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Neuroscience & Behavior
Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
Attribution of knowledge refers to equating a shared visual perspective with shared information, a characteristic of human behavior. However, there is considerable debate as to whether nonhuman primates understand the significance of gaze and will select a treat from an experimenter that looks at them as opposed to one that does not. In previous studies, chimpanzees could not differentiate between looking and nonlooking experimenters. However, treats were held in the hands, a considerable distance from the face. We asked whether a group of five rhesus monkeys (Macaca mulatta) could discriminate lookers from nonlookers. We eliminated the problem of focusing on the hands by holding treats in close proximity to the experimenters’ eyes. Monkeys were trained to use an apparatus to select an experimenter. All five subjects were subsequently able to discriminate between experimenters holding different food rewards, even when these rewards were placed out of the monkey’s view. Two of the monkeys could also select the experimenter who initially held a desirable treat after the treat was hidden and that experimenter changed location. On the seeing and knowing task, two probe types of visual occlusion were used: Probe 1- one experimenter turned his head away from the monkey, Probe 2- one experimenter covered his eyes with a blindfold. Position, experimenter, probe trial, and reward type (on standard trials) were block randomized. Data were analyzed using binomial probabilities with =0.05. At the group level, all five monkeys requested food from the experimenter looking at them significantly more than would be expected by chance, but individual subject performance differed depending on probe condition. These data suggest that some rhesus macaques have the ability to understand the connection between seeing and knowing.
Melinda A. Novak