Effects of environmental novelty on distress vocalizations of ducklings following withdrawal of an imprinting object
Imprinted ducklings typically pause several seconds before initiating distress vocalizations following withdrawal of an imprinting object. In the present research, this pause was found to be shorter in the presence of a novel, presumably fear-inducing stimulus. This in turn implies that environmental novelty added to withdrawal of the imprinting object in determining the affective state of the ducklings. Although opponent process theory has no trouble with such additive effects, the very occurrence of the poststimulus pause presents problems for the theory. © 1990, The Psychonomic Society, Inc.. All rights reserved.