Etcoff & Magee (1992) investigates the theory that actual perception of facial expressions is categorical. If expressions are perceived categorically, the “probability of identifying the expression as a particular emotion should not vary linearly across the series but should change relatively quickly at some boundary” (p. 229). Furthermore, the study argues that pairs of faces differing by a physical amount should be identified more accurately when that difference straddles the category boundary. The study hypothesizes that subjects will be able to label the surprised faces in the identification task while showing categorical perception when discriminating them from happy or afraid faces. Also, in terms of identification findings, the study hypothesizes that participants will show agreement in labeling an expression even when a second emotion is visible in it. For methodology, 88 MIT undergraduates participated in the study. Pictures of facial expressions were generated by a computer. Pictures displayed several expressions, such as happiness, sadness, anger, disgust, fear, surprise, and neutral expression from a standardized set. Some continua were created from emotions that can be identified by the participants. On each trial, participants saw a fixation signal, followed by three successive faces. The first two pictures of faces were always physically different from each other, but the third picture was identical to one of the two previously viewed pictures. The results of the study showed that categorical boundaries are perceived between emotions and between emotions and neutral faces. These show instances of association. An instance of dissociation is shown when subjects were able to label the surprised faces, but they were not able to show “categorical perception when discriminating them from happy or afraid faces” (p. 236). The concept of mental representation is implied when participants stored information about the person’s facial expression, such as smile, eyebrows, eyelids, and mouth that signal for emotions. The concept of mental process is expressed when participants see pictures and state the emotions based on facial expressions.
Etcoff, N. L., & Magee, J. J. (1992). Categorical perception of facial expressions. Cognition, 44(3), 227–240. doi: 10.1016/0010-0277(92)90002-y