Do apes have language?

Jan 25, 2011 by

So dogs may be smart and dilligent, but they do not have language. What about apes? After all, apes are closer to us genetically, and chimps — our closest relatives in the animal world — share about 98.4% of DNA with us. Still, as it turns out, even they don’t come close to learning human language.

One thing that’s become quite clear in the early studies of animal communication is that it is impossible for apes (chimps included) to pronounce sounds used in human language. This has to do with a different anatomy of the vocal tract and especially with the higher position of the larynx in apes compared to human (ironically, this difference makes humans more likely to choke). So something else must be tried with apes. Most studies of ape “language” used human sign language, like ASL (American Sign Language). Some other studies used graphic symbols like the ones in the picture below.

ASL-based studies include the study made by Beatrix and Allen Garnder, who raised Washoe the chimp like a human child in a comfortable domestic environment. They taught her ASL as they’d teach a deaf child. Through this experiment, Washoe learned approximately 350 words of ASL and was even able to combine them to express complex messages. A similar strategy was used with Koko the gorilla and Nim Chimpsky, a chimp whose name is a pun on that of Noam Chomsky, the main proponent of the idea that language is (partially) inherited.

Nim Chimpsky is typically considered the highest achievement of animal language experiments. While Nim did learn 125 signs (some say that by more standard criteria his “word count” is closer to 25), researchers had to conclude that Nim hadn’t acquired anything they were prepared to designate worthy of the name “language”. Despite all the efforts to teach him, he did not show any meaningful sequential behavior that rivaled human grammar. Nim’s use of language was strictly pragmatic, as a means of obtaining an outcome, unlike a human child’s, which can serve to generate or express meanings, thoughts, or ideas. In fact, Nim’s longest sentence was the 16-word-long “Give orange me give eat orange me eat orange give me eat orange give me you” — doesn’t that sound like a two-year old having a tantrum?

A new frontier was crossed by Kanzi the bonobo (a pygmy chimpanzee). Unlike the apes mentioned above who were specifically taught human language, Kanzi seems to have learned from mere exposure to human language (or rather a language-like symbolic system that was made up for the purpose of this experiment). The experimenter Sue Savage-Rumbaugh worked with Kanzi’s adoptive mother Matata, while Kanzi was simply present.

So whatever Kanzi learned was learned not by being taught, but by being exposed to, and observing, language at an early age. Kanzi developed what researchers referred to as “a large symbol vocabulary” (over 250 forms). We are supposed to be impressed. If you are not, you are not alone. After all, this vocabulary size is typical of an average 19-month old human child! By comparison, a 6-year old knows approximately 14,000 words. In other words, by the age of eight, Kanzi was able to understand language at the level of a two-and-a-half-year-old human child. However, a typical bonobo lifespan is about 40 years, similar to that of humans (modulo modern medicine and so on). Not only was Kanzi lagging behind a human child, but he never caught on.

Thus, it appears that even our closest relatives in the animal world, the chimps, do not have what we have — language, defined as an infinite recursive system of rules for the manipulation of arbitrary symbols. What may be responsible for this major gap between language-less apes and us, homo sapiens? If you think that the answer must be in the genes, you are probably right. As far as we know now, there is at least one gene (FOXP2) responsible for language. We have it (or rather a certain variant of it), they don’t. When exactly did we get it? The current consensus hovers around 200,000 years ago, but the evidence from Neanderthal DNA may change that. Stay tuned!

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