Jan Freyberg; Caroline E. Robertson; Simon Baron-Cohen

A Close Eye on the Eagle-Eyed Visual Acuity Hypothesis of Autism

publication date
2011 Jun 10
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Autism spectrum disorders (ASD) have been associated with sensory hypersensitivity. A recent study reported visual acuity (VA) in ASD in the region reported for birds of prey. The validity of the results was subsequently doubted. This study examined VA in 34 individuals with ASD, 16 with schizophrenia (SCH), and 26 typically developing (TYP). Participants with ASD did not show higher VA than those with SCH and TYP. There were no substantial correlations of VA with clinical severity in ASD or SCH. This study could not confirm the eagle-eyed acuity hypothesis of ASD, or find evidence for a connection of VA and clinical phenotypes. Research needs to further address the origins and circumstances associated with altered sensory or perceptual processing in ASD.


The present study could not confirm the eagle-eyed VA hypothesis of autism as postulated by Ashwin et al. (2009a, b). VA in ASD was consistent with the one measured in TYP and SCH when using a short viewing distance, the default number of trials and no “post-hoc maximum likelihood analysis” in FrACT. Moreover, we did not find sex differences in terms of males outperforming females, as might be expected by the systemizing/empathizing theory of gender differences and hypersystemizing approach to ASD (Baron-Cohen et al. 2009). Indeed, as females with ASD are often more severely affected by core and peripheral symptoms than males, the opposite prediction might be similarly justified. In accord with Ashwin et al., ASD subgroups (autism, Asperger’s syndrome, atypical autism/PDD-NOS) did not differ on VA, excluding the possibility of eagle-eyed vision being a valid phenomenon for a more circumscribed clinical picture of ASD. It seems that the previously reported results which lead to the hypothesis of eagle-eyed VA in ASD may indeed be based on a cascade of disadvantageous events owing to changes in the FrACT default settings as suspected by Bach and Dakin (2009) and Crewther and Sutherland (2009), particularly the combination of short viewing distance, high amount of trials and extrapolation of results.

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