A nonverbal false belief task: The performance of children and great apes

A nonverbal task of false belief understanding was given to 4- and 5-year-o ld children (N = 28) and to two species of great ape: chimpanzees and orang utans (N = 7). The task was embedded in a series of finding games in which an adult (the hider) hid a reward in one of two identical containers, and a nother adult (the communicator) observed the hiding process and attempted t o help the participant by placing a marker on the container that she believ ed to hold the reward. An initial series of control trials ensured that par ticipants were able to use the marker to locate the reward, follow the rewa rd in both visible and invisible displacements, and ignore the marker when they knew it to be incorrect. In the crucial false belief trials, the commu nicator watched the hiding process and then left the area, at which time th e hider switched the locations of the containers. When the communicator ret urned, she marked the container at the location where she had seen the rewa rd hidden, which was incorrect. The hider then gave the subject the opportu nity to find the sticker. Successful performance required participants to r eason as follows: the communicator placed the marker where she saw the rewa rd hidden; the container that was at that location is now at the other loca tion; so the reward is at the other location. Children were also given a ve rbal false belief task in the context of this same hiding game. The two mai n results of the study were: (1) children's performance on the verbal and n onverbal false belief tasks were highly correlated (and both fit very close ly with age norms from previous studies), and (2) no ape succeeded in the n onverbal false belief task even though they succeeded in all of the control trials indicating mastery of the general task demands.