Academic journal article Attention, Perception and Psychophysics

Sequential Dynamics in Visual Short-Term Memory

Academic journal article Attention, Perception and Psychophysics

Sequential Dynamics in Visual Short-Term Memory

Article excerpt

Published online: 17 September 2014

© The Psychonomic Society, Inc. 2014

Abstract Visual short-term memory (VSTM) is thought to help bridge across changes in visual input, and yet many studies of VSTM employ static displays. Here we investigate how VSTM copes with sequential input. In particular, we characterize the temporal dynamics of several different components of VSTM performance, including: storage probability, precision, variability in precision, guessing, and swapping. We used a variant of the continuous-report VSTM task developed for static displays, quantifying the contribution of each component with statistical likelihood estimation, as a function of serial position and set size. In Experiments 1 and 2, storage probability did not vary by serial position for small set sizes, but showed a small primacy effect and a robust recency effect for larger set sizes; precision did not vary by serial position or set size. In Experiment 3, the recency effect was shown to reflect an increased likelihood of swapping out items from earlier serial positions and swapping in later items, rather than an increased rate of guessing for earlier items. Indeed, a model that incorporated responding to non-targets provided a better fit to these data than alternative models that did not allow for swapping or that tried to account for variable precision. These findings suggest that VSTM is updated in a first-in-first-out manner, and they bring VSTM research into closer alignment with classical working memory research that focuses on sequential behavior and interference effects.

Keywords Visual short-term memory * Working memory . Sequential dynamics . Retroactive interference . Computational modeling

(ProQuest: ... denotes formulae omitted.)

Introduction

Visual input is constantly in flux, with frequent changes occurring due to eye movements, locomotion and object mo- tion. Visual short-term memory (VSTM)-a subset of the working memory (WM) system that maintains visual infor- mation for a few seconds with relatively low executive de- mands-has often been proposed to help bridge across such changes. For example, VSTM plays a key role in integrating information across saccadic eye movements (Irwin, 1991), possibly by aligning subsequent snapshots of visual informa- tion (Henderson & Hollingworth, 1999). However, despite its oft-cited role in dynamic visual processing, few studies have examined how VSTM deals with input that is intrinsically dynamic (cf. Kumar & Jiang, 2005; Woodman, Vogel, & Luck, 2012;Xu&Chun,2006).

Recent years have seen great advances in scientific knowl- edge about VSTM. The hallmark property of VSTM is that its storage capacity is exceedingly limited, as evidenced by a marked drop in performance when people are asked to re- member more than 3-4 items (Cowan, 2001;Luck&Vogel, 1997). Some researchers have argued that this capacity limit reflects a fixed number of items that the system can maintain (Awh, Barton, & Vogel, 2007; Cowan, 2001; Fukuda, Awh, & Vogel, 2010; Luck & Vogel, 1997; Zhang & Luck, 2008), whereas others argue that it reflects a limited resource that can be distributed flexibly among any number of items (Alvarez & Cavanagh, 2004; Bays, Catalao, & Husain, 2009; Bays & Husain, 2008, 2009; Fougnie, Suchow, & Alvarez, 2012; Frick, 1988; van den Berg, Shin, Chou, George, & Ma, 2012).

This research provided important findings and behavioral paradigms, but, for the most part, focused on static memory arrays in which all items are presented simultaneously. Because of the dynamic nature of visual information, it is important to examine how VSTM deals with such input. How does the system deploy its limited capacity in a dynamic environment? In what way is a sequence of incoming infor- mation processed and maintained over time?

Similar questions have long been entertained in research on the more canonical form of WM-a system dependent on prefrontal cortex that maintains and manipulates information in the service of goal-directed behavior (Baddeley, 2003). …

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