[show abstract][hide abstract] ABSTRACT: According to a traditional assumption about working memory, participants retain a series of verbal items for immediate recall using covert verbal rehearsal, without much need for attention. We reassessed this assumption by imposing a speeded, nonverbal choice reaction time (CRT) task following the presentation of each digit in a list to be recalled. When the memory load surpassed a few items, performance on the speeded CRT task became increasingly impaired. This CRT task impairment depended only on attention-related components of working memory; it was not alleviated by the presence of an auditory memory trace that automatically helped the recall of items at the ends of spoken lists. We suggest that attention-demanding refreshing of verbal stimuli occurs along with any covert rehearsal.
[show abstract][hide abstract] ABSTRACT: Verbal working memory may combine phonological and conceptual units. We disentangle their contributions by extending a prior procedure (Chen & Cowan, 2005) in which items recalled from lists of previously seen word singletons and of previously learned word pairs depended on the list length in chunks. Here we show that a constant capacity of about 3 chunks holds across list lengths and list types, provided that covert phonological rehearsal is prevented. What remains is a core verbal working-memory capacity.
[show abstract][hide abstract] ABSTRACT: We review the evidence for various kinds of limit in the capability of working memory, the small amount of information that can be held in mind at once. To distinguish between types of limit in working memory, we invoke metaphors of space (capacity), time (decay and speed), and energy (control of attention). The review focuses primarily on recent evidence on a limit in how many chunks can be held in working memory, how this kind of limit can be measured, and how it can be distinguished from other types of limits. We explore the theoretical and practical importance of different working memory limits in research that is nomothetic (referring to general laws) and ideographic (referring to individual and group differences). The appropriate measure of working memory depends on one's holistic or analytic scientific interest.
[show abstract][hide abstract] ABSTRACT: We assessed the contribution of two hypothesized mechanisms to impaired memory performance of older adults in an immediate serial recall task: decreased temporary information storage in a capacity-limited mechanism, such as the focus of attention, and a deficit in binding together different components into cohesive chunks. Using a method in which paired associations between words were taught at varying levels to allow an identification of multiword chunks (Cowan, Chen, & Rouder, 2004), we found that older adults recalled considerably fewer chunks and, on average, smaller chunks than did young adults. Their performance was fairly well simulated by dividing attention in younger adults, unlike what has been found for long-term associative learning. Paired-associate knowledge may be used in an implicit manner in serial recall, given that younger adults under divided attention and older adults use it well despite the relatively small chunk capacities displayed by these groups.
[show abstract][hide abstract] ABSTRACT: Whereas some research on immediate recall of verbal lists has suggested that it is limited by the number of chunks that can be recalled (e.g., N. Cowan, Z. Chen, & J. N. Rouder, 2004; E. Tulving & J. E. Patkau, 1962), other research has suggested that it is limited by the length of the material to be recalled (e.g., A. D. Baddeley, N. Thomson, & M. Buchanan, 1975). The authors investigated this question by teaching new paired associations between words to create 2-word chunks. The results suggest that both chunk capacity limits and length limits come into play. For the free recall of 12-word lists, 6 pre-learned pairs could be recalled about as well as 6 pre-exposed singletons, suggesting a chunk limit. However, for the serially ordered recall of 8-word lists, 4 pre-learned pairs could be recalled about as well as 8 pre-exposed singletons, suggesting a length limit. Other conditions yielded intermediate results suggesting that sometimes both limits may operate together.
Journal of Experimental Psychology Learning Memory and Cognition 11/2005; 31(6):1235-49. · 2.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: We assessed a hypothesis that working memory capacity should include a constant number of separate mental units, or chunks (cf. Miller, 1956). Because of the practical difficulty of measuring chunks, this hypothesis has not been tested previously, despite wide attention to Miller's article. We used a training procedure to manipulate the strength of associations between pairs of words to be included in an immediate serial-recall task. Although the amount of training on associations clearly increased the availability of two-item chunks and therefore the number of items correct in list recall, the number of total chunks recalled (singletons plus two-word chunks) appeared to remain approximately constant across association strengths, supporting a hypothesis of constant capacity.
[show abstract][hide abstract] ABSTRACT: Abstract We sketch our recent research leading towarda revision of the concept of working memory capacity. This includes a rationale for believing that working memory,capacity is a fundamental ability, and for estimating working memory based on the number of independent chunks of information recalled. We provide evidence that the often-noted relation between working memory,and both individual and developmental,differences in intellectual aptitudes does not depend on using a dual task to measure working memory, even though that has become a standard practice in the field. Basic intellectual aptitudes can be studied more cleanly using working-memory tasks that impede mnemonic strategies, so that a core capacity must come into play. Last, we offer evidence that this core capacitymay be attention serving as a storage device. Cowan et al., Page 2 What Do Estimates of Working Memory,Capacity Tell Us? ,Working memory,can be viewed as the collection of mental processes that preserve a limited amount of information in an especially accessible form, long enough for it to be of use in ongoing cognitive tasks. By almost all accounts,working memory is indeed a collection of processes (e.g., for diverse theoretical descriptions of working memory, see the chapters of Miyake & Shah 1999). In our laboratory, we have been investigating "flavors" of working