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evolution of the brain

the concept that the brains of complex animals have evolved over many millions of years from a network of simple nerve fibers connecting various body areas, as in primitive multicellular animals. At a more advanced stage, a neural axis developed to connect and integrate peripheral neurons and to house cell bodies; this axis became a spinal cord. Still later, collections of neurons with control functions developed at the head end of the spinal cord, as in the brains of higher invertebrates, birds, fish, and reptiles. From those concentrations of brain tissue evolved the forebrain, with its highly convoluted cerebral cortex, of mammals, especially prominent in whales, great apes, and Homo sapiens. See also cephalization; encephalization.

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Psychology term of the day

March 2nd 2024

ascertainment bias

ascertainment bias

error in selecting individuals or units for a sample, such that those units selected are not representative of the relevant population. For example, a medical researcher who studies a sample of patients that omits certain types of people who have the disorder of interest is likely to obtain results having an ascertainment bias. The term is often preferred over sampling bias in clinical contexts.