Social Anosimia: Altered Social Chemosignaling in Individuals with Autism Spectrum Disorder

Background:  Social chemosignals are volatiles secreted by one individual to affect behavioral, physiological and hormonal state of other individuals. Growing evidence implies that social chemosignals likely play a large role in human behavior, mostly without conscious awareness.

Objectives:  Because individuals with autism spectrum disorder (ASD) exhibit difficulties in social communication, we hypothesized that a portion of their inability to read social cues may reflect an inability to read social chemosignals.

Methods:  We measured chemosignal modulation of the startle response in 19 typically developed (TD) and 11 high-function ASD young adults. Startle response is a particularly appealing paradigm because it is non-verbal, independent of comprehension and motivation, intact in ASD, and influenced by chemosignals in TD subjects. We measured the startle response using EMG of the orbicularis oculi muscle (eye blink) twice; once following administration of the putative chemosignal hexadecanal and once following neutral control odor.

Results:  An analysis of variance uncovered a significant interaction (F_1,28 = 6.05, p < 0.05) whereby hexadecanal reduced startle in TD (t(18) = 2.99, p < 0.01) but not in ASD (t(10) = 0.76, p = 0.46). In other words, whereas TD subjects respond to a social chemosignal, ASD subjects do not.

Conclusions:  These results imply that ASD individuals are differently tuned to olfactory social signals. We propose a novel term: Social Anosmia, which may be involved in part of the symptoms of ASD.