The roles of memory and environmental context in chimpanzee communication
Charlie Menzel
Language Research Center, Georgia State University
A chimpanzee’s knowledge of its habitat influences its decisions regarding where to go and what to do. This knowledge of environmental features and daily routines provides an important background for interpreting the moment-to-moment behavior and signals of other social beings including humans. It provides a basis for discriminating their goals and competencies and for controlling their behavior in space. The roles of memory and environmental context in communication have been assessed in studies of a small number of chimpanzees at Georgia State University’s Language Research Center. The chimpanzees’ memory of the structures and layout of their nonsocial environment is detailed and specific. They can recall and report objects that are located beyond sight or hearing, after substantial delays. They can fill in informational gaps through inference. They can learn about environmental changes through indirect signs (e.g. lexigrams, video representations) and retain such information for hours or days. They can rank-order invisible, spatially dispersed foods according to an overall preference scheme. The LRC chimpanzees rely on this information base in directing human caregivers. They recruit the assistance of otherwise uninformed caregivers and direct them sequentially to the locations of hidden foods in a small wood, one after the next, according to their preference scheme. They appear to discriminate the competency of a given human for a given type of search task and retain this information over days. The chimpanzees’ knowledge of their nonsocial environment also influences their evaluation of human gestures. For example, an adult female chimpanzee’s behavior after viewing a video representation of a human pointing in a familiar environment was very different from that after viewing a video representation of the same human pointing in an unfamiliar environment. The informational content of the pointing depended on the chimpanzee’s knowledge of the environmental context. For chimpanzees living in a fission-fusion social system, the ability to recall or rank-order unseen objects or beings (whether the location and condition of preferred foods, the core areas and estrous condition of females, or the dominance ranking of competitors) is especially important. Knowledge of the location, movements, and behavioral and psychological capabilities of others is derived, in part, from the same information processing capabilities used to monitor the nonsocial environment. There is much overlap between the ecological and social domains.