Abstract: PURPOSE: To investigate the cognitive mechanism of facial expression recognition in patients with depression and healthy people, using the paradigm of pairwise comparisons.
METHODS: The face stimuli included images of six types of facial expressions posed by 10 individual human models from the Ekman database (Ekman & Friesen, 1976). 42 patients with depression (20 women) and 30 healthy subjects (equally prevalent in women and men) were recruited for the experiments.
RESULTS: After analyzing the discriminative index of facial expression recognition, the results showed that the recognition of different expressions varied significantly. According to the Euclidean cluster analysis, 15 pairs of basic expressions were classified into three categories, among which fear/surprise, sadness/disgust, disgust/anger, fear/sadness, fear/disgust were the most difficult to discriminate, and fear/happiness, sadness/happiness, happiness/disgust, happiness/anger were relatively easier to discriminate. Meanwhile, on the basis of these expression categorizations, we compared the differences of facial expression recognition between patients with depression and healthy people. The results showed that patients with depression had significantly lower performance than healthy people in anger/surprise, sadness/anger, fear/anger, fear/disgust, fear/sadness, disgust/anger, sadness/disgust discriminations, which indicates that recognition disorders of patients with patients mainly showed in relation to negative facial expressions.
CONCLUSIONS: New paradigm provides more evidence about the rapid facial expression recognition. Difficulty differences are existed in categorizing facial expressions. Recognition disorders of patients with patients mainly showed in relation to negative facial expressions.

Key words: Rapid facial expression, discrimination, depression