Hemispheric specialization for categorical and coordinate spatial relations during an image generation task: evidence from children and adults.

Hemispheric specialization of categorical and coordinate image generation was assessed in adults, 8-year-old and 10-year-old children. In a standardized image generation task, participants decided whether probes, presented in a blank grid (categorical task) or bracketed square (coordinate task), would have appeared on a previously studied letter. To ensure that participants mentally generated the target letter, probe location was varied. "Early" probes appeared on letter segments that are first produced when the letter is drawn; while "late" probes appeared on later produced segments. Like previous adult studies, the grid task elicited a left hemisphere "categorical" strategy; while the bracket task elicits a right hemisphere "coordinate" strategy. However, contrary to previous research, the results reveal the significant and complex effects of probe location on categorical and coordinate image generation abilities. Specifically, early probes elicited a strong right hemisphere advantage for both tasks across all ages, whereas late probes produced a left hemisphere dissociation between categorical and coordinate processing. The left hemisphere dissociation was evident only for 10-year-olds and adults, suggesting that younger children are not yet proficient in generating spatial representations.