Storage and processing in working memory : a single, domain-general resource explains multi-tasking

An ongoing major debate centers around whether multi-tasking in working memory, that is, performing several mental activities at once, is supported by multiple specialized domain-specific or by a single-purpose domain-general cognitive resources. Working memory theories differ in their explanations and predictions about when performing two mental tasks causes performance failures, versus when two processes can be carried out concurrently with negligible cognitive costs. In particular, the predictions of domain-specific and domain-general views on working memory are in conflict with one another when it comes to the cognitive cost associated with concurrent verbal and visuo-spatial processing and storage tasks. Previous tests of these predictions using traditional methods have led to ambiguous and inconsistent conclusions, however. To make critical progress in this theoretical debate, we used a radically different approach combining Bayesian state-trace analysis with an experimental design fully crossing processing and storage tasks differing only in the domain of representation (verbal vs. visuo-spatial). Across two experiments, we show unambiguously that a single, domain-general factor can account for briefly maintaining verbal and visuo-spatial information in a multi-tasking scenario.