Do the hemispheres watch each other? Evidence for a between-hemispheres performance monitoring.

This study tested the hypothesis that when tasks are complex, response selection and performance monitoring are divided across the hemispheres, and when tasks are simple, response selection and error monitoring are done in the same hemisphere. Using a divided visual field paradigm, the authors presented a target and an interference stimulus, either to the same visual field or to different visual fields, and encouraged error correction. The interference stimulus was timed to interfere with posited error processing. Four tasks were used: bar graph identification, lexical decision, and complex and simple versions of the flankers task. The first three tasks revealed a pattern of contralateral interference, suggesting that error processing occurred in the hemisphere that did not process the initial target. The fourth task showed ipsilateral interference, suggesting that the same hemisphere processed the target and monitored itself. The authors conclude that the pattern of hemispheric cooperation in error processing is affected by task complexity.