It鈥檚 a study that could throw a monkey wrench into our understanding of the primate brain. Vittorio Gallese of the University of Parma, Italy, has found that macaques can predict the future actions of others, casting doubt on the long-held idea that monkeys cannot understand other beings as agents with their own perspectives and intentions.
Six macaque monkeys were shown a simple goal-related task 鈥� a woman reaching over a tall obstacle to pick up a toy resting on the other side. Once the monkeys had got used to this, the obstacle was removed so that the woman could simply reach out and pick up the toy.
The team found that when she did this, the monkeys showed a minimal amount of interest in her actions: each gazed at her face for an average of just 7 milliseconds. If, however, she continued to behave as if the obstacle were still in place and used the 鈥渞each-over鈥� path to the toy, the monkeys showed more interest, gazing at her face for around 18 milliseconds on average (Current Biology, ).
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Gallese concludes that the results show that monkeys recognise intention in goal-related tasks, and use that ability to predict how others will act. When no obstacle was in place but the woman still reached for the toy as if it were, she was acting in an unexpected manner, and Gallese says the monkeys spent longer gazing at her face because they were looking for clues to explain her behaviour.
鈥淢onkeys recognise intention in goal-related tasks, and use that ability to predict how others will act鈥�
His interpretation is at odds with many researchers鈥� understanding of what monkey brains are capable of. In children, prolonged gazing after seeing the 鈥渞each-over鈥� behaviour is thought to show that the child understands that the person is a rational being with a mind of its own. Now, says Gallese, we have to allow that monkeys can understand intention, too. Whether the 鈥渞each-over鈥� experiment shows that monkeys are rational or not is a moot point.
Michael Tomasello at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, points out that chimpanzees have been shown to understand intention, and that they can at least imitate rationality. If a chimp sees an actor turn on a light switch with his forehead even though his hands are free, the chimp is likely to use its own forehead to turn the switch. Yet if the actor uses his forehead to turn the switch only because his hands are full, the chimp recognises that the action was controlled by circumstance. When given the chance to turn the switch, the chimp imitates the task rationally by using its hands and not its forehead (Developmental Science, ).
Even if we do not extend the ability to understand rationality to monkeys, the results are still interesting, says anthropologist Josep Call, also at the Max Planck Institute. 鈥淚t just shows that something we thought happened in humans alone is also seen in other animals.鈥�
However, Call says that more experiments will have to be done before we can say that chimps, let alone monkeys, are rational beings. 鈥淭his research won鈥檛 modify the minds of philosophers,鈥� he says.
