Personal Space and Interpersonal Distance in Autism: Insights From the SRS

Background: Research on social behavior in autism has focused considerably on face processing and mentalizing abilities. Relatively ignored have been other equally important real-world social behaviors that can be more difficult to quantify in laboratory experiments, and about which less is known neurobiologically. One such behavior is the regulation of interpersonal distance (the physical distance between individuals). Distance regulation is critical for successful social interaction, and its impairment can result in violations of personal space. This topic is ripe for investigation in part because we recently showed that the amygdala plays a key role in it, and because anecdotal observations suggest it is impaired in autism. Objectives: Given the lack of research on interpersonal distance in autism together with its patent importance in social interaction, we began by analyzing questionnaire-based data from a large sample of individuals with autism. We were interested both in quantifying possible impairments in general, as well as in identifying individual differences that might carve out potential subtypes of autism. Methods: One item on the Social Responsiveness Scale (SRS), a 65-item parent- or teacher-report questionnaire that quantifies severity of autistic impairment, deals explicitly with personal space and interpersonal distance (Question 55: “knows when he or she is too close to someone or is invading someone's space”). The question is rated on a 4-point scale with higher scores reflecting more common interpersonal distance violations. We examined differences in this parent-report measure between autistic probands and their siblings, by using a large sample of phenotypic data from the Simons Simplex Collection and the Autism Genetic Resource Exchange (representing 766 autism-sibling pairs in total), as well as our own sample of identical and fraternal twins (J.C.). Results: Autistic probands had significantly higher levels of parent-reported interpersonal distance violations than their siblings (proband mean = 2.22, sibling mean = 0.70, p <.0000001). There were no differences in mean ratings across the various autism spectrum diagnostic categories (autism mean = 2.20; Asperger's mean = 2.22; PDD-NOS mean = 2.17). Results of additional analyses, including an analysis of the heritability of interpersonal distancing, will also be presented. Conclusions: Individuals with autism have impaired interpersonal distance regulation. This deficit is pervasive, in that it affects the majority of individuals with an autism spectrum diagnosis, and in that it is observed to a similar degree across the various diagnostic categories (i.e., autism, Asperger's, and PDD-NOS). Given recent findings of the role of the amygdala in interpersonal distance regulation and in one's sense of personal space (Kennedy et al., 2009), it is of particular interest to determine whether such abnormalities in autism might reflect an endophenotype of amygdala dysfunction. The present results should lead to a greater understanding (and perhaps acceptance) of personal space violations made by individuals with autism, and might also prove helpful in resolving situations arising from such violations.