Modality-specific and process-related organization of list-learning performance in principal component and network...

Objective: List-learning tests provide learning, recall, and recognition indices that are often interpreted as reflecting partly distinct memory processes. We used principal component analysis (PCA) and network analysis (NA) as complementary approaches to examine the organization of verbal and visual-design list-learning performance, with particular attention to very-long-delay memory assessed after approximately 1 week. Method: Data were drawn from two normative cohorts of healthy adults (N = 805). Analyses of the conventional learning, delayed-recall, and recognition measures were based on 800 complete cases, and 233 participants had complete data for analyses including very-long-delay recall and recognition approximately 1 week later. PCA was used to identify dominant dimensions of performance, whereas NA was used to examine relationships among individual measures. Results: PCA yielded two correlated components organized by stimulus modality, accounting for 73.2% of the variance for the conventional learning, delayed-recall, and recognition measures and 70.6% when very-long-delay measures were included. NA likewise showed clear modality-specific organization but additionally differentiated the relationships among learning, recall, and recognition measures, with recall measures occupying comparatively central and recognition measures more peripheral positions. Very-long-delay measures remained embedded within the modality-specific PCA structure but showed a distinctive pattern of relationships in the network. Conclusions: PCA and NA provided complementary descriptions of the same list-learning data. PCA primarily highlighted organization by stimulus modality, whereas NA differentiated relationships among individual learning, recall, and recognition measures. Very-long-delay assessment added information about the organization of memory performance, but the present findings do not establish a separate very-long-delay cognitive process.