Crying in infant primates: insights into the development of crying in chimpanzees

Crying' is a common feature of infants among most primate species (Newman 1985). or, to be more accurate, most primate infants emit some specific types of vocalizations upon separation from their mother, or upon physical discomfort and/or injury. We might say that some species of nonhuman primate infants emit pain cries and discomfort cries, much like human infants. Crying in nonhuman primates is often thought of differently than crying in human infants. Recent books that include references to infant crying do not focus on crying per se but rather discuss crying in the context of aspects of nonverbal vocal communication. These other aspects include developmental and comparative approaches to the study of vocal communication (Papousek et al.l992),the evolution of communication (Hauser 1996), social influences on vocal development (snowdon and Hausberger 1997), and the influence of nature and culture on nonverbal communication (Segerstrale and Molnar 1997). One theme of importance in regard to primate vocalizations is the link with language in humans. This focus on discovering parallels between primate vocalizations and human verbalization includes research on the referential nature of certain vocalizations, such as calls to recruit help during agonistic encounters (e.g. Gouzoules et a|.1984) and alarm calls emitted by vervet monkeys to specific predators (Seyfarth et al. 1980'). Another theme witl.rin the area of primate vocalization is flexibility in the development of calls (e.g. Hopkins and Savage-Rumbaugh 1991). This includes research on cross-fostering experiments (e.g. Owren et al. 1993), operant conditioning of calls (e.g. Owren and Rendall 1997), and individual differences in calls (Mitani et al. 1996) and in 'dialects' (e.g.Mitani et al.1992).