Susceptibility to Ebbinghaus and Müller-Lyer illusions in autistic children: a comparison of three different methods.
Catherine Manning, Michael J Morgan, Craig T W Allen and 1 others
PMID 28344759WHAT IT FOUND
Autistic children and typically developing children showed similar susceptibility to the Ebbinghaus and Müller-Lyer illusions when a method reduced guessing.
In an adjustment task, autistic children showed a stronger Müller-Lyer effect, but that difference was absent when guessing was reduced.
Key findings
01When a method was used that made it harder for children to rely on guessing, autistic and typically developing children did not differ in susceptibility to either illusion.
02In the card judgment task, the proportion of children fooled by each illusion did not differ significantly between groups.
03In the adjustment task, autistic children showed a larger Müller-Lyer illusion difference than typically developing children, while Ebbinghaus illusion differences did not.
STILL TO COME
How it was doneWhat they found
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What it does not show
Only cognitively able children were included, because all children had IQ scores above 70. The study was run at a public science event, and many children reported knowing the illusions from science books or TV shows. Sample sizes varied between experiments and between illusion tasks, and not all children completed all experiments. Some children were excluded for poor task performance or incorrect control responses. The Ebbinghaus card task was insensitive to group differences, and larger samples were needed to settle some questions. Verbal ability differed between groups in several analyses, although controlling verbal ability did not change the internal noise result in experiment 1. The stronger Müller-Lyer finding in the adjustment task had only weak Bayesian evidence. The stimuli used here differed from some earlier illusion studies, so past results may not be directly comparable.
Declared interests
Funding was provided by the Medical Research Council. The supplied text does not report author conflict disclosures.
The easy way to misread this
Do not conclude that autistic children have a stronger Müller-Lyer illusion because of perception. The larger Müller-Lyer difference appeared only in the adjustment task, was only weak evidence, and was not seen in the method designed to reduce guessing.