Automatic and intentional memory processes in saccade target selection

Short-term memory traces are known to encourage "visual foraging" by inhibiting eye movements toward objects or locations that have recently been inspected (e.g., Klein & MacInnes, 1999). Here, we employed a variant of Jacoby's (1991) process dissociation procedure to examine whether the memory processes involved in saccade guidance are primarily automatic or intentional. Subjects performed a saccade targeting task with gaze-contingent stimulus presentation. Each trial included a series of two-alternative, forced-choice events on which the subject could saccade toward either an old item, one which had been seen and fixated earlier in the course of the trial, or a new item, one which had not yet been seen. Three experimental conditions were employed. In the go-to-old condition, the subject was asked to saccade toward the old item. In the go-to-new condition, the subject was asked to saccade toward the new object. In the go-to-either condition, the subject was asked to saccade toward whichever of the two items he or she preferred. Data revealed that subjects were poor at targeting old items, even when explicitly instructed to do so; performance in the go-to-new condition was high, while performance in the go-to-old condition was near chance. Performance was similar in the go-to-either and go-to-new conditions. Results indicate that the memory processes that facilitate visual foraging are largely automatic, and difficult to suppress through intention.