Overshadowing (Psychology)

Overshadowing is a phenomenon in classical conditioning in which, when two stimuli are presented together and paired with an unconditioned stimulus, the more noticeable or salient of the two stimuli is conditioned more readily, while the other, less salient stimulus is conditioned weakly or not at all. The effect can appear as early as the first trial of training, before either stimulus has built up any associative strength on its own. Researchers have explained it either as a result of selective attention toward the more salient stimulus or as a consequence of how prior learning about the compound of stimuli as a whole shapes learning about each individual part.