement

victim impact statement a spoken or written statement made during the sentencing phase of a trial by the victim of a crime or, in cases where the crime resulted in death, by the family of the victim, describing the harm and suffering experienced as a result of the defendant’s acts.

victimization

victimization n. the act or process of singling someone out for cruel or unfair treatment, typically through physical or emotional abuse.

victimology

victimology n. see criminal profiling.

video conferencing

video conferencing see teleconferencing.

video-recall technique

video-recall technique a research procedure in which participants review a video recording of their behavior in a previous situation and report what they were thinking, feeling, or otherwise experiencing at that time. The video-recall technique is intended to reduce distortion in self-reports, the premise being that reimmersion in the situation generates a more representative set of recollections with less defensive justification than memory alone.

videotape method

videotape method in clinical psychology and psychiatry, the use of video recordings of therapy sessions for therapeutic, research, or teaching purposes. Recorded sessions are typically reviewed as a part of clinical supervision and are useful in providing trainees with feedback. Occasionally patients are invited to view the recordings with the therapist and to recall their thoughts and emotions.

Vienna Circle

Vienna Circle a group of philosophers, logicians, and mathematicians who were based in Vienna in the 1920s and 1930s. The unifying theme of their work was an attempt to systematize the empirical and positivist tradition using the methods of modern symbolic logic—an approach that became known as logical positivism. Prominent members of the group included German philosopher Rudolf Carnap (1891–1970) and Czech-born mathematical logician Kurt Gödel (1906–1978).

Vienna Psychoanalytic Society

Vienna Psychoanalytic Society see Wednesday Evening Society.

Viennese School

Viennese School a group of early 20th-century practitioners of psychoanalysis, based in Vienna, who followed the theories of Sigmund Freud. Also called Vienna School; Wiener Schule. See also Wednesday Evening Society.

Vierordt’s law

Vierordt’s law the principle that the two-point threshold for a stimulus is lower in mobile body parts than in those that are less mobile. [Karl von Vierordt (1817–1884), German physiologist]

Vieth–Müller circle

Vieth–Müller circle a theoretical circle in space in front of an observer containing points that will fall on corresponding retinal locations in the two eyes when a point on the circle is fixated. A Vieth–Müller circle is an example of a horopter. [G. U. Vieth; J. P. Müller]

view invariance

view invariance in recognition by components theory, an unchanging property of three-dimensional elements called geons that enables them to be identified when looked at from different angles. Such properties include the curvature of a sphere and the parallel lines of a cube. More broadly, the term view invariant may be used in the context of object recognition, meaning that an object can be identified from any angle. For example, a horse can be identified if it is viewed from above or from the side.

vigilance

vigilance n. a state of extreme awareness and watchfulness directed by one or more members of a group toward the environment, often toward potential threats (e.g., predators, intruders, enemy forces in combat). In animal behavior, vigilance increases in females after the birth of their young and in response to alarm calls. In large groups, there can be a division of labor, with individuals taking turns in vigilance. In a military context, vigilance tasks (e.g., sentry duty, ship and air traffic control, antiaircraft and missile defense tracking) demand maximum physiological and psychological attention and readiness to react, characterized by an ability to attend and respond to stimulus changes for uninterrupted periods of time. This level of vigilance can produce significant cognitive stress and occasional physiological stress reactions. Also called vigilant attention. Compare ambient awareness; situation awareness. —vigilant adj.

vigilance decrement

vigilance decrement in a vigilance task, a decrease in the number of targets detected that occurs after a short period on the task. In many situations, the decrement is due to a shift in the response criterion, although in some cases it reflects a decrease in sensitivity for detecting the target.

vigor

vigor n. physical and mental robustness and energy. —vigorous adj.

vindicatory damages

vindicatory damages a sum of money a defendant is ordered to pay the plaintiff in a civil lawsuit for infringement of the latter’s constitutional rights. For example, a plaintiff who receives $100,000 for false imprisonment by the defendant has been awarded vindicatory damages.

Vineland Adaptive Behavior Scales (VABS)

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violation of assumptions

violation of assumptions a situation in which the theoretical assumptions associated with a particular statistical or experimental procedure are not fulfilled. Common assumptions for statistical tests include normality of the distribution, equal variances within the cells of treatment levels, homogeneity of variance, and linearity. Research designs also need to meet certain assumptions, such as random sampling and random assignment, sample representativeness, and the like. Because violation of assumptions introduces bias, the validity of assumptions must be confirmed prior to data analysis to ensure that the methods and strategies chosen are appropriate and will yield valid results.

violation-of-expectation method

violation-of-expectation method a technique for studying infant cognition, based on habituation and dishabituation procedures, in which increases in an infant’s looking time at an event or other stimulus are interpreted as evidence that the outcome he or she expected has not occurred. For example, while a baby watches, a researcher may repeatedly return a toy to a blue box. If the researcher sometime later retrieves the same toy from a nearby red box (after a confederate surreptitiously moved it) and the baby looks longer at that red box, it is assumed that he or she has some understanding of object permanence and was not expecting the toy to be there.

violence

violence n. 1. the expression of hostility and rage with the intent to injure or damage people or property through physical force. See also pathological aggression. 2. passion or intensity of emotions or declarations. —violent adj.

viral hypothesis

viral hypothesis the theory, first suggested in the early 20th century, that psychoses resembling schizophrenia are associated with influenza epidemics. It was later observed that several types of viral encephalitis may involve schizophrenia-like symptoms, and many studies have investigated the effect of exposure to viral agents, especially in utero, on subsequent development of schizophrenia. In particular, U.S. psychiatrist E. Fuller Torrey (1937– ) has noted that the viral hypothesis accounts for the greater number of people with schizophrenia born from January to April (see seasonality effect), a period during which there is a high incidence of viral infections. More recently, however, it has been suggested that virus exposure is a risk factor for—rather than a key causative event in—the development of schizophrenia.

viral marketing

viral marketing a form of Internet marketing in which businesses encourage consumers to publicize their products or services by forwarding advertising material in e-mails or posting links on blogs or social media.

viral meningitis

viral meningitis see meningitis.

Virchow–Seckel syndrome

Virchow–Seckel syndrome see Seckel syndrome.

virgin

virgin 1. n. a person who has never had sexual intercourse. 2. n. a person who has never had sexual contact of any sort, including fellatio and cunnilingus. 3. adj. referring to a pure or natural state, as in a virgin forest. —virginal adj.

virginity

virginity n. the state of a person who has not participated in sexual intercourse. Traditionally, a woman was assumed to be a virgin if her hymen was not ruptured, but a ruptured hymen is no longer regarded as prima facie evidence of loss of virginity, as other events can cause this.

virilism

virilism n. the presence in a female of secondary sexual characteristics that are peculiar to men, such as muscle bulk and hirsutism. The condition is due to overactivity of the adrenal cortex with excessive secretion of androgen, which can be corrected in some cases. Also called masculinization.

virility

virility n. the state of possessing the qualities of an adult male, especially capacity for coitus. See also maleness; masculinity. —virile adj.

virilocal

virilocal adj. see patrilocal.

virtual pitch

virtual pitch the low pitch of a complex sound. For a complex periodic sound, the virtual pitch generally corresponds to that of the fundamental frequency even when the fundamental is not present in the sound (the phenomenon of the missing fundamental). The terms periodicity pitch and residue pitch are now used synonymously with virtual pitch, although they have different historical antecedents.

virtual reality

virtual reality a simulated three-dimensional environment created through the memory, graphics, and processes of a computer. It is often used to create simulated environments for activities such as flying a plane or exploring space, which are expensive or dangerous to experience directly. Supporting hardware and software tools, including gloves and head monitors with real-time feedback, are often used to immerse and train humans in this virtual reality.

virtual reality therapy

virtual reality therapy a form of in vivo exposure therapy in which clients are active participants in a three-dimensional computer-generated interactive environment that allows them a sense of actual involvement in scenarios related to their presenting problems. This treatment is currently used primarily for anxiety-related disorders, such as fear of flying.

virtual team

virtual team two or more people in separate locations who work as a group toward a common goal or related goals and who interact electronically via e-mail, teleconferencing, and other means.

virtue

virtue n. 1. a quality or characteristic that has positive connotations in a particular society and that is considered beneficial to psychological health. 2. moral goodness. —virtuous adj. —virtuousness n.

virus

virus n. 1. a microscopic parasitic agent that consists of an RNA or DNA core surrounded by a protective protein coat. Because viruses cannot replicate on their own but must invade a living host cell in an organism to do so, they are generally considered nonliving. Viral infection is responsible for many human illnesses and diseases, including influenza, poliomyelitis, mumps, several forms of cancer, and AIDS (see HIV). 2. a computer program designed to disrupt the functioning of other programs or to scramble or destroy computer files. It gains access to programs or systems surreptitiously, often by means of an attachment to an innocent-looking e-mail message. Viruses are typically designed to spread from computer to computer; for that reason, they can be extremely destructive.

viscera

viscera pl. n. (sing. viscus) the organs in any major body cavity, especially the abdominal organs (stomach, intestines, kidneys, etc.). —visceral adj.

visceral brain

visceral brain in MacLean’s theory of emotion, the area of the brain that is involved in the neurophysiological control of emotional behavior and experience (including motivated behavior). It is now more commonly known as the limbic system.

visceral drive

visceral drive a drive that is derived from a physiological need. Also called viscerogenic drive. See physiological motive.

visceral learning

visceral learning the use of instrumental conditioning procedures, particularly biofeedback techniques, to enable an individual to deliberately modify physiological processes that are ordinarily and nonconsciously regulated by the autonomic nervous system, such as heart rate and blood pressure.

visceral reaction

visceral reaction a response of the visceral (internal or abdominal) organs, such as contractions of the stomach.

visceral sensation

visceral sensation see organic sensation.

visceral sense

visceral sense the sense associated with functions of the viscera.

viscerotonia

viscerotonia n. the personality type that, according to Sheldon’s constitutional theory of personality, is associated with an endomorphic physique (see endomorph) and is characterized by a tendency toward love of comfort, food, relaxation, and sociability. —viscerotonic adj.

viscus

viscus n. see viscera.

visible spectrum

visible spectrum see spectrum.

vision

vision n. 1. the sense of sight, in which the eye is the receptor and the stimulus is radiant energy in the visible spectrum. See also visual system. 2. a visual hallucination often involving a religious or mystical experience. 3. a mental image of something or someone produced by the imagination. —visual adj.

vision impairment

vision impairment see visual impairment.

vision rehabilitation

vision rehabilitation the rehabilitation of individuals with visual impairment ranging from blindness to low vision. Services provided include functional assessments of a person’s visual abilities, if any; orientation and mobility training; rehabilitation teaching (e.g., adaptive skills training in managing one’s activities of daily living); instruction in the use of optical devices and assistive technology; career services and training; and psychological counseling.

visitation rights

visitation rights see child visitation.

visiting nurse

visiting nurse a registered nurse who provides nursing services to patients in their homes. Visiting nurses are usually employed by a local visiting nurse association.

Vistaril

Vistaril n. a trade name for hydroxyzine.

visual acuity

visual acuity the degree of clarity, or sharpness, of visual perception. It may be measured in several ways; for example, by testing one’s ability to detect very small gaps between two parts of a figure (the minimum separable method), or to discern a fine dark line on a light background or a fine light line on a dark background. See also acuity grating; Landolt circles; Snellen chart.

visual adaptation

visual adaptation the changes that occur in the visual system itself or in visual perception as a result of continuous stimulation. For example, the range of light intensities over which photoreceptors are responsive changes with prolonged exposure to dark, and many visual aftereffects are caused by adaptation of neurons within the visual system. See also dark adaptation; light adaptation.

visual agnosia

visual agnosia loss or impairment of the ability to recognize and understand the nature of visual stimuli. Classically, a distinction between apperceptive and associative forms of visual agnosia has been made. Individuals with the former are said to have deficits in the early stages of perceptual processing, whereas those with the latter either do not display such problems or do so to a degree not sufficient to substantially impair the ability to perform perceptual operations. Subtypes of each form exist based on the type of visual stimulus the person has difficulty recognizing, such as objects (visual object agnosia or visual form agnosia), multiple objects or pictures (simultanagnosia), or colors (color agnosia). See also integrative agnosia; prosopagnosia.

visual agraphia

visual agraphia an impaired ability to write resulting from a failure to recognize letters, numbers, or words. The condition is caused by lesions in the occipitoparietal area of the brain. See agraphia.

visual allesthesia (visual allaesthesia)

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visual amnesia

visual amnesia loss of the ability to recognize familiar objects, printed words, or handwriting by sight, due to neurological disease or injury.

visual analogue scale

visual analogue scale a psychometric instrument used to evaluate subjective characteristics that extend over a range of continuous values. Respondents specify their level of the characteristic of interest by indicating a position along a continuous line, anchored at its end points by word descriptors. For example, a visual analogue scale for performance might have poor on the left end with a blank line across to excellent on the right end. The respondent would mark a place along that line to indicate his or her perceived performance level. Also called unnumbered graphic rating scale.

visual angle

visual angle the angle subtended by a visual target at the nodal point of the eye. The width of an adult thumb at arm’s length subtends about 1° of visual angle, and there are 360° of visual angle around the entire head.

visual anomia

visual anomia failure to name visual stimuli correctly despite intact visual recognition.

visual anosognosia

visual anosognosia see Anton’s syndrome.

visual apperception test

visual apperception test a projective technique in which participants (most often children and adolescents) are presented with a visually oriented task, such as drawing a person, object, or situation; finishing an incomplete drawing; or creating a narrative from a single or multiple visual stimuli.

visual area

visual area any of many regions of the cerebral cortex in which the neurons are primarily sensitive to visual stimulation. Together, all the visual areas comprise the visual cortex. Most visual areas can be distinguished from one another on the basis of their anatomical connections (i.e., their cytoarchitecture) and their specific visual sensitivities. Individual areas are designated by “V” and a number that indicates roughly how distant the area is from striate cortex. See V1; V2; V3; V4; V5.

visual area MT

visual area MT see V5.

visual association cortex

visual association cortex any of the visual areas in the cerebral cortex that lie outside the striate cortex, including V2, V3, V4, and V5. See also prestriate cortex.

visual attention

visual attention the process by which one item (the target) is selected for analysis from among several competing items (the distractors). See also feature-integration theory.

visual attention disorder

visual attention disorder any disturbance of a person’s ability to detect and attend to visual stimuli. Examples include Bálint’s syndrome and visual neglect. See also perceptual extinction.

visual aura

visual aura see aura.

visual axis

visual axis a straight line that extends from the external fixation point through the nodal point of the eye to the fovea. Compare primary line of sight.

visual blurring

visual blurring the sensation resulting from impairment of the ability to perceive form in the central field region, which is typically associated with poor visual acuity and reduced spatial contrast sensitivity. Visual blurring can occur as a result of retinal disease (e.g., macular degeneration, diabetic retinopathy) or damage to the optic nerve (e.g., associated with multiple sclerosis) or visual cortex; it has also been reported as a side effect of anticholinergic drugs and as a consequence of accommodative spasm. Patients experience difficulties with reading and face perception (especially in black-and-white photographs).

visual cache

visual cache see visuospatial sketchpad.

visual capture

visual capture the tendency for vision to override the other senses. It is responsible for the ventriloquism effect.

visual cliff

visual cliff an apparatus to investigate the development of depth perception in nonverbal human infants and in nonhuman animals, and in particular, whether depth perception is an innate ability or learned through visuomotor experience. The apparatus consists of a table with a checkerboard pattern, dropping steeply down a “cliff” to a surface with the same pattern some distance below the tabletop. The apparatus is covered with a transparent surface, and the participant is positioned on this at the border between the tabletop and the cliff. Reluctance to crawl onto the surface covering the cliff is taken as an indication that the participant can discriminate the apparent difference in depth between the two sides of the apparatus. Most infants as young as 6 months of age will not cross to the side over the cliff. [devised by Eleanor J. Gibson]

visual closure

visual closure the ability to identify a familiar object from an incomplete visual presentation.

visual comfort probability (VCP)

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visual communication

visual communication the use of distinctive colors, shapes, or movements that are detected by the visual system as a means of communication between individuals. For example, nonhuman animals may have distinctive colors in the breeding season to indicate reproductive state, fluff out fur to appear larger in a threat context, or gesture with limbs or head in a variety of other contexts.

visual consciousness

visual consciousness those contents of consciousness that have a visual origin. Operationally, such consciousness consists of those visual events that can be reported, distinguished from each other, and acted upon on request. Given these criteria, visual consciousness does not include blindsight.

visual constructional impairment

visual constructional impairment see visuoconstructional impairment.

visual cortex

visual cortex the cerebral cortex of the occipital lobe, specifically the striate cortex (primary visual cortex). In humans this occupies a small region on the lateral surface of the occipital pole of the brain, but most is buried in the banks of the calcarine fissure on the medial surface of the brain. The visual cortex receives input directly from the lateral geniculate nucleus via the optic tract and sends output to the multiple visual areas that make up the visual association cortex.

visual cycle

visual cycle the biophysical and biochemical sequence of events that includes the release of all-trans retinal from rhodopsin during light stimulation, followed by its conversion to 11-cis retinal in the retinal pigment epithelium, and then the return of the 11-cis retinal to the photoreceptor for the reconstitution of rhodopsin.

visual discrimination

visual discrimination the ability to distinguish shapes, patterns, hidden figures, or other images from similar objects that differ in subtle ways.

visual dominance

visual dominance 1. the phenomenon in which visual stimuli, when presented simultaneously with auditory or other stimuli, tend to dominate awareness. 2. the phenomenon in which the view from one eye dominates the percept when viewing a scene with two eyes. See ocular dominance.

visual dyslexia

visual dyslexia a form of acquired dyslexia characterized by multiple reading errors involving the substitution or transposition of letters within words (see paralexia). The resulting misread words are often very similar to the actual words (e.g., reading wife as life, or bug as dug). [proposed in 1973 by British neuropsychologists John C. Marshall (1939–2007) and Freda Newcombe (1925–2001)]

visual encoding

visual encoding the neural processes by which stimuli seen in the external world are converted into internal (mental) representations that can subsequently be processed and stored in memory. For example, when a person looks at a photograph, photoreceptors in the individual’s retina receive the visual sensory information and convey it to additional neurons, which in turn convey the information to populations of retinal ganglion cells. The cylindrical extensions (axons) of the retinal ganglion cells form the optic nerve, which projects to the lateral geniculate nucleus in the thalamus and the superior colliculus in the midbrain. The sensory input reaches visual areas in the cerebral cortex and ultimately the hippocampus within the medial temporal lobe, where—by mechanisms yet to be explained—it is analyzed and combined with input from the amygdala, entorhinal cortex, and other brain regions into a single abstract representation of the visual experience that is suitable for incorporation into short-term and possibly long-term memory. In other words, visual encoding may be conceptualized as a process intermediate to the extraction of meaning. Parallel neural conversion processes occur for stimuli that are heard (acoustic encoding), smelled (olfactory encoding), tasted (gustatory encoding), or felt (tactile encoding).

visual environment

visual environment in natural or built settings, the aggregate of external features (e.g., objects) and conditions (e.g., light) that surround an organism and influence its visually guided behavior.

visual evoked potential (VEP)

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visual extinction

visual extinction a form of visual neglect in which a previously visible stimulus in one half of the visual field is not consciously reported when a second stimulus appears simultaneously in the other half of the visual field. Visual extinction occurs as a result of brain damage, usually to the parieto-occipital cortex contralateral to the visual field in which the extinction occurs.

visual fatigue

visual fatigue the fading of visual images, particularly in bright light. Visual fatigue is often experienced by patients with optic neuritis; it can also occur after head injuries, especially after prolonged visual testing or when reading, as a result of reduced visual attention.

visual field

visual field the extent of visual space over which vision is possible with the eyes held in a fixed position. In humans, the outer limit of vision for each eye extends approximately 60° nasally, 90° temporally, 50° superiorly, and 70° inferiorly. The extent varies with age: Very young children and older people have a smaller visual field. Objects nearest to the fixation point are seen with greatest clarity because visual acuity, spatial contrast sensitivity, and color vision are best in the foveal region.

visual field defect

visual field defect a reduction in the normal extent of the visual field, characterized by partial or total blindness. This is caused by an interruption in the flow of visual impulses between the retina and the visual cortex, which may be caused by a lesion before, after, or in the optic chiasm or in all or a part of the optic radiations; it can involve tracts of one or both eyes. Each possible lesion produces a different defect.

visual field sparing

visual field sparing the extent to which normal vision is preserved in a visually impaired or deprived half of a visual field, expressed in degrees of visual angle measured from the fovea. Foveal sparing means that the foveal region (1°) is spared; macular sparing refers to the preservation of the macular region (5°); macular splitting denotes sparing ranging from 1° to 5°.

visual fixation

visual fixation the orientation of the eyes so that the image of a viewed object falls on each fovea, in the central part of the retina.

visual form agnosia

visual form agnosia see visual agnosia.

visual form discrimination

visual form discrimination the ability to discriminate visually between different shapes. The Visual Form Discrimination Test (VFDT), a multiple-choice, matching-to-sample test developed in the 1980s by Arthur L. Benton, assesses an individual’s ability to discriminate fine details of visual shapes and is designed to screen for visual perceptual deficits. Each of the 16 test items contains a target with three elements: two large geometric shapes and a peripheral figure. The task is to choose a correct match to the target out of four options presented below the target. Up to 2 points are awarded for responses to each of the 16 test items, with the total score for all items then compared to normative data.

visual function

visual function the ability to process visual stimuli.

visual hallucination

visual hallucination visual perception in the absence of any external stimulus. Visual hallucinations may be unformed (e.g., shapes, colors) or complex (e.g., figures, faces, scenes). In hallucination associated with psychoses (e.g., paranoid schizophrenia, alcohol- or hallucinogen-induced psychotic disorder), the individual is unaware of the unreality of the perception, whereas insight is retained in other conditions (e.g., pathological states of the visual system). Visual hallucinations may arise in association with lesions of the peripheral or central visual pathway or visual cortical areas; they are often present in temporal-lobe epilepsy and may appear during prolonged isolation. See also peduncular hallucinosis.

visual hearing

visual hearing the substitution of vision for hearing. This may be accomplished, within limits, by lipreading and gesture interpretation.

visual illusion

visual illusion a misperception of external visual stimuli that occurs as a result of a misinterpretation of the stimuli, such as a geometric illusion. Visual illusions are among the most common type of illusion.

visual imagery

visual imagery mental imagery that involves the sense of having “pictures” in the mind. Such images may be memories of earlier visual experiences or syntheses produced by the imagination (e.g., visualizing a pink kangaroo). Visual imagery can be used for such purposes as dealing with traumatic events, establishing desensitization hierarchies, or improving physical performance. See visualization.

visual impairment

visual impairment partial or total inability to see, or to see normally, due to partial or complete loss or absence of vision or to visual dysfunction. Visual impairment encompasses the continuum from blindness to low vision. It can result from disease or degenerative disorder (e.g., cataract, glaucoma, diabetic retinopathy, or macular degeneration), injury, or congenital defects (e.g., refractive errors, astigmatism). The degree of visual impairment is assessed in terms of disability in everyday life. Also called vision impairment. See also adventitious visual impairment; congenital visual impairment.

visual indexing theory

visual indexing theory see FINST theory.

visual induction

visual induction the influence that one visual stimulus or part of the visual field can have on the perception of an adjacent stimulus or the remainder of the visual field. Color contrast effects are examples of visual induction.

visual learning

visual learning training or conditioning that depends upon visual cues. The brain center for visual learning is believed to be in the inferotemporal cortex, where cortical cells have been demonstrated to be highly active in analyzing visual inputs.

visual masking

visual masking the ability of one visual stimulus to render another stimulus invisible when presented in close temporal proximity. See masking.

visual memory

visual memory the capacity to remember what has previously been seen in the form of visual images. Compare motor memory; verbal memory.

visual memory span

visual memory span see memory span.

visual narrative

visual narrative see verbal narrative.

visual neglect

visual neglect a form of neglect in which the individual is unaware of one side of the visual field. This occurs most often in the left visual field following right parietal damage or dysfunction. See also unilateral neglect.

visual object agnosia

visual object agnosia see visual agnosia.

visual organization

visual organization in gestalt principles of perception, a visual field that appears to be organized and meaningful.

visual organization test

visual organization test any test that involves the organization of visual, nonverbal stimuli.

visual perception

visual perception the awareness of visual sensations that arises from the interplay between the physiology of the visual system and the internal and external environments of the observer.

visual perseveration

visual perseveration see palinopsia.

visual persistence

visual persistence a sensation of visual stimulation that continues briefly after the actual stimulus is extinguished, perhaps caused by integration lag of visual signals. The light trail of a glowing stick moved rapidly in the dark is an example of visual persistence. Also called persistence of vision.

visual phosphene

visual phosphene see phosphene.

visual pigment

visual pigment see photopigment.

visual preference paradigm

visual preference paradigm a research technique for studying visual discrimination in infants in which the amount of time spent looking at different visual stimuli is measured to determine which stimulus the infants prefer. It is assumed that the stimulus looked at most often is the one that is preferred and that such preferences indicate an ability to discriminate among stimuli.

visual processing

visual processing the modification and analysis of visual signals at all levels of the visual system.

visual projection

visual projection 1. the rendering of a three-dimensional object into two dimensions to produce a silhouette. 2. any technique for the presentation of visual stimuli.

visual purple

visual purple see pigment bleaching; rhodopsin.

visual pursuit

visual pursuit movements of the eyes in an attempt to maintain fixation on a moving target. Also called ocular pursuit; visual tracking.

visual receptive field

visual receptive field the region of visual space in which stimulation will evoke a response from a neuron in the retina. Also called retinal receptive field. See also retinotopy.

visual receptor

visual receptor see photoreceptor.

visual recognition

visual recognition the ability to recognize an object visually.

visual recognition test

visual recognition test any test in which participants are asked to identify a series of familiar objects during single or multiple visual presentations of the objects.

visual reproduction

visual reproduction the ability to draw or create an object presented visually.

visual screening

visual screening 1. the process of assessing individuals for eye infections or disorders, for vision deficits and impairments caused by disease (e.g., glaucoma, macular degeneration) or trauma, or for visual performance on specific tasks (e.g., driving). 2. an aversive procedure, such as holding a hand over an individual’s eyes to block visual input for a brief period, that is occasionally used in the management of aggressive, self-injurious, or stereotyped behavior of children with severe intellectual or developmental disabilities.

visual search

visual search the process of detecting a target visual stimulus among distractor stimuli. In experimental studies, the characteristics of the target and distractors are manipulated to explore the mental operations that underlie visual attention. See also feature-integration theory.

visual sensory memory

visual sensory memory see iconic memory.

visual space

visual space the three-dimensional perspective of the visual field.

visual stimulation

visual stimulation stimulation by light that triggers a response in the receptor cells in the retina.

visual system

visual system the components of the nervous system and the nonneural apparatus of the eye that contribute to the perception of visual stimulation. The anterior structures of the eye, such as the cornea and lens, focus light on the retina, which transduces photons into neural signals. These are transmitted via the optic nerve and optic tract to nuclei in the thalamus and brainstem. These in turn transmit the signals either to the visual areas of the cerebral cortex for hierarchical processing and conscious analysis or directly to motor centers in the brainstem and spinal cord to produce eye movements.

visual texture

visual texture an attribute of a two-dimensional figure or a two-dimensional rendering of a three-dimensional object that describes its surface characteristics. Visual texture is related to, but not the same as, texture in the tactile sense. For example, the words shiny or speckled describe visual texture, whereas smooth or wavy can also describe tactile texture. Gradients of visual texture are often used to infer depth in a two-dimensional scene and also indicate slant.

visual threshold

visual threshold 1. the minimum level of stimulation that can be detected visually. 2. any of the thresholds for detecting various aspects of visual stimulation, including intensity, resolution, contrast sensitivity, movement acuities, position acuities, and so on.

visual tracking

visual tracking see visual pursuit.

visual transduction

visual transduction the biochemical and biophysical process in which light energy is converted to a neural signal in a photosensitive cell containing a retinal photoreceptor. See also isomerization; visual cycle.

visual word-form dyslexia

visual word-form dyslexia an acquired dyslexia characterized by difficulties related to analyzing the attributes of written words visually. Its major types include attentional dyslexia, neglect dyslexia, and spelling dyslexia. Also called peripheral dyslexia; word-form dyslexia. Compare central dyslexia.

visual yellow

visual yellow the bleached form of the photopigment rhodopsin, all-trans- retinal. Also called xanthopsin. See pigment bleaching.

visual-construction test

visual-construction test see visuoconstructive test.

visual-placing reflex

visual-placing reflex the reflex act of animals in placing their legs to reach a surface they can see. Animals that have undergone surgical decortication may lose this normally automatic response and fail to stretch their legs toward a visible surface.

visual-righting reflex

visual-righting reflex any of the reflexes that automatically orient the head to the visual fixation point of the moment.

visual-search perceptual disorder

visual-search perceptual disorder a disorder exemplified by difficulty in locating a specific number in a random array on a board as a result of a lesion in one cerebral hemisphere. Normally, individuals perform better when the number sought is to the left of the midline. Individuals with left-hemisphere damage also do better when the number is to the left of the midline, whereas those with right-hemisphere damage perform better when the number is to the right of the midline.

visual–motor coordination

visual–motor coordination the ability to synchronize visual information with the movements of different parts of the body.

visual–spatial ability

visual–spatial ability the ability to comprehend and conceptualize visual representations and spatial relationships in learning and in the performance of tasks such as reading maps, navigating mazes, conceptualizing objects in space from different perspectives, and executing various geometric operations. Beginning in adolescence, males, on average, show a definite superiority in certain aspects of visual–spatial ability, whereas females, on average, display superiority in certain aspects of verbal ability.

visualization

visualization n. 1. the process of creating a visual image in one’s mind (see visual imagery) or mentally rehearsing a planned movement in order to learn skills or enhance performance. 2. in psychotherapy, the intentional formation by a client of mental visual images of a scene or historical incident that may be inhibited or the source of anxiety. The purpose is to bring the visualized scene into the present therapeutic situation where it can be discussed and worked out to reduce its negative implications. See also guided affective imagery. 3. a hypnotic method used to induce or increase relaxation in which the individual is asked to imagine, for example, sitting comfortably at home and then to use all senses in perceiving the scene (e.g., the curtains blowing in the windows, the texture of the armchair). The more fully the individual concentrates on these features, the more deeply relaxed he or she becomes. 4. in consumer psychology, a motivation-research technique using imaginary or fictitious situations or conditions in order to induce consumers to reveal the true reasons for their choice of products. For example, instead of being asked why they like or dislike a product, consumers may be asked to characterize the type of individual they would expect to buy the product. —visualize vb.

visually guided reaching

visually guided reaching movements in which concurrent visual information is used to locate a target and avoid obstacles. Visually guided reaching is contrasted with movements to remembered, but unseen, targets and with movements guided by other senses (e.g., touch).

visuoconstructional impairment

visuoconstructional impairment an impairment characterized by difficulty in construction tasks, such as drawing or assembling the various parts of an object into a complete structure. See constructional apraxia. Also called visual constructional impairment.

visuoconstructive test

visuoconstructive test any of a wide range of tests that require a combination of visual and motor skills in the construction of an end product as an evaluation of these nonverbal skills. The most common examples of these tests are drawing tests, block-design tests, and jigsaw-puzzle tests. Also called visual-construction test.

visuomotor ataxia

visuomotor ataxia see optic ataxia.

visuomotor behavior rehearsal

visuomotor behavior rehearsal a program of combining progressive relaxation and imagery for performance enhancement.

visuospatial agnosia

visuospatial agnosia a disorder of spatial orientation, which may be tested by asking the individual to point to objects or other stimuli located in different parts of his or her visual field. Individuals can report objects in their visual fields, but not the spatial relationships of the objects to one another.

visuospatial function

visuospatial function the ability to perceive the spatial (relational) aspects of a figure or object in two and three dimensions.

visuospatial sketchpad

visuospatial sketchpad in the model of working memory proposed in 1974 by British cognitive psychologists Alan D. Baddeley (1934– ) and Graham J. Hitch (1946– ), a component that briefly holds and manipulates information about the appearance of objects and their location in space. For example, if one tried to determine which of two countries is larger or to rate their proximity to one another, this would involve mentally picturing and comparing both countries within the visuospatial sketchpad. As with the analogous phonological loop for sound, the visuospatial sketchpad is divided into two parts: the visual cache, specializing in information about form, color, and other aspects of visual identity, and the inner scribe, specializing in information about spatial location and movement representation and planning. Although not as extensively researched as the phonological loop, the idea of the sketchpad and its conceptualization as a multidimensional structure is increasingly supported by neuropsychological and functional imaging evidence in addition to experimental findings. Other components of the Baddeley and Hitch working memory model include the central executive and the more recently introduced episodic buffer.

visuotopic map

visuotopic map see retinotopic map.

vital capacity

vital capacity the capacity of the lungs to hold air, measured as the maximum volume of air that can be exhaled after maximum inspiration.

vital exhaustion

vital exhaustion a state characterized by excessive fatigue, lack of energy, increased irritability, sleep disturbances, and feelings of demoralization. It has been associated with increased risk of cardiovascular disease and cardiovascular-related events, particularly myocardial infarction and sudden cardiac arrest. See also burnout. [defined and first investigated in the 1980s by Dutch researcher A. Appels and colleagues]

vital functions

vital functions functions of the body (e.g., respiration, blood circulation of the blood) that are necessary to sustain life. Many vital functions are controlled by the brainstem.

vital spirits

vital spirits see animal spirits.

vital statistics

vital statistics data, such as those compiled in a medical or governmental record, on specific life events (e.g., birth, death, disease, marriage, etc.) in a population.

vitalism

vitalism n. 1. the theory that the functions of living organisms are determined, at least in part, by a life force or principle. German biologist Hans Driesch (1867–1941) was the chief exponent of this view, holding that life processes are autonomous and purposive and that potentialities for growth and development are realized through the operation of an agent to which he applied the term entelechy. French philosopher Henri Bergson (1859–1941) named this creative, vital force the élan vital. 2. more generally, any theory that opposes naturalism and the reduction of psychological life to biological structures and processes. —vitalist adj., n.

vitality

vitality n. physical or intellectual vigor or energy; zest. See also fitness.

vitamin

vitamin n. an organic substance that in minute quantities is essential for normal growth and health. Many vitamins function as coenzymes, aiding in the metabolism of carbohydrates, fats, and proteins. A few vitamins can be synthesized in the human body, but most must be supplied in the diet. The most important are vitamin A, the vitamin B complex (including thiamine, riboflavin, pyridoxine, cyanocobalamin [B12], folic acid, nicotinic acid, and pantothenic acid), vitamin C (ascorbic acid), vitamin E, and vitamin K. Vitamins were so named in 1913 by Polish-born U.S. biochemist Casimir Funk (1884–1967), based on his belief that all vitamins were amines.

vitamin A

vitamin A a fat-soluble vitamin. Its aldehyde,retinal, is a component of the photopigments in the retina. Vitamin A deficiency results in night blindness and other visual disorders. Also called retinol. See also visual cycle.

vitamin A toxicity

vitamin A toxicity a condition caused by excessive intake of vitamin A (retinol). A large overdose of vitamin A—500,000 IU or more—can cause headache, vomiting, bone pain, weakness, blurred vision, irritability, and skin flaking. Long-term intake of 100,000 IU or more per day can also lead to toxicity. Symptoms include hair loss, headache, bone thickening, enlarged liver and spleen, anemia, menstrual problems, stiffness, joint pain, weakness, and dry skin. Although high doses of beta-carotene (which can be converted to vitamin A in the body) are not toxic, they can lead to a distinctive deep yellow pigmentation of the skin.

vitamin and mineral therapy

vitamin and mineral therapy the treatment of mental or physical conditions through a daily intake of diagnostic-specific vitamins or mineral supplements (or both) in specific dosages. These are typically prescribed in conjunction with some psychopharmacological agent, and effectiveness is still a matter of debate and research. See also megavitamin therapy.

vitamin D toxicity

vitamin D toxicity a condition caused by excessive intake of vitamin D. Long-term overdose of vitamin D can cause irreversible damage to the kidneys and cardiovascular system and can retard growth in children. Excessive amounts of the vitamin may lead to high blood pressure and premature hardening of the arteries. Nausea, abdominal pain, loss of appetite, weight loss, seizures, and an irregular heartbeat may be signs of overdose.

vitamin deficiency

vitamin deficiency lack of a vitamin needed for normal bodily functions. For example, deficiency of thiamine (vitamin B1) is often associated with severe and chronic alcoholism (see Wernicke’s encephalopathy; Wernicke–Korsakoff syndrome).

vitamin model

vitamin model a model proposing nine attributes of work that influence employee satisfaction. As with vitamins, employees will require some minimal amount or dosage of each attribute to be satisfied with their jobs. In the case of three attributes (money, physical security, and valued social position), employees can have an overabundance with no negative effects. However, too much of the remaining six attributes (externally generated goals, variety, clarity, control, skill use, and interpersonal contact) can lead to problems. [proposed by British organizational psychologist Peter B. Warr]

vitex agnus castus

vitex agnus castus see agnus castus.

vitreous hemorrhage

vitreous hemorrhage a complication of diabetes mellitus marked by bleeding within the eyeball due to the rupture of capillaries of the retina. See also diabetic retinopathy.

vitreous humor

vitreous humor the thick, transparent fluid filling the cavity (the vitreous body) between the lens of the eye and the retina.

viviparity

viviparity n. literally, live birth: reproduction in which the embryo develops within the female until a well-formed individual emerges. Compare oviparity. —viviparous adj.

vivisection

vivisection n. dissection performed on a living animal for research or experimental purposes. Many scientists and researchers oppose the practice, questioning its scientific validity and necessity, and numerous others criticize it as inhumane and unethical. See also animal care and use; animal rights.

Vivitrol

Vivitrol n. a trade name for naltrexone.

VLBW

VLBW abbreviation for very low birth weight.

VMH

VMH abbreviation for ventromedial hypothalamus.

VMI

VMI abbreviation for Developmental Test of Visual–Motor Integration.

VNO

VNO abbreviation for vomeronasal organ (see vomeronasal system).

vocabulary growth

vocabulary growth the development of vocabulary in children. In estimating vocabulary size, a distinction is commonly drawn between receptive vocabulary and productive vocabulary; more recent research has concentrated on the process of vocabulary acquisition and the organization of the child’s mental lexicon.

vocabulary spurt

vocabulary spurt see naming explosion.

vocabulary test

vocabulary test a test designed to determine the number and level of words that an individual can use (i.e., productive vocabulary) or understand (i.e., receptive vocabulary).

vocal communication

vocal communication communication through auditory signals usually produced by a vibrating organ, such as the larynx in the throats of some mammals or the two syringes located in the bronchial branches in birds. Vibrations produced by these organs are altered by changing configurations of the tongue and lips and the shape of the oral and nasal cavities. Other sound-producing mechanisms in nonhuman animals include stridulation, the rubbing together of body parts, as in crickets. See also animal vocalization.

vocal cords

vocal cords a pair of tissue folds that project from the walls of the larynx. They vibrate, producing sounds, when expired air passes through the narrow space (glottis) between them. Also called vocal folds.

vocal reaction time

vocal reaction time in studies of cognition, the time that a participant takes to begin a spoken response to a stimulus. See reaction time.

vocal register

vocal register the tonal or pitch range of an individual’s voice. See also chest voice; falsetto; head voice.

vocal tract

vocal tract the structures, collectively, that are involved in vocalization, including the vocal cords and glottis of the larynx together with the pharynx, nasal cavity, mouth, and articulators.

vocal-image voice

vocal-image voice audible speech patterns that have been electronically transformed into visual patterns that can be read by people with severe hearing loss.

vocalization

vocalization n. the production of sounds by means of vibrations of the vocal cords, as in speaking, babbling, singing, screaming, and so forth. See also animal vocalization. —vocalize vb.

vocation

vocation n. an occupation or profession to which one is particularly suited, especially one involving a sense of mission or calling. —vocational adj.

vocational adjustment

vocational adjustment the degree to which an individual succeeds in choosing the kind of work or career best suited to his or her interests, traits, and talents. The term differs from occupational adjustment in emphasizing the match of career to personal goals and aptitudes, rather than the match of the individual to objective work conditions.

vocational appraisal

vocational appraisal the prediction by a vocational counselor of a client’s potential for success and fulfillment in a particular occupation. A vocational appraisal is based on the counselor’s understanding of occupational opportunities in relation to the client’s personality, intelligence, abilities, and interests as revealed in interviews and tests. See vocational counseling.

vocational aptitude

vocational aptitude the personal abilities and traits required for successful performance of the tasks involved in a particular occupation.

vocational aptitude test

vocational aptitude test any instrument designed to assess the abilities, interests, personality traits, and other factors deemed essential for success in a particular occupation. Such tests are often used to assess how well the participant’s profile on these dimensions matches the profile of the typical or ideal person in the occupation.

vocational counseling

vocational counseling 1. a service provided to employees who seek guidance on such matters as adjusting to new jobs or roles, developing their careers within organizations, or any personal or other problems affecting job satisfaction or job performance. See also outplacement counseling. 2. see vocational guidance.

vocational education

vocational education see vocational training.

vocational guidance

vocational guidance the process of helping an individual to choose an appropriate vocation through such means as (a) in-depth interviews; (b) administration of aptitude, interest, and personality tests; and (c) discussion of the nature and requirements of specific types of work in which the individual expresses an interest. Also called vocational counseling.

vocational maturity

vocational maturity a developmentally advanced and competent orientation to issues of employment and occupational choice. A person with high vocational maturity is realistic about his or her options and takes a relatively rational approach to exploring the possibilities and making career decisions.

vocational rehabilitation

vocational rehabilitation a program designed to develop or restore productivity in individuals with mental or physical disabilities or those who have been injured or ill. A vocational rehabilitation program includes assessment, vocational guidance, and training; it involves helping the individual to develop skills that have been lost or neglected and to find or return to employment in the competitive job market or another setting (see sheltered workshop; transitional employment). Also called occupational rehabilitation. See also work rehabilitation center.

vocational services

vocational services vocational guidance, aptitude testing, and vocational training, together with practical assistance in finding employment, as provided by a school, college, hospital, clinic, or rehabilitation center.

vocational training

vocational training an organized program of instruction designed to equip individuals with the requisite skills and qualifications for placement in specific jobs or trades. Also called vocational education. See also vocational rehabilitation.

vodun

vodun n. see voodoo.

voice

voice n. 1. the sound produced by the larynx and modified by other elements of the vocal tract (e.g., lips, tongue) before it issues from the mouth. 2. in phonetics, the quality of a voiced, as opposed to an unvoiced, speech sound. 3. in linguistics, see active voice; passive voice. 4. the distinctive tone or quality of a person’s speaking or singing voice.

voice disorder

voice disorder any disorder that affects the pitch, loudness, tone, or resonance of the voice.

voice key

voice key an electronic device that interfaces between a microphone and a computer, used for recording vocal response times in language-production tasks, such as word or picture naming. When a stimulus is presented the voice key is activated and begins to monitor the sound level from the microphone; if the sound level then exceeds a specific threshold level, indicating speech, the voice key records the amount of time that has elapsed since it was activated.

voice therapy

voice therapy the diagnosis and remediation of voice disorders by a specialist in the physiology and pathology of voice production. See also speech therapy.

voice-activated control

voice-activated control see speech-activated control.

voice-activated switch

voice-activated switch an interface between a device and the user that is activated by the user’s voice and is often useful for individuals with certain disabilities. For example, an individual with a motor impairment can use a voice-activated switch to turn lights, appliances, and other household devices on and off.

voice-onset time (VOT)

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voice-output system

voice-output system a system that creates a voice for a computer to provide auditory feedback for individuals with visual impairment. For example, the system may create verbal output describing a computer file.

voice–stress analyzer

voice–stress analyzer an instrument that detects minute alterations in the voice, undetectable to the human ear, that presumably occur when a person is under stress. It is sometimes used as a lie detector, although its reliability and validity are controversial, and the results are not accepted as evidence in many U.S. courts of law.

voiced

voiced adj. denoting speech sounds that are articulated with accompanying vibration of the vocal cords. Voiced sounds include all the vowels, semivowels, and diphthongs, and a number of consonants. The dichotomy voiced–unvoiced is an important binary feature in English and many other languages.

voiceless sound

voiceless sound see unvoiced.

voiceprint

voiceprint n. a digital image of a voice, produced by electronic recording, that can be used for identification and authentication purposes. Voiceprints may also be used to analyze such vocal and speech characteristics as frequency, duration, and amplitude.

voicing

voicing n. 1. the use of vocal cord vibrations to produce speech sounds. See voiced; unvoiced. 2. giving expression to ideas, observations, opinions, and the like through spoken communication.

voir dire

voir dire the process of questioning prospective jurors to determine if they hold biases that may reasonably interfere with their ability to act impartially in a particular trial (from Norman French, literally: “to speak the truth”). The questions may be asked in private or in open court and may be posed by the attorneys, the judge, or both. Jurors may be asked to stand down by a challenge for cause or a peremptory challenge.

volatile marriage

volatile marriage a long-lasting marriage marked by both passionate arguments and expressions of affection, but with more positive than negative interactions.

volition

volition n. 1. the faculty by which an individual decides upon and commits to a particular course of action, especially when this occurs without direct external influence. The term encompasses a crucial set of activities involving the self, including choice and decision, self-control, intentional action, and an active rather than passive response to events. According to self-regulatory resources theory, volition depends on a limited resource that is expended whenever the self makes a decision or exerts control. 2. the act of exercising this faculty. See also free will; will. —volitional adj.

volitional tremor

volitional tremor see action tremor.

volley

volley n. a synchronous discharge, as when nerve impulses occur in phase along different fibers of a nerve.

volley theory

volley theory the principle that individual fibers in an auditory nerve respond to one or another stimulus in a rapid succession of rhythmic sound stimuli, whereas other fibers in the nerve respond to the second, third, or nth stimulus. The result is that successive volleys of impulses are fired to match the inputs of stimuli, yet no single fiber is required to respond to every stimulus. Thus, a nerve can reflect a more rapid frequency of stimulation (e.g., 1000 Hz) than any individual fiber could follow. Also called volley principle. See also hearing theories. [proposed in 1949 by Ernest Glen Wever]

volt

volt (symbol: V) n. the SI (International System) unit for measuring the difference of electric potential between two regions.

voltage-gated ion channel

voltage-gated ion channel an ion channel that opens or closes in response to the voltage difference across the membrane, such as the voltage-gated sodium (Na+) channel that mediates the action potential. Also called voltage-activated gate. Compare ligand-gated ion channel.

volubility

volubility n. excessive, uncontrollable talkativeness: a common symptom of a manic episode.

volume color

volume color see bulky color.

volume of distribution

volume of distribution (symbol: Vd) the amount of a drug in the body in relation to its concentration in various body fluids (e.g., blood, plasma, extracellular fluid). It is expressed by the equation Vd = dose (amount of drug in body)/concentration in body fluid.

volumetric thirst

volumetric thirst see hypovolemic thirst.

voluntarism

voluntarism n. 1. in psychology, the view that human behaviors are, at least in part, the result of the exercise of volition. See also free will. 2. the general position that will and choice are important factors in all human activities. For example, in ethics, voluntarism emphasizes that commitment to any moral principle is, in large part, a “will to believe,” over which the person has some control. In epistemology, the same is held to be true of knowledge. In the field of historical studies, voluntarism holds that the exercise of will has been a major factor in the course of human events. It is therefore opposed to such approaches as Marxism, which emphasizes the role of impersonal economic forces. 3. in metaphysics, the position that will, rather than mind, spirit, or some other substance, is the basis of reality. The best known philosophy of this kind is that of Arthur Schopenhauer.

voluntary

voluntary adj. describing activity, movement, behavior, or other processes produced by choice or intention and under cortical control, in contrast to automatic movements (e.g., reflexes) or action that is not intended (see ideomotor activity). Compare involuntary.

voluntary admission

voluntary admission admission of a patient to a psychiatric hospital or other inpatient unit at his or her own request, without coercion. Such hospitalization can end whenever the patient sees fit, unlike involuntary hospitalization, the length of which is determined by a court or the hospital. Also called voluntary commitment; voluntary hospitalization.

voluntary agencies and organizations

voluntary agencies and organizations nonprofit groups supported in whole or in part by public contributions and devoted to the amelioration of public health or social welfare problems. The term voluntary distinguishes such groups from government agencies.

voluntary attention

voluntary attention attention that is deliberately applied and controlled by the individual, as opposed to attention that is spontaneously captured by a stimulus in the environment. Brain-activation studies have investigated the extent to which voluntary and involuntary attention are controlled by separate neural systems. Also called endogenous attention. Compare postvoluntary attention. See also secondary attention.

voluntary behavior

voluntary behavior behavior that is intentional in nature (e.g., walking, typing), as opposed to reflexive behavior. See also operant behavior.

voluntary commitment

voluntary commitment see voluntary admission.

voluntary dehydration

voluntary dehydration see dehydration.

voluntary hospitalization

voluntary hospitalization see voluntary admission.

voluntary muscle

voluntary muscle see skeletal muscle.

voluntary response

voluntary response a deliberately chosen reaction to a stimulus that may require a complex coordination of excitatory and inhibitory impulses with feedback from visual, motor, and other systems.

voluntary retrieval

voluntary retrieval see involuntary retrieval.

voluntary turnover

voluntary turnover the number of employees who choose to leave an organization or unit during a given period, usually to take a position in another organization. A high rate of voluntary turnover can be an indicator of low job satisfaction. Compare involuntary turnover. See turnover.

volunteer

volunteer n. an individual who contributes his or her services through personal choice and without compensation, for example, to a public or private health or social welfare agency or organization.

volunteer bias

volunteer bias any systematic difference between individuals who volunteer to be in a study versus those who do not, which may potentially render the resulting group or sample of participants unrepresentative of the larger population.

volunteerism

volunteerism n. the act or practice of donating (i.e., without pay) one’s time and energy to activities that contribute to the common good.

vomeronasal system

vomeronasal system a set of specialized receptor cells that in nonhuman mammals is sensitive to pheromones and thus plays an important role in the sexual behavior and reproductive physiology of these animals. In humans, this system responds physiologically to chemical stimulation and, in turn, excites brain centers, but its role in human olfaction is not known. Also called Jacobson’s organ; vomeronasal organ (VNO).

vomiting

vomiting n. ejecting the contents of the stomach through the mouth. Normally occurring as an autonomic physiological reaction, vomiting may also be self-induced, as in bulimia nervosa, as an inappropriate means of managing body weight (see purging).

vomiting center

vomiting center a nerve center in the medulla oblongata of the brain that is thought to partially govern vomiting. Another area, the chemoreceptor trigger zone, also contributes to vomiting.

von Domarus principle

von Domarus principle an explanation of schizophrenic thinking based on the concept that the individual perceives two things as identical merely because they have identical predicates or properties. [developed by Eilhard von Domarus, 20th century German psychiatrist]

von Economo’s disease

von Economo’s disease see encephalitis lethargica. [Constantin von Economo (1876–1931), Austrian neurologist]

von Frey hairs

von Frey hairs see esthesiometry. [Maximilian von Frey (1852–1932), German physiologist]

von Frey specificity theory

von Frey specificity theory a 19th-century theory, now disputed, that attempted to explain sensations of coldness, warmth, contact, and pain by linking them to different, specific receptors in the skin. The von Frey theory was premature, because not enough was known about anatomy at the time. [proposed in 1894 by Maximilian von Frey]

von Recklinghausen’s disease

von Recklinghausen’s disease see neurofibromatosis. [described in 1882 by Friedrich D. von Recklinghausen (1833–1910), German pathologist]

von Restorff effect

von Restorff effect see distinctiveness effect. [Hedwig von Restorff (1906–1962), German psychologist]

voodoo

voodoo n. a synthetist religion, practiced chiefly in the Caribbean, in which west African traditions of magic and ancestor worship are combined with rites derived in part from Roman Catholicism. These typically involve the use of singing or chanting, drumbeating, and dancing to induce an ecstatic trance, in which it is believed that spirits take possession of the worshippers, speaking and acting through them. Also called vodun; voodooism. —voodooistic adj.

voodoo death

voodoo death a culture-bound syndrome observed in Haiti, Africa, Australia, and islands of the Pacific and the Caribbean. An individual who has disobeyed a ritual or taboo is hexed or cursed by a medicine man or sorcerer (often by pointing a bone at the culprit) and dies within a few days. Walter B. Cannon, one of the first researchers of voodoo death, suggested that the individual’s strong belief in the curse caused physiological reactions in the body resulting in death. Also called bone pointing; thanatomania. See also psychic suicide.

VOR

VOR abbreviation for vestibulo-ocular reflex.

VOT

VOT 1. abbreviation for Hooper Visual Organization Test. 2. abbreviation for voice-onset time.

vowel

vowel n. 1. a voiced speech sound that is produced when the breath stream vibrating the vocal cords has unobstructed passage through the vocal tract. 2. one of the letters of the alphabet used to represent these sounds in writing. Compare consonant.

voyeurism

voyeurism n. a paraphilia in which preferred or exclusive sexual interest and arousal is focused on observing unsuspecting people who are naked, in the act of undressing, or engaging in sexual activity. Although the voyeur seeks no sexual activity with the person observed, orgasm is usually produced through masturbation during the act of “peeping” or later, while visualizing and remembering the event. Also called inspectionalism. See also peeping Tom. —voyeuristic adj.

vPCC

vPCC abbreviation for ventral posterior cingulate cortex.

VPS

VPS abbreviation for Values and Preferences Scale.

VR

VR abbreviation for variable ratio. See variable-ratio schedule.

Vroom–Yetton–Jago decision model

Vroom–Yetton–Jago decision model a model that can be used by leaders in judging how much they should allow followers to participate in decision making in different situations. The model consists of a set of decision rules and a decision tree in which the leader assesses several key situational attributes, such as the nature of the task (e.g., whether high or low in task structure), the degree of conflict expected among followers over preferred solutions, the degree of confidence that followers will accept decisions they do not agree with, and the extent to which such acceptance is important. On the basis of this assessment, the leader chooses from among several degrees of employee participation, ranging from autocratic decision making by the leader, through consultative approaches, to full participation and delegation. [Victor H. Vroom (1932– ), Canadian organizational psychologist; Philip W. Yetton (1942– ), Australian management expert; Arthur G. Jago (1949– ), U.S. organizational psychologist]

VT

VT 1. abbreviation for variable time. See variable-time schedule. 2. abbreviation for vicarious traumatization.

vulnerability

vulnerability n. susceptibility to developing a condition, disorder, or disease when exposed to specific agents or conditions. —vulnerable adj.

vulnerability factor

vulnerability factor a variable that, if experienced or triggered, affects the probability that an individual will develop a condition, disorder, or disease.

vulva

vulva n. (pl. vulvae) the external female genitalia, including the clitoris, the labia, and the vestibule of the vagina. Also called pudendum. —vulval adj.

vulval orgasm

vulval orgasm orgasm produced from stimulation of the vulva (including the clitoris and labia). Sex researchers Josephine Singer and Irving Singer proposed in 1974 that there are two types of orgasm, vulval orgasm and uterine orgasm, the latter involving deep vaginal penetration that results in contractions of the uterus during orgasm. Uterine contractions are said not to occur with vulval orgasms; they are also said to result in a more complete or satisfying orgasm from intercourse than from stimulation of the vulva alone. However, many women have reported that whether uterine contractions accompany orgasm does not depend on the type of stimulation or sexual activity but rather on how intense the orgasm is, and that the most intense orgasms occur during activities such as cunnilingus or vibrator stimulation of the clitoris. See also vaginal orgasm.

vulvectomy

vulvectomy n. the surgical excision of all or part of the vulva (external female genitalia). A vulvectomy is performed as a form of treatment for cancer of the vulva. It is also traditionally performed for cultural reasons (see female genital mutilation).

Vygotskian theory of intelligence

Vygotskian theory of intelligence the theory that intelligence develops largely as a result of internalization; that is, by children absorbing what they observe in the environment and making it a part of themselves. Development occurs in part through a zone of proximal development, which distinguishes what children can do on their own from what they can do with the assistance of others. [Lev Vygotsky]

Vyvanse

Vyvanse n. a trade name for lisdexamfetamine.

Psychology Terms Starting With 'V'