THERE goes another sophisticated mental feat once thought to be uniquely human. Apes may be sufficiently self-aware to doubt their own knowledge.
of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, put food in one of two opaque plastic pipes and had watching bonobos, chimpanzees, gorillas and orangutans pick the one with the food. If they were made to wait, the apes sometimes forgot where the food was, but by and large they did well on the task.
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To test if the apes doubted their own decisions, Call gave them the option to peek into the end of the pipes before they chose one. He found that the apes were more likely to check the pipes if they had to wait before picking one (Animal Cognition, DOI: ). Call says this suggests that the apes had begun to doubt their memory.
Earlier studies have shown that apes and other mammals can be aware that they do not know the answer to a test. However, Call claims that the doubt apparently revealed by his trials represents a subtle thought process not previously seen beyond humans.
