In the last decade, major strides have been made in understanding visual working memory through mathematical modeling of color production responses. In the delayed color estimation task (Wilken & Ma, 2004), participants are given a set of colored squares to remember and a few seconds later asked to reproduce those colors by clicking on a color wheel. The degree of error in these responses is characterized with mathematical models that estimate working memory precision and the proportion of items remembered by participants. A standard mathematical model of color memory assumes that items maintained in memory are remembered through memory for precise details about the particular studied shade of color. We contend that this model is incomplete in its present form because no mechanism is provided for remembering the coarse category of a studied color. In the present work we remedy this omission and present a model of visual working memory that includes both continuous and categorical memory representations. In two experiments we show that our new model outperforms this standard modeling approach, which demonstrates that categorical representations should be accounted for by mathematical models of visual working memory.

We re-examine the role of time in the loss of information from working memory, the limited information accessible for cognitive tasks. The controversial issue of whether working memory deteriorates over time was investigated using arrays of unconventional visual characters. Each array was followed by a post-perceptual mask, a variable retention interval (RI), and a recognition probe character. Dramatic forgetting across an unfilled RI of up to 6 s was observed. Adding a distracting task during the RI (repetition, subtraction, or parity judgment using spoken digits) lowered the level of recall, but not increasingly so across RIs. Also, arrays of English letters were not forgotten during the RI unless distracting stimuli were included, in contrast to the finding for unconventional characters. The results suggest that unconventional visual items include some features inevitably lost over time. Attention-related processing, however, assists in the retention of other features, and of English letters. We identify important constraints for working memory theories and propose that an equilibrium between forgetting and reactivation holds, but only for elements that are not inevitably lost over time.

Understanding forgetting from working memory, the memory used in ongoing cognitive processing, is critical to understanding human cognition. In the last decade a number of conflicting findings have been reported regarding the role of time in forgetting from working memory. This has led to a debate concerning whether longer retention intervals necessarily result in more forgetting. An obstacle to directly comparing conflicting reports is a divergence in methodology across studies. Studies which find no forgetting as a function of retention-interval duration tend to use sequential presentation of memory items, while studies which find forgetting as a function of retention-interval duration tend to use simultaneous presentation of memory items. Here, we manipulate the duration of retention and the presentation method of memory items, presenting items either sequentially or simultaneously. We find that these differing presentation methods can lead to different rates of forgetting because they tend to differ in the time available for consolidation into working memory. The experiments detailed here show that equating the time available for working memory consolidation equates the rates of forgetting across presentation methods. We discuss the meaning of this finding in the interpretation of previous forgetting studies and in the construction of working memory models.

Why does visual working memory performance increase with age in childhood? One recent study ruled out the possibility that the basic cause is a tendency in young children to clutter working memory with less-relevant items (within a concurrent array, colored items presented in one of two shapes). The age differences in memory performance, however, theoretically could result from inadequate encoding of the briefly-presented array items by younger children. We replicated the key part of the procedure in children 6-8 and 11-13 years old and college students (total N=90), but with a much slower, sequential presentation of the items to ensure adequate encoding. We also required verbal responses during encoding to encourage or discourage labeling of item information. Although verbal labeling affected performance, age differences persisted across labeling conditions, further supporting the existence of a basic growth in capacity.It is well-accepted that younger children perform more poorly than older children and adults on tests of working memory, the current-task information kept in an active state for shortterm recall. It is clear that the development of working memory ability is an important component of cognitive development across many tasks (e.g., Andrews & Halford, 2002;Cowan et al., 2005Gathercole, Pickering, Ambridge, & Wearing, 2004;Hitch, Towse, & Hutton, 2001;Johnson, Im-Bolter, & Pascual-Leone, 2003). What has been more controversial for many years is the reason behind the age differences in working memory performance. One simple hypothesis, the one advocated here, is that some brain system operates by retaining a limited number of items in an active form, and that this brain system holds fewer items in young children than in older participants (e.g., Burtis, 1982;Case, 1995;Cowan, 2001;Pascual-Leone & Smith, 1969). The notion that there is a working memory faculty limited to no more than a few items is supported by considerable recent research in adults (Awh, Barton, & Vogel, 2007;Cowan & Rouder, 2009;Rouder et al., 2008;Zhang & Luck, 2008; for an opposing view see Bays & Husain, 2008).The challenge for advocates of a capacity-growth hypothesis, however, is that it is not logically necessary; other possibilities exist (e.g., Barrouillet, Gavens, Vergauwe, Gaillard, & Camos, 2009;Case, Kurland, & Goldberg, 1982;Dempster, 1991;Hulme & Tordoff, 1989). The older participants may excel at focusing on more task-relevant information, in which case the holding system in the brain may be more cluttered by information irrelevant to the task at hand in younger children. Also, older participants may be better able to encode the stimuli in a manner that allows the information to be retrieved. In particular, they may form verbal labels for the stimuli that allow these stimuli to be retained using multiple brain systems, adding redundancy to the representation and making recall more reliable. In fact, Flavell, Beach, & Chinsky, 1966;Ornstein, Naus, & Liberty, 1975;Tam, Jarrold, Baddeley, & Sabatos-DeVito, 2010)...

Short-term consolidation is the process by which stable working memory representations are created. This process is fundamental to cognition yet poorly understood. The present work examines short-term consolidation using a Bayesian hierarchical model of visual working memory recall to determine the underlying processes at work. Our results show that consolidation functions largely through changing the proportion of memory items successfully maintained until test. Although there was some evidence that consolidation affects representational precision, this change was modest and could not account for the bulk of the consolidation effect on memory performance. The time course of the consolidation function and selective influence of consolidation on specific serial positions strongly indicates that short-term consolidation induces an attentional blink. The blink leads to deficits in memory for the immediately following item when time pressure is introduced. Temporal distinctiveness accounts of the consolidation process are tested and ruled out. (PsycINFO Database Record