Validity The extent to which a test measures what it was intended to measure.
Variable In an experimental setting, a factor that varies in amount and kind.
Variable-interval schedule A schedule of reinforcement in which a reinforcer is delivered for the first response made after a variable period of time whose average is predetermined.
Variable-ratio schedule A schedule of reinforcement in which a reinforcer is delivered for the first response made after a variable number of responses whose average is predetermined.
Vestibular sense The sense that tells how one's own body is oriented in the world with respect to gravity.
Visual cortex The region of the occipital lobes in which visual information is processed.
Volley principle An extension of frequency theory which proposes that when peaks in a sound wave come too frequently for a single neuron to fire at each peak, several neurons fire as a group at the frequency of the stimulus tone.