Is Speech as Old as Language?

 

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Stephen Colbert not only talks about gestures, he makes them throughout his talk. My favorite is the gesture accompanying the reference to a foaming mug of pinot grigiot.

One of the steady disputes on this blog concerns the role of gesture (hand signs) in language origins, so I always welcome new evidence on this issue. PlosOne has recently published a paper titled, "Chimpanzee Signaling Points to a Multimodal Origin of Human Language," by Jared Taglialatela, Jamie Russell, Jennifer Schaeffer, and William Hopkins. Alert regulars at Babel's Dawn may recall previous discussions of work by Taglialatela. He is investigating speech origins by studying chimpanzee brains and determining how language-ready the ape brain was. (See: Broca's Area in Chimpanzees?; Ape Cries are Complex; How Different are Ape Brains from Ours?) This latest paper argues that from the beginning human language has combined vocalization and gesture. That's in keeping my arguments on this blog, but how much confidence can we have in this latest work?

The main argument for the first language having been a sign language comes from the fact that chimpanzees make voluntary gestures but do not make voluntary vocalizations. That argument rests of a bit of an overstatement. Some chimpanzees do make a voluntary vocalizations on the equivalent of, "Ahem." Then, having gotten your attention, they can put out a hand and beg for food or make some other gesture. The authors wondered whether there is any difference in brain function between chimpanzees that make ahem type vocalizations and those that don't.

The region of the chimpanzee brain that interested the authors is in the left inferior frontal gyrus of the cerebral cortex, in Brodmann's area 44 and 45. This region has been previously identified by Taglialatela as a homologue of the human region known as Broca's area. It used to be said that Broca's area controlled speech. Today's understanding is more complex, but Broca's area is still considered critical for the motor output of language. The authors wanted to know if the role of this area in chimpanzee signaling.

The point of this research is to determine paths to speech. Possible scenearios are:

1. Language began as a set of hand signals and later switched to speech. Evidence supporting this scenario would be activity in the chimp-Broca's area during gesture but not vocalization. Broca's area only began to control vocalizations after the last common ancestor of chimps and us.
2. Language began as a set of vocal signals and later included gesture. Since apes are already gesturing and can learn to make words in sign language, it is hard to imagine what brain evidence might exist to support this scenario.
3. Language began by combining gesture and vocalization. Supporting evidence would be that vocalization increases activity in the chimp-Broca's area, indicating that the human-lineage brain was already to control voluntary vocalizations at the time of the last common chimp/human ancestor.

The authors conducted a series of experiments to determine conditions that activate the chimp-Broca area. They used four captive chimpanzees, two who make the ahem vocalization and two who don't. The chimps were fed a substance that makes it possible to determine metabolic activity in the brain. They were then, individually, put in a position to try to catch a human's attention and beg for food. Finally, the chimpanzees were given PET scans to determine recent metabolic activity in the brain.

The two chimpanzees that vocalized as part of their effort to get human attention showed an increase metabolic activity in the chimp-Broca's area, while the two that relied on gesture alone did not. The authors interpret this finding as supporting scenario 3, language began by combining vocalization with gesture and does not support scenario A, that language began as gesture alone.

Their point is that we know the last common ancestor gestured because both humans and apes gesture. Now we know that the last common ancestor also had a region of the brain that was important to voluntary vocalization and is now important to speech. Thus, there is no reason to argue that language began with gesture because that's the only thing one could do with an ape brain.

There are a number of commenters on this blog who defend the gesture-first origins of language. Am I now saying it is time for them to go quiet? Not at all. Let's look at the possible objections to this paper:

• Chimp vocalizations are hard to classify. What's the difference between ahem and the ordinary chimp bark? The authors point out that attention-getting calls "have a clear recipient." They are much closer to the speech triangle, with a speaker and listener, lacking only a topic. It is often possible to distinguish a chimp ahem in this manner although it is not always easy, and there is plenty of room for wondering about interpreting particular sounds. But the point that is hard to overcome is that while all four subjects made vocalizations, only two made vocalizations that were interpreted as ahem sounds and only those two showed extra activity in their chimp-Broca's area.
• The logic isn't tight. The evidence 'supports' a scenario. It doesn't prove it. It is like an expert testifying that some piece of evidence is consistent with the prosecution's case. As somebody who has sat on many juries I like the evidence to be evidence of something. At the same time, it looks like the evidence does at least knock down a piece of anti-speech evidence. It gets rid of the argument that apes cannot make voluntary vocalizations and therefore an ape brain cannot get you started speaking.
• Then why don't apes do more voluntary vocalizing? Some skepticism is allowed just because of the surprising nature of the finding. It suggests apes could be doing more attention-getting vocalizing than they do, so what's keeping them mum? I've gone over this point many times on the blog. This evidence is just the latest in a long line of details that suggest apes could engage in at least protolanguage, yet they don't. The crucial change was in their sociability, particularly their willingness to trust, not in their intelligence or brains.

Comments

[Uzza]

A caveat: equating gesture with hand signs sets up a false dichotomy that is potentially very misleading. Formal signed languages crucially utilize orofacial and body movements, and Taglialatela discusses orofacial gestures through the paper.

The important distinction is not between hands and voice, but between visual or audio productions organized linguistically, versus those of either type that are not so organized.

ASL for example uses the lips and tongue as articulators, both syntactically and lexically. Obviously, the same lips and tongue also produce random visual images and random noises, as well as linguistically organized sounds.

[Jeremy Goard]

The main argument for the first language having been a sign language comes from the fact that chimpanzees make voluntary gestures but do not make voluntary vocalizations.

Is that your own assessment, or if not, whose is it? My ranking of arguments would look more like this:
(1) The massively greater iconicity in existing signed languages (not merely for concrete nouns and verbs, but for things like transitivity, verbal aspect, mental verbs, and about a bazillion others) shows that the manuofacial-visual channel is well suited for a gradual transition from simple and very iconic constructions, through various intermediate stages, through to more complex and arbitrary-seeming symbolic constructions. (Contemporary signed languages are of course massively more complex than a visual protolanguage could have been, a point which is in no way denied by pointing out that they are far more iconic than spoken languages. Languages in both channels exploit iconicity when they can, but it's available for a much broader range of meanings in the visual channel.)

(2) The very fact of native, unschooled, visual language acquisiton -- following an even earlier timecourse than auditory languages -- strongly suggests that at some point the underlying perceptual and cognitive mechanisms involved were relevant to the whole species, not just the deaf ones.

(3) The famous, substantial deficiencies of the human laryngeal tract are more understandable if there was already a really great cognitive system in place that precise speech sounds could tap into, versus having the gradually increasing efficiency of spoken language have to overcome increasing selective obstacles at each step of the way. (If rich symbolic manual-visual language were already in place, I take it that the evolutionary advantages of switching to speech in the ancestral environment are too obvious to mention.)

(4) Research about the effects of motion or visualization tasks upon choice of spoken langauge constructions.

(5) The supposed involuntariness of ape vocalizations.

I suppose one's ranking has almost everything to do with what what considers to be the most challenging stage in the development of language. For me, it's mostly about complex, schematic constructions, many of which may be used to construe the same objective scene in very different ways. That's where I think the iconicity of the visual channel offers a crucial bootstrapping. Voluntary calls could have existed in the hominid line for a long time, but so what? The gestural origin story would be that the calls would have remained mostly atomic and specific until the visual channel led to proto-syntax.

[Raymond Weitzman]

How does one determine whether the behaviors or sets of behavior of an animal, including human beings, are voluntary or involuntary? Or to put it another way, under what conditions do we say that a certain behavior is involuntary and under what conditions do we say that a certain behavior is voluntary? Also is it possible that some behaviors are voluntary and involuntary at the same time? If so, then under what conditions does this happen? I would prefer that these questions be discussed in a scientific, empirical framework, rather than a philosophical or metaphysical framework, unless those frameworks are empirically grounded.

To get things started off it might be worth listing some definitions of voluntary and involuntary. These are from the Merriam-Webster Dictionary online:

Definition of VOLUNTARY
1: proceeding from the will or from one's own choice or consent
2: unconstrained by interference : self-determining
3: done by design or intention : intentional
4: of, relating to, subject to, or regulated by the will
5: having power of free choice
6: provided or supported by voluntary action
7: acting or done of one's own free will without valuable consideration or legal obligation
Definition of INVOLUNTARY
1: done contrary to or without choice
2: compulsory
3: not subject to control of the will : reflex

The third definition for involuntary seems appropriate for a scientific definition of involuntary behavior. Psychologists have studied reflex behavior in a systematic way since Pavlov. However, none of the definitions for voluntary, however, seem to be good candidates as a scientific definition. They all seem to carry very subjective connotations. Certainly “free will” or “free choice” doesn’t seem to be particularly helpful. Are they even scientific concepts? I know they are used a lot in reference to human beings, but are they applicable in discussing the behavior of other animals?

I also checked some recent books on animal behavior and don’t even find the terms voluntary and involuntary, or even volitional, listed in their indices. The Dictionary of Ethology and Animal Learning did have an entry for voluntary behavior, but its discussion was about the differences in how behavioral scientists use the term.

So when we say that the action of a human being or other animal is voluntary what do we mean? It seems to me that there is little point of arguing about the origin of language and why other animals seem to lack language as we usually think of it in terms of voluntary and involuntary behavior unless we agree to using these terms in the same scientifically sound way. I have my own view on what is called voluntary behavior, but I doubt that others on this list would necessarily agree with it.