Association of Tactile Symptoms with Core Features of Autism: Evidence From Direct Observation and Parent Report

Background: Differences in sensory processing have been noted in autism spectrum disorders (ASD) across modalities, and sensory processing differences discriminate children with ASD from those with both typical development (TD) and generalized intellectual disability (ID). Evidence exists for both sensory seeking and defensiveness in ASD, as well as for both hypo- and hyper-responsiveness to sensory input.  Of note, at least one study found that hyporesponsiveness best discriminated individuals with ASD from those with ID. While visual and auditory processing have been the focus of many studies, less is known about tactile processing in ASD.  Further, despite the fact that sensory processing abnormalities have been proposed for inclusion in the DSM-V diagnostic criteria for ASD, little is known about the relation between tactile processing deficits and core ASD features.

Objectives: To examine the relation between tactile processing and autism symptomatology in young children with ASD.

Methods:  Tactile processing was examined in 33 children with ASD between 5 and 7 years of age (mean CA= 6.8 years, mean MA= 5.2 years) using the Tactile Defensiveness and Discrimination Test-Revised (TDDT-R).  Parent report of tactile processing (including defensiveness, seeking, and hypo- and hyper-responsiveness) was collected using the Sensory Profile Caregiver Report (SP) and the Sensory Experiences Questionnaire (SEQ).  Autism symptomatology was assessed directly with the ADOS, and parent report was obtained from the ADI-R.  Bivariate correlations were conducted between direct assessment and parent-report measures of tactile defensiveness, seeking, and hyporesponsiveness and direct and parent-report assessments of social, communicative, and behavioral differences in ASD. A significance threshold of p < .05 was used for all correlations.

Results:  Increased tactile seeking behaviors, as indexed on the TDDT-R and SEQ tactile scale, was associated with increased social impairment on the ADOS and ADI-R and increased repetitive behaviors on the ADOS.   In contrast, increased tactile defensiveness on the TDDT-R was associated with decreased repetitive behaviors on the ADOS.  Higher levels of tactile hyporesponsiveness, as measured by the SP tactile high threshold items, were related to increased social impairment on the ADOS and ADI-R, increased nonverbal communication impairments on the ADI-R, and increased repetitive behaviors on the ADOS.  The SEQ index for tactile hyporesponsiveness was correlated with ADI-R report of increased social and non-verbal communication symptoms.  However, neither the SP or SEQ measures of tactile hyperresponsiveness were correlated with any core ASD symptom domains, as measured by the ADOS and ADI-R.

Conclusions:  Results suggest that increased hyporesponsiveness to external tactile input as well as increased internally-driven tactile seeking behavior are associated with increased social-communicative impairment and higher levels of  restricted and repetitive behaviors in young children with ASD.  Tactile defensiveness and hyper-responsiveness, however, seem less related to core ASD symptoms, though preliminary evidence for decreased repetitive behaviors with increased defensiveness was found.  Results regarding hyporesponsiveness and sensory seeking behaviors confirm previous findings suggesting that these symptoms may represent the sensory differences most specific to ASD. Future research exploring the neural mechanisms underlying relations between tactile processing and core ASD symptoms is warranted.