Is synesthesia more common in patients with Asperger syndrome?

Abstract

There is increasing evidence from case reports that synesthesia is more common in individuals with autism spectrum conditions (ASC). Further, genes related to synesthesia have also been found to be linked to ASC and, similar to synaesthetes, individuals with ASC show altered brain connectivity and unusual brain activation during sensory processing. However, up to now a systematic investigation of whether synesthesia is more common in ASC patients is missing. The aim of the current pilot study was to test this hypothesis by investigating a group of patients diagnosed with Asperger Syndrome (AS) using questionnaires and standard consistency tests in order to classify them as grapheme-color synaesthetes. The results indicate that there are indeed many more grapheme-color synaesthetes among AS patients. This finding is discussed in relation to different theories regarding the development of synesthesia as well as altered sensory processing in autism.

Is Synaesthesia More Prevalent in Autism Spectrum Conditions? Only Where There Is Prodigious Talent

“…However, these findings have been replicated in a second study (Neufeld et al, 2013) that showed elevated rates of synaesthesia in people with ASC using both self-report and an objective test for synaesthesia. Neufeld et al screened 29 individuals with Asperger Syndrome for grapheme-colour synaesthesia using a validated test of genuineness (described below).…”

“…Our current study aims to further understand the association between synaesthesia, ASC, and savant syndrome by asking whether synaesthesia is related to ASC in general, as has been suggested by Baron-Cohen et al (2013) and Neufeld et al (2013), or whether this relationship is more specifically linked to the presence of savant skills. To answer this question, we recruited three groups of individuals: individuals diagnosed with ASC who also report having a prodigious savant skill (henceforth 'ASC-savants'); individuals diagnosed with ASC but without an accompanying savant skill (henceforth 'ASC-non-savants'); and 'controls' who have neither a diagnosis of ASC nor a reported savant skill.…”

“…Behaviourally, both conditions are characterised by unusual sensory experiences Marco et al, 2011;Neufeld et al, 2013;Rogers and Ozonoff, 2005;Tavassoli et al, 2014a, b). Sensory hyposensitivities and hyper-sensitivities are frequently found in ASC, with individuals reporting difficulties adjusting to changes in lighting conditions, sounds, smells, tactile stimulation etc.…”

“…We tested for grapheme-colour synaesthesia in particular to follow the methods of Neufeld et al (2013), and because it is a well-understood variant of synaesthesia with a well-accepted diagnostic test. Previous studies Neufeld et al, 2013) suggest grapheme-colour synaesthesia may also be more prevalent in ASC, but our own hypothesis is slightly different. If savant skills can arise from the combination of synaesthesia and ASC, we predict that synaesthesia should be particularly common in ASC, but only in those ASC individuals who also report savant syndrome.…”

Introduction

“…Then we also have Baron-Cohen et al (2013) and Neufeld et al (2013), who raise the question of the extent of synesthesia amongst those on the autistic spectrum, proposing that the synesthesia in this group might be, in effect, a spandrel of the more broad-scale hyper-connectivity resulting in autism. And the topic of hyper-connectivity then may lead us back to such items as Gregersen et al's (2013) recent study, further exploring the similarities between absolute pitch as certain forms of synesthesia, a topic also being explored by Zamm et al (2013).…”