Abstract
Crowding, the inability to recognize objects in clutter, can be alleviated through long-range grouping mechanisms. For example, recognition was facilitated when a peripheral target and an additional item presented at fixation were identical compared to when they were different. Here, we investigated whether imagining a central item was sufficient to elicit long-range grouping that could alleviate crowding. We presented an item (letter or digit) at fixation, followed by a crowded target in the periphery (8°). The central item, either identical to or different from the peripheral target, was presented for 1.5 seconds. Next, observers were asked to either imagine the central item for 4 seconds or to fixate the center without imagery. After 4 seconds, the crowded target was presented for 150 ms to the left or right of fixation. In a dual task, observers reported first whether the target was a letter or a digit, and second if the target and the central item were identical (to ensure attention to both). We found that target recognition was better when observers imagined an identical central item compared to (1) imagining a different central item, and (2) not imagining any item. In a control experiment, we presented uppercase and lowercase letters and found better performance for imagined central letters that were of the same name and same case as the target (e.g., AA) compared to the same name and a different case (e.g., aA), indicating that the results were due to shape-specific mechanisms and not due to cueing of the target name. Our results demonstrate that signals of crowded targets can be enhanced by imagining a central item identical to the target. We suggest that signals generated by visual imagery can be sufficiently strong to mimic the effects of real stimuli that facilitate target recognition in clutter.