This work is significant because there is still relatively little data in support of the view that learning plays a role in monkey vocal ontogeny, a serious problem for nonhuman primate models of language development. The project addresses the question of where learning may play a significant role in natural vocal communication. Advances in cognitive ethology have made possible the study of complex social phenomena such as recruitment, alliance formation, reconciliation, and punishment. To date, our work on recruitment screams has focused on identifying and comparing the calls used and studying their communicative significance and development. Functionally, these calls are important for eliciting support from allies in the group against aggressive opponents.
Interesting questions remain concerning the consequences of attempting recruitment.
While successful intervention by an ally is assumed to benefit the victim of attack, the consequences of soliciting support may be more complex than previously imagined, as illustrated by the following questions. Theoretically, the occurrence of recruitment and intervention will be determined by proximate and evolutionary factors relating to the costs and benefits of each behavior. Research to date has pointed to involvement of factors such as kinship, familiarity, and the severity of the aggression. Sex differences in vocal communication. Critical though unresolved issues in the study of human language development are those of the existence of sex differences in the acquisition of competence and the origins for any such differences.