Aping Dr Dolittle
A Japanese researcher reckons he will soon have monkeys communicating with humans. And, Laura Spinney finds, it could reveal how language evolved.
Thursday November 25, 2004
The Guardian
In a laboratory in Saitama, central Japan, monkeys are behaving strangely. If someone sticks out a tongue, they do the same. If a person goes to unclip the latch on a box, the monkeys follow suit. If they need a rake to reach a piece of fruit, they ask for it with a special call. All of which is confounding experts, because none of it should be possible. Monkeys in the wild rarely ape, and as far as we know, they never, ever, ask for rakes.
The Japanese macaques raised in Atsushi Iriki's lab are not particularly gifted. But intriguingly, he expects them soon to be communicating with him vocally, using simple linguistic rules. This isn't just an elegant Dr Dolittle curiosity: it holds the real possibility of understanding autism in humans and unlocking the vast unused power of the human brain.
Iriki, head of the laboratory for symbolic cognitive development at the Riken Brain Science Institute, says his experiment will tap into neural systems monkeys always had, but have never been activated. He hopes to learn something about monkey thought, but more dramatically, about how language emerged in humans -and what happens when it breaks down in autistic children, for example.
So what lies behind Iriki's attempt? As the ape brain evolved, it accumulated the components of a language. By the time the vocal tract could support speech, we were already human. But our brains, according to Iriki, were "language-ready" much earlier. In the monkey, this happened in a more fragmented form. The only reason it did not emerge was that the conditions were never right. "Maybe in the wild, vocal communication was not necessary for monkeys to survive, or was even harmful," says Iriki. "Those functions were not expressed or were even suppressed, even though their brains were furnished with the machinery."
Iriki knew that monkeys would never be able to speak, lacking as they do the necessary vocal apparatus, but he became convinced he could perhaps exchange meaningful coos and grunts with them. To do so, he realised he would have to rear monkeys in an environment where to communicate in this way was not only safe, but in their interest. Could he encourage them to vocalise a primitive language? Would they use it to communicate not only with other monkeys, but even with him?
The experiment has excited his peers and won Iriki the Golden Brain Award, presented annually for brain research by the Minerva Foundation in the US. "This is a guy who is on to a really exciting research programme," says neuroscientist Michael Arbib of the University of Southern California. Monkeys in the wild produce a limited range of calls - alarm calls to warn of approaching predators, for instance. But, says Arbib, "the general consensus would be that the set of calls is pretty much innate. Iriki now seems to show that the call system may be much more flexible than we thought".
Iriki has a reputation for lateral thinking. Trained as a dental surgeon, he became interested in pain and by that route came to study the brain. Several years ago, he showed that a macaque trained to use a rake to grab a piece of fruit could operate just as skillfully whether it could see its own hand, or was prevented from seeing it and shown instead a video image of the hand, rake and fruit reward.
Based on those findings, Iriki argued that monkeys had a concept of body image that matched a nine-year-old child. The findings seemed to demonstrate a level of abstract thinking that nobody had suspected in monkeys - though researchers had long argued for it in chimps, orang utans and gorillas. And they created a dilemma for Iriki.
The problem was this: if monkeys have a relatively advanced view of themselves, how is it that they appear to be so oblivious to the behaviour of others, unable to follow the gaze of another monkey or imitate gestures, as even human toddlers can do? It mattered to Iriki because imitation and joint attention are considered key building blocks of the kind of shared understanding that makes communication possible. In the wild, monkeys rarely imitate. But two pieces of evidence suggested to Iriki that they could learn to - and they hinge on a recently discovered type of brain cell called a "mirror neuron".
Animal behaviour experts have very occasionally observed both imitation and joint attention - which lets one follow another's gaze - between mother and infant macaques in the wild. And, though macaques seem to show no interest in others' actions, activity in their brains suggests they do. It harbours a type of neuron that fires not only when it performs an action, but also when it sees another monkey perform the same action.
These mirror neurons were first identified by Giacomo Rizzolatti of the University of Parma, Italy, and colleagues in the early 1990s in an area of the macaque brain called the premotor cortex, and specifically in a sub-section called F5. Subsequently they have turned up in other areas. Luciano Fadiga at the University of Ferrara then found evidence that the human brain contained a mirror system of its own.
When Rizzolatti's group investigated the human brain more closely, using functional magnetic resonance imaging, they showed that, among other places, mirror neurons show up in Broca's area, which in the human brain is responsible for speech production. F5 in monkeys is associated mainly with hand movements, but is the anatomical equivalent of Broca's area.
There followed frenzied speculation about the role of mirror neurons. Rizzolatti and Arbib claimed that by providing the platform for imitation and shared understanding, they made language possible. Nevertheless, the question remained for Iriki: if humans and monkeys have mirror neurons, why are humans natural mimics while monkeys hardly ever imitate?
"Maybe monkey brains are unaware of the mirror neurons' potential," he says. "When their brains realised the possible uses of this system, perhaps due to the expression of a gene trig gered by some accidental incident in the course of evolution, that could have been the beginning of the explosion of intelligent functions."
Iriki suspects that a likely trigger for that realisation was human child-rearing practices. Using eye contact, mothers teach their babies to look in the same direction and to copy their actions. So in Iriki's lab, monkeys are reared as closely as possible to humans, with an intense relationship between the young monkey and its human carer.
In a study published last year, his group showed that three in four monkeys brought up in this way learned joint attention, and once they had learned it, began to imitate a human's actions without having to be taught.
Iriki is not the only scientist to experiment in this area. At Georgia State University, Atlanta, primatologist Sue Savage-Rumbaugh has taught a human-reared pygmy chimp to become adept at communicating with symbols. But the difference is that Iriki's macaques choose their own calls to express what they want. When he trained two macaques to use a rake to retrieve a fruit reward, and then to call for either food or the tool, he found the monkeys produced different cooing noises depending on what they wanted. "I think this is the evolutionary precursor of naming," he says.
Psychologist Klaus Zuberbühler of the University of St Andrews says that what Iriki reports is new: monkeys are not known to produce acoustically distinct sounds associated with novel events or objects - certainly not with a man-made tool.
Zuberbühler studies Campbell's and Diana monkeys in West Africa, whose calls are innate. "The acoustic structures of the different predator calls vary from one monkey species to the next, but those species are still able to understand each other," he says.
By contrast, Iriki's monkeys' new calls do not yet have much communicative power. Each monkey has a different call for a given object, and the sounds are not the same. Iriki thinks it might be possible to teach naive monkeys to imitate the calls of others, and in so doing, help them learn what they mean. They might then use the calls themselves, to express the same idea. He can envisage, say, a macaque calling to another macaque for a tool, which is then dutifully handed over.
"This is fascinating," says Fadiga, who thinks Iriki's work has the potential to reveal the origins of human language. But he also has doubts, not least that the monkeys will maintain any primitive language they develop. "The question is, do you think the monkeys need this language? Because if they do not need it, they will not teach others."
Rizzolatti, meanwhile, is excited by the possibility that monkeys have mirror neurons but are unable to use them. "That has some interesting implications," he says. "For instance, perhaps autistic children have the mirror system but cannot use it. Or perhaps it is there, but not fully developed."
One common symptom among autistic children is that they repeat words spoken to them without apparently understanding them - a phenomenon known as echolalia. At the same time, their language development is delayed, suggesting their mirror system may be malfunctioning. Rizzolatti speculates one could use tricks similar to Iriki's to improve the system's functioning in those kids.
Iriki does not think it too far-fetched to suggest that humans could one day tune into his monkeys' enriched repertoire of sounds, using it to converse with them at a simple level. Then there will be a debate as to whether it deserves to be called language.
"I think it's going to remain the case that language as we know it in humans is different from language that even the best brought-up ape is going to get to," says Arbib.
But Iriki is already thinking laterally again. If monkey brains have redundant capacity, why not human brains? "Human language and intelligence could be brought up to a much higher level than we are at now," he says.
"We are still in the middle of evolution. We can dream of the future."
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Further reading:
www.brain.riken.go.jp/english/ Atsushi Iriki at the Laboratory for Symbolic Cognitive Development, Riken, Saitama, Japan
Mirror Neurons and the Evolution of Brain and Language by Maxim Stamenov and Vittorio Gallese, 2002 paperback (John Benjamins, Amsterdam). ISBN 1588112152
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