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Wyatt Hilyard
M. Scoggin
ANTH 410
April 19, 2013
Overview of Studies on Human-Primate Communication
Abstract
Primatology, a subdivision of biological anthropology, has many definitions and uses. To
some, it is a study of primates on their own, separate from human evolution and ethology. Most
modern and historical primatology research, however, is linked to human evolution behavioral
studies. One of the major interests of this kind of research is human-primate communication. In
this paper I will argue that the great apes are capable of understanding and utilizing human
language to some extent. The degree to which each species is ultimately able to communicate
with humans will be shown using case studies. I will also argue that both views of the discipline
are valid, but must be kept separate in order to maintain scientific integrity.
A Brief History of Primatology
Before we talk about primate language studies, it is important to understand the history of
the relatively new science of primatology. Many consider Robert Yerkes to be the founder of
primatology, publishing several animal psychology works in the early to mid 20th
century. In the
early 1920's, inspired by a recent trip to primate research facilities in Cuba, he bought two
chimpanzees from a local zoo in Pennsylvania and raised them in his home. The methods he used
are viewed by many as unscientific and unethical, but there was little objection at the time. He
founded the first research laboratory specific to primate research in 1929. Being primarily a

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psychologist, Yerkes' most notable work was outside primatology. In the mid 1910's, he created a
series of alpha/beta tests that turned into IQ tests given to the U.S. Army, and ended up being
used to fuel the debates on immigration restriction in 1924. Yerkes claimed his tests measured
native intelligence, but the way they were formulated unintentionally relied on a certain amount
of education and cultural knowledge. His personal and professional views on hereditary eugenics
and intelligence make him unpopular today. His work is often discredited due to the inherent
influence those views had on his research and interpretation of his findings. Regardless of both
areas of politically-incorrect research, he is still viewed as a sort of pioneer of primatology. The
Yerkes Regional Primate Research Center is still fully-functioning, and his name has been used
in tribute to refer to a form of symbolic primate language, Yerkish, which will be discussed later
in this paper.
“Leakey's Angels” is a term used to refer to three pioneering female primatologists: Jane
Goodall (chimpanzees,) Dian Fossey (gorillas,) and Birute Galdikas (orangutans.) All three
recieved a substantial amount of funding and publicity from Louis Leakey, a major figure in
archaeology and paleoanthropology. Goodall was the first of this group, and probably the most
publicized primatologist to date. She started her field work in 1960 in Tanzania, then
Tanganyika. She is often criticized by modern primatologists for her training and methodology.
She had no scientific field training; she was a secretary. In her field work she greatly
anthropomorphized the individuals in the group she studied. This drew popularity to her work
(people love stories of cute chimps running around and creating mischief,) but was a hindrance
to the emerging science of primatology. For decades after it was impossible to get funding if your
field work didn't have some sort of tie to human evolution. I think part of that stems from the fact

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that Louis Leakey's work was human evolution, and that concept was unintentionally attached to
the first major steps in popular primatology. That, coupled with anthropomorphization on the part
of the scientists, hurt the discipline's reputation as a science. Although relatively unpopular, it is
now possible to do research on primates without tying in human evolution.
Frans de Waal, a Dutch primatologist and ethologist, is one of the most popular currently
active primate behavior scientists. He has published numerous books on the subject, which focus
mainly on the social lives of primates. He links the behaviors of chimpanzees and bonobos to
human behavioral traits. An issue I personally have with de Waal's bonobo field work in
particular is that it was conducted at the San Diego Zoo. Factors such as unnaturally high stress
levels are consequential to a captive environment, meaning the behavioral observations he made
are skewed. His research has contributed to the slogan “make love, not war” based on his
observations that bonobos use sex instead of fighting to settle high-tension situations. This is
true, but due to the fact his studies were conducted in captivity, the rates he recorded are not the
same as the natural ethology of bonobos. I would have no objection if this distinction wasn't
overlooked by the general media and had affected views the public now has of the species.
Through my brief history of primatology, I have pointed out one common factor in the
work of each of the aforementioned players: anthropomorphizing their research. De Waal's
approach is the same, and has even spoken out against its resistance, calling it “anthropodenial.”
He offers the analogy of a brick wall; people in anthropodenial attempt to build a brick wall
separating humans from their evolutionary ancestors. “They carry on the tradition of René
Descartes, who declared that while humans possessed souls, animals were mere automatons. This
produced a serious dilemma when Charles Darwin came along: If we descended from such

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automatons, were we not automatons ourselves? If not, how did we get to be so different?” (de
Waal, “Are We in Anthropodenial”). According to this analogy, a brick is pulled from the wall
each time one of these questions is asked. He attributes our “anthropodenial” to parsimony, “that
we must make as few assumptions as possible when trying to construct a scientific explanation”
(de Waal, “Are We in Anthropodenial”). Personally, I agree with this idea, and liken it to the
legal concept of “innocent until proven guilty.” The reason behind a given behavior must be
tested, not immediately explained by our own reason for similar behavior. And this sort of testing
has been applied in certain circles of scientists, but isn't over yet.
When we anthropomorphize in field work, it invites a set of assumptions that may clutter
the data. In the subfields of archeology and paleontology, for example, it is a well-accepted
practice that every piece of data be collected with as little assumption as possible. This allows for
a wider range of possible conclusions during lab analysis. If we record that a particular behavior
is anything other than the behavior itself, it muddies the results. Research that uses other
primates in order to better understand ourselves isn't the only research that is being carried out.
Inferring meaning is admissible when dealing in that realm of study, but harms the data when
studying the ecology of a species on its own. As far as I'm aware, fields like ichthyology and
ornithology don't have this problem. Our evolutionary proximity shouldn't come into the picture
when studying species ecology for conservation and rehabilitation uses.
Language Studies of the Great Apes
When it comes to experiments dealing with apes' abilities to learn and understand human
language, there have been a few different approaches: sign language, physical tokens with
symbols, and an asymmetric form of communication that utilizes drawn symbols. Each has its

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own theoretical and methodological advantages and setbacks. The degree to which the
communication is two-way is important, as well as the ability for the ape in question to retain the
taught information.
Signing
The most famous sign language experiment has to be Koko the gorilla, who has gotten an
incredible amount of media attention over the years. She is currently 41 years old, and is
somewhat of a pop culture phenomena. She is thought to be able to sign over 1,000 words, and
understand more than 2,000 words of spoken English. Project leader Dr. Francine “Penny”
Patterson has documented Koko inventing new words for objects on her own (The Gorilla
Foundation). Knowing sign language and understanding spoken language is all well and good,
but what she does, while impressive, is not full communication. She does not use sentences, but
rather strings together words that suggest her implied meaning. She does not know how to apply
grammar, and uses signing for mostly self-serving purposes; it is not necessarily what I would
call a conversation. Another objection is the way her handlers interact with her, especially in
training. In a psychological process known as operant conditioning, Koko is rewarded for
producing a sign. Some issues with proper word use have arisen with her training, for example
the use of the word “dirty.” To train the concept, the researchers associated the word with her
feces. Once learning the word, she referred to people and even events as “dirty” (Candland).
All of Koko's behaviors and abilities have been anthropomorphized to some extent. Her
paintings have been viewed by the public and art critics, and both have praised her abilities. She
has adopted pets, and is said to still mourn her first kitten. Her keepers see her as an individual
who is completely capable of emotional feeling and expression. I'm sure she innately has some
degree of emotional depth, but I'm skeptical of the way in which it is expressed. Of interest is the

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fact that, after the first year of the project, the zoo Patterson was working with was uneasy with
the her work because they believed Koko was becoming “less of a gorilla than a human-tamed
animal” (Candland.) To me, the use of the word “tamed” implies there is little self-awareness of
her behavior, it is strictly a reward system. All behavior is taught by mimicry, but the individual
must eventually understand deeper levels of meaning implied in the communication, and I'm not
sure she's there yet.
Symbols
David Premack's primatology work dates back to 1954 when he joined the Yerkes
National Primate Research Center. The opening note in his paper “Animal Communication”
nicely summarizes his approach on the topic of human-primate communication: “This might
have been called 'animal language,' but purposely it was not. In fact, the difference between the
nature of language and communication in man and animals is the basis of an ongoing theoretical
discussion among researchers in behavioral and biological sciences.” His approach is more
scientific than Patterson's, and poses a series of research questions that attempt to answer what
level of communication other primates are capable of. Instead of sign language, he used
magnetic-backed plastic symbols, each standing for a word or concept.
First working with Cebus monkeys in 1959, he published a paper on reinforcement, what
is now known as Premack's Principle. He postulates that the more probable behavior will
reinforce less probable behaviors. For example, students will often execute a less favorable task
if they know a more favorable one will be next as a result. One experiment Premack conducted
on children used eating candy as the reinforcing activity, and playing pinball as the instrumental
activity. He found that the children who prefered candy over pinball would perform the second
activity for the joy of eating the candy afterward. As stated in his 1959 paper, “Toward Imperical

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Behavior Laws. I. Positive Reinforcement,” his theory outlines six conditions:
1. Reinforcement is a relative property. Responses A, B, C have a descending rank order of probability. A will
therefore reinforce both B and C. C will reinforce neither. This suggests that reinforcement is an absolute
property. However, B corrects this view. B will reinforce C, but not A. B is both a reinforcer and not a
reinforcer. Reinforcement is therefore a relative property.
2. Reinforcement is a reversible property. When drinking is more probable than running, drinking reinforces
running. When the probabilities are reversed, running reinforces drinking.
3. Historically, consummatory responses, eating and drinking, have served exclusively as reinforcers, but
consummatory responses are, like any other response, subject to reinforcement.
4. Reinforcement and punishment, traditionally contrasted as opposites, are in fact equivalent except for sign.
If response A leads contingently to B, and B is more probable than A, A will increase in frequency
(reinforcement); conversely, if A leads contingently to B, and B is less probable than A, A will decrease in
frequency (punishment). The major contrast is not between reward and punishment; but between reward
and punishment as contrasted with freedom. Freedom is the condition in which stimuli are freely (not
contingently) available to an individual.
5. When motorized running is more probable than lever pressing but less probable than drinking, then running
reinforces lever pressing and punishes drinking. In other words, the same response can be both a reinforcer
and a punisher - at the same time and for the same individual.
6. The equivalence of reinforcement and punishment is further suggested in this interesting fact: rats are either
sensitive to both reinforcement and punishment, or insensitive to both; they are never sensitive to one but
insensitive to the other.
All six conditions are consistent with what we generally think of as the reward system. I think it's
important to include his theory here because it applies to the other two case studies, Koko and
Kanzi/Panbanisha. Premack's work in the field of primatology has been mostly with
chimpanzees, and while he has shown that they can mimic certain facial expressions and use
symbols to communicate, it is not full communication. His studies showed a lack of ability for
syntactical understanding, which is a key part of the English language.
Lexigrams
The names Kanzi and Panbanisha don't quite elicit the same response from the general
public as Koko, but they are also very well-known apes in this field. The project they are under,
the Great Ape Trust, is lead by Sue Savage-Rumbaugh, whose approach is very controversial.
She believes great apes, specifically bonobos, can exist in a world where they are partly both
ape-like and partly human-like. Her approach for communication uses boards of lexigrams, a
“language ”called Yerkish in a nod to Robert Yerkes which is comprised of colored pictographic

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symbols that stand for words or concepts. The boards emit the spoken word when the lexigram is
pressed, as well as the trainers speaking the word for reinforcement of the symbol. Savage-
Rumbaugh says Kanzi picked up the use of symbols when he started repeatedly drawing a
symbol in sand on the floor. I believe the system the Great Ape Trust uses more fully resembles
communication, as the apes are able to communicate more deeply than Koko or historical cases.
Other primates simply do not have the vocal cord range that we do, and this system somewhat
addresses that by having the board speak the word on behalf of the individual.
In their 1985 paper entitled “The Capacity of Animals to Acquire Language: Do Species
Differences have Anything to Say to Us?” Savage-Rumbaugh et. al. begin by attempting to
tackle the public and academic notions of what human-primate communication is or should look
like.
Thus, it must be recognized that the real issues involved in ape-language go far deeper than words and
syntax. They involve the very nature of inter-individual relationships as we as human beings know and
experience them, for a most distinctive human characteristic is that we do “tell” each other things, whether
it be in words, gestures, or pictures drawn in the dirt. We do knowingly, and with intent “tell” each other
things that allow us to transmit indirect experiences from generation to generation, to produce myth from
fact, to build and maintain unique cultures, and to know other human minds in ways that we do not know
the minds of other species on this planet. It is no small thing, therefore, to assert that apes are “telling”
people things, or that they are “telling” each other things.
Unlike the objections I've had to the previous cases, they acknowledge the issue of syntax but go
past it, going deeper into what communication actually means. In the conclusion to their paper,
they fully agree that the symbols and sentences Kanzi uses are learned, but assert that the
acquisition was not through conditioning or “training any more than the words and the symbols
used in this paper are so conditioned.” His understanding of the symbols on his lexigram board

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seems to be bolstered by spoken language. Savage-Rumbaugh claims he had difficulty finding
the symbol for “apple” but as soon as the word was spoken, he seemed to immediately
understand and touched the appropriate symbol.
Some critics of her work have said the researchers use subtle facial gestures, such as
hinting with the eyes, to aid the bonobos in understanding what is being said. To counter these
claims, she wore a welding mask and asked Kanzi to “get the ball that is outside and bring it to
me.” Kanzi immediately goes outside, passing by another ball on his way out, and brings her the
required ball. Tasks such as “take off Sue's shoe” and “put the keys in the refrigerator” were also
successfully completed, with the welding mask on the researcher. The extent to which Kanzi and
Panbanisha understand spoken English is still being tested, but what we know at the moment is
pretty impressive. However, this is still not full communication, two-way communication.
Continuing Issues Within the Field
Since this paper assesses the capacity for the great apes to learn human language, it would
seem these two viewpoints, “anthropodenial” and anthropomorphization, are contradictory when
argued in the same paper. I think both aspects have their place and it is vital that they remain
separate. In terms of public perception, the de Waal camp is certainly predominant. However, if
other taxonomic studies like ornithology and ichthyology are more or less free of these concepts
that alter scientific perceptions, why can't there be a section of research carved out for
primatology that is ideally un-anthropomorphic?
That is probably the largest problem with these kinds of behavioral experiments,
choosing a theoretical side. Being categorized under anthropology, there is an inherent
anthropomorphic viewpoint to primatology. The extent to which you mix that with the

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methodologies of “hard science” will determine what kind of primate behavior research you do,
as well as the kind of criticism you receive from both academia and the public.
Conclusion
Due to basic biological differences, the great apes are not able to reproduce the sounds of
the human vocal range. However, it is Savage-Rumbaugh's mix-and-match approach that most
closely resembles “communication” to me. A thread that runs through all of the human-primate
communication studies, and most of the current primate research, is anthropomorphization. It is
sometimes very difficult to know what the appropriate situation is to allow ourselves to
anthropomorphize, but it depends on the kind of research being done. As a general rule, I believe
that if the research is centered around the ecology of a primate species, then the practice of
anthropomorphization should be avoided. If there is some connection to humans, an attempt to
understand ourselves better, then it is more admissible but care should be taken to maintain
scientific integrity.

11. Works Cited
Candland, Douglas K. “Feral Children and Clever Animals: Reflections on Human Nature”
October 2, 1995. Print.
de Waal, Frans B. M. “Are We in Anthropodenial? | DiscoverMagazine.com.” Discover
Magazine. Web. 7 Mar. 2013.
<http://discovermagazine.com/1997/jul/areweinanthropod1180>.
de Waal, Frans B. M. “The Communicative Repertoire of Captive Bonobos (Pan Paniscus),
Compared to That of Chimpanzees.” Behaviour 106.3/4 (1988): 183–251. Web. 15 Feb.
2013. <http://www.jstor.org/stable/4534707.>.
de Waal, Frans B. M. “Complementary Methods and Convergent Evidence in the Study of
Primate Social Cognition.” Behaviour 118.3/4 (1991): 297–320. Web. 15 Feb. 2013.
<http://www.jstor.org/stable/4534969>.
Fouts, Roger. "Chimpanzees And Sign Language: Darwinian Realities Versus Cartesian
Delusions." Pluralist 6.3 (2011): 19-24. OmniFile Full Text Mega (H.W. Wilson). Web. 7
Mar. 2013. <http://search.ebscohost.com/login.aspx?
direct=true&db=ofm&AN=527178775&site=ehost-live>.
Gardner, R. Allen, and Beatrice T. Gardner. "Teaching sign language to a chimpanzee." Science
165.3894 (1969): 664-672.
<http://www.psych.yorku.ca/gigi/documents/Gardner_Gardner_1969.pdf>.
The Gorilla Foundation. “Mission Part 1: Research” Website.
<http://www.koko.org/friends/research.koko.html>.
Greenberg, Joel. “Koko.” Science News 114.16 (1978): 265–270. JSTOR. Web. 8 Mar. 2013.
<http://www.jstor.org/stable/3963439>.
McGrew, W. C. “New Wine in New Bottles: Prospects and Pitfalls of Cultural Primatology.”
Journal of Anthropological Research 63.2 (2007): 167–183. Web. 15 Feb. 2013.
<http://www.jstor.org/stable/20371148>.
Patterson, Francine. “Review of Savage-Rumbaugh's Ape Language: From Conditioned
Response to Symbol” Man 22.2 (1987): 361–362. JSTOR. Web. 8 Mar. 2013.
<http://www.jstor.org/stable/2802870?origin=JSTOR-pdf>.
Premack, David. “Human and Animal Cognition: Continuity and Discontinuity.” Proceedings of
the National Academy of Sciences of the United States of America 104.35 (2007): 13861–
13867. JSTOR. Web. 7 Mar. 2013. <http://www.jstor.org/stable/pdfplus/25436587.pdf>.
Premack, David. “Is Language the Key to Human Intelligence?” Science 303.5656 (2004): 318–
320. JSTOR. Web. 7 Mar. 2013. <http://www.jstor.org/stable/pdfplus/3835976.pdf>.
Premack, David. "Language in chimpanzees." Science 172 (1971): 808-822.
<http://karen.stanley.people.cpcc.edu/docs%20for%20EFL%20074/Animal
%20Communication%20rev.doc>.
Premack, David. “Toward Imperical Behavior Laws. I. Positive Reinforcement” Psychol Rev.
1959 Jul;66(4):219-33.
Rodman, P. S. “Whither Primatology? The Place of Primates in Contemporary Anthropology.”
Annual Review of Anthropology 28 (1999): 311–339. Web. 15 Feb. 2013.
<http://www.jstor.org/stable/223397>.
Savage-Rumbaugh, E. Sue et al. “The Capacity of Animals to Acquire Language: Do Species
Differences Have Anything to Say to Us?” Philosophical Transactions of the Royal
Society of London. Series B, Biological Sciences 308.1135 (1985): 177–185. Web. 15
Feb. 2013. <http://www.jstor.org/stable/2396292>.

12. Savage-Rumbaugh, E. Sue, and Duane M. Rumbaugh. “Ape Language Research Is Alive and
Well: A Reply.” Anthropos 77.3/4 (1982): 568–573. Web. 15 Feb. 2013.
<http://www.jstor.org/stable/40460489.>.