The Role of Attentional Priority and Saliency in Determining Capacity Limits in Enumeration and Visual Working Memory

Abstract

Many common tasks require us to individuate in parallel two or more objects out of a complex scene. Although the mechanisms underlying our abilities to count the number of items, remember the visual properties of objects and to make saccadic eye movements towards targets have been studied separately, each of these tasks require selection of individual objects and shows a capacity limit. Here we show that a common factor—salience—determines the capacity limit in the various tasks. We manipulated bottom-up salience (visual contrast) and top-down salience (task relevance) in enumeration and visual memory tasks. As one item became increasingly salient, the subitizing range was reduced and memory performance for all other less-salient items was decreased. Overall, the pattern of results suggests that our abilities to enumerate and remember small groups of stimuli are grounded in an attentional priority or salience map which represents the location of important items.

Changing concepts of working memory

“…Similar recall advantages and costs have been observed for objects that are visually salient 11,26,29 , even when test probability is equal, indicating an automatic component to memory allocation that might be linked to visual attention. Further evidence that resource is associated with allocation of visual attention has arisen from demonstration of recall advantages for targets of saccades 11,29,30 and for targets of covert shifts of attention, as inferred from micro-saccades 25 .…”

Developmental changes in visual short-term memory in infancy: evidence from eye-tracking

“…Individuation may be necessary before items can be encoded into VSTM (Xu and Chun, 2009) and may underlie the capacity limitations in a number of tasks including VSTM and subitizing (Melcher and Piazza, 2011; Ester et al, 2012). Moreover, the posterior parietal cortex is important for these individuation processes in adults (Xu, 2009; Xu and Chun, 2009), and the extant evidence suggests dramatic changes in parietal regions in human infants in the first 6 months of postnatal development.…”

The temporal window of individuation limits visual capacity

“…Specifically, capacity limits may reflect the spatial and temporal nature of attentional priority (saliency) maps in PPC (Melcher and Piazza, 2011; Franconeri et al, 2013; Knops et al, 2014). Unlike the priority maps in early visual areas (Zhang et al, 2012), attention priority maps in parietal cortex are thought to integrate bottom-up and top-down saliency estimates for objects over time (Bogler et al, 2011), allowing for object information to be accumulated and maintained (Mirpour et al, 2009; van Koningsbruggen et al, 2010).…”