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Neiworth’s first study of categorization in monkeys was during her postdoctoral experience in Neurobiology at the University of Texas Health Science Center in Houston TX. Neiworth wondered whether the rhesus monkeys she studied had a more concrete sense of objects with which they interacted regularly. She asked them to make same/different discriminations with pictures of familiar and less interactiive objects when those items were captured in unique orientations and unique backgrounds with every picture. In fact, monkeys were more prone to claim “different” with objects pictured in different orientations and with different backgrounds if those objects were not really known by the monkeys (including researchers, appliances, and cleaning tools that monkeys don’t use but see often). They could claim “same” with varying pictures of apples, orange juice, gloves, hypodermic needles, and monkeys and researchers whom they knew well.


Items rhesus could recognize as same independent of perspective.


Read the published article on same/different discriminations with familiar and unfamiliar items by rhesus monkeys (1994).

CITATION: Neiworth, J. J., & Wright, A. A. (1994). Monkeys (Macaca mulatta) learn category matching in a nonidentical same-different task. Journal of experimental psychology. Animal behavior processes, 20(4), 429–435.

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