Do the hands shift the eyes?

Bimodal visual-tactile receptive fields have been found attached to body parts, such as the hand. Later studies have shown that visual attention has been modulated by the nearby presence of a hand. Based on the evidence for oculomotor control of visual spatial attention, we asked whether the attentional modulation produced near the hand is integrated into the oculomotor system/saliency map. Subjects were tasked with fixating a spot on the screen. That spot disappeared as another appeared and subjects shifted their gaze to the new spot. In one experiment, on half of the trials, the subject's hand was placed near the midpoint of the saccade trajectory, palm facing towards it. On the other half of the trials, the subject's hand was placed on the lap. In a second experiment, on half of the trials the subject's hand was placed near the midpoint of the saccade trajectory, palm facing towards it. On the other half of the trials, the hand was again placed near the midpoint of the saccade, however the palm faced away from it. We analyzed the metrics of the saccades to see if hand proximity and palm/back of hand facing affected saccade trajectories. If attentional modulation produced by the hand is independent of oculomotor control of visual spatial attention, then hand proximity and facing should have no effect on saccade trajectories. However, we find effects of hand position on saccade trajectories, suggesting that the bimodal visual-tactile receptive fields are part of an integrated visual spatial attention mechanism controlled by the oculomotor system.