Apomorphine: Effects on the timing and sequencing of pecking behavior in chicks

Abstract

Stereotyped behavior induced by apomorphine is thought to be “autistic”, that is, impervious to environmental influence. This assumption is tested by analyzing the patterning of pecks at two differently colored stimuli in three-day old chicks treated with either 0.3 mg-kg −1 or 0.4 mg-kg −1 apomorphine. While normal chicks strongly prefer one stimulus over the other, apomorphine appears to render the choice behavior of chicks insensitive to differences between the stimuli. This result might suggest that apomorphine-treated chicks no longer perceive differences between the stimuli, but an analysis of the timing of pecks reveals that differences are still perceived since the two stimuli elicit different rates of pecking.