Can chimpanzees learn human language?

Two primary theories explain how our hominid ancestors began speaking. The vocal theory proposes that primates' innate vocalizations evolved into speech thanks to changes in the structure of the mouth and larynx and the enlargement of the brain [source: Dubuc]. The gestural theory, on the other hand, describes language as a step up from manual communication. Bipedalism freed our hands for signaling, then talking liberated our hands for other tasks [source: Dubuc].

Today, language fundamentals begin in the fetal stage. Studies have found that fetuses can differentiate between male and female voices and recognize novel syllables [source: Dubuc]. After birth, infants babble, imitate sounds and gradually string together familiar syllables, often saying their first words around 10 months [source: Dubuc].

Once we have the gift of gab, what's going on upstairs when we verbally express ourselves, and how do humans process language? The speech centers in our brains are Broca's area and Wernicke's area. Broca's area in the left frontal cortex controls language production, and Wernicke's in the posterior temporal lobe analyzes the words you see and hear and also places those words in the correct order before you speak.

Of course, these areas of the brain don't function in isolation. Imagine that someone asks, "How are you?" Once that message travels through the ear, the electrical impulse from the vibration enters the primary auditory cortex, which figures out that the source is a human voice. Then, the information moves to Wernicke's area for interpretation, followed by Broca's area where you select the words for a response. That message then goes to the primary motor cortex that signals your larynx and mouth to vocalize, "I'm fine, thanks" [source: Chudler].

One portion of tissue in Wernicke's area -- the planum temporale -- has been called our "language center" since it plays an integral role in comprehending the speech that we hear [source: Blakeslee]. This region is highly asymmetrical in most people's brains, causing a bulk of it to reside in the left hemisphere. The planum temporale's odd shape was once believed to be exclusive to humans. In 1998, three anthropologists and a neurologist shook up that notion [source: Blakeslee]. Guess which nonhuman primate they discovered had the same oddly shaped planum temporale? You guessed it: chimpanzees.

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A female chimpanzee named Washoe kicked off man's earnest quest to teach chimps human language. She was born in Africa in 1965 and eventually taken to Washoe County, Nev. (her namesake); that's where Washoe became the subject of cognitive research performed by Allen and Beatrix Gardener. The chimp wowed the world when she successfully learned American Sign Language, which had never happened before with a nonhuman primate. Washoe then passed her skills on to her adopted son Loulis, and by the time she died in 2007, Washoe had mastered around 130 signs [source: Carey].

In 1973, Columbia University psychologist Herbert Terrace wanted to see what happened with a chimp's language if it were raised as a human [source: Adler]. Nim Chimpsky -- named in snide homage for Noam Chomsky -- moved in with a family in New York City and was taught American Sign Language. Although Nim memorized 150 signs, researchers discovered his proficiency sprang from imitation of his teacher rather than unprompted communication [source: Adler]. Like Washoe, Nim hadn't cracked the code on spontaneous, humanlike communication.

Nevertheless, there are some interesting things going on in the apes' brains when signing or communicating with their innate gestures and vocalizations. PET scans conducted during a study for the Yerkes National Primate Research Center at Emory University found that chimpanzee communication activated the same regions of the brain as human language, particularly Broca's area and Wernicke's area [source: Moskowitz].

That breakthrough likely came as little surprise to lead primatologist for the Great Ape Trust, Susan Savage-Rumbaugh. Savage-Rumbaugh firmly believes that apes are capable of linguistic communication with humans and points to Kanzi and Panbanisha -- bonobo pygmy chimps she has worked with for more than 20 years -- as evidence. Instead of relying solely on sign language, Savage-Rumbaugh created lexigrams, or symbolic word representations, to teach the bonobos. She has also strived to meld the chimpanzee and human lifestyles to give the apes context for the words they're learning.

The result? Kanzi knows an impressive 360 lexigrams. Using a specialized series of keyboards with a lexigram on each key, Kanzi can point to a symbol to "say" a word. Panbanisha knows even more lexigrams. Savage-Rumbaugh also cites instances of creativity and word play in the bonobos, demonstrating that they are not simply memorizing words. For instance, Panbanisha pointed to the lexigram for "monster" in response to a poorly behaved visitor [source: Hamilton]. They also seem to understand syntax when tested. If Savage-Rumbuagh asks Kanzi to put raisins in a cup of water, the bonobo understands the difference between that and if she were to ask him to pour water on top of the raisins [source: Begley].

Even with those skills, Kanzi and Panbanisha's language abilities match up to that of a toddler [source: Cohen]. And the lack of spontaneous, noninstigated communication lingers. Scientists at the Yerkes National Primate Research Center may have pinpointed the key to that chimpanzee language gap in spring 2008.

Using Diffusion Tensor Imaging that traces neural paths, the researchers compared the brains of humans, rhesus monkeys and chimpanzees. Zeroing in on the arcuate fasciculus, the bundle of nerves that connects the brain's language centers, the imaging showed more widespread nerve connections spanning across the mid-temporal region in humans [source: Moskowitz]. Those expanded connections imply a greater ability of humans to analyze and contextualize linguistic information and could be the key difference between how we communicate versus chimps.

But as long as Kanzi and others continue to baffle us with their recognition and use of humanlike communication, the case of chimpanzees mastering our language is far from closed.