Relational information in visual short term memory: The structural gist

Abstract

Storage of items in visual short term memory has been extensively studied over the past twenty years. In addition to questions concerning the format of object storage is a more global question that focuses on the organization of information in visual short term memory (Jiang, Olson and Chun (2000)). In a series of experiments using a change detection paradigm, we investigated how the inter-relations between visual items in a display determined the accessibility of each individual item. We conducted four experiments using the same paradigm as Jiang et al.. We presented a sample screen composed of 2, 4 or 6 geometrical shapes and, after a blank, a test screen where one of the items was cued as target. The subject had to decide if the target had changed color (Exp1), orientation (Exp2) or shape (Exp3). Two kinds of changes could be made : a minimal change (only the target might change between the sample and the test screen) and a maximal change (all the non-targets changed). Target and non-targets changes could be restricted to the same feature dimension or not (Exp4). A decrement in change detection performance was observed for the maximal change condition, showing that relational information deriving from irrelevant contextual items plays a role in recall from visual short term memory. The effect did not occur in Experiment 4, showing that relational information plays a role only within a given feature dimension. A fifth experiment using precueing of a subset of the items showed that attention was not necessary for the establishment of relational information. The experiments lead us to suggest that the notion of visual object should be widened to include the relations that the object has with surrounding objects. The results suggest a broadening of the parallel store model of visual short term memory proposed by Wheeler and Treisman (2002) to include the notion of what we call “structural gist”.