Robustness of the two-dimensional structure of recognition of facial expression: evidence under different intensities of emotionality.

Many studies have indicated that recognition of facial expression is geometrically represented in terms of two underlying bipolar dimensions, pleasure-displeasure and the intensity of arousal. A psychological space defined by these two dimensions has been found under particular conditions using prototype faces: however, the question arises whether this two-dimensional psychological space is also an accurate representation for faces with lower emotional intensity. To test this we prepared four different conditions of emotional intensity (100%, 75%, 50%, and 25% of emotionality) for six basic facial expressions using morphing. Participants (29 for the 100%, 30 for 75%, 35 for 50%, and 34 for the 25% condition) in each condition rated the facial stimuli on a 6-point scale of "not at all" and "very much so". Multidimensional scaling for each condition clearly indicated a two-dimensional representation and multiple correlations showed significant similarity across conditions (p < .001). This shows that the two-dimensional representation of recognition of facial expression is robust.