Remembering in tool-use tasks in children and apes: the role of the information at encoding

Providing adults with relevant information (knowledge that they will be tested at some future time) increases motivation to remember. Research has shown that it is more effective to have this information prior to, rather than after, an encoding phase. We investigated this effect in apes and children in the context of tool-use tasks. In Experiment 1 we presented chimpanzees, orangutans, and bonobos with two tool-use tasks and three different two-tool sets. We had two conditions: prospective (PP) and retrospective (RP). In the PP subjects were shown the task that they would have to solve before they were shown the tools with which they could solve it. In the RP this order was reversed. Apes remembered the location of the useful tool better in the PP than in the RP. In Experiment 2 we presented 3- and 4-year-olds with the same conditions. Both age groups remembered the location of the correct tool in the PP, but only the 4-year-olds did so in the RP. Thus providing apes and preschool children with relevant information prior to, rather than after, the encoding phase enhances memory. These results have important implications for the understanding of the evolution of memory in general, and encoding mechanisms in particular.