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Abstract

We explored the interaction between visual search, memory, and action using a simple visuomotor task. Stimuli were eight light-grey disks (targets; ~1 deg diameter) on a medium-grey background. Targets were numbered 1 - 8, and placed randomly within a 12 deg × 11.5 deg rectangle. The task was to move a mouse pointer to each target and click on it in numerical order, as quickly as possible, starting with number 1. Twelve subjects performed 60 trials in each of two conditions: vanish -- each target was removed from the screen after the subject clicked on it; no change -- clicking on a target did not change the display. Reaction time (RT) decreased roughly linearly by 22.89 ms per item with each response (not counting RT to the first target). There was no effect of condition, nor an interaction.

We conclude that all targets initially compete at some level to control responses. Each response completely eliminates that target from competition. In a further study, we attempted to separate retrospective (what you did) and prospective (what you will do) elements of the task. We did this by scrambling items ahead of the current target after each response. Preliminary results suggest prospective memory may be driving the decrease in RT.