In this month’s column:a tale of the mythical Sea King Rin-Jin; a jellyfish that can walk on land; and a monkey that gazes, like the wicked witch in Snow White, at its own reflection in a mirror — though, unlike the wicked witch, the monkey is not so interested in looking at its face.
Last week, biologists published a paper suggesting that monkeys could pass the mirror test. This is a classic test given to animals to measure the amount of self-awareness they have. Show a cat or a dog — or a 1-year-old human, for that matter — a mirror, and the animal won’t know that it is looking at a reflection of itself. Chimps, on the other hand, and older children, understand that they are seeing their own image.
What of monkeys? And in particular, macaques. They are smart — they are famous in Japan for washing sweet potatoes in the sea and taking baths in hot springs in the winter. Macaques also have a central place in Japanese myths. They are in the A-team of animals in folklore, along with foxes and tanuki (Japanese raccoon dogs). Do macaques also have the mental ability to be self-aware?
Despite the skills and cunning attributed to animals in folk tales, scientists have thought that only a select few animals — great apes, including orangutans, bonobos and gorillas, and perhaps elephants, dolphins and crows — may have the brain power to be classed as self-aware. But no lower primates: no monkeys.
To pass the test, the animal is marked — with a colored dot, for example — on its face. When it is then shown a mirror, if the animal examines the dot it is concluded that it is self-aware. It seems monkeys have now passed that test. If confirmed, it means we have to think again about the mental life of these animals.
It was, however, a special kind of test.
Luis Populin, a professor of anatomy at the University of Wisconsin-Madison, found that under specific conditions, a rhesus macaque monkey that normally would fail the mark test can still recognize itself in the mirror and perform actions that scientists would expect from animals that are self-aware. I would imagine that Japanese macaques are similarly capable of recognizing themselves in mirrors.
The finding casts doubt on both the relevance of the mark test and on the existence of a definitive cognitive divide between higher and lower primates.
Populin, who studies the neural basis of perception and behavior, had placed head implants on two rhesus macaque monkeys, while preparing to study attention deficit disorder. This is obviously a far more invasive mark on the animal that a colored dot, and when given a mirror it seems the animals were self-aware: Monkeys that got the implants were clearly looking in the mirror while examining and grooming their foreheads, near the implant.
Tellingly, they were also examining other areas of their body, particularly the genitals, which they had never seen before. In some cases, the monkeys even turned themselves upside down during these examinations. In other cases, they grasped and adjusted the mirror to get a better view of themselves (the paper in the journal Public Library of Science describing the results is available here: www.dx.plos.org/10.1371/journal.pone.0012865 ).
There has long been a concept of a cognitive divide in primates: On one level of brain power, you’ve got the great apes (which include humans), and then there are the monkeys, who just ain’t as smart. Instead of a divide, however, it now seems more likely that there is a continuum of self-awareness.
I think the mark test may not be sensitive enough to detect self-awareness in the lower species. Such species may have it but in a different form, and it may show up in different situations, using different tests, says Populin.
There is a tale from Japanese folklore that underlines not only the historical importance of the monkey to Japan but also the inherent understanding of animal behavior that science is sometimes slow to catch up with.
The story is set thousands of years ago, when Rin-Jin the Sea King’s wife becomes sick. The only cure, the Sea King is told, is a monkey’s liver. So the king sends a jellyfish onto land to find a monkey and bring him back, riding the shell of the jellyfish. I know — jellyfish don’t have shells and anyway, how can a jellyfish climb onto land to bring a monkey back to the king? — but wait.
The jellyfish finds a monkey and gets him to ride on his shell out to sea. During the journey, the jellyfish reveals that the Sea King’s wife is ill and needs a monkey’s liver to survive. Perceiving the danger he is in, the cunning monkey says to the jellyfish: “Oh, but I left my liver hanging in a tree, take me back to land and I’ll get it for you.”
When the jellyfish delivers him back to land, the monkey flees to safety up a tree and mocks the gullible jellyfish. Rin-Jin punishes the jellyfish by removing his shell and bones, and then condemns him and his kind to float forever in the ocean.
It seems that the Japanese have long appreciated the cognitive powers of the macaque. Though I can’t see my story of a monkey examining its own genitals becoming as popular as the story of Rin-Jin and the jellyfish.
Follow Rowan Hooper on Twitter at twitter.com/rowanns. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is “Hito wa Ima mo Shinka Shiteru (The Evolving Human).”