2
Book re~~iew.~ /Acta Psychologica 85 (1994) 263-268 267 References Adams, J., 1979. Conceptual blockbusting. New York: W.W. Norton. Gehani, R., 1993. Fighting fires. OR/MS Today, June, 8-9. Gettys, C.F., R.M. Pliske, C. Manning and J.T. Casey, 1987. An evaluation of human act generation performance. Organizational Behavior and Human Decision Processes 39. 23-51. SSDI OOOl-6918(93)E0053-5 C. Hulme and S. Mackenzie, Working Memory and Ser:ere Learning Difficulties. Erlbaum, Hillsdale, NJ, 1992. In this small monograph, Charles Hulme and Susan Mackenzie describe some new research on the development of working memory and its relation to memory span. They focus their discussion on the role of working memory skills (or the lack thereof) in the cognitive development of children with very low IQ’s, i.e. IQ’s below 50. Such children have been referred to in the past as idiots or imbeciles, as mentally subnormal or as mental retardates. In the UK, such persons are now described (at least when their IQ is above 20) as having ‘severe learning difficul- ties’ (SLD). This group includes persons with Down’s syndrome (30%), other chromosomal and genetic disorders as well as prenatal and postnatal infections (e.g. maternal rubella). Hulme and Mackenzie convincingly argue that children with severe learning difficulties have specific problems with rehearsal processes in verbal memory span tasks. Their research is based on the working memory framework proposed by Baddeley and Hitch, and in particular on the articulatory loop component in Baddeley and Hitch’s model of short-term memory. This articulatory loop (a system for recycling or rehearsing verbal information) is crucial for performance in memory span tasks. Previous research has shown that the verbal memory span is quite accurately predicted by the number of words or items that subjects can pronounce in approximately two seconds. After a brief introduction to working memory and the memory span task, Hulme and Mackenzie review previous research on developmental trends in memory span, that shows that the increase in memory span can be explained by increases in articulation speed. Such increases make it possible to rehearse (refresh) the memory representations of the items before they will have decayed too much. They argue that persons with severe learning deficits have particular problems with short-term memory tasks and that this can be explained by assuming that this is a deficit in the use of articulatory rehearsal. They next present five experiments that demonstrate that memory span does not increase much in children with severe learning difficulties (both Down’s syndrome as well as of mixed aetiology) compared with children matched with respect to mental age and, further, that training in articulatory rehearsal leads to improve- ments on memory span measures (although simply repeated testing leads to nearly

Working memory and severe learning difficulties: C. Hulme and S. Mackenzie, Erlbaum, Hillsdale, NJ, 1992

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Page 1: Working memory and severe learning difficulties: C. Hulme and S. Mackenzie, Erlbaum, Hillsdale, NJ, 1992

Book re~~iew.~ /Acta Psychologica 85 (1994) 263-268 267

References

Adams, J., 1979. Conceptual blockbusting. New York: W.W. Norton.

Gehani, R., 1993. Fighting fires. OR/MS Today, June, 8-9.

Gettys, C.F., R.M. Pliske, C. Manning and J.T. Casey, 1987. An evaluation of human act generation performance. Organizational Behavior and Human Decision Processes 39. 23-51.

SSDI OOOl-6918(93)E0053-5

C. Hulme and S. Mackenzie, Working Memory and Ser:ere Learning Difficulties.

Erlbaum, Hillsdale, NJ, 1992.

In this small monograph, Charles Hulme and Susan Mackenzie describe some new research on the development of working memory and its relation to memory span. They focus their discussion on the role of working memory skills (or the lack thereof) in the cognitive development of children with very low IQ’s, i.e. IQ’s below 50. Such children have been referred to in the past as idiots or imbeciles, as mentally subnormal or as mental retardates. In the UK, such persons are now described (at least when their IQ is above 20) as having ‘severe learning difficul- ties’ (SLD). This group includes persons with Down’s syndrome (30%), other chromosomal and genetic disorders as well as prenatal and postnatal infections (e.g. maternal rubella). Hulme and Mackenzie convincingly argue that children with severe learning difficulties have specific problems with rehearsal processes in verbal memory span tasks. Their research is based on the working memory framework proposed by Baddeley and Hitch, and in particular on the articulatory loop component in Baddeley and Hitch’s model of short-term memory. This articulatory loop (a system for recycling or rehearsing verbal information) is crucial for performance in memory span tasks. Previous research has shown that the verbal memory span is quite accurately predicted by the number of words or items that subjects can pronounce in approximately two seconds. After a brief introduction to working memory and the memory span task, Hulme and Mackenzie review previous research on developmental trends in memory span, that shows that the increase in memory span can be explained by increases in articulation speed. Such increases make it possible to rehearse (refresh) the memory representations of the items before they will have decayed too much. They argue that persons with severe learning deficits have particular problems with short-term memory tasks and that this can be explained by assuming that this is a deficit in the use of articulatory rehearsal. They next present five experiments that demonstrate that memory span does not increase much in children with severe learning difficulties (both Down’s syndrome as well as of mixed aetiology) compared with children matched with respect to mental age and, further, that training in articulatory rehearsal leads to improve- ments on memory span measures (although simply repeated testing leads to nearly

Page 2: Working memory and severe learning difficulties: C. Hulme and S. Mackenzie, Erlbaum, Hillsdale, NJ, 1992

as large an increase). Although the experiments are well designed and represent a clever application of basic memory research to the area of severe learning difficulties, the results are not entirely clear-cut and do not provide unambiguous support for the hypothesis (as is the case for most experiments). The authors conclude with a review of the research findings and its implications for the understanding of the memory problems in severe learning difficulties and the general working memory framework. While reading this book, 1 kept asking myself why the authors decided to publish their research as a monograph. It seems to me that it would have been more appropriate to present the work as one or two regular research articles. One of the reasons for this is that the results are not conclusive which is what I would expect in a monograph. The second. and perhaps more important, reason is that the research focuses on only a small aspect of working memory. Perhaps this should not be held too much against the present authors since it is a characteristic of much of the research within the working memory framework. Although this approach started out as an attempt to specify the role of short-term memory processes in the performance of complex mental tasks such as reading or compre- hension, it has in fact paid only lip-service to these goals. It is almost entirely concentrated on the maintenance aspect of short-term information processing with little concern for other processes such as those involved in elaborative encoding and comprehension. In their final chapter, the authors acknowledge this problem, both for the general working memory framework as well as for their own research. All in all. although this book provides interesting information for a specific group of researchers, I do not believe that the decision to publish it as a monograph was a wise one at the present stage of this research. I suspect that many readers who read this book based on its title, will feel a bit disappointed in their expectations.

Jeroen G.W. Raaijmakers Dept. of‘ Psychology

Unil lersity of Amsterdam Koetersstraat 15

lOlK WB Amsterdarl The Netherlands