Monday, December 10, 2007

Oh, I Forgot Something

In my last post I wrote that two main approaches to comparing human and other animals’ cognition are ethological and genetic comparisons, but I think with such a statement I strongly downplayed the importance of anatomical features when comparing two species, such as the differences in brain anatomy (for a stake at this topic, see my earlier posts on brain evolution), and other features that bear a more indirect bearing on the structure of human cognition, yet it has a much stronger bearing on questions of human uniqueness.

These considerations are of course not exactly new. as early as in 1589, for example, George Puttenham wrote in his Arte of English Poesie that:
“Speach is not naturall to man sauing for his onely habilitie to speake, and that he is by kinde apt to vtter all his conceits with sounds and voyces diuersified many maner of wayes, by meanes of the many & fit instruments he hath by nature to that purpose, as a broad and voluble tong, thinne and mouable lippes, teeth euen and not shagged, thick ranged, a round vaulted pallate, and a long throte, besides and excellent capacitie of wit that maketh him more disciplinable and imitatiue then any other creature […].”
I will stick with this example because language evolution is this blog’s main topic.
What I find interesting in this paragraph is that Puttenham actually directs attention to a lot of physiological features that are acknowledged by modern linguists and phoneticians to be crucial for the production of speech. As Jean Aitchision puts it, we are “The Articulate Mammal” (1998), and many of her observations actually concur with that of Puttenham.
Just as he does she stresses the difference between the long thin tongues of monkey and the muscular, thick and mobile tongues of humans, which allows them to vary the size of the oral cavity, and thus allows the pronunciation of a great range of vowels.
She also stresses the fact that the muscles in the lips of humans are more intricately interlaced and more developed than the muscles in the lips of other primates. Aitchision also observes that the regularity of human teeth is not needed for eating but probably for articulatory purposes. (Aitchison 1998: 48f., Lieberman 2007: 40-47 , Fitch 2005: 198f.)

I doubt that Puttenham was the first to notice the importance of the specially structured and descended larynx of humans for speech, but he definitely wasn’t the last. Whereas in most mammals, simultaneous breathing and swallowing is possible, humans (or at least those who aren’t babies anymore), don’t posses this ability because their larynx lies too low to be engaged into the nasal passages. (Fitch 2000: 260)
This anatomical change expands the vocal repertoire of humans significantly and can be seen as “a key innovation in the evolution of speech” (Fitch 2000: 261) because it enabled us to form highly discriminable different phonetic sounds (“formant patterns”) (Fitch 2000:261),
However, it has lately been discovered that animals exhibit a remarkable plasticity in regards to the lowering of the larynx during vocalization (for a example, a dog bark) Furthermore, the descension of the larynx doesn’t seem to be unique to humans, and is also found in lions, koalas, and deer. (Fitch 2005: 199).

This has led some researchers, such as Tecumseh Fitch, to suggest that this shared property is an instance of convergent evolution and thus evolved for a different purpose than speech production, namely size exaggeration, the function the descension of the larynx fulfills, for example, in deer (Fitch and Reby 2001, Fitch 2005).
In this view, the descension of the larynx was prior to speech and was only later co-opted for language. The first fully modern human speech anatomy is dated to 50,000 years ago, and is missing in earlier humans as well as Neanderthals. (Lieberman 2007). This still fits with the a scenario in which the speech tract was only later adapted and further shaped for language, and it definitely shows that language/speech is a driving force in human evolution, given the long evolutionary trajectory it has had.

But what then, is special to speech? Again it seems that Puttenham was on the right track. Hauser et al. (2002), for example, also stress the importance of vocal imitation in language learning and production. Whereas dolphins, whales, seals, songbirds, parrots, hummingbirds and some other species seem to share humans’ aptness regarding vocal imitation, it seems that in other primates this trait is either absent or only exists in a rather rudimental form (Hauser et al. 2002, Fitch 2000, Fitch 2005).
This is supported for example by evidence from cross-fostered Japanese/rhesus macaques. Although both species have a very similar social structure, their vocalizations are quite different in some context. Whereas juvenile Japanese macaques give clear cooing sounds when playing, rhesus macaques give gruffy grunts in the same situation. Did the Japanese macaques growing up in the Rhesus macaque adopt the vocalizations of their foster species? What about the Rhesus macaques growing up among Japanese Macaques?
Interestingly, although they are in fact able to produce such sounds (and do so in other contexts), the Japanese Macaque splaying with Rhesus macaques gave coos whereas their playmates gave gruffs. The same lack of vocal adaptation could be seen in the cross-fostered rhesus macaques. Certain calls in the macaques seem to be genetically bound to specific contexts(Cheney & Seyfarth 2007: 225, Owren et al. 1993), something which clearly isn’t the case with humans (otherwise there wouldn’t be 250 different languages spoken alone in Brooklyn, for example).

So the case Hauser et al. make for vocal imitation seems quite a strong one. Yet, as they themselves acknowledge, the question what vocal imitation evolved for is still hotly debated. There is still further evidence that supports the notion that vocal imitation is a more crucial component that led to human language than mere voluntary vocal control per se.
As we have seen, in some situations primate and generally animal signaling is closely bound to specific contexts. However, there are other situations where call production is much more plastic and seems to be much more under voluntary control.

One example is a study by Hihara et al. (2003), in which they trained macaques to use a rake in order to retrieve food, and subsequently brought them to either request the food directly, or request the rake, via cooing (Something the monkey is probably inclined to utter naturally in the context of food.) Astonishingly, the monkeys came up with two distinct calls all on their own, one for requesting the rake, the other for requesting for food (Cheney & Seyfarth 2007: 227, Hihara et al. 2003).
An even more intriguing example of signal transformation (albeit not in the auditory modality), called schematization of action, is the following: (Which I took from Hurford 2007, who took it from Gomez 2005 – yeah, recursion rocks!)
“Thorndike (1898) found that cats that were released from a puzzle-box upon performance of an arbitrarily chosen action (e.g., licking their paw), instead of by the accidental activation of the releasing device, tended to develop an abridged, sketched-out version of the relevant behaviour — something like a “gesture” of paw-licking“ (Gomez 2005: 93, Hurford 2007: 199,)
Of course, Puttenham wasn’t only referring to vocal imitation. In fact, things lie a bit differently when we speak about general imitation, and I’ll discuss some of the evidence on human vs. non-human imitation in my next post.


Aitchison, Jean. 1998. The Articulate Mammal. An Introduction toPsycholinguistics. London / New York: Routledge.

Cheney, Dorothy L. and Robert M. Seyfarth. 2007. Baboon Metaphysics: The Evolution of a Social Mind. University of Chicago Press, Chicago

Fitch W. Tecumseh. 2000. The evolution of speech: a comparative review. Trends in Cognitive Sciences. 4: 258 – 267.

Fitch, W. Tecumseh. 2005. “The Evolution of Language: A Comparative Review” P Biology and Philosophy 20: 193–230

Fitch, W. Tcusmeh and David Reby. 2001. “The descended larynx is not uniquely human.” Proclamations of the Royal Society B: Bioliogical Sciences 268: 1669 – 1675.

Gómez, Juan Carlos. 2005. “Requesting gestures in captive monkeys and apes: Conditioned responses or referential behaviours?“ Gesture 5.1/2: 91-105.

Hauser, Marc D., Noam Chomsky and W. Tecumseh Fitch 2002. “The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?” In: Science 298, 1569-1579

Hihara, Sayaka, HirokoYamada, Atsushi Iriki, and Kazuo Okanoya. 2003. “Spontaneous vocal differentiation of coo-calls for tools and food in Japanese monkeys” Neuroscience Research 45.4

Hurford, James M. 2007. The Origins of Meaning: Language in the Light of Evolution. Oxford: OUP.

Lieberman, Phillip. 2007. “The Evolution of Speech: Its Anatomical and Neural Bases.” Current Anthropology 48.1: 39-66.

Owren MJ, Dieter JA, Seyfarth RM, Cheney DL.. 1993 “Vocalizations of rhesus (Macaca mulatta) and Japanese (M. fuscata) macaques cross-fostered between species show evidence of only limited modification “ Developmental Psychobiology 26.7: 389-406.

Thorndike, Edward L. 1898. “Animal intelligence: An experimental study of the associative processes in animals.” Psychological Review: Series of Monograph Supplements, 2.4: 1-109.

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