Relationship Between Working Memory, Fluid Intelligence and Age Based on the Results of Mediation and Moderation Analyses

The positive relationship between working memory (WM) and fluid intelligence (Gf) is a well-established phenomenon, yet numerous studies reveal the age-related decline in both WM and Gf. From the perspective of the changes that WM and Gf undergo in adult development it may be assumed that accounting for age in studies of the relationship between these two is important, particularly in age-diverse groups. However, the issue of the WM-Gf link has rarely been considered from a developmental perspective, especially in adults. The analyses presented here focused on the role of age in the relationship between WM and Gf. The study sample comprised 63 participants in early adulthood (N = 33, aged 20–34) and late adulthood (N = 30, aged 60–73). They performed a computerised n-back task on 6 difficulty levels (from 1-back to 6-back) and Raven’s Standard Progressive Matrices (SPM) in Polish standardisation. The obtained results indicated that although WM and Gf were found to be inferior among older than young adults, age was not a significant moderator of the association between WM and Gf. The relationship between age and Gf was not mediated by WM, which does not confirm that age-related changes in Gf may partially result from the developmental trajectory of WM. At the same time, age fully mediated the relationship between WM and Gf, suggesting the existence of a general factor of cognitive aging and implying that it may underlie an apparent relationship between WM and Gf in age-diverse groups.