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Seven chimpanzees were tested for their understanding of the intentional aspect of visual perception at 5-6 years of age and again at 7 years of age. They appeared not to understand that they should use a species-typical, visually based begging gesture in front of someone who could see them, as opposed to someone who could not. Four experiments that were conducted when these same subjects were adolescents are reported here. The results suggest that there was no development between 5 and 9 years of age in the animals' understanding of visual perception as an internal state of attention. The subjects appeared to learn procedural, stimulus-based rules related to the frontal orientation, the face, and the eyes of the experimenters. Even subjects most adept at these tasks appeared to rely on stimulus-based rule structures, not an attribution of "seeing."

To assess the influence of different procedures on chimpanzees' performance in object-choice tasks, five adult chimpanzees were tested using three experimenter-given cues to food location: gazing, glancing, and pointing. These cues were delivered to the subjects in an identical fashion but were deployed within the context of two distinct meta-procedures that have been previously employed with this species with conflicting results. In one procedure, the subjects entered the test unit and approached the experimenter (who had already established the cue) on each trial. In the other procedure, the subjects stayed in the test unit throughout a session, witnessed the hiding procedure, and waited for a delay of 10 s during which the cue was provided. The subjects scored at high levels far exceeding chance in response to the gaze cue only when they approached the experimenter for each trial. They performed at chance levels when they stayed inside the test unit throughout the session. They scored at chance levels on all other cues irrespective of the procedure. These findings imply that (a) chimpanzees can immediately exploit social gaze cues, and (b) previous conflicting findings were likely due to the different meta-procedures that were used.

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