Extrafoveal preview benefit during free-viewing visual search in the monkey

Previous studies have shown that subjects require less time to process a stimulus at the fovea after a saccade if they have viewed the same stimulus in the periphery immediately prior to the saccade. This extrafoveal preview benefit indicates that information about the visual form of an extrafoveally viewed stimulus can be transferred across a saccade. Here, we extend these findings by demonstrating and characterizing a similar extrafoveal preview benefit in monkeys during a free-viewing visual search task. We trained two monkeys to report the orientation of a target among distractors by releasing one of two bars with their hand; monkeys were free to move their eyes during the task. Both monkeys took less time to indicate the orientation of the target after foveating it, when the target lay closer to the fovea during the previous fixation. An extrafoveal preview benefit emerged even if there was more than one intervening saccade between the preview and the target fixation, indicating that information about target identity could be transferred across more than one saccade and could be obtained even if the search target was not the goal of the next saccade. An extrafoveal preview benefit was also found for distractor stimuli. These results aid future physiological investigations of the extrafoveal preview benefit.