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Catherine Manning, Michael Morgan, Craig Allen, Elizabeth Pellicano; Do children with autism show reduced susceptibility to the Ebbinghaus illusion?. Journal of Vision 2015;15(12):646. doi: 10.1167/15.12.646.
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© ARVO (1962-2015); The Authors (2016-present)
Reports of reduced susceptibility to visual illusions in autistic individuals have generally been attributed to differences at the level of the percept. However, group differences could instead reflect differences in higher-level decision-making strategies. Here, we measured the perceptual biases of 28 children with autism aged 6 to 14 years and 32 age- and ability-matched typical children using a 2-alternative-forced-choice method with a roving pedestal designed to minimise response and decision biases (Morgan, Melmoth & Solomon, 2013, Visual Neuroscience 30:197-206). Children were presented with a reference stimulus and two comparison stimuli (see Figure 1), and asked to identify which comparison stimulus had a central circle most similar in size to that of the reference stimulus. One comparison stimulus was a pedestal, which had a central circle either 5% larger or 5% smaller than the reference stimulus. The other comparison stimulus had a central circle that was an increment larger than the pedestal. The pedestal size (+5%, -5%) was randomly interleaved throughout the task, so that children did not know which of the two comparison stimuli was the pedestal on a given trial. Children completed this task in two context conditions: with small surrounding circles on the reference and large surrounding circles on the comparison stimuli (S-L), and vice versa (L-S; see Figure 1). The data were fit with a cumulative normal psychometric function using the maximum likelihood estimate technique, modelling the effect of context condition as an equivalent pedestal with no effect on internal noise. Children with autism had typical levels of internal noise and exhibited a similar degree of perceptual bias to that of typically developing children. Our results are inconsistent with theories proposing reduced contextual integration in autism and suggest that previous reports of reduced susceptibility to illusions arise from differences in response or decisional criteria, not perceptual differences.
Meeting abstract presented at VSS 2015
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