Spatial memory and monitoring of hidden items through spatial displacements by chimpanzees (Pan troglodytes)

This study examined chimpanzee (Pan troglodytes) short-term memory for food location in near space. In Experiments I and 2, either I or 2 items (chocolate pieces) were hidden in an array of 3 or 5 containers that either remained stationary or were rotated 180degrees or 360degrees. When the array remained stationary, the chimpanzees remembered both item locations. When arrays were rotated, however, chimpanzees found only I item. In Experiment 3, 2 items were hidden in an array of 7 cups. Both items were found at levels significantly better than chance. Ninety percent of errors were made after the 1st item was found, and errors reflected memory failure rather than a failure of inhibitory control.