[LINK] "Deciphering the Chatter of Monkeys and Chimps"

[rfmcdonald]

3 Quarks Daily's Azra Raza linked to Nicholas Wade's New York Times article "Deciphering the Chatter of Monkeys and Chimps". Non-human primates, it turns out, can be quite sophisticated.

Vervet monkeys were found in 1980 to have specific alarm calls for their most serious predators. If the calls were recorded and played back to them, the monkeys would respond appropriately. They jumped into bushes on hearing the leopard call, scanned the ground at the snake call, and looked up when played the eagle call.

It is tempting to think of the vervet calls as words for “leopard,” “snake” or “eagle,” but that is not really so. The vervets do not combine the calls with other sounds to make new meanings. They do not modulate them, so far as is known, to convey that a leopard is 10, or 100, feet away. Their alarm calls seem less like words and more like a person saying “Ouch!” — a vocal representation of an inner mental state rather than an attempt to convey exact information.

But the calls do have specific meaning, which is a start. And the biologists who analyzed the vervet calls, Robert Seyfarth and Dorothy Cheney of the University of Pennsylvania, detected another significant element in primates’ communication when they moved on to study baboons. Baboons are very sensitive to who stands where in their society’s hierarchy. If played a recording of a superior baboon threatening an inferior, and the latter screaming in terror, baboons will pay no attention — this is business as usual in baboon affairs. But when researchers concoct a recording in which an inferior’s threat grunt precedes a superior’s scream, baboons will look in amazement toward the loudspeaker broadcasting this apparent revolution in their social order.

Baboons evidently recognize the order in which two sounds are heard, and attach different meanings to each sequence. They and other species thus seem much closer to people in their understanding of sound sequences than in their production of them. “The ability to think in sentences does not lead them to speak in sentences,” Drs. Seyfarth and Cheney wrote in their book “Baboon Metaphysics.”

These primates all fall short of producing true language, nonetheless.

Once the infrastructure of language is in place, as is almost the case with monkeys and apes, the faculty might be expected to develop very quickly by evolutionary standards. Yet monkeys have been around for 30 million years without saying a single sentence. Chimps, too, have nothing resembling language, though they shared a common ancestor with humans just five million years ago. What is it that has kept all other primates locked in the prison of their own thoughts?

Drs. Seyfarth and Cheney believe that one reason may be that they lack a “theory of mind”; the recognition that others have thoughts. Since a baboon does not know or worry about what another baboon knows, it has no urge to share its knowledge. Dr. Zuberbühler stresses an intention to communicate as the missing factor. Children from the youngest ages have a great desire to share information with others, even though they gain no immediate benefit in doing so. Not so with other primates.

“In principle, a chimp could produce all the sounds a human produces, but they don’t do so because there has been no evolutionary pressure in this direction,” Dr. Zuberbühler said. “There is nothing to talk about for a chimp because he has no interest in talking about it.” At some point in human evolution, on the other hand, people developed the desire to share thoughts, Dr. Zuberbühler notes. Luckily for them, all the underlying systems of perceiving and producing sounds were already in place as part of the primate heritage, and natural selection had only to find a way of connecting these systems with thought.