Abstract
Attention is directed to the upcoming goal location of both saccades and reaches . It remains unknown however, how attention is allocated during simultaneous eye and hand movements. We investigated attentional allocation through a 4-alternative forced-choice shape discrimination task (Deubel & Schneider, 1996) while subjects made either a saccade or a reach (or both) when cued by an arrow to one of five peripheral locations. The discrimination shape appeared during the latency period either at the goal (50% of the time) or at one of the other 4 locations. We found that target discrimination was better when the discrimination stimulus appeared at the movement goal than when it appeared elsewhere. Discrimination performance at the movement goal was not better in the combined condition compared to either effector alone, suggesting limited shared attentional resources rather than separate attentional resources specific to each effector. To test which effector dominated in guiding attentional resources, we then separated the goals for the hand and the eye. This was done using two paradigms, 1) cued reach/constant saccade - subjects made a saccade to the same peripheral location throughout the block, while the reach goal was cued by the arrow and 2) cued saccade/constant reach - subjects made a reach to the same location, while the saccade goal was cued. During both eye-hand goal dissociation paradigms, discrimination performance was consistently better at the eye goal than the hand goal. This indicates that limited attentional resources are guided predominantly by the eye during eye and hand movements.