The role of global layout in visual short-term memory

Among the most fundamental questions we can address in visual cognition research is what the basic unit of analysis is for a particular visual function. Work on visual memory has contrasted three candidate units: objects, spatial locations, and feature dimensions. An implicit assumption in this search for the basic units of memory is that the units are independent: whether objects, locations, or features are the basic unit of analysis, presumably each unit is encoded and stored in memory independently of the others. Although some earlier research suggested that visual short-term memory operates over discrete objects (Lee & Chun, 2001; Luck & Vogel, 1997), more recent work suggests that the independence assumption may be false. Specifically, it appears that the spatial relationship between objects plays a role in memory for both spatial and featural information about objects. For example, disrupting the spatial layout of a display between the study display and the test display interferes with retrieval of both the location and the identity of objects (e.g., Jiang, Olson, & Chun, 2000).