The effect of age and fluid intelligence on working memory in different modalities among elderly individuals: a moderated mediation analysis

Working memory (WM), the capacity to temporarily hold and manipulate information, is evaluated using the span paradigm, which consists of forward and backward recall tasks to assess storage and manipulation, respectively. In accordance with the dedifferentiation theory, which suggests that different cognitive abilities compensate for the decline of others during the aging process, the current study aimed to examine whether fluid intelligence mediates the relationship between forward and backward recall across verbal, visuospatial, and tactile modalities while including age as a moderator. A total of 106 healthy older adults aged 60-89 years underwent the Digit Span, Visuospatial Span, Tactual Span, and Raven Colored Progressive Matrices Test. We found positive correlations between forward and backward recall in all three span tasks. Additionally, the tactile and visuospatial moderated mediation models were significant, whereas the tactile model seemed more robust. However, the verbal model was found to be non-significant. These findings suggest that storage and manipulation are associated across different modalities, but fluid intelligence becomes a more significant factor as age progresses, thus compensating for WM decline. Nevertheless, this pattern varies between modalities, indicating a WM modality-specific differentiation dependent on the cognitive load. Our findings have implications for understanding cognitive aging processes and theoretical frameworks concerning WM.