Atypical Tactile Preferences in Autism Spectrum Disorder: Reduced Pleasantness Responses to Soft Objects Resembling Human Body Parts

Touching an object can elicit affective sensations. Because these sensations are critical for social interaction, tactile preferences may be adapted to the characteristics of the human body. Our group has demonstrated that compliance (a physical correlate of softness) increased the tactile pleasantness of a deformable surface until it reaches around the same level as those of human body parts. However, individuals such as those with autism spectrum disorder (ASD) often avoid being touched by others. Does ASD have atypical affective response patterns to soft objects like human body parts? Herein, adults with ASD and typically developed (TD) adults numerically estimated the perceived pleasantness or softness while lightly pressing urethane rubbers with their right index fingers. The results revealed that pleasantness increased as a function of compliance, but this increase was smaller for ASD than TD, particularly at compliance levels including human body parts. However, the perceived softness increased as a function of compliance similarly between the ASD and TD groups. This result demonstrates an atypical preference of ASD individuals for soft objects, which may explain the avoidance of ASD to social touch.