What makes working memory spans so predictive of high-level cognition?

Working memory (WM) span tasks involving a complex activity performed concurrently with item retention have proven to be good predictors of high-level cognitive performance. The present study demonstrates that replacing these complex self-paced activities with simpler but computer-paced processes, such as reading successive letters, yields more predictive WM span measures. This finding suggests that WM span tasks evaluate a fundamental capacity that underpins complex as well as elementary cognitive processes. Moreover, the higher predictive power of computer-paced WM span tasks suggests that strategic factors do not contribute to the relationship between WM spans and high-level cognition.