The Extended Mind in Young Children: Cost-Dependent Trade-Off Between External and Internal Memory.

Most work on working memory development has children remember a set of items as well as they can. However, this approach sidesteps the , the integration of external information with memory. Indeed, adults prefer to use external resources (e.g., lists, models) but will remember more as the cost to access them increases. Here, in our shopping game, we investigated this trade-off in 5- to 8-year-olds. Using a touchscreen, children shopped in a virtual store. Their shopping list and the store were not visible simultaneously but could be toggled. We manipulated access cost by varying a delay (0-4 s) before the list's reappearance. Across three preregistered experiments at two sites (the United States and China, = 141), a pattern emerged: When it was costlier to do so, children revisited the list less often, studied it longer, and selected more correct items. Also, children recognized the costs, identifying the no-delay condition as easier. Young children showed a cost-dependent trade-off of external-resource use versus working memory.