Working memory capacity and its relation to general intelligence

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Abstract

Early investigations of working memory capacity (WMC) and reasoning ability suggested that WMC might be the basis of Spearman's g. However, recent work has uncovered details about the basic processes involved in working memory tasks, which has resulted in a more principled approach to task development. As a result, claims now being made about the relation between WMC and g are more cautious. A review of the recent research reveals that WMC and g are indeed highly related, but not identical. Furthermore, WM span tasks involve an executive-control mechanism that is recruited to combat interference and this ability is mediated by portions of the prefrontal cortex. More combined experimental–differential research is needed to understand better the basis of the WMC–g relation.

Section snippets

Differential approach to the relation between WMC and g

The following review of individual differences studies of WMC and g (or general reasoning ability) is restricted to projects that used latent variable analyses (see Box 1). This criterion was adopted for two reasons. First, latent variables provide a cleaner measure of the construct under investigation and therefore these analyses provide the clearest picture of the true relation between WMC and g. Second, the number of published papers containing at least one correlation between a single

Cognitive-experimental investigations of the basic processes underlying WM span tasks

One way in which the processes that contribute to WM span tasks has been explored has been to contrast the cognitive contexts in which individual differences in WM span relate, and do not relate, to performance. For example, a large and diverse group of subjects are screened using WM span tasks, and individuals with greater WMC are compared with individuals with lesser WMC in different experimental contexts. Although it is not ideal to categorize a continuous variable in this fashion, the

Neuroimaging studies of WMC and g

The distinction between tasks that require storage versus those that require storage and some form of processing can also be found in the neuroimaging literature [12]. For instance, several studies have shown that storage-only tasks reveal activation primarily in areas related to the content of the to-be-remembered material (e.g. Broca's area for verbal material, right-hemisphere pre-motor cortex for spatial material) [12], whereas storage-plus-processing tasks reveal content-specific

Future issues: the current range of WMC tasks is still too wide

It is clear that the creation and selection of WMC tasks is more principled today than it was in 1990. However, the fact remains that a wide range of tasks are still being used to measure WMC and it is not clear how all these tasks relate to one another or to g. Here we consider tasks other than WM span and call for future research that addresses (1) the basic processes involved in these tasks, and (2) the relation between these tasks, WM span tasks, and g.

One problem with WM span tasks is that

Conclusion

In summary, several recent latent variable analyses suggest that WMC accounts for at least one-third and perhaps as much as one-half of the variance in g. What seems to be important about WM span tasks is that they require the active maintenance of information in the face of concurrent processing and interference and therefore recruit an executive attention-control mechanism to combat interference. Furthermore, this ability seems to be mediated by portions of the prefrontal cortex.

Although

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