Working Memory Constrains Long-Term Memory in Children and Adults: Memory of Objects and Bindings

Abstract

We explored how individual and age-related differences in working memory (WM) capacity affected subsequent long-term memory (LTM) retrieval. Unlike past studies, we tested WM and LTM not only for items, but also for item-color bindings. Our sample included 82 elementary school children and 42 young adults. The participants performed a WM task with images of unique everyday items presented sequentially at varying set sizes in different colors. Later, we tested LTM for items and item-color bindings from the WM task. The WM load during encoding constrained LTM, and participants with a higher WM capacity retrieved more items in the LTM test. Even when accounting for young children's poor item memory by considering only the items that they did remember, they exhibited an exacerbated difficulty with remembering item-color bindings in WM. Their LTM binding performance, however, as a proportion of remembered objects, was comparable to that of older children and adults. The WM binding performance was better during sub-span encoding loads, but with no clear transfer of this benefit to LTM. Overall, LTM item memory performance was constrained by individual and age-related WM limitations, but with mixed consequences for binding. We discuss the theoretical, practical, and developmental implications of this WM-to-LTM bottleneck.

Keywords: child development; information transfer; long-term memory; memory binding; working memory.

Figure 1

Outline of some typical trials. Panel A, working memory (WM) task trial, at set size 2. Panel B, two trials in the long-term memory (LTM) task. The memory array set size in the WM task varied between 2, 3, and 4 items. Participants responded using one of three response options “same object–same color”, “same object–different color”, or “different object”.

Figure 2

Memory accuracy by WM set size and age group. Panel A, p(WM) (i.e., the estimated probability that items were held in WM); Panel B, p(LTM) (i.e., the estimated probability that items were held in LTM); Panel C, the p(LTM)/p(WM) ratio. Black circles show adult data, squares data from the 5 to 7th graders, and diamonds represent data from the 1st to 2nd graders. Error bars represent 95% confidence intervals.

Figure 3

Binding memory accuracy rates by WM set size and age group, in trials which tested binding memory (Same Object, Same Color and Same Object, Different Color), in which items were not forgotten. Panel A, working memory binding error rates. Panel B, long-term memory binding error rates. Black circles show adult data, squares data from the 5 to 7th graders, and diamonds represent data from the 1st to 2nd graders. Error bars represent 95% confidence intervals.