Sensitivity to Social Touch In School-Age Children with Autism Spectrum Disorders

Background: Atypical sensitivity to touch has been described frequently in children with autism spectrum disorders (ASD). Existing reports cover a wide array of behaviors, including under-sensitivity to pain, over-sensitivity to light touch, preference for deep pressure, and atypical reaction to social touch.  Most of these reports have been either anecdotal or qualitative, however, and few studies exist with direct, quantitative measurements of sensitivity to social touch in individuals with ASD.

Objectives: The aim of the present study was to measure selective sensitivity and response to contingent social touch in school-age children with autism spectrum disorders in comparison with typically-developing peers matched on age and non-verbal IQ.  Control conditions measured basic motor function during mechanical manipulation in absence of social touch.

Methods: We designed and built a novel device for measuring haptic interaction between two individuals. The device consisted of horizontal rollers, linked remotely, that could be turned by either of two participants using left and right hands independently. The rollers of each participant were coupled mechanically, so that if one participant moved a roller the other participant would feel that movement on his or her own roller.  Participants performed twelve separate tasks. In baseline mechanical manipulation tasks, participants moved the rollers forwards and backwards at slow and fast rates.  In social interaction tasks, participants moved the rollers in interaction with the experimenter. BEI optical encoders and a National Instruments data acquisition system with Labview software measured rotational movements of the rollers. Measures of amplitude, period, and duty cycle ratio served as dependent variables.

Results: We compared the behavior of 60 children with ASD and 20 age- and  non-verbal IQ-matched, typically-developing controls during non-social, mechanical manipulation tasks and during haptic social interaction. The behavior of children with ASD was distinguished by stereotyped and repetitive movements and, in a subset of the children, by the favoring of select parts of the hand and forearm during task completion. These patterns were not observed in typically-developing children.  In addition, children with ASD, in contrast to controls, showed little change in behavior between the haptic interaction condition and the non-social, mechanical manipulation condition.

Conclusions: These results quantify altered sensitivity and response to social touch in individuals with ASD, and serve as a platform for future studies of the development of haptic intersubjectivity: how typically-developing children, beginning in infancy, are highly sensitized to recognize certain kinds of touch as social, and to react and respond in kind.  This will be an important part of understanding atypical behavioral and neural specialization in individuals with ASD.