placebo

n. (pl. placebos)

1. a pharmacologically inert substance, such as a sugar pill, that is often administered as a control in testing new drugs. Placebos used in double-blind trials may be dummies or active placebos. Formerly, placebos were occasionally used as diagnostic or psychotherapeutic agents, for example, in relieving pain or inducing sleep by suggestion, but the ethical implications of deceiving patients in such fashion makes this practice problematic.

2. any medical or psychological intervention or treatment that is believed to be “inert,” thus making it valuable as a control condition against which to compare the intervention or treatment of interest. See placebo effect.

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Psychology term of the day

September 1st 2024

transfer function model

1. a model used in functional magnetic resonance imaging to describe the shape of responses. A neuron receives a number of inputs, each of which comes via a connection that has a strength or weight; these weights correspond to the synaptic efficacy of the neuron. Each neuron also has a single threshold value. Activation of the neuron is determined by the weighted sum of the inputs minus the threshold. The activation signal is passed through a transfer function to produce the output of the neuron.

2. in time-series analysis, a type of model used to forecast a time series that is influenced by present and past values of other time series.