Candice Coker Morey

On the Capacity of Attention: Its Estimation and Its Role in Working Memory and Cognitive Aptitudes

Working memory (WM) is the set of mental processes holding limited information in a temporarily accessible state in service of cognition. We provide a theoretical framework to understand the relation between WM and aptitude measures. The WM measures that have yielded high correlations with aptitudes include separate storage-and-processing task components, on the assumption that WM involves both storage and processing. We argue that the critical aspect of successful WM measures is that rehearsal and grouping processes are prevented, allowing a clearer estimate of how many separate chunks of information the focus of attention circumscribes at once. Storage-and-processing tasks correlate with aptitudes, according to this view, largely because the processing task prevents rehearsal and grouping of items to be recalled. In a developmental study, we document that several scope-of-attention measures that do not include a separate processing component, but nevertheless prevent efficient rehearsal or grouping, also correlate well with aptitudes and with storage-and-processing measures. So does digit span in children too young to rehearse.

An assessment of fixed-capacity models of visual working memory

Visual working memory is often modeled as having a fixed number of slots. We test this model by assessing the receiver operating characteristics (ROC) of participants in a visual-working-memory change-detection task. ROC plots yielded straight lines with a slope of 1.0, a tell-tale characteristic of all-or-none mnemonic representations. Formal model assessment yielded evidence highly consistent with a discrete fixed-capacity model of working memory for this task.

How to measure working memory capacity in the change detection paradigm

Although the measurement of working memory capacity is crucial to understanding working memory and its interaction with other cognitive faculties, there are inconsistencies in the literature on how to measure capacity. We address the measurement in the change detection paradigm, popularized by Luck and Vogel (Nature, 390, 279–281, 1997). Two measures for this task—from Pashler (Perception & Psychophysics, 44, 369–378, 1988) and Cowan (The Behavioral and Brain Sciences, 24, 87–114, 2001), respectively—have been used interchangeably, even though they may yield qualitatively different conclusions. We show that the choice between these two measures is not arbitrary. Although they are motivated by the same underlying discrete-slots working memory model, each is applicable only to a specific task; the two are never interchangeable. In the course of deriving these measures, we discuss subtle but consequential flaws in the underlying discrete-slots model. These flaws motivate revision in the modal model and capacity measures.

When visual and verbal memories compete: Evidence of cross-domain limits in working memory

Recently, investigators have suggested that visual working memory operates in a manner unaffected by the retention of verbal material. We question that conclusion on the basis of a simple dual-task experiment designed to rule out phonological memory and to identify a more central faculty as the source of a shared limitation. With a visual working memory task in which two arrays of color squares were to be compared, performance was unaffected by concurrent recitation of a two-digit list or a known seven-digit sequence. However, visual working memory performance decreased markedly when paired with a load of seven random digits. This was not a simple tradeoff, inasmuch as errors on the visual array and high digit load tasks tended to co-occur. Working memory for digits and visual information thus are both subject to at least one type of shared limit, not just domain-specific limitations. The nature of the shared limit is discussed.

When Do Visual and Verbal Memories Conflict?: The Importance of Working-Memory Load and Retrieval.

Examinations of interference between verbal and visual materials in working memory have produced mixed results. If there is a central form of storage (e.g., the focus of attention; N. Cowan, 2001), then cross-domain interference should be obtained. The authors examined this question with a visual-array comparison task (S. J. Luck & E. K. Vogel, 1997) combined with various verbal memory load conditions. Interference between tasks occurred if there was explicit retrieval of the verbal load during maintenance of a visual array. The effect was localized in the maintenance period of the visual task and was not the result of articulation per se. Interference also occurred when especially large silent verbal and visual loads were held concurrently. These results suggest central storage along with code-specific passive storage.

Seven-year-olds allocate attention like adults unless working memory is overloaded

Previous studies have indicated that visual working memory performance increases with age in childhood, but it is not clear why. One main hypothesis has been that younger children are less efficient in their attention; specifically, they are less able to exclude irrelevant items from working memory to make room for relevant items. We examined this hypothesis by measuring visual working memory capacity under a continuum of five attention conditions. A recognition advantage was found for items to be attended as opposed to ignored. The size of this attention-related effect was adult-like in young children with small arrays, suggesting that their attention processes are efficient even though their working memory capacity is smaller than that of older children and adults. With a larger working memory load, this efficiency in young children was compromised. The efficiency of attention cannot be the sole explanation for the capacity difference.

Visual working memory depends on attentional filtering

Working memory holds information actively being used in cognitive performance. Two important aspects of working memory are how many items it can hold, and how efficiently it can be used. Recently, Vogel and colleagues used event-related brain potentials to show that these two things are related. People who could remember more objects from a spatial array also more efficiently excluded irrelevant objects. The results raise important questions about what aspect of working memory is most fundamental.

How Can Dual-Task Working Memory Retention Limits Be Investigated?

Resource limitations are assessed by examining performance on concurrent tasks. Pitfalls in attributing dual-task conflicts to central attention rather than specific processing conflicts (Navon, 1984; Norman & Bobrow, 1975) are often underestimated. In this report, we identify a limitation in the interpretation of existing dual-task studies of working memory and describe a dual-task procedure that may be the first to assess concurrentretention costs fairly. Our results support claims of a central capacity (e.g., Baddeley, 2001; Cowan, 2001) and challenge evidence for certain task-specific limits. In dual-task procedures for studying working memory, two stimulus sets are presented in succession, to be retained concurrently, and memory for one or both sets is tested. Concurrentretention costs are decrements in memory performance on one set caused by the need to retain the other set concurrently. Concurrent-retention costs are larger when the two sets share many features (e.g., two spatial arrays or two verbal lists) than when they share few features (e.g., one spatial array and one verbal list; Baddeley & Hitch, 1974; Cocchini, Logie, Delia Sala, MacPherson, & Baddeley, 2002; Fougnie & Marois, 2006). Does this mean that working memory storage is largely domainspecific? Perhaps not. Although the theoretically relevant demand in dual-task studies of working memory is concurrent retention in two tasks, performance also could suffer from the inevitable overlap between retention in one task and encoding or responding in the other task. Set 2 encoding occurs in the presence of Set 1 retention, and responding to whichever set is tested first suffers from concurrent retention of the other set (which, in turn, suffers from response interference). If encoding or responding depends on the same resource as retention, dual-task conflicts are not solely due to the difficulty of concurrent retention. We sought to isolate effects of dual retention without any possible contribution of conflicts with encoding or responding, and to assess whether the effects of dual-task retention depend on intertask similarity. Because we collected only one response per trial, the overlap between responding and retention was eliminated. A more difficult problem was the overlap between Task 2 encoding and Task 1 retention. Our solution was to present four events on every trial in which two stimulus sets were included: Stimulus Set 1; Stimulus Set 2; a postcue to retain Set 1 only, Set 2 only, or both sets; and a memory test on one retained set. With this procedure, demands during encoding and responding are identical on trials with two stimulus sets when the postcue instruction is to retain a single set and when the postcue instruction is to retain both sets.

The Peer Reviewers’ Openness Initiative: Incentivizing open research practices through peer review

Openness is one of the central values of science. Open scientific practices such as sharing data, materials and analysis scripts alongside published articles have many benefits, including easier replication and extension studies, increased availability of data for theory-building and meta-analysis, and increased possibility of review and collaboration even after a paper has been published. Although modern information technology makes sharing easier than ever before, uptake of open practices had been slow. We suggest this might be in part due to a social dilemma arising from misaligned incentives and propose a specific, concrete mechanism—reviewers withholding comprehensive review—to achieve the goal of creating the expectation of open practices as a matter of scientific principle.

Flexible attention allocation to visual and auditory working memory tasks: manipulating reward induces a trade-off

Prominent roles for general attention resources are posited in many models of working memory, but the manner in which these can be allocated differs between models or is not sufficiently specified. We varied the payoffs for correct responses in two temporally-overlapping recognition tasks, a visual array comparison task and a tone sequence comparison task. In the critical conditions, an increase in reward for one task corresponded to a decrease in reward for the concurrent task, but memory load remained constant. Our results show patterns of interference consistent with a trade-off between the tasks, suggesting that a shared resource can be flexibly divided, rather than only fully allotted to either of the tasks. Our findings support a role for a domain-general resource in models of working memory, and furthermore suggest that this resource is flexibly divisible.