Facial Expression in Primates With Remarks On a Parallel Development in Certain Carnivores (a Preliminary Report On Work in Progress)

Abstract

AbstractIn this report of an unfinished study of the evolution of facial expressions the author draws a brief comparison between the most important facial muscles of various primates and of two carnivores, the suricate and the dog. Before discussing the expressions, definitions of the various elementary emotions are given and the criteria from which the author judges the emotional condition of the animals. The main conclusions reached from the observations are:- 1. Certain basic rules govern the facial expressions of the animals studied. 2. Joy and happiness are expressed by a general lifting of the face and a tightening of the upper lip. The expression originates from preparation for a play-bite. The posture has become completely ritualised in man. 3. Unhappiness expresses itself by a lowering of the face. In horror there is a general tension of the facial muscles and the mouth tends to open while the animal screams. In sadness the animal tends to become less active. 4. Anger is recognisable from a tightening of the facial muscles, particularly those around the mouth in preparation for a hard bite. 5. Threat varies in expression but it contains components of anger and fear. 6. Love and affection find expression through such actions as lipsmacking, love-biting, sucking and kissing. The oral caressing has its origin in the juvenile sucking for comfort. 7. Concentration is not an emotion but it usually shows itself by a tension of the facial muscles. 8. There is a similarity between the two carnivores under discussion and some of the primates. A common pattern of the facial muscles of the suricate and the lemur indicate a common ancestry and brings the two animals to the same level in their ability to express their emotions. The dog, although very different from the monkey in its facial musculature nevertheless resembles it in its mode of expression. This feature seems related to similarities in their biology which have been facilitated by the development of a bifocal vision.