Do people with an ASD experience sight differently?

If so, is it more objective and how is it qualitatively different?

Do people with an ASD experience problems in visual orienting and other facets of attention?

If so, are these difficulties to blame for problems in social communication and language?


The eyes look and the brain sees.

Looking is the eyes gathering information while seeing is the integration of this information. Atypical visual integration may lead to problems in successful functioning. In the case of autism, this may manifest in difficulties seeing the forest for the treesfavouring details at the expense of the bigger picture. A recent theory proposed by Pellicano & Burr (2012) has started to gain considerable favour in explaining visual perception in autism. Their theory is rooted in Bayesian thought. According to Bayesian theories of vision, what we experience as sight is the result of an active process formulating and testing hypotheses about the physical world. It then follows that previous experiences, called priors, are important in shaping visual experiences. Pellicano & Burr (2012) propose that persons with an ASD are unable to rely on priors to the same extent as typically developing people and therefore the active process of formulating and testing hypotheses about the physical world is more immune to suggestion, which results in a tendency to perceive the world more objectively and a desire to be in more familiar settings.

Some of the experiments we carry out are aimed at examining enhanced abilities in discriminating visual details in autism. This is relatively easy to test. Other experiments are aimed at examining whether or not visual perception is more objective in autism. This is much harder to test. Consider this: How does one go about quantifying whether or not a typically developing person sees a shade of blue as being different than what a person with an ASD sees? If so, whose perception is more objective and closer to physical reality? One way of answering questions of this genre is to use optical illusions, such as the one shown below.


In this illusion, called the Shepard’s tabletops, most people perceive the tabletop on the left to be narrower and longer than the one on the right when in fact they have the same dimensions. This illusion is one of the strongest optical illusions that exists, on average the apparent size difference is 20-25%. Our preliminary work (in preparation) and earlier work performed by others (Mitchell, Mottron, Soulieres, & Ropar, 2010) reveal how susceptibility to this particular illusion is diminished considerably in persons with an ASD.

Orienting is the mental process of directing attention to a particular spatial location, which is something we do all the time. For example, the sudden appearance of a set of headlights will cause us to shift our attention to where the lights are located. In this case, the reflex is inherent. However, in most cases, the response behaviour is learned, whereby the presentation of a cue, such as pointing or the gaze of another person looking somewhere else, will cause us to shift our attention to a different location. This is because our previous experiences, beginning from early infancy, reinforced us to react this way.

Orienting emerges in early infancy and is thought to be a pivotal skill for the subsequent acquisition of a number of other mental processes, especially those required for the development of social cognition and language, arguably two of the most critical domains of human function. Our experiments aim to examine how orienting might influence social and language abilities. A typical visual orienting task consists of the following. Participants maintain fixation on a central cue, such as the arrow illustrated below, and then move their eyes to a target, such as the giraffe illustrated below, when it appears. The cue may or may not accurately predict the location of the target.

Why study visual cognition in autism? The study of cognition provides clues as to how the mind operates. Unlocking how the mind operates and how these operations may or may not differ in autism is not only fascinating to us conceptually, and philosophically, but should be considered in the development of any kind of intervention, providing a conceptual and evidence-based framework as to how one can develop an effective intervention.


Mitchell, P., Mottron, L., Soulieres, I., & Ropar, D. (2010). Susceptibility to the Shepard illusion in participants with autism: reduced top-down influences within perception? Autism Res, 3(3), 113-119.

Pellicano, E., & Burr, D. (2012). When the world becomes ‘too real’: a Bayesian explanation of autistic perception. Trends Cogn Sci, 16(10), 504-510.