Newly hatched domestic chicks (Gallus gallus domesticus) that have rec
eived a period of exposure to a visual stimulus (V1) approach V1 in pr
eference to a novel stimulus (V2). The learning process that underlies
such changes in chicks' behavior is known as filial imprinting. Under
natural conditions, and in laboratory studies, V1 is often accompanie
d by an auditory stimulus, the maternal call of a hen (Al). Experiment
s la and Ib demonstrated that simultaneous exposure to V1 and Al poten
tiated chicks' preference for V1 in a test in which Al was absent. Sub
sequent experiments revealed that additional exposure to Al after (Exp
eriment 2) or before (Experiment 3) exposure to the V1A1 compound redu
ced the preference for V1. These findings suggest that the potentiatio
n of visual imprinting is a product of within-event learning that is u
ndermined when one element of the compound is presented in isolation.