Perception of facial expressions

Abstract

Naïve and "monkey expert" human participants viewed a variety of human and monkey (Cebus apella) facial expressions (e.g. happiness, anger, fear, disgust, and neutral) in three experiments: (1) search task in which expression was task-irrelevant, (2) speed rating in which participants categorized expressions’ valence, and (3) slow rating in which participants indicated expressions’ emotion-type and intensity. Button-press latencies in Experiment 1 varied as a function of expression and species. Experiments 2 and 3 revealed individual differences for both sex and expertise. Females were more sensitive to negative monkey expressions, while males were more sensitive to positive monkey expressions. This demonstrates that sex differences in expression perception may extend to the processing of nonhumans’ faces. Naïve participants were less accurate at rating monkey expressions, but still well above chance performance. This highlights the role of experience and evolutionary continuity in cross-species emotion perception.