Nelson Cowan is the Curators' Distinguished Professor Emeritus of Psychological Sciences at the University of Missouri. He specializes in working memory, the small amount of information held in mind and used for language processing and various kinds of problem solving. To overcome conceptual difficulties that arise for models of information processing in which different functions occur in separate boxes, Cowan proposed a more organically organized "embedded processes" model. Within it, representations held in working memory comprise an activated subset of the representations held in long-term memory, with a smaller subset held in a more integrated form in the current focus of attention. Other work has been on the developmental growth of working memory capacity and the scientific method. His work, funded by the National Institutes of Health since 1984 (primarily NICHD), has been cited over 66,000 times according to Google Scholar. The work has resulted in over 250 peer-reviewed articles, over 60 book chapters, 2 sole-authored books, and 4 edited volumes. In addition to basic scientific work, Cowan's collaborative research related to working memory has led to clarification of the role of memory in language disorders, dyslexia, autism, schizophrenia, Parkinson's disease, amnesia, and alcoholic intoxication, as explained further on his web site and CV. For example, the work on amnesia indicates that individuals who usually cannot form new memories because of stroke or brain damage often demonstrate considerable ability to do so when the information to be memorized is surrounded by several minutes with minimal visual or acoustic interference.
Main scientific contributions
Working memory capacity limits Cowan's theoretical model addresses key puzzles in information processing using a new approach in which there are two aspects of working memory: the activated portion of long-term memory, which includes rapidly-learned information limited only by decay and interference among similar features and, within this activated portion, a focus of attention limited to about 3-4 separate items or chunks in typical adults. Cowan contends that previous models did not sufficiently distinguish between these temporary-storage mechanisms. In this theory, why is there interference between words and visual objects like colors when both are held in mind? Because the focus of attention is involved in maintaining information of all types and, when the procedure discourages mnemonic strategies like grouping and rehearsal, the focus of attention is limited to just a few separate units of information - as argued in a review cited over 6,900 times according to Google Scholar. In the brain, an area of the intraparietal sulcus plays a large role in the focus of attention, perhaps serving as an index connected to posterior areas representing the content of active memories.
Attention filtering by habituation of orienting In another part of the theory of Cowan, conceptual difficulties of the idea of an attention filter were addressed. If unattended information is filtered out, how can it come to attract attention? In the theory, the attention filter is replaced by the well-known mechanism of orienting of attention. Stimuli with changed physical features attract attention, whereas stimulus features or patterns that are repeated or continuous become a part of the neural model of the environment; there is habituation of the orienting response, and such stimuli stop attracting attention. For example, Emily Elliott and Cowan showed that pre-exposure to sounds to be used as distractors reduced their capability to distract. In another kind of research on attention, Noelle Wood and Cowan replicated an often-discussed but until then poorly-understood phenomenon termed the cocktail party phenomenon. Using methodology improved from the 1950s, they found that people take a long time to notice subtle acoustic changes in an ignored channel of speech while repeating different speech presented in the other ear, a selective listening task. They also used the improved methodology to replicate the early, poorly-studied finding that about a third of participants notice their names unexpectedly presented in a channel to be ignored . That finding, however, was ambiguous. It could be that high-working-memory-span individuals are better able to monitor the channel to be ignored, or it could be that the low-span individuals cannot fix their attention on the assigned task, so that it wanders over intermittently to sample the channel to be ignored. The results have come out strongly in that direction, with many more low-span individuals noticing their names in the ignored channel. Proving that the results did not have to turn out that way, they were different for healthy older adults; their spans are like relatively low-span younger adults, yet the older adults rarely noticed their names in the channel to be ignored, suggesting that their focus of attention is strategically intact but with possibly a smaller capacity than young adults.
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