There are concerns that reliance on external resources (e.g., information on digital devices) may be harmful to our own internal memory. Here, in a pre-registered study, we investigated how the of an external resource (i.e., whether the information will be available when needed) affects young children's use of it. In our tablet-based Shopping Game, children picked items from a store based on a shopping list. Importantly, the store and the list were not visible simultaneously, but children could toggle between them. In the condition, the list was always available. In the condition, children were led to believe that the list might disappear. We found that 5-6-year-old children ( = 37) relied more on the list - referring back to it more often and more briefly, and remembering fewer items - when they perceived the list as reliably available (and vice versa, reducing trips to the list by studying it longer, and remembering more, when it was perceived as unreliably available). Nearly all children also identified the reliable condition as easier and preferred. In short, young children not only recognize the opportunity provided by reliably available external resources, but adapt their cognitive effort accordingly.
