Long-term memory effects on working memory updating development

Abstract

Long-term memory (LTM) associations appear as important to cognition as single memory contents. Previous studies on updating development have focused on cognitive processes and components, whereas our investigation examines how contents, associated with different LTM strength (strong or weak), might be differentially updated at different ages. To this end, we manipulated association strength of information given at encoding, in order to focus on updating pre-existing LTM associations; specifically, associations for letters. In particular, we controlled for letters usage frequency at the sub-lexical level. We used a task where we dissociated inhibition online (i.e., RTs for updating and controlling inhibition from the same set) and offline (i.e., RTs for controlling inhibition from previously updated sets). Mixed-effect analyses were conducted and showed a substantial behavioural cost when strong associations had to be dismantled online (i.e., longer RTs), compared to weak ones; here, in primary school age children. Interestingly, this effect was independent of age; in fact, children from 7-8 to 9-10 years were comparably sensitive to the strength of LTM associations in updating. However, older children were more effective in offline inhibitory control.

Fig 1. An example of a trial from the letter updating task (strong-to-weak).

After encoding the first triplet (CHB), participants had to maintain it actively in memory (pre-updating maintenance process: + + +). Next, they were instructed to update part of the association, that is, to remove the item C and substitute the G. Thus, the triplet they were now maintaining was GHB. Lastly, they had to maintain the recently updated triplet (post-updating maintenance process). At recognition, a single red probe was displayed: here, participants had to recognize if the probed item belonged to the most recent studied/updated item or not. In the example, a target probe was presented (B), to which they had to give a positive answer.

Fig 2. Plot representing the effects of Strength on the two Phases of encode and update.

Plot dots represent mean predicted RTs (ms) and bars represent 95% CIs.

Fig 3. Plot representing the effects of Strength on the two Age groups (younger, older children).

Plot dots represent mean predicted RTs (ms) at lure rejection and bars represent 95% CIs.