Refining the resource model: Cortical competition could explain hemifield independence

A growing number of studies find that we can select independently from the right and left hemifields, prompting some to suggest separate resources in the two hemispheres. Here we report an experiment suggesting that competition between representations, rather than exhaustion of resources, underlies these effects. Subjects searched a briefly displayed array for one of two targets. Subjects were slower to detect a target when it shared a hemifield with the distractors than when the distractors appeared in the opposite hemifield. Importantly however, this only occurred when the array was dense, suggesting that competition, rather than hemifield-specific resources, explains the decrement.