Differential age effects in semantic and episodic memory, Part II: Slope and intercept analyses.

This study tested for dissociations between age-related slowing in peripheral and central processes across semantic and episodic memory tasks. We report the mixed-model analysis of variance (ANOVA) results using reaction time (RT), error, and data from four different experimental tasks and eight data sets (the four tasks involved either multiple sessions or different stimuli) conducted on the same 80 participants (40 younger and 40 older adults). An earlier paper (Allen, Sliwinski, Bowie, & Madden, in press) reported the factor analysis and structural equation modeling results of this study. We employed two semantic memory tasks (lexical decision and multiplication verification) using data from two different sessions (for a total of four semantic data sets), and two episodic memory tasks (hybrid visual search and memory search with digits and with words as stimuli). For RT analyses, we found Age x Task interactions for all four episodic memory data sets, but no Age x Task interactions for the four semantic memory data sets. Also, the intercept (assumed to index peripheral processes) and slope (assumed to index central processes) analyses demonstrated that older adults (relative to younger adults) showed both intercept and slope decrements for episodic memory tasks, but only intercept decrements for semantic memory tasks. These data are consistent with a theoretical framework in which there are age-related dissociations between peripheral and central processes across semantic and episodic memory.