Abstract
Visual short-term memory (VSTM) is limited to representing only about four items in detail, yet we have the perception of seeing the world around us in full resolution from moment-to-moment. One way the limited capacity visual system might accomplish this illusion of stable and complete perception is by relying on higher-order statistics inherent in the surrounding environment to parsimoniously organize and represent information. Given recent reports that the visual system represents average properties of Gestalt-grouped sets of individual objects, we hypothesized that grouping and averaging may enhance memory capacity (as indexed by the amplitude of the contralateral delay activity (CDA)) beyond the traditional four-item limit. We presented observers with study displays of four or 16 differently-sized circles, and then asked them to adjust two subsequently-presented test circles to match the remembered sizes of the two corresponding circles in the study display. The circles in the study display could be ungrouped, or grouped into two sets, one with a large mean size and one with a small mean size, according to the Gestalt principles of Similarity, Proximity, Connectedness, or Common Region. Unbeknownst to participants, the two test circles were always the same physical size. However, when the test circle was a member of the previously presented Gestalt-defined set with the large mean size, they adjusted it larger than when it was a member of the small mean size set. Furthermore, CDA amplitude decreased in the grouped compared to ungrouped conditions when there were 16, but not four items in the study displays. Taken together, these results imply that Gestalt grouping boosts memory capacity beyond the traditional four-item limit by biasing the memory for individual items toward the mean of the Gestalt-defined group.
Meeting abstract presented at VSS 2018