Influence of visual distractors on movement trajectory

In the present study, we explored the influence of a visual distracter on t he trajectory of movements made to join two dots. The two dots could be unc onnected (D) or connected by a straight (L) or curved line, convex either t o the left (LL) or to the right (RL). The connecting line constituted the v isual distracter. In Experiment 1, subjects were asked to perform the joini ng movement as straight as possible. The results showed that hand trajector y moved to the left of the midsagittal axis in LL and to the right in RL, w hile it was almost straight both in L and D. In Experiment 2, subjects were explicitly required to follow the connecting line during their movements t o verify whether, in the previous experiment, they had used curved lines as guide for their movements. An increase of movement time and different hand paths showed that this was not the case. In Experiment 3. subjects were as ked to move as straight as possible without vision of their hand. Hand traj ectories were shifted to the left in all experimental conditions, but the l eftward shift was greater in LL than in all other conditions, and also grea ter in D and L than in RL. These findings suggest that the visual distracte r influenced hand trajectory by attracting subjects attention and competing with target for motor response. It is hypothesized that the attracting inf luence operated by the distracter was sustained by involuntary attentional mechanisms.