Matching-to-meaning: Emotional awareness in chimpanzees

Lisa A. Parr

Emory University and Yerkes Regional Primate Center, USA

Comparative studies on emotion in primates are relatively nonexistent, despite the important implications that these studies would have for understanding the evolution of human emotion. Previous studies on chimpanzees have demonstrated their ability to use facial cues to discriminate unfamiliar conspecifics, and categorize their own facial expressions (Parr, Hopkins & de Waal, 1998; Parr, Winslow, Hopkins & de Waal, 2000). To date, no studies have examined whether chimpanzee facial expressions have an inherent emotional meaning, or whether they understand this emotional significance in the absence of immediately available contextual information. This study examined emotional awareness in chimpanzees using a novel version of the matching-to-sample task, here called matching-to-meaning because the similarity between the sample and correct comparison stimulus is one of emotional meaning, and not perceptual features. Chimpanzees viewed short digitized videos showing positive and negative emotional scenes, and were then required to select one of two conspecific facial expressions that conveyed an emotional meaning similar to that depicted in the video. Three subjects spontaneously associated negative facial expressions, e.g. screams and bared-teeth displays, with scenes of veterinary procedures, injection needles, and distressed conspecifics, and positive facial expressions, e.g. play faces, with scenes of favorite food and objects. Performance on these discriminations was significantly better than control trials that arbitrarily paired facial expressions with scenes of conspecifics sleeping. In addition to cognitive performance, we measured physiological arousal using variables that have traditionally been associated with emotion in humans, e.g. electrodermal activity and skin temperature (Dawson, Schell & Filion, 1990; Rimm-Kaufman & Kagan, 1996). These showed stronger responses to negative emotional scenes compared to control videos. These results provide evidence for basic emotional awareness in our closest-living relative that is not based on training or reinforcement history. These results will be discussed in relation to basic emotion theory.

Dawson, M. E., Schell, A. M., & Filion, D. L. (1990). The electrodermal system. In J. T. Cacioppo & L. G. Tassinary (Eds.), Principles of psychophysiology: Physical, social and inferential elements (pp. 295-324). Cambridge: Cambridge University Press.

Parr, L. A., Hopkins, W. D., & de Waal, F. B. M. (1998). The perception of facial expressions in chimpanzees (Pan troglodytes). Evolution of Communication, 2, 1-23.

Parr, L. A., Winslow, J. T., Hopkins, W. D., & de Waal, F. B. M. (2000). Recognizing facial cues: Individual recognition in chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). Journal of Comparative Psychology, 114, 1-14.

Rimm-Kaufman, S. E., & Kagan, J. (1996). The psychological significance of changes in skin temperature. Motivation and Emotion, 20, 63-78.

Parr, Lisa A.

Department of Psychology, Emory University,

and Yerkes Regional Primate Center

532 N. Kilgo Circle, Psychology Building, Atlanta, GA 30322-1950, USA