Have you ever watched a toddler play with an iPhone?
Most likely, the child was completely captivated and surprisingly adept at manipulating the tiny icons. Two-year-old Teco is no different. Sitting with his Motorola Xoom tablet, he’s rapt, his dark eyes fixed on the images, fingers pecking away at the touch screen. He can’t speak, but with the aid of the tablet app I created for him, he’s building a vocabulary that will likely total several thousand words. What’s more, he’ll be able to string those words together into simple sentences and ask questions, tell jokes, and carry on conversations.
Such talents wouldn’t seem exceptional in a human child, but Teco is an ape—a bonobo, to be precise. To the uninitiated, bonobos look very much like chimpanzees, but they are in fact a separate species with distinct physical and behavioral traits. More collaborative and sociable than their chimp cousins, bonobos also seem to be more adept at learning human language. And they are endangered, found in the wild only in the Democratic Republic of the Congo. Recent estimates put the wild bonobo population at between 10 000 and 50 000. Fewer than 150 live in captivity. Along with the chimpanzee, they are our species’ closest relatives.
For more than three decades, researchers have been working with a small group of bonobos, including Teco, to explore their amazing cognitive and linguistic abilities. Teco’s father, Kanzi, is the group’s most famous member: Anderson Cooper has interviewed him, and he’s played piano with Paul McCartney and Peter Gabriel. Animal lovers worldwide have marveled at his ability to communicate by pointing to abstract symbols. He recognizes nearly 500 of these “lexigrams,” which he uses to make requests, answer questions, and compose short sentences. The spoken words he understands number in the thousands.
Even so, many people question these abilities. Indeed, for more than a century scientists have debated whether apes could ever truly comprehend human language. Many researchers argue that language is the exclusive domain of humans, and several influential studies in the 1980s concluded that supposedly “talking” apes were merely demonstrating their capacity for imitation, with lots of unintentional cuing by the animals’ handlers. Linguist Noam Chomsky has likewise argued that the human brain contains a species-specific “language acquisition device,” which allows humans, and only humans, to acquire language.
But the bonobo research I’ve been involved with, led by primatologist Sue Savage-Rumbaugh at the Bonobo Hope Great Ape Trust Sanctuary, in Des Moines, strongly suggests otherwise. Today, the wide availability of touch screens, tablet computers, digital recording, and wireless networking is giving researchers the world over powerful new ways to study and unambiguously document ape communication. The results of these studies are in turn helping to spark a renaissance of technology-aided research into primate development and cognition and shedding light on the origins of culture, language, tools, and intelligence.
It’s a typical workday, and Panbanisha, Kanzi’s younger sister, is sitting before a 42-inch touch-screen display. She’s doing a match-to-sample task: When she presses a green button in the middle of the screen, the computer’s text-to-speech synthesizer says “apple,” and then the lexigram for the word apple appears on screen, along with two other lexigrams, for dog and sorry. Panbanisha touches the one for apple. After five correct responses, she gets to pick a short video to watch. She selects one of her favorites: a clip from Tarzan the Ape Man.
Our research group is using tasks like this to measure the bonobos’ vocabularies. We estimate that Panbanisha, like her brother, understands several thousand words. These match-to-sample experiments are enabling us to determine the exact number and should also help dispel criticisms that the bonobos are simply displaying the “Clever Hans effect.” Clever Hans was a horse that became renowned at the turn of the last century for solving arithmetic problems, telling time, and reading and understanding German. Later it was revealed that his trainer was subconsciously nodding whenever the horse tapped out the correct answer. Hans was indeed clever—clever at reading subtle cues from his trainer, not at adding and subtracting.
To avoid the Clever Hans effect, the bonobos aren’t encouraged to use sign language, because it leaves too much open to interpretation. Instead they “talk” to us almost exclusively with lexigrams; the computer helps remove any ambiguity. One day, for instance, Savage-Rumbaugh was using the match-to-sample program to familiarize Panbanisha with new words. The computer’s synthesized voice spoke the word “carrot” and then its screen displayed the lexigrams for carrot, carry, and potato. Panbanisha was about to hit the lexigram for carrot, but Savage-Rumbaugh, who’d misheard the word as “carry,” told the ape she was mistaken. The ape, though, knew better and selected the carrot lexigram anyway.
For more free-form communication, the apes can use their lexigram program, which displays up to 600 symbols on screen [for examples, see the image “True Meaning”]. The bonobos can tap multiple keys to construct a sentence, and each sentence they write is time-stamped and recorded for further analysis.
In 1971 a primatologist named Duane Rumbaugh (Savage-Rumbaugh’s ex-husband) came up with the idea of teaching language to apes by displaying abstract geometrical symbols on a computer screen. The first set of 120 symbols was then designed by Ernst von Glasersfeld [PDF], who also coined the word lexigram. Each symbol represented a noun, verb, adjective, or name. The lexigram lexicon was later expanded to 384 symbols, which were displayed on a keyboard. Researchers also used (and sometimes still use) a folding poster-board keyboard when greater mobility was required.
The latest version of the keyboard is created with software on a touch screen. These keyboards are easier to update and much less expensive to make than their hardware predecessors. Written in Java, the program will run on any reasonably up-to-date desktop or laptop. The keyboard software can also be wirelessly shared among several computers so that more than one researcher can communicate with a single bonobo. For easier translation, the researcher’s keyboard displays the English word just below each lexigram. Or the researcher can type in a word or sentence in English, and the software does its best to translate it into a meaningful string of lexigrams. For example, there is no lexigram for pizza, so the program translates that word into the three-lexigram sequence for bread cheese tomato, a description the bonobos came up with themselves. [To view the complete set of lexigrams, see the interactive lexigram keyboard created by the Bonobo Hope Great Ape Trust Sanctuary. As you hover over each symbol, its English-language meaning will pop up.]