Infant chimpanzees spontaneously perceive both concrete and abstract same/different relations.

We used a familiarization-novelty procedure to determine whether 4 infant chimpanzees spontaneously perceive the sameness of and the difference between both concrete objects and relations between objects. In Experiment 1, a single object was presented on the Familiarization Trial 1 and the animal's looking time recorded. On the Test Trial 2, an object was presented that was either identical to or different from that shown on Trial 1. Looking times on Test Trial 2 were less when the same item had been presented on the preceding familiarization trial. Novel items on Trial 2 were attended to longer, indicating that the infant chimpanzees perceived concrete objects were either the same or different. In Experiment 2, a single pair of objects was presented on the Familiarization Trial 1, and handling time was measured. The objects in a pair were either the same or different (e.g., AA vs. CD). On the Test Trial 2, a new object pair (e.g., BB vs. EF) was presented that instantiated either the relation shown on Trial 1 or the alternative relation. Handling time on Trial 2 was influenced by the relation instantiated on Trial 1. Handling times on Test Trial 2 were less when the identical relation had been presented on the preceding familiarization trial. Novel relations on Trial 2 were attended to relatively longer. This result indicates that infant chimpanzees perceive similarities and differences between abstract relations as well as between concrete objects. That is to say, they perceived relations between relations in Experiment 2. Despite this ability to perceive both concrete and abstract "same/different" relations, the same chimpanzees subsequently failed to use the latter knowledge in a matching-to-sample task in Experiment 3. Although they successfully matched single objects, they were unable to match object pairs instantiating the same relation (e.g., if AA then match BB; if CD then match EF). These results contradict claims that failure to learn an instrumental discrimination involving abstract relations reflects an inability to detect such relations. In every species there may be a disparity between the ability to perceive spontaneously a property of the world and the ability to use the concept instrumentally.