This book describes the results of a cross-fostering §experiment to investigate the effects of experience §on emotional and informational content in rhesus §macaque (Macaca mulatta) vocal communication. The §subjects of the study were twelve rhesus macaques: §six were foster-reared by abusive mothers and six §were foster-reared by control mothers. §Vocalizations were recorded from the subjects in §their social groups for two years. The acoustic §variables measuring positive emotional expression §were lower in abused than control subjects. On the §other hand, abused subjects expressed exaggerated §levels of fear during mild contact aggression with §other animals. The second part of the study §statistically classified the calls of cross-fostered §monkeys to either their biological or foster §family. In the present study, matrilineal §signatures were clearly discriminated among §different families of rhesus macaques. Furthermore, §the calls of the majority of cross-fostered subjects §classified to the foster matriline, suggesting that §these signatures were learned rather than §inherited.