The classification of facial emotions: a computer-based taxonomic approach

This study investigated whether the six ‘fundamental’ expressions of emotion each have configurational properties which would result in their being grouped into classes by a classification program. Twenty-three actors posed the six ‘fundamental’ emotions of happiness, surprise, fear, disgust, anger, sadness and a neutral expression. Still images of these videotaped expressions were digitised and distance measures between facial landmark points were obtained. These measures were subjected to a numerical taxonomy procedure which generated five classes. Class 1 contained almost 70% of the happiness expressions. In Class 2 the majority of expressions were of surprise. Each of classes three, four and five consisted of mixtures of emotions. Class 5 however, was distinguished from all other classes by the complete absence of happiness expressions. The typical facial appearance of members of each class is described (based on distance measures). These findings support the salience of happiness among emotional expressions and may have implications for our understanding of the brain's function in the early development of the human infant as a social organism