Comparative behavior of primates. I. Delayed reaction tests on primates from the lemur to the orang-outan.

Using both the direct and indirect method, the authors tested the delayed-reaction ability of 2 anthropoid apes (an orang-utan and a white-handed gibbon), 19 old-world monkeys, 2 new-world monkeys, and 1 lemur. The animals were tested in their cages in the zoo. Delays of 0, 5, 15, 30, 60, 120, 180, and over 180 seconds […]