A review of visual memory capacity: Beyond individual items and toward structured representations

Abstract

Traditional memory research has focused on identifying separate memory systems and exploring different stages of memory processing. This approach has been valuable for establishing a taxonomy of memory systems and characterizing their function, but has been less informative about the nature of stored memory representations. Recent research on visual memory has shifted towards a representation-based emphasis, focusing on the contents of memory, and attempting to determine the format and structure of remembered information. The main thesis of this review will be that one cannot fully understand memory systems or memory processes without also determining the nature of memory representations. Nowhere is this connection more obvious than in research that attempts to measure the capacity of visual memory. We will review research on the capacity of visual working memory and visual long-term memory, highlighting recent work that emphasizes the contents of memory. This focus impacts not only how we estimate the capacity of the system - going beyond quantifying how many items can be remembered, and moving towards structured representations - but how we model memory systems and memory processes.

Perceptual consciousness overflows cognitive access

“…Alvarez and Cavanagh [77] showed (see Figure I) that how many object-representations are held in working memory and their resolution depends on their complexity, with a 4 item limit for colors but a 2 item limit for 3-D cubes [73,77], disconfirming a simple 'slot' model [78,79]. The work reported in Figure I suggests a limit between 4 and 5 for ideally simple items.…”

“…The work reported in Figure I suggests a limit between 4 and 5 for ideally simple items. More recent work suggests a more complex version of a model that combines something like slots with hierarchical structures representing objects and their properties [79,80]. The work discussed in the main text concerning three forms of visual short-term memory separately estimates variants of iconic memory and working memory.…”

Parietal Contributions to Visual Working Memory Depend on Task Difficulty

“…Given this central role, cognitive researchers have devoted considerable efforts developing and refining theoretical models of WM (for reviews see Baddeley and Hitch, 1974;Cowan, 1993;Baddeley, 2000;Miyake et al, 2001;Oberauer, 2002;Curtis and D'Esposito, 2003;Cowan et al, 2005;Chein and Fiez, 2010). More recent work has focused on extending cognitive models to identify the neural correlates of WM, including the contributions of the inferior and superior parietal lobes comprising posterior parietal cortex (PPC; for reviews see Jonides et al, 1993;Cohen et al, 1997;Courtney et al, 1997;Ungerleider et al, 1998;Chein and Fiez, 2001;Munk et al, 2002;Pessoa et al, 2002;Linden et al, 2003;Sala et al, 2003;Olson and Berryhill, 2009;Brady et al, 2011). WM studies commonly identify PPC activations in functional magnetic resonance imaging (fMRI), yet only recently have these activations been functionally associated with WM rather than attention (Wager and Smith, 2003;Marois, 2004, 2005;Song and Jiang, 2006;Xu and Chun, 2006;Xu, 2007Xu, , 2009.…”

Gestalt Effects in Visual Working Memory

“…An important area of evidence regarding factors that influence actual VWM capacity pertains to the influence of global organization of perceptual scene, that is, the fact that objects are not stored in memory independently from other items, but there exist substantial contextual effects (Brady, Konkle, & Alvarez, 2011). For example, when context of an item (e.g., surrounding objects) changes or disappears between the to-be-memorized scene and the probe scene, retrieval of this item is worse than when the unchanged context accompanies the probe (Jiang, Olson, & Chun, 2000).…”