Perceived Ambiguity of Facial Expression -Contribution of the Combination of Facial Parts of Different Emotions-

Although facial expressions serve as important emotional cues in our daily interaction with others, we sometimes have a difficulty in reading others’ emotions when their facial expressions are ambiguous. Previous research has investigated the ambiguous facial expression based on the assumption that it conveys some sort of emotions, requiring observers to determine which single emotion (e.g., happiness or sadness) it expresses. However, we could indeed perceive more than one emotion from the other's facial expression or leave it “ambiguous" without an identification of emotions. There is currently no empirical research on how we perceive the ambiguity of the facial expression, which was the focus of this study. We first made line-drawing faces comprised of eyebrows, eyes, and mouth, which expressed happiness, anger, and surprise respectively. Next, we shuffled facial parts and made 27 facial stimuli in total. Participants rated the ambiguity of the facial expression, which was defined as faces expressing more than one emotion or being difficult to be emotionally identified, as well as the strength of perceived expressions of six basic emotions for each stimulus. First, the perceived ambiguity increased as the number of emotions involved in a face. Second, even though the number of emotions contained in a face was same, the perceived ambiguity increased when it involved the angry expression. Third, the perceived ambiguity decreased when perception of the happiness and surprise were salient. These results suggest that the perceived ambiguity depends on the quantity and quality of emotions involved. Given that the anger contributes to the perceived ambiguity and that it depends on the saliency of the happiness (or positive expression) and surprise (or neutral expression), we are likely to perceive the ambiguous expression as somewhat negative, rather than neutral offset of multiple emotions.