Small deviations from bilateral symmetry (fluctuating asymmetries) are cues to fitness differences in some animals. Therefore, researchers have considered whether animals use these small asymmetries as visual cues to determine appropriate behavioral responses (e.g., mate preferences). However, there have been few systematic studies of animals'…

Six retarded young adults were trained to select grocery items using picture cards as cues and to reject either (1) maximally different negative examples or (2) minimally different negative examples. Training with minimally different negative examples was functionally related to improved rejection of nontrained negative items in a nontrained…