<p>Task demands often exceed internal limitations, leading people to use external memory aids. When adults save information externally, they refrain from encoding it internally, leading to internal memory loss. We investigated whether children show similar effects. Forty 10-11-year-old children and 40 adults completed a baseline memory test and three experimental blocks, in which they studied lists of 20 words they saved externally by writing them down. In the first two blocks, participants used the list to retrieve the words during test, whereas in the final block, the written list was unavailable at test. Half of the participants were informed beforehand about the list unavailability and therefore relied on internal memory, while the remaining participants expected list access. Baseline measures indicated better overall performance among adults, yet the age-related performance differences were eliminated when children and adults used the written list during test. In the final block, children and adults who expected the list’s availability recalled fewer words than participants who relied on internal memory and reported using fewer encoding strategies. Thus, 10-11-year-olds who expect external aid availability reduce internal encoding of externalized information, leading to internal costs. We discuss how these effects could impact children’s knowledge acquisition and memory development.</p>