Enhancement of effectiveness of learning by testosterone in domestic chicks.

In young male domestic chicks, the presentation of a nonaversive colored bead to be pecked (pretraining) interfered with subsequent avoidance training, in which the bead presented tasted unpleasant, when two conditions were fulfilled: (a) Beads used at pretraining and training were of similar appearance, and (b) testosterone was injected either before or a little after pretraining. This effect of the hormone was not a consequence of changes in behavior at training or at test. It appeared to reflect changes during the consolidation of the pretraining memory trace which made it more effective in subsequent competition with training. Beads that are blue in color were unusual in evoking high levels of avoidance in naive chicks and, when used in pretraining in the presence of testosterone, in failing to oppose subsequent training on the blue bead. Such pretraining became effective when paired with avoidance training with a bead of different color, apparently by changing the information stored about pretraining.