Perceptual bias of patients with schizophrenia in morphed facial expression

Limited research has specifically examined the nature of the dysfunction in emotion categorization representation in schizophrenia. The current study aimed to investigate the perception bias of morphed facial expression in subjects with schizophrenia and healthy controls in the emotion continua. Twenty-eight patients with schizophrenia and thirty-one healthy controls took part in this study. They were administered a standardized set of morphed photographs of facial expressions with varying emotional intensities between 0% and 100% of the emotion, in 10% increments to provide a range of intensities from pleasant to unpleasant and approach to withdraw. Shift points, indicating the time point that the subjects’ emotion identification begins to change, and response slopes, indicating how rapidly these changes have happened at the shift points in the emotion continuum, were measured. Patients exhibited a significantly greater response slope (i.e., patients’ perception changed more rapidly) and greater shift point (i.e., patients still perceived mild expressions of anger as happy faces) with increasing emotion signal compared with healthy controls when the facial expression morphed from happy to angry. Furthermore, patients with schizophrenia still perceived mild expressions of fear as angry faces(a greater shift point) and were less discriminative from angry to fearful emotion(a flatter response slope). They were sensitive to sadness (a smaller shift point) and the perception changed rapidly (a sharper response slope) as compared with healthy controls in the emotion continuum of happy to sad. In conclusion, patients with schizophrenia demonstrated impaired categorical perception of facial expressions, with generally ‘rapid’ but ‘late’ discrimination towards social threat-related stimuli such as angry facial expression. Compared with healthy controls, these patients have a sharper discrimination perception pattern in the emotion continua from positive valence to negative valence.