Abstract
Although people can remember a massive number of pictures (e.g.10,000 in Standing, 1973), the fidelity with which human memory can represent such a large number of items has not been tested. Most researchers in visual cognition have assumed that in such studies, only the gist of images were remembered and the details were forgotten. We conducted two large-scale memory experiments to determine the details remembered per item, by systematically varying the amount of detail required to succeed in subsequent memory tests. In the first study, 2500 conceptually distinct objects were presented for 3 second each. Afterwards, observers reported with remarkable accuracy which of two items they had seen when the foil was a categorically-novel item (92%), an item of the same basic level category (87%), or the same item in a different state or pose (87%). In the second study, 2560 items were presented and the number of exemplars presented from each category varied from 1 to 16. Observers reported which exemplar they had seen for categories with 1 previously viewed exemplar (87%) and maintained high accuracy even for categories with 16 previously viewed exemplars (80%). Thus, contrary to the commonly accepted view that long-term memory representations contain only the gist of what was seen, we demonstrate that long-term memory can store thousands of items with a large amount of detail per item. Further, item analyses reveal that memory for an object depends on the extent to which it is conceptually distinct from other items in the memory set, and not on the featural distinctiveness along shape or color dimensions. These findings suggest a “conceptual hook” is necessary for maintaining the large number of high-fidelity memory representations, and imply that the precision of visual content in long-term memory is determined by conceptual and not perceptual structure.