Synaesthesia and its relation to social and sensory aspects of autism

In synaesthesia, individuals experience additional sensations for specific sensory input, e.g., seeing colours for letters. Synaesthesia occurs roughly five times more often in individuals on the autism spectrum, but it is not known how synaesthesia affects autistic individuals. We set out to discover whether having synaesthesia in addition to autism coincides with the presence of specific autistic traits. Because of synaesthesia’s perceptual and sensory characteristics, we hypothesized that the presence of synaesthesia would be associated with stronger sensory alterations in autism, such as increased reports of hypersensitivity to sensory stimulation, and increased scores on the Autism Spectrum Quotient (AQ) subscale related to perception (Attention to Details). Both individuals on the autism spectrum with synaesthesia (N=25) and individuals on the autism spectrum without synaesthesia (N=36) completed a part of the Glasgow Sensory Questionnaire (GSQ), three subscales of the Dutch AQ, and a synaesthesia consistency test. Data collection is still ongoing, but preliminary results show that the synaesthetes scored significantly higher on the GSQ questions, indicating stronger hypersensitivity than the non-synaesthetic autistic individuals. A repeated measures ANOVA with the factors of AQ subscale (Social Skills, Communication, Attention to Details) X group (synaesthesia present/absent), showed a significant subscale by group interaction: synaesthetes scored numerically lower for Social Skills and numerically higher for Attention to Details than the non-synaesthetes, although follow-up tests comparing subscale scores between groups were not significant. The preliminary results suggest that individuals on the autism spectrum with synaesthesia experience more hypersensitivity than individuals on the autism spectrum without synaesthesia.