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Chichi Ogbonna, Melanie Palomares, Barbara Landau, James Hoffman, Howard Egeth; The perception of visual illusions in Williams Syndrome.. Journal of Vision 2004;4(8):768. doi: 10.1167/4.8.768.
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© ARVO (1962-2015); The Authors (2016-present)
Williams Syndrome (WS) is a rare genetic disorder in which language is relatively intact, but visuospatial cognitive abilities are impaired. Evidence from visuomotor tasks such as block construction and drawing support the notion that WS individuals lack global organization and may be biased in processing local information (see Bellugi et al, 1999). On the other hand, Pani et al (1999) have suggested that WS people have intact visual integration, but may be impaired in visual segmentation. To investigate this issue, we measured thresholds using a method of limits for three different visual illusions: the Ponzo Illusion, the Muller-Lyer Illusion, and the Kanizsa Illusion. We also had a baseline condition in which there was no illusion. Using a forced-choice paradigm, we asked normal adults (18–22 years old), WS children (12–18 years old), and 3 year old children to discern which of two lines was longer. If WS children are impaired in visual integration, they should be less affected by the illusions. We found that normal adults and WS children have similar thresholds in the baseline condition; whereas normal 3-year olds had higher thresholds. We also found that all groups were susceptible to the illusions. We subtracted thresholds in the baseline condition from the thresholds in the illusion condition. WS children were affected by all three illusions twice as much as normal adults, and 3 year olds were more strongly affected than adults in the Muller-Lyer Illusion. The results indicate that both WS and normal children are able to integrate visual information. If anything, the WS spatial deficit may reflect an abnormally strong integration mechanism (or an abnormally weak segmentation mechanism).
NIH grants T32-EY07143, FY970670, FY980194, NSF grants BC9808589, BCS0117744
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