Objectives: Here, we used a task that is sensitive to subtle aspects of the perception of emotional expression to determine whether high-functioning adults with autism are impaired at judging the intensity of and recognizing emotional facial expressions.
Methods: Fifteen high-functioning male adults with autism and 19 age-, gender- and IQ-matched control participants took part in this experiment. Each participant rated the emotional intensity of 36 faces, each displaying 1 of the 6 basic emotions (i.e., happiness, surprise, fear, anger, disgust, sadness). Each of these 36 faces was rated 6 times - once for each emotion category (e.g., rating the intensity of happiness in happy, surprised, fearful, angry, disgusted, and sad faces; then rating the intensity of fear on these same faces, etc.), with the order of images and rating categories randomized within and across participants. Intensity was rated on a Likert scale from -4 to +4, with a +4 indicating that the face very strongly displayed the emotion of the rating category, while a -4 indicated that the face very strongly displayed an emotion opposite to the rating category (a rating of 0 indicated that the face was neutral for the rating category). A subset of participants from each group performed the experiment twice (autism n = 11, control n = 8), and we used this data to examine differences in response reliability between groups. Category specificity was calculated by comparing the rating of each face on it’s true category compared to ratings given for all other emotion categories.
Results: The autism group demonstrated overall reduced category specificity for emotional faces, and particularly for happy and surprised faces. Follow-up analyses revealed that this reduction could be accounted for by abnormally low intensity ratings for happy faces, and by broader than normal attribution of emotions for surprised faces (reduced selectivity). An analysis of response reliability across groups demonstrated that individuals with autism gave less reliable ratings for emotional extremes (i.e., -4, -3, +3, +4) compared to control participants. There was no group difference for less extreme ratings (i.e., -2, -1, 0, 1, 2).
Conclusions: We found evidence for altered perception of emotions from facial expressions in a group of high-functioning adults with autism. Abnormalities were found either in the intensity or the selectivity of specific emotions (happiness and surprised, respectively). Additionally, an analysis of response reliability revealed reduced stability for ratings of emotional extremes in the autism group. These results are consistent with altered emotion recognition and emotion intensity judgments in high-functioning adults with autism.
Funded by grants from the NIMH and the Simons Foundation.
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