Individual Differences in the Three-Embedded Components of Working Memory and their Relation to Fluid Intelligence

Working memory (WM) capacity and fluid intelligence (Gf) have consistently been shown to be related, but it is unclear why. The Three-Embedded Components (3Cs) model of WM proposes the focus of attention (FA), representing a single attended memorandum, the region of direct access (RDA), representing memoranda bound to active context, and the activated part of long-term memory (aLTM), representing activated memoranda not bound to active context. This study examined the unity and diversity of WM. Bifactor analysis – which avoids previous analytical challenges of difference scores – was used to separate Common WM (i.e., common variance among the 3Cs; representing unity) from individual differences unique to each of the 3Cs (representing diversity); however, no variance unique to the FA could be identified. Furthermore, whereas Common WM correlated highly with WM capacity and Gf, only the aLTM but not the RDA correlated with WM capacity, and neither correlated with Gf. Psychometric network analysis was performed to additionally explore partial correlations among the manifest 3Cs, WM capacity, and Gf measures. Only WM capacity measures, but not 3Cs measures, consistently partially correlated with Gf. Taken together, these findings indicate that isolated individual components of WM cannot explain the WM-Gf relationship. Instead, the results suggest that only what is common across these components – and likely their interplay – underpins the relation between WM capacity and Gf, suggesting the whole of WM is greater than its parts.