a skeptical analysis of the evidence
for nonhuman primate language
by Clive Wynne
Copyright © 2007 the Skeptics Society
and Clive Wynne
August 1969 the pre-eminent journal Science published a
paper which, in its own way, marked as giant a leap for mankind as the
first moon landing a month earlier.1 Allen and Beatrice Gardner
of the University of Nevada reported that, for the first time in human
history, they had conversed with a member of another species. Washoe, a
female chimpanzee who had been reared in a trailer in the Gardner’s
backyard, had a vocabulary of over one hundred words that she used to
effectively communicate with her caregivers.
Centuries earlier, the French philosopher René
Descartes observed that, “it is very remarkable that there are none so
depraved and stupid, without even excepting idiots, that they cannot
arrange different words together, forming of them a statement by which
they make known their thoughts; while, on the other hand, there is no
other animal, however perfect and fortunately circumstanced it may be,
which can do the same.”2 Descartes’ opinion had survived three
centuries unthreatened by possible contradiction. Until Washoe, every
speaking beast had been shown to be just a circus trick. Parrots might be
trained to repeat certain phrases, but they had no understanding of what
they were saying. Dogs could respond to commands, but they had no grasp of
But Washoe was the real McCoy. She didn’t just
respond to rote commands, she could correctly react to novel combinations
of words. And she created her own little sentences like gimme sweet,
come open, and listen dog.3 Taken out on a
lake, Washoe saw a swan for the first time and signed water bird
for this unfamiliar creature.
Many had tried to communicate with chimpanzees
before — but none had got very far. Before the Gardners, the record for
chimpanzee communication was just three words — Mama, Papa,
and Cup — recorded in the early 1950s.4 These attempts
had attracted a lot of public attention and even inspired one of Ronald
Reagan’s better movies, Bedtime for Bonzo. (Reagan later joked
“I’m the one with the watch.”) But they had only reinforced Descartes’
conclusions about nonhuman linguistic possibilities.
The Gardners succeeded where so many before them had
failed because they had the brilliant insight to teach Washoe to use her
hands to communicate instead of her vocal chords. Many early observers of
chimps had noted how much more facile they were with their hands and feet
than with their voices, but none before the Gardners had thought to use
this as a way to teach them language. The Gardners trained Washoe in the
sign language used by the deaf in North America: ASL.
ASL is a complete human language. Though a few signs
are fairly clear pantomimes of the actions they imply, most are as
incomprehensible to the uninitiated as the sounds in an unfamiliar spoken
language. ASL also has its own grammar and syntax.
Washoe inspired legions of imitators. By the early
1970s there were about two dozen apes in language training: one even made
it onto The Tonight Show with Johnny Carson.5 Francine
(Penny) Patterson, at the time a graduate student at Stanford University,
became the first to train a gorilla in sign language. Duane Rumbaugh at
Emory University developed a communication system in which the apes had to
press keys with patterns on them to express themselves. Their human
companions could either press keys back at them, or just talk in plain
The most significant of Washoe’s imitators was
probably a chimpanzee cheekily named Nim Chimpsky by Herbert Terrace of
Columbia University. The joke was that linguist Noam Chomsky was the most
vocal defender of Descartes’ belief that language was uniquely human.
Terrace held a quite different view. He told an interviewer in early 1975,
“I’m not the only one trying to teach a chimp a sign language. There are
others … but I hope to be the one who is going to do it right.”6
He would, “nail to the wall proof that a subhuman primate can acquire a
syntactical competence that at least overlaps with that of man …the
age-old distinctions concerning man’s uniqueness would no longer hold.”
At first Nim’s progress matched Washoe’s closely. By
September 1977 Nim had acquired 125 signs — not too dissimilar from
Washoe’s rate of vocabulary acquisition. He also started stringing signs
together in little sentences. Terrace and his colleagues collected over
20,000 instances where Nim put words together in potentially grammatical
sequences. For example, if Nim wanted more of something he was more likely
to say more something (where something could be anything
he knew the name of) than to say it backwards (something more).
Similarly, when Nim put a verb and a noun together, he was much more
likely to do it that way (eat grape for example), than the
reverse (grape eat). Patterns like this had convinced the Gardners that
Washoe understood grammar, but Terrace realized that in themselves these
word order patterns were not enough to prove that an animal understood
To see why word order alone is not enough to prove
the comprehension of grammar consider one of Nim’s most frequent two word
phrases. In line with stereotypes about chimpanzees, Nim was very fond of
bananas and would frequently sign: banana me. And he signed it
that way about three times more often than he would sign me banana.
Does this show us that Nim understood the rules of English grammar and is
correctly saying “Give a banana to me” in the abbreviated form quite
common to young children just beginning to learn their native language?
Terrace understood that just recording the ape’s use of signs alone could
never tell us the answer. We could never be sure that Nim was really
trying to say, “Give a banana to me” and not, for example, “My Banana”
(given that the language he was taught did not distinguish “me” from
“my”). If Nim was really trying to say “My Banana” then he was actually
usually in error and was only occasionally getting the grammatical
structure right. Everything depends on Nim’s intention. We simply cannot
know whether a particular utterance is grammatical or not just by looking
at the words used. We have to see the context.
Terrace and his team had collected videotapes of Nim
with his trainers and proceeded to analyze these frame by frame, looking
not just at what signs Nim used, but at the exact context — everything
that was going on before and after Nim’s utterances. Terrace released his
results in November 1979. Dava Sobel in the New York Times
summarized Terrace’s new position thus: “Herbert S. Terrace … now asserts
that the success of his own and related efforts can be explained as mere
prompting on the part of the experimenters and mistakes in reporting the
data. ‘Much of the apes’ behavior is pure drill,’ he said. ‘Language still
stands as an important definition of the human species.’”
Incredible! And a complete reversal of what he set
out to find. Terrace now argued that Nim’s use of ASL signs was quite
unlike how children learn language. Nim failed to initiate conversations,
he seldom introduced new vocabulary and just imitated what the humans
around him said. Nim’s sentences failed to grow in length. In human
children there is a close relationship between the number of words known
and the number of words used in a sentence. Not so in Nim. Throughout his
time in the language project he stuck to using one or two words at a time.
And his longer utterances were without any regard for grammatical
structure. Nim’s longest recorded “sentence” was give orange me give
eat orange me eat orange give me eat orange give me you. Not hard to
understand — but not very grammatical either.
The others who had apes in training were furious
with Terrace. Science reported that the “mutual criticisms among
ape language researchers … have made the War of the Roses look like a
teddy-bears’ picnic.”7 The other ape language projects
criticized Terrace’s treatment of Nim and attempted a rearguard action to
defend their claims for ape language. But by the early 1980s the tide of
opinion had swung back. Descartes was right after all. Animals do not
Several researchers continue working with apes on
sign language to this day. Washoe is now in the care of Roger Fouts who
started out as a student of the Gardners’. Penny Patterson still has Koko
the gorilla. But, by and large these projects have dipped below the radar
of scientific publication — though they still appear with enthusiasm in
the popular media.
But one ape language project maintained its
scientific respectability. Duane Rumbaugh’s system, in which the
chimpanzees communicated by pressing buttons on a keyboard, had always
been subject to tighter experimental control than the ASL-based attempts
at ape language.
In 1974 Duane Rumbaugh had been joined in his
project by Sue Savage, whom the New Yorker described in 1978 as
“a very pretty psychobiologist.”8 Duane and Sue had married a
year earlier. In 1980 Duane Rumbaugh and Sue Savage-Rumbaugh started
working with a new species of ape: bonobos — also known as pygmy
chimpanzees. At this time, bonobos were almost entirely unstudied. They
had only been recognized as a distinct species from chimps a few years
earlier. Initial efforts with a mature female, Matata, were hopeless. But
when they separated Matata from the adopted infant Kanzi who had been
hanging onto her throughout her fruitless training, something very
According to Savage-Rumbaugh, the moment the special
keyboard was set up in front of Kanzi to start his language training, he
began using the signs on the keys to communicate. On the very first day he
pressed twelve of the keys over 120 times. He asked for banana, juice,
raisin, peanuts, chase, bite, tickle, orange, outdoors, swing, cherry,
ball and sweet-potato.9 There was even evidence
that first day that Kanzi could combine signs meaningfully. He indicated
raisin peanut and sweet-potato tickle and seemed
grateful when given each of those things. Kanzi went on to master rapidly
the 256 signs, which was the most that could be fitted conveniently onto a
The Rumbaughs reported that Kanzi learned language
“spontaneously” without explicit training. His education in language was
no more and no less than that customarily offered to young human beings.
Although he communicated with the people around him by pressing keys on
his keyboard, they customarily spoke to him in ordinary English.
Starting in the mid 1980s the Rumbaughs started
claiming that Kanzi had mastered the rudiments of grammar.10 In
a major study carried out when Kanzi was eight years old, his
comprehension of over six hundred different sentences was tested.11
An experimenter went behind a one-way mirror (so that she could not convey
any nonverbal cues, such as eye movements, to Kanzi) and asked him to
carry out a command. For example, Kanzi was asked to do such things as “Go
put some soap on Liz,” “Put on the monster mask and scare Linda,” and to
“Take the mushrooms to Matata.” As far as possible the experimenters tried
to formulate commands that were unlikely to have previously arisen in
Kanzi’s daily life.12 In a majority of cases Kanzi did as he
was asked to do. Kanzi, concluded the Rumbaughs, “clearly processed
semantic and syntactic features of each novel utterance.” In other words,
here was a nonhuman ape who understood meaning and grammar. Descartes and
Terrace were wrong. The grail of the ape language studies had been found.
When I first heard of Kanzi’s achievements I was
very excited indeed. I really felt that our understanding of the nature of
the world and our place in it as human beings had been altered by what
this bonobo had done. But when I studied the complete report of what Kanzi
had been asked to do and started going carefully through the six hundred
and sixty commands he had been given and how he had responded to each one,
my excitement changed to disappointment.
For a start Kanzi — like Nim before him — did not
show the increase in sentence length that is typical of children learning
language. In fact, at 1.15 symbols per sentence, Kanzi’s average utterance
is even shorter than Nim’s. And it turns out that to complete many of the
requests that were put to him Kanzi did not need to understand grammar.
For example when Kanzi was asked to “Take the hat to the colony room” —
which Kanzi did successfully — all he needed was some sense of “hat” and
of “colony room.”14 A hat may be taken to a colony room, but a
room cannot be brought to a hat. Successful completion of this instruction
suggests an understanding of some vocabulary, but it is not in itself
proof of grammatical comprehension. To test grammar what are needed are
pairs of reversible commands like: “Dog bites man” and “Man bites dog.”
Just knowing those three words — man, bites, and dog
— is not enough to comprehend the difference between these two statements.
For that difference to be understood grammar is crucial.
Of the 660 commands that Kanzi was given, a mere 21
formed pairs of the “man bites dog” “dog bites man” variety that
constitute a critical test of grammatical comprehension. Savage-Rumbaugh
and her colleagues reported that Kanzi responded accurately to 12 of these
21 pairs — a modest 57% correct. On closer inspection, however, it became
clear to me that their method of coding Kanzi’s responses was unreasonably
generous. To take one example: They commanded Kanzi, “Pour the juice in
the egg.” Kanzi proceeded to pick up the bowl with the egg in it, sniff
it, and shake it. They repeated the command three times — each time
changing the wording slightly — before Kanzi did what they asked him to.
They nonetheless scored his response as correct. When they asked Kanzi to
“Pour some water on the raisins,” he held a jug of water over a lettuce.
This was coded as correct. Kanzi’s first reaction to the request to pour
milk into water was to stick a tomato in the water. When asked to chase
Liz he remained seated; when asked again he touched Liz’s leg and she
chased him. All of these were scored correct. When Kanzi was given the two
commands, “Make the [toy] doggie bite the [toy] snake” and “Make the snake
bite the doggie,” in both cases the snake ended up in the dog’s mouth but
both responses were coded as correct. Re-scored to exclude these false
positives, Kanzi achieves less than 30% correct.
Why be so nitpicky? The point here is not to deny
Kanzi’s achievements — what other nonhuman can convey so much to his
caregivers, or understand so much of what they say to him? — but to
quantify them correctly. The point is not to see whether Kanzi does
something involving toy dogs and snakes when asked to “Make the doggie
bite the snake,” but to see if he understands grammar. And, on any
assessment not tinted with rose-colored glasses, Kanzi just doesn’t get
Kanzi has declined my requests for interviews. He
did recently speak with John Berman of ABC’s Nightline. Now 26
years old, and in language training for almost his entire life, this is
how Kanzi conversed with Berman:15
Kanzi: Surprise (pointing to a box of candy).
Berman averred: “Moments like this are proof that
these conversations help scientists learn about apes, from the apes
themselves.” I don’t disagree, though I fear the conclusion I draw is not
the one Berman intended. Moments like this tell us that Descartes was
right, there really are no beasts, no matter how fortunately
circumstanced, that can make known their thoughts through language. Next
time you see Kanzi or one of his kind on a television documentary, turn
down the sound so you can just watch what he is doing without
interpretation from the ape’s trainers. See if that really appears to be
language. Somewhere in the history of our kind there must have been the
first beings who could rearrange tokens to create new meanings, to
distinguish Me Banana from Banana Me. But the evidence
from many years of training apes to press buttons or sign in ASL, is that
this must have happened sometime after we split off from chimps, bonobos,
and gorillas. Since then we have been talking to ourselves.
References & Notes
- Gardner, Allen and Beatrice Gardner.
1969. “Teaching Sign Language to a Chimpanzee.” Science, 165,
- Descartes, René. 1976. “Animals Are
Machines.” In T. Regan & P. Singer (Eds.). Animal Rights and Human
Obligations. Englewood Cliffs: NJ: Prentice Hall, 60–66.
- Fouts, Roger. 1997. Next of Kin.
London: Michael Joseph.
- Hayes, Keith and Cathy Hayes. 1951.
The Ape in Our House. New York: Harper and Brothers. A video of
this ape ‘talking’ to its caregivers is on the web at:
- Dewsbury, Donald. 2007. Monkey
Farm. Lewisburg, PA: Bucknell University Press.
- Baur, Stuart. 1975. “First message
from the planet of the apes.” New York. Feb 24.
- Nicholas Wade. 1980. “Does Man Alone
Have Language? Apes Reply In Riddles, and a Horse Says Neigh.”
Science, 208, 1349–1351.
- Hahn, Emily. 1978. “A Reporter At
Large. Getting Through to the Others II.” New Yorker, April 24,
- Savage-Rumbaugh, E. Sue & Roger Lewin,
1994. Kanzi: An Ape at the Brink of Human Mind, New York:
Wiley. Savage-Rumbaugh, E. Sue, Stuart G. Shanker & Talbot J. Taylor,
1998, Apes Language and the Human Mind. New York: Oxford
- Savage-Rumbaugh, E. Sue, Janine
Murphy, Rose Sevcik, Karen E. Brakke, Shelly L. Williams, & Duane M.
Rumbaugh. 1993. “Language comprehension in ape and child.”
Monographs of the Society for Research in Child Development, 58,
nos. 3–4. pp. 62ff.
- ibid, p. 45.
- ibid, p. 53.
- ibid, p. 98.
- Ibid, p. 177.
- Berman, John. 2007. �Hello, How are
you doing?", ABC News. May 29, Available online at: