PROCESSING OF ORDINALITY AND TRANSITIVITY BY CHIMPANZEES (PAN-TROGLODYTES)

Three chimpanzees (Pan troglodytes) were trained to discriminate among pairs of boxes in an ABCDE-ordered series. The 2nd member of each pai r was reinforced, until all 4 training pairs were learned. During nove l tests the nonadjacent BD pair was presented, and all 3 animals relia bly selected D. In Experiment 2, numerals 1-5 served as stimuli. One c himpanzee reliably selected the larger numeral 4 during testing with a nonadjacent pair (2-4), and 2 chimps showed no preference. In a 2nd p hase, the same chimp demonstrated proficiency at reversing the task, r eliably selecting the smaller of the 2-4 pair. In Experiment 4, after additional training, a 2nd test, which included novel test pairs compo sed of numbers that had not been used during training, was completed. Two of 3 animals were 100% con-ect on Trial 1 for all novel pairs. The results suggest that chimpanzees with experience in number concepts m ay recognize the ordinal character of numbers.