by us. In order to classify behavioral patterns hierarchically and to describe social relationships, both anatomical and functional terms are needed. This books major aim is to list the names of all the behavioral elements in terms of anatomical details, but we also need functional terms in order to denote behavior that is meaningful in the natural environment. For example, approach is a functional term. Although it is simply walk or run from the anatomical perspective, when one chimpanzee comes closer to another, some interaction will likely occur between them. Therefore, we must have a term approach in addition to walk, and so on. Moreover, from the perspective of cognitive psychology, we need functional terms. For example, a chimpanzee who detours illustrates an important aspect of social cognition,