These studies use neuroethological and ethopharmacological methods to investigate the mechanisms related to production and perception of the isolation call and related vocalizations in nonhuman primates as a model for understanding the neurology and physiology of vocal expressions of affect in human infants and the impact of crying on the listener. Major findings this year were as follows: 1) Significant correlations were found between heart rate and vocal rate in socially separated rhesus macaque infants. Not all individuals showed significant correlations, suggesting individual differences in the development of autonomic function. By dividing vocalizations into three categories (coo, leap, scream), it could be shown that not all vocal categories had significant correlations with heart rate (scream showing the fewest correlations), and that for a given individual monkey heart rate could correlate with one vocal category in the absence of a significant correlation with the other vocal categories. This suggests that different vocal subtypes emitted during social separation have differing relationships with mechanisms that regulate autonomic reactivity. 2) a study of the effects of D-amphetamine on squirrel monkey behavior demonstrated that motor stereotypes and episodes involving extreme behavioral withdrawal have differing time courses of development, and are differentially expressed according to the testing environment (social separation vs. home colony).