Academic journal article Attention, Perception and Psychophysics

Effect of Decision Load on Whole-Display Superiority in Change Detection

Academic journal article Attention, Perception and Psychophysics

Effect of Decision Load on Whole-Display Superiority in Change Detection

Article excerpt

Published online: 13 February 2015

© The Psychonomic Society, Inc. 2015

Abstract Visual short-term memory (VSTM) refers to our ability in remembering visual information for a limited amount of time. In the VSTM literature, mixed findings have been reported regarding whether items are encoded individually or globally in the context of other items. This study adopted a color change detection task and manipulated color and spatial relations of the items on display to test whether inter-item relational information and processing can facilitate change detection performance. Results showed that only when a post-cue was presented to reduce decision load (Experiments 1 and 3), both color and spatial relations facilitated color change detection. However, when there was no post-cue to lessen the decision load, preserving spatial relations at test impaired color change detection (Experiment 2). Furthermore, spatial and color relational processing interactively affected color change detection. Benefit of the spatial relations was observed only when color grouping cues can aid change detection, and the utilization of color relations was optimized when spatial relations were preserved to cue the retrieval of color relations. Our results support the hierarchical representation hypothesis, which assumes that both individual items and item relations are encoded and maintained in VSTM. The amount of cognitive resources for retrieving different levels of representations is highly constrained by the decision load.

Keywords Change detection . Color grouping . Spatial configuration . Visual short-term memory


When one views a brief display of multiple items, are the items encoded individually or are they encoded globally with inter-item relations? This question has to do with the fundamental nature of visual short-term memory (VSTM), the temporary storage buffer that stores visual information for retrieval and manipulation, and is an essential element to our visual awareness. Ever since Phillips began a series of experiments on VSTM (Phillips 1974), studies investigating the nature of VSTM have flourished in the past four decades, mostly focusing on three different but interrelated aspects of VSTM: 1) capacity, 2) precision, and 3) contents and organization (for a comprehensive review covering all these areas, please see Luck, 2008). Of these different aspects, contents and organization are the most fundamental of all, because the way information is encoded and organized in VSTM has a direct impact on its capacity and precision. For example, whether items are encoded individually (Woodman, Vogel, & Luck, 2012)or globally with item relations (Brady & Alvarez, 2011;Brady, Konkle, & Alvarez, 2011; Brady & Tenenbaum, 2013; Clevenger & Hummel, 2014; Jiang, Olson, & Chun, 2000) may ultimately decide how many items can be stored (capacity) and how detailed their representations can be (precision).

The literature does not have a coherent account regarding the contents and organization of VSTM yet. We outline two hypotheses that have each gained empirical support. First, the independent encoding hypothesis specifies that each individual item is encoded and stored independent of each other (Woodman et al., 2012). This idea can be viewed as an extension of the slot-based model (Luck & Vogel, 1997)thatspecifies a fixed number of slots (3-4 objects) in VSTM (Cowan, Chen, & Rouder, 2004). Based on the idea of object-based VSTM (Walker & Davies, 2003;Xu,2002), this hypothesis states that the basic units of VSTM are objects rather than features. Thus, each object, regardless of the number of its features, is encoded as a whole yet separate from other object representations. Although not explicitly stated, this also is the underlying assumption across different estimating functions for VSTM capacity (Cowan, 2001; Cowan et al., 2004; Pashler, 1988). Consequently, the independent encoding hypothesis predicts that the encoding and storage of one particular item will not be influenced by the same processes for other items (e. …

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