Hemispheric asymmetries for selective attention apparent only with increased task demands in healthy participants.

This study examined the possibility that lack of behavioral evidence indicating hemispheric specialization for selective attention in healthy individuals is due to the use of tasks that are not sufficiently demanding to require selective attention. In a group of 43 participants (ages 17-23), we compared selective attention on a cued-response time task when the target was presented alone and when a distractor was simultaneously presented. The costs of invalid cueing were minimal when the right hemisphere (RH) processed the target relative to when the left hemisphere (LH) processed the target, but only for the high load condition. These results are interpreted as RH specialization in light of evidence suggesting that the RH can direct attention to a larger portion of the visual field.