Monkeys (Macaca mulatta) learn category matching in a nonidentical same-different task.

Same-different judgments of familiar objects and animals were investigated in rhesus monkeys (Macaca mulatta) in a task based on category matches rather than identity matches. Eighteen categories of familiar animals and objects were each composed of 12 color slides and were presented as pairs of slides. Ss indicated "same" or "different" on a response lever for reinforcement. On Same trials, 2 different views of the same object were presented, typically with differences in perspective, lighting, and background. On Different trials, 2 pictures of different objects were presented. Ss acquired the category discriminations and transferred their response judgments accurately to novel pictures from the categories. Transfer was better to objects with which the monkeys had actually interacted rather than those with which they did not interact.