Physiological Responses to Circumscribed Interests, Non-Social and Social Stimuli in Adults with Autism and Neurotypical Controls

Background:

Autism has been characterized as reduced social motivation and an enhanced drive towards non-social processing, which includes repetitive behaviours and circumscribed interests. These behaviours may be related to the employment of different mechanisms for processing and orienting towards non-social stimuli (e.g. a car) and social stimuli (e.g. a face). Previous research with a neurotypical (NT) sample has found that a higher number of subclinical autistic-like traits was related to more pronounced physiological responses to non-social stimuli, but not social stimuli or stimuli related to individual circumscribed interests. The greater emotional arousal to items of circumscribed interest were interpreted as reflecting greater salience for these items in people from the general population with higher autism traits, but no study has reported about this in adults diagnosed with autism and matched controls.

Objectives:

To investigate physiological responses to social and non-social stimuli, including stimuli related to participants’ individual circumscribed interests in an autism group and neurotypical controls.

Methods:

17 participants with an autism diagnosis (10 male, 7 female) and 16 NT controls (10 male, 6 female) were recruited and were matched by age, sex and education level. Participants viewed 24 images that included 6 social images of human faces and 6 of cartoon faces, and 6 non-social images of various objects (e.g. a train or car) and 6 non-social images relating to each participant’s particular interest or hobby. Skin conductance responses (SCR) were recorded as the images were passively viewed. A mean SCR magnitude was calculated for each condition and group differences were explored.

Results:

A Mann-Whitney U test revealed that SCR to the social-faces (U=117, z=1.691, p=.51) social-cartoon (U=104, z=-1.19, p=.26) and non-social (U=117, z=.689, p=.51) conditions were not statistically different between the two groups. However, there were significant differences between autism (Mdn=48.42) and NT (Mdn=47.20) groups in SCR to the non-social of interest condition (U=80, z=-2.023, p=0.043), with the ASD group exhibiting larger responses to images of their individual circumscribed interests than the NT group.

Conclusions:

The findings show a heightened emotional arousal response to items of special interests in adults with autism compared to adult controls, similar to the effects found with nonclinical adults with higher autism traits. However, no group differences were found in emotional arousal response to social stimuli in the adults with autism. These results suggest that items of circumscribed interest have enhanced salience for adults with autism compared to controls, but that social items aren’t associated with reduced salience. The findings have implications for social motivation theories of autism.