Biased Perception of Mean Emotion in Abstinent Heroin Abusers

Although evidence suggests that drug abusers exhibit biases when coding individual emotional facial expressions, little is known about how they process multiple expressions simultaneously. The present study evaluated the mean emotions perceived by abstinent heroin abusers. Male abstinent heroin abusers (AHs) and healthy controls (HCs) were randomly assigned into three emotional conditions (happy, sad, or angry), viewed sets of four faces (Experiment 1) or individual faces (Experiment 2) that varied in emotionality (neutral to happy/sad/angry), and judged whether a test face presented later was more/less emotional than the preceding stimuli. Average points of subjective equality were calculated to reflect participants' biases in perceiving emotions of sets or single faces. Relative to HCs, AHs overestimated mean emotions for sad and angry faces in Experiment 1; however, no such biases were found in Experiment 2. This suggests biased ensemble coding towards negative emotional facial expressions in AHs. Furthermore, when controlling for depression and anxiety, AHs' enhanced perception of mean emotion for angry or sad faces in Experiment 1 decreased, indicating a possible mediating effect of these psychopathological variables in the relationship between drug addiction history and abnormal ensemble processing for sets of emotional expressions.