We Need Closure: Inequality in Perceptual Grouping for Visual Working Memory

摘要

Early research suggested a visual working memory (VWM) capacity limit of three to four objects (Luck & Vogel, 1997), but recent studies have indicated that the informational bandwidth of an object, which can vary with factors like complexity and amenability to perceptual grouping, can interact with this capacity (Brady, Konkle & Alvarez, 2011). For example, many individual features can be grouped into objects for an added benefit in VWM capacity (Xu, 2002). Along these lines, the Gestalt principles of proximity and connectedness have been shown to benefit VWM, although not necessarily in an equivalent manner (Xu 2006; Woodman, Vecera & Luck, 2003). The less explored principle of closure, akin to connectedness and proximity, promotes the perception of a coherent object without physical connections. In the current experiment, we evaluated whether closure produces similar or greater VWM capacity advantages compared to proximity by having participants engage in a change detection task. Four L-shaped features were grouped in tilted clusters to either form an object (object condition) or not (no-object condition), with a set size of either four (16 L features) or six clusters (24 L features). Following a brief mask (1000 ms), the orientation of one cluster was changed (tilted 20 or -20 degrees) on half of the trials. Participants were more accurate to report the change when features induced a sense of closure (58.89% set size 4, 55.09% set size 6) compared to when they did not (54.07% set size 4, 51.20% set size 6), suggesting that closure affords better VWM benefits than proximity. As evidenced through this subtle manipulation to feature groupings, our data suggests that perceptual grouping by closure is valid for forming objects representations, and, in at least some cases, it perhaps provides a greater indicator of "objectness" than other factors, such as feature proximity.