Exploring the thresholds of vision for perception and action.

Based upon evidence that vision for action has quicker access to visual information than vision for perception, we hypothesized that the two systems may have differentiated visual thresholds. There is also evidence that, unlike vision for perception, vision for action is insensitive to cognitive dual-task interference. Using visual masking, we determined the visual thresholds of 15 participants in a perception task, an action task and an action plus concurrent cognitive secondary task. There was no difference in threshold between the perception task and the action task, but the action plus concurrent secondary task was accompanied by a greater visual threshold than both the perception task and the action task alone, indicating dual-task interference. The action task was thus most likely informed by vision for perception. The implications of these results are reviewed in the context of recent discussions of the two visual systems model.