Cumulative intertrial inhibition in repeated visual search

In the present study the author examined visual search when the items remain visible across trials but the location of the target varies. Reaction times for inefficient search cumulatively increased with increasing numbers of repeated search trials, suggesting that inhibition for distractors carried over successive trials. This intertrial inhibition held across at least 16 items and when the search items moved randomly; however, it disappeared when the search items were removed from the display in an intertrial interval. In contrast, improvements to search when a target appeared at the same location on successive trials were weakened in a dynamic display, and this effect was resistant to the removal of search items. This dissociation implies that intertrial inhibition is based on a different mechanism than intertrial facilitation. The potential mechanisms for these effects are discussed.