Academic journal article Memory & Cognition

Effects of Spatial Configurations on Visual Change Detection: An Account of Bias Changes

Academic journal article Memory & Cognition

Effects of Spatial Configurations on Visual Change Detection: An Account of Bias Changes

Article excerpt

In order to determine whether people encode spatial configuration information when encoding visual displays, in four experiments, we investigated whether changes in task-irrelevant spatial configuration information would influence color change detection accuracy. In a change detection task, when objects in the test display were presented in new random locations, rather than identical or different locations preserving the overall configuration, participants were more likely to report that the colors had changed. This consistent bias across four experiments suggested that people encode task-irrelevant spatial configuration along with object information. Experiment 4 also demonstrated that only a low-false-alarm group of participants effectively bound spatial configuration information to object information, suggesting that these types of binding processes are open to strategic influences.

In the last decade, the visual change detection paradigm has been widely used to investigate visuospatial working memory (e.g., Alvarez & Cavanagh, 2004; Awh, Barton, & Vogel, 2007; Jiang, Olson, & Chun, 2000; Luck & Vogel, 1997; Zhang & Luck, 2008). In visual change detection, individuals are asked to encode and remember a set of stimuli and then compare this set with a second set of stimuli and identify changes in object identities, their features, or their locations. Previous research has shown that task-irrelevant changes influence the likelihood of detecting task-relevant changes. This has been attributed to the fact that task-irrelevant information is sometimes maintained in short-term memory along with task-critical information. By looking at the effects of task-irrelevant spatial configuration changes on color change detection accuracy, we investigated whether and under which conditions spatial configuration information is maintained in visual short-term memory.

Recently Hyun and his colleagues have proposed a comprehensive model of visual change detection (Hyun, Woodman, Vogel, Hollingworth, & Luck, 2009). According to Hyun et al., viewers in a visual change detection task first encode the initial stimulus display. Then viewers form stable working memory representations from these early, relatively unstable perceptual representations. These representations are maintained during a retention interval. Then, when the second display is presented, viewers initially determine the correspondences between the two displays. That is, they identify which object from the first display should be compared with which object from the second display. Once correspondences are established, the viewer then detects whether a change is present. This is achieved via an unlimited-capacity system; thus, it is a relatively easy task. However, at this stage, the nature of the change is not yet identified. During a subsequent verification stage, the identity of the change is determined by a limited-capacity system. Once the change is identified, the appropriate decision rule is activated and the proper response is carried out (e.g., a keypress indicating a color change). Hyun et al. presented both behavioral and electrophysiological data to support the dissociation of the change detection and verification stages.

According to this model, erroneous change responses can occur with failures at the verification phase. Specifically, Hyun et al. (2009) showed that when there was only a task-irrelevant visual feature change, there was approximately a 10% increase in the proportion of change responses, suggesting that people had mistaken a task- irrelevant change for a task-critical one. On the basis of this finding, Hyun et al. concluded that "the irrelevant dimension was clearly encoded . . . even though it was maladaptive to do so" (p. 1154). Hyun and his colleagues explained that people can detect task-irrelevant feature changes and that these task-irrelevant changes can misguide viewers to give a change response when the exact identity of the change is not determined in the verification stage (Hyun et al. …

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