Atypical tactile preferences in autism spectrum disorder: Reduced pleasantness responses to soft objects resembling human body parts.

AIM: Previous studies have reported atypical sensory responses in individuals with autism spectrum disorder (ASD) and their implications for social touch. Although adults with ASD often report discomfort with being touched by others, their preferences for the physical properties of objects are less well understood. In a prior study, we observed that, in typically developed (TD) adults, compliance (a physical correlate of softness) increased tactile pleasantness for deformable surfaces up to levels comparable to those of human body parts. In the present study, we conducted psychophysical experiments to test whether individuals with ASD show atypical affective responses to soft objects resembling human body parts.

METHODS

Thirty-six adults with ASD and 36 TD adults numerically estimated the perceived pleasantness or softness while lightly pressing urethane rubbers with their right index fingers.

RESULTS

The results revealed that pleasantness increased as a function of compliance, but this increase was significantly smaller for patients with ASD than TD adults, particularly at compliance levels including human body parts. However, the perceived softness increased as a function of compliance highly similarly between the ASD and TD groups.

CONCLUSIONS

These findings demonstrate an atypical preference of individuals with ASD for soft objects such as human body parts, which may help explain their tendency to avoid social touch.