Abstract
Visual attention has a finite spatial resolution that limits the ability to track an object moving amongst identical distractors (Intriligator & Cavanagh, 2001, Cog Psych, 43, 171–216). This limitation on spatial attention is much coarser than the visual acuity limit suggesting that there are two stages of spatial delineation in visual processing. Here, we tested whether controlling the motion of an object was limited by visual attention or visual acuity. Participants performed two tasks. In the tracking task, participants were asked keep track of the target, which was one out of nine identical disks moving randomly about a square display. In the controlling task, participants were asked to use a joystick to control the target's direction of motion. At the end of each 27-second trial in both tasks, participants had to judge whether a cued disk was the target or not. We used small visual displays (2.5 to 0.32 degrees of visual angle) to test beyond the spatial attention limit. Results showed that participants were better able to report the target at smaller display sizes after controlling than after tracking. These results might have suggested that visually-guided action uses a representation with finer resolution than visual attention. However, in a second experiment, we found that the advantage of controlling was greatly reduced when the target's direction of motion was given (visually) during tracking. It seems that visually-guided action may be limited by the resolution of visual attention, though additional cues from manual control are also available to improve performance.
NIH R01 EY014984