APA Dictionary of Psychology

n. a central brain process in which the somatosensory area is primed to expect the particular sensory inputs (sights, sounds, etc.) that are predicted as the consequence of an intended motor action. It is the means by which, for example, a person turning their head understands immediately that the motion perceived is in the body and not in the external world. Preafference has also been proposed as a neural basis for what is experienced subjectively as attention or expectancy. Compare reafference. See also brain comparator; corollary discharge; reafference principle. [described by U.S. neuroscientist Walter J. Freeman III (1927–  )]