Saccade target selection in visual search: accuracy improves when more distractors are present.

We report four experiments with search displays of Gabor patches. Our aim was to study the accuracy of gaze control in search tasks. In Experiment 1, a target was presented with a single distractor Gabor of a different spatial frequency on the same axis. Subjects could locate the target with the first saccade if the distractor was more distant, but when the distractor was between the fixation point and the target, the first saccade landed much closer to the distractor. In Experiment 2, the number of display items was increased to 16 in a double ring configuration. With this configuration, first saccades were accurately directed to the target, even when there was an intervening distractor in exactly the same configuration as in Experiment 1. Experiment 3 suggested that the improvement in accuracy was not due to distractor homogeneity but rather may be attributable to the increased first saccade latency with the ring configuration. In the final experiment, latency was shown to covary with saccade accuracy. The results are related to a general framework whereby the presence of distractors operates to hold fixation for a longer period of time, thus allowing a greater period of visual processing and more accurate eye movements.