Sex differences, dominance, and personality in the chimpanzee.

This study demonstrates a useful methodology for judging the personality of chimpanzees (Pan troglodytes schweinfurthi). Observers rated the chimpanzees on a forced-choice rating scale which yielded measures on eight emotion dimensions. The rating scale, Emotions Profile Index, is derived from a theory of personality which stresses the adaptive significance of emotions at all evolutionary levels. This method has theoretical generality, having been successfully applied previously to humans, baboons and dolphins. Observers were able to rate chimpanzees with reasonable reliability. Sex differences in personality were evident in this chimpanzee sample. In addition, dominance rank was found to correlate with certain emotion dimensions.