In 1892, Charles Darwin categorized human affects into seven or eight discrete expressions, each with its own facial display: happiness, sadness, fear, anger, disgust, surprise, interest, perhaps shame, and their combination. (The Expression of the Emotions in Man and Animals) According to Darwin, "The same state of mind is expressed throughout the world with remarkable uniformity." He postulated that these innate patterns of feeling and facial display evolved as social signals "understood" by all members to enhance species survival. (cf ritualization ) For Darwin, our expressions of emotion are universal (that is, innate not learned) and they are products of our evolution. They are also, at least to some extent, involuntary, and feigned emotions are rarely fully convincing.
Neither our expressions nor our emotions are unique to human beings; other animals have some of the same emotions, and some of the expressions shown by animals ressemble our own. For Darwin, "He who admits on general grounds that the structure and habits of all animals have been gradually evolved, will look at the whole subject of expression in a new and interesting light." (Introduction to First Edition) Thus, while the illustrations below are found in the chapter on "Special Expressions of Animals", Darwin points out at the outset that "With mankind some expressions, such as the bristling of the hair under the influence of extreme terror, or the uncovering of the teeth under that of furious rage, can hardly be understood, except on the belief that man once existed in a much lower and animal-like condition." (intro.)
