Body Perception

Typically developing people perceive bodies as a whole, taking into account where the constituent parts (limbs) are located in relation to each other (the configuration), termed ‘configural processing’ (Johnson, Perlmutter, & Trabasso, 1979). When we see a body, activation in the brain makes us aware of the positions of limbs followed by a whole (configural) representation of the body being formed (Peelen &

Downing, 2007). This allows us to identify that what we are seeing is a body and not an object. Whilst TD people are adept at discriminating bodies from other types of stimuli (Pavlova, 2012; Simion, Regolin, & Bulf, 2008) it is unclear whether body perception is normal in people with autism.

Studies which have examined whether body perception is intact in autism have so far shown mixed findings (Ham, Corley, Rajendran, Carletta, & Swanson, 2008; Jones et al., 2011; Reed et al., 2007). This may in part be due to the different methods used to examine how people perceive bodies. One way of examining body perception is to use point light walkers. Point light walkers depict a moving body with points of light at each joint and thus provide only motion information without form (Cutting, 1978). Many studies have shown that typical individuals can judge gender, emotion and even familiarity from seeing point light figures (Kozlowski & Cutting, 1978) however findings in autism are not so clear cut. Blake, Turner, Smoski, Pozdol, and Stone (2003) found poorer performance by children with ASD when discriminating biological motion (human movement) compared to global form recognition (‘what stimulus are you seeing?’). Specifically they found that children with ASD were able to discriminate a static object from a cluttered background, but struggled to discriminate humans from non- humans in a point light display. Contrary to these findings, a recent large scale study with well-matched ASD and typical groups found no evidence of impairment in perception of point-light walkers in ASD

(Jones, et al., 2011). The authors compared 89 adolescents with autism to 52 age and IQ matched TD individuals and found that there were no significant differences between groups on biological motion involving point light walkers. They also found that biological motion performance was correlated with ToM ability, in that those who were better at performing ToM were also better at discriminating biological motion. These results suggest that whilst people with autism do not have an issue in body perception using point light displays, the ability to perceive bodies does appear to impact on social cognition. This is consistent with the suggestion that bodies may also be relevant for abilities such as VPT, as they provide the information we use to form a representation of another person prior to transforming ourselves into their place.

Another way to examine body perception is to use posture matching tasks. The body inversion paradigm examines a participant’s ability to match bodies from different points of view. Findings in TD individuals show that they find it more difficult to match bodies that are inverted as opposed to upright (Reed, Stone, Bozova, & Tanaka, 2003). Reed, et al. (2007) examined the body inversion effect in people with autism. Here participants had to decide whether two pictures of an upright or inverted (upside down) body, face or house were the same or different. Previous research has shown that typical participants are slower to react when faces and bodies are inverted compared to when they are upright. This is taken as an indication of configural processing as inverting a body or face disrupts the familiar spatial configuration of

the features, making it more difficult to process the stimulus as a whole. In Reed’s study, typical participants showed an inversion effect, that is, slower reaction times to inverted bodies compared to upright ones whereas adults with ASD did not. This provides initial evidence for atypical configural processing of bodies in adults with ASD, suggesting that they do not use the same configural processing strategy as TD people. However it is difficult to conclude from this study whether body perception is impaired in autism, or is simply different. It has been suggested that a lack of configural processing in body perception may be related to weak central coherence and difficulty processing a stimulus as a global form. Participants with autism may try to match bodies based on the use of surface features, picking out the position of specific limbs and comparing them across stimuli. Further support for difficulties in body perception comes from Ham, et al. (2008) who found children with ASD were impaired at a posture matching task. Children with ASD and a group of age and IQ matched TD children completed a gesture imitation task in which they had to imitate hand/finger positions and a posture matching task similar to that of Goldenberg (1999). Ham’s study only used meaningless gestures/postures to eliminate any memory components for familiarity being present in recognition. They found that participants with ASD showed a significant deficit in hand/finger matching as well as posture imitation compared to the TD controls. These results suggest that children with autism may struggle with body perception compared to typical children.

In summary it is unclear whether people with autism are impaired at perceiving bodies. While some studies indicate that they are able to identify bodies and discriminate them from other types of stimuli (Jones, et al., 2011) others show that body perception appears to be abnormal (Ham, et al., 2008; Reed, et al., 2007).