Hemispheric specialization for skilled perceptual organization by chessmasters.

The right cerebral hemisphere may be relatively specialized for parsing simple visual stimuli according to default rules, such as the Gestalt laws of perceptual organization, whereas the left cerebral hemisphere may be relatively specialized for overriding such default rules. We extend this model to 'semantically rich domains' by performing a divided-visual-field experiment on 16 chessmasters. Such subjects are able to recall and recognize complex chess positions by chunking the basic elements of the stimuli--the chess pieces--into meaningful groupings according to certain rules that are specific to the semantic structure of the chess domain. We show that the right hemisphere is superior to the left at parsing according to the default rules of chess chunking, but that the left hemisphere is superior to the right at grouping pieces together in violation of those rules. These results suggest that the right hemisphere is better able to acquire and apply new sets of default parsing rules for specific contexts. We conclude, consistent with other neuropsychological evidence, that the right hemisphere is critical for chess skill.