Recent research suggests that individuals with autism spectrum condition (ASC) have particular difficulty in taking the visual perspective of others, that is, being able to say what a scene would look like from another person’s point of view (Hamilton, Brindley, & Frith, 2009). Successful VPT depends on the ability to spatially transform a scene and the ability to consider what another person can see. Here we focus on the first of these, and examine the spatial processes which may underpin perspective taking in ASC.
Two types of spatial transformation are relevant. Egocentric transformations use the self as a reference frame, while mental rotation transforms an object independent of the self. There is little previous research into egocentric transformations in autism; however, research has shown mental rotation to appear unimpaired. Different classes of spatial transformations are often studied using different stimuli (bodies in egocentric transformations and objects in mental rotation), which makes it difficult to know whether effects are driven by group, task or stimulus.
The aim of this study is to understand the processes underlying visual perspective taking in autism. To examine this, we contrast egocentric transformations and mental rotation in typical and autistic adults.
18 adults with autism spectrum condition and an IQ over 70, and 18 age and IQ matched typical adults took part in the study. Diagnosis of ASC was confirmed by ADOS. Each participant completed two reaction time tasks assessing their abilities to perform mental rotation and egocentric transformations on stimuli shaped like the human body or like a car. In the egocentric task, participants judged if the arm (of the body) or door (of the car) was extended on the left or right. In the mental rotation task, they judged if a body or car with one hand/door stretched out matched an exemplar body or car. In each task, stimuli were presented at different orientations on each trial. Overall, this gave a 2x2x2x4 factorial design, comparing effects of task (egocentric and mental rotation), group (Autism and typical), stimulus (body or object) and stimulus orientation (4 levels).
Results showed that people with autism were slightly slower to perform mental rotation (p=0.041) compared to the typical participants, but no less accurate. However, in the egocentric task, participants with autism were significantly slower (p<0.001) and less accurate (p=0.026) than the typical participants.
These data show that adults with autism may struggle with some of the basic processes underlying perspective taking. In particular, egocentric transformations are hard for this group, and were more impaired that mental rotation. Performance was not affected by the form of the stimuli (body or car). These data suggest that the fundamental process of relating a seen object to the self may be abnormal in participants with ASC.
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