We examined how action goals influence the distribution of visuospatial attention near the body (Experiment 1) and how the temporal relationship between the nontask relevant visual distractors and targets modifies shifts in visuospatial attention (Experiment 2). Targets were cylinder-mounted light emitting diodes (LEDs) in the left and right hemispace of a visual display. Following the illumination of either the left or right target LED, participants either reached to point-to or grasp the top of the target object in blocked trials. Coincident with onset of the target a distractor onset (smaller cylinder with mounted LED) in the same or opposite hemispace halfway between the initiation point and target, or no distractor appeared. In Experiment 1, during grasping there was a greater temporal interference effect (slower reach initiation) compared with pointing. When grasping versus pointing, participants deviated more towards same side distractors and away from opposite side distractors. In Experiment 2, distractor onset was either 200ms prior to (-200ms), coincident with (0ms) or 200ms following (+200ms) the target. For both point and grasp actions -200ms distractors were associated with greater temporal interference in reach onset compared with 0ms and +200ms. For grasping +200ms distractors resulted in larger temporal interference effects compared with 0ms. In the -200ms condition, participant’s reach trajectories deviated more towards opposite side distractors and away from same side distractors, the reverse of the pattern for 0ms and +200m.
Keywords: pointing, grasping, visuospatial attention, reference frames, action activation, competing action