Previous research suggests that chimpanzees understand single invisible displacement. However, this Piagetian task may be
solvable through the use of simple search strategies rather than through mentally representing the past trajectory of an object.
Four control conditions were thus administered to two chimpanzees in order to separate associative search strategies from
performance based on mental representation. Strategies involving experimenter cue-use, search at the last or first box visited
by the displacement device, and search at boxes adjacent to the displacement device were systematically controlled for. Chimpanzees
showed no indications of utilizing these simple strategies, suggesting that their capacity to mentally represent single invisible
displacements is comparable to that of 18–24-month-old children.
Keywords Chimpanzees - Invisible displacement - Mental representation - Secondary representation - Object permanence - Associative strategies