Listen to the waving arm

The search continues for the origins of human speech. How did we learn to talk to each other? Many scientists have been looking for the answer in the FOXP2 gene.

In an article published November 18th by Scientific American, Ewan Callaway writes that “the mutation to FOXP2 might have helped our species learn the complex muscle movements needed to form basic sounds and then combine these sounds into words and sentences.”

FOXP2 research has been “hot” in studies of human language acquisition for a decade. But there is another possible answer to the question.

In an article titled “Baby apes’ arm waving hints at origins of language,” published by New Scientist November 10th, Nora Schultz writes:

After a long search for the origins of language in animal vocalisations, some evolutionary biologists have begun to change tack. The emerging “gesture theory” of language evolution has it that our ancestors’ linguistic abilities may have begun with their hands rather than their vocal cords.

Schultz reports that researchers at the Max Planck Institute for Evolutionary Anthropology have “discovered that all four great apes … develop a complex repertoire of gestures during the first 20 months of life,” including extending the arms and head shaking. To work as communication, these gestures “require that a young ape be aware that another individual is paying attention before using them, if they want to get their message across.” Michael Corballis at the University of Auckland, New Zealand, agrees. “In monkeys, intentional arm movements are dedicated mainly to grasping,” he says. “Communicative gestures probably emerged in apes, and began to assume grammatical forms in hominins.”

While human babies also quickly learn a range of visual gestures, including direct finger pointing that other apes never learn, monkeys “typically do not learn to use visual gestures until later in life.” This, Schultz writes, “puts great apes and humans on a different evolutionary branch from monkeys,” giving more credence to comparative research among great apes. One persistent criticism of gesture theories of language is that they don’t explain why the inborn capacity to vocalize would have been abandoned in favour of a secondary, learned form of communication. Even if this criticism could be explained away, the pointing finger gap remains.

How to explain this key difference has occupied the minds of a number of thinkers, notably including developmental psychologist Michael Tomasello, also at the Max Planck Institute. Tomasello’s research provides a useful example of how new evidence affects old ideas.

Tomasello’s earlier research in the comparative communication of baby apes and human infants originally amounted to a rejection of the idea that other great apes have the kind of “theory of mind” suggested other recent studies, one of which was presented here recently in the article, “When wild chimps adopt.”

In his 2006 article “Why Don’t Apes Point?”Tomasello framed the issue this way:

The question arises: If chimpanzees have the ability to gesture flexibly and they also know something about what others do and do not see—and there are certainly occasions in their lives when making someone see something would be useful—why do they not sometimes attempt to direct another’s attention to something it does not see by means of a pointing gesture or something equivalent?

Chimpanzees, like the rest of the great apes, gesture from an early age. But only human infants point. Tomasello identified two kinds of infant pointing: imperative (I want that!’) and declarative (Look at that!) Tomasello wrote that “although some apes, especially those with extensive human contact, sometimes point imperatively for humans, no apes point declaratively ever.”

He meant “no other apes,” but there’s no real getting rid of our species bias, is there?

Tomasello had a number of explanations for the absence of declarative pointing in the other great apes. In simplest terms, his view could be boiled down to the assertion that “only humans engage with one another in acts of what some philosophers of action call shared intentionality … in which participants have a shared goal and coordinated action roles for pursuing that shared goal.”

He argued that non-human ape gestures are not products of a “theory of mind,” but rather of ritualized repetitive behaviours.:

Virtually all of chimpanzees’ flexibly produced gestures are intention movements that have been ritualized in interaction with others. For example, an infant chimpanzee who wants to climb on its mother’s back may first actually pull down physically on her rear end to make the back accessible, after which the mother learns to anticipate on first touch, which the infant then notices and exploits in the future.

To Tomasello, “This means that chimpanzees use and understand their gestures as one-way procedures for getting things done, not as intersubjectively shared, bidirectional coordination devices or symbols.”

In the dynamic of science, as research continues, theorists modify their explanations.

In the 2006 article, Tomasello notes that in 1999 he published the position that “only human beings understand one another as intentional agents—with goals and perceptions of their own—and this is what accounts for many uniquely human social cognitive skills, including those of cultural learning and conventional communication, that would seem to involve one or another form of shared intentionality.”

By 2006, Tomasello acknowledged that  “we now have data, however, that has convinced me that at least some great apes do understand that others have goals and perceptions (not, by the way, thought and beliefs).”

As a result of the new data, Tomasello and his co-authors refined their explanation, presenting a “new proposal that identifies the uniquely human social cognitive skills not as involving the understanding of intentionality simpliciter, but as involving the ability to create with others in collaborative interactions joint intentions and joint attention (which in the old theory basically came for free once one understood others as intentional agents).”

And a cursory survey of Tomasello’s latest publication in this area shows that the newest data continues to expand our knowledge of the repertoire of primate cognitive ability. In “Chimpanzees know that others make inferences” (2011)Tomasello and his colleagues report that chimpanzees take the likely actions of others into account when they make choices in a structured food search task:

If chimpanzees are faced with two opaque boards on a table, in the context of searching for a single piece of food, they do not choose the board lying flat (because if food was under there it would not be lying flat) but, rather, they choose the slanted one — presumably inferring that some unperceived food underneath is causing the slant. Here we demonstrate that chimpanzees know that other chimpanzees in the same situation will make a similar inference. In a back-and-forth foraging game, when their competitor had chosen before them, chimpanzees tended to avoid the slanted board on the assumption that the competitor had already chosen it. Chimpanzees can determine the inferences that a conspecific is likely to make and then adjust their competitive strategies accordingly.

Results like this have moved Tomasello significantly off his earlier position that only humans have any kind of metacognition:

If we define thinking as going beyond the information given in perception to make inferences, we may conclude that not only is thinking not the exclusive province of human beings, but thinking about thinking is not either.

As interesting as these reports are in themselves, they are even more significant as examples of how science works. What those who willfully or ignorantly decry science’s lack of “final truth” don’t get is that the fluidity of our scientific understanding is not only not a weakness — it’s the investigative method’s greatest strength.


One thought on “Listen to the waving arm

  1. The implications for Ameslan and all the mime games we will play at Christmas parties is interesting. And also interesting by implication is the denial of this way of thinking as valid in the face of expressed truth. Our huge ability to confabulate makes the gesture language and the denial both effective.

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