To what extent do domestic animals understand language?

To what extent do domestic animals understand language?

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Note: Please tell me to re-post this in Cogsci or pets if this doesn't belong here.

Hello All,

I want to know how dogs or other domesticated animals differentiate between normal chat and a command. Do they understand their master's language or body language?

If they understand the body language of the master alone, then how come they can do the same trick (in most of the cases) if some other person gives the same command?

And to what extent do they have this understanding, meaning how many words does a domesticated animal understand?

Yes, they can understand some words and even simple sentences.

Here is what Animal Planet says:

Studies show that the average dog can understand about 165 different words, in some cases more if you make a point of training them. This includes the basic commands such as "sit," "stay," and "go," as well as a range of other terms, assuming they're tangible words and not abstract ideas.

Here are some supporting studies:

Some domestic dogs learn to comprehend human words, although the nature and basis of this learning is unknown [1].

A female mongrel dog, Sofia, was initially trained to respond to action (point and fetch) and object (ball, key, stick, bottle and bear) terms which were then presented as simultaneous, combinatorial requests (e.g. ball fetch, stick point). Sofia successfully responded to object-action requests presented as single sentences, and was able to flexibly generalize her performance across different contexts [2].


  1. Tempelmann S, Kaminski J, Tomasello M (2014) Do Domestic Dogs Learn Words Based on Humans' Referential Behaviour? PLoS ONE 9(3): e91014. doi:10.1371/journal.pone.0091014
  2. Ramos D, Ades C (2012) Two-Item Sentence Comprehension by a Dog (Canis familiaris). PLoS ONE 7(2): e29689. doi:10.1371/journal.pone.0029689

Language in Apes:How Much Do They Know and How Much Should We Teach Them

If you find yourself flummoxed by the terminology, you can look at my primate glossary.

Humans have often asserted a fundamental difference between themselves and other animals. One of these assertions which has had many proponents into the twentieth century is that humans differ from animals in their use of language. In the past thirty years this assertion has been the subject of much debate as scientists have researched language use by apes. (I use the term "ape" to refer to "great ape" in this essay, as many of my sources do. There have apparently been no language experiments with gibbons or siamangs.) Extraordinary claims have been made by some researchers about the linguistic capabilities of their subjects, mostly chimpanzees. These claims have been refuted and counter-refuted many times, and the literature on the subject is extensive. In this essay I will examine the question of how much, if at all, primates are able to communicate using language. I will then examine the ethical issues surrounding the teaching of language to apes.

First, what is language, and how does it differ from other forms of communication? There does not exist a universally accepted definition of language, or criteria for its use this is one of the reasons for the disagreement among scientists about whether apes can use language. Language consists of various aspects which people believe are more or less important, for example, grammar, symbol usage, the ability to represent real-world situations, and the ability to articulate something new (Wallman 1992: 6). Duane Rumbaugh describes language as "an infinitely open system of communication" (Rumbaugh 1977b: xx). Some people say that anything an ape can do is not language of course, if these are the same people who say that language defines us as humans, and an ape can learn sign language, then they are saying that deaf people who use sign language are not human (Patterson & Linden 1981: 119-120). One famous view of language is Charles Hockett's seven key properties: duality, productivity, arbitrariness, interchangeability, specialization, displacement, and cultural transmission (Linden 1974: 137). I will return to these properties later in the essay.

Why teach language to apes?

Why should we try to teach language to apes? In their introduction to Language in Primates, the editors answer the question: "This project would shed light not only on the nature of language and cognitive and intellectual capacities, but also on such issues as the uniqueness of human language and thought" (de Luce & Wilder 1983: 1). Such projects also shed light on the development of language in early humans. A very different reason for teaching language to apes is that the research would discover better methods for training mentally retarded children "who for various reasons fail to develop expressive linguistic skills during their early years" (Rumbaugh, Warner & von Glasersfeld 1977: 90).

How apes communicate in the wild

In the wild, primates use a wide variety of methods of communication (Jolly 1985: 192-217). Many primates rely on olfactory communication, for example, scent marking or urine washing to mark their territory. Primates use tactile communication to develop or confirm relationships mothers carry their young, adults may sit and/or sleep together, and adults of many species groom each other. Visual communication is important especially for higher primates, who look at what they are paying attention to, as we do. Some visual elements are facial expression, hair erection, general posture, and tail position. Primates use vocal communication, from soft grunts to whoop-gobbles, when they want to catch the attention of others. Often vocalizations signal emotional situations, like danger of an attack or the location of a large food source. The meaning of primate communication depends on the social and environmental context as well as the particular signals that are being used (Strum 1987: 263). Sue Savage-Rumbaugh notes that reports of the complexity and intentionality of chimpanzee communication in the wild have not yet had the recognition they deserve (Savage-Rumbaugh 1986: 400). The monkeys called vervets have the most sophisticated animal communication that we know of the sounds they use are learned, not instictive (Diamond 1993:143). There are various studies of primates in the wild going on right now, but it is difficult to do an in-depth study of communication in apes.

History of the apes & language question

The question of whether apes can use language has been asked for some time. In 1661 Samuel Pepys wrote in his diary about what he called a "baboone": "I do believe it already understands much english and I am of the mind it might be taught to speak or make signs" (Wallman 1992: 11). In 1748 Julien Offray de la Mettrie published a document which speculated that apes could be taught to speak (Hewes 1977: 12). During the first half of the twentieth century, the first experimental forays into the area of ape language were, in fact, attempts to teach apes to speak. Robert Yerkes experimented with chimpanzees in the 1920's, and concluded that they could not learn speech. He made a suggestion that was not followed up on for forty years: perhaps apes could learn sign language (Rumbaugh 1977a: 76). Others continued to attempt to teach speech to apes, the most successful of whom were Keith and Cathy Hayes who taught chimpanzee Viki to speak four words (Gardner & Gardner 1989: 5). Experiments in which chimpanzees were raised as children were successful in other respects: the chimpanzees learned to understand a great deal of human speech, and they often communicated with their "family" to some extent by gestures.

Why apes cannot speak

There are several reasons cited why apes cannot speak. One is that apes are just not intelligent enough this reason is losing popularity as ape language research continues to discover new facets of ape intelligence. Robert Yerkes believed that apes cannot speak because they lack "the tendency to reinstate auditory stimuli--in other words to imitate sounds" (Rumbaugh 1977a: 77). The reason that was commonly cited by scientists in the latter half of the twentieth century is that apes' vocal chords (or some other part of their anatomy) are not built for speaking (de Luce & Wilder 1983: 3). A relatively recent suggestion is that the vocal habits of apes prevent them from speaking. When apes use vocal communication, they are almost always very excited, perhaps "too excited to engage in casual conversation" (Gardner, Gardner & Drumm 1989: 29). Whatever the reason, once it was apparent that apes could not learn to speak, the apes' propensity for using gestures made sign language the next obvious choice.

Allen and Beatrice Gardner began teaching sign language to an infant chimpanzee named Washoe in 1966. The Gardners provided Washoe with a friendly environment that they thought would be more conducive to learning. The people who cared for and taught Washoe used sign language almost exclusively in her presence. Washoe learned signs by various methods, including imitation and instrumental conditioning. Washoe was able to transfer her signs spontaneously to a new member of a class of referents for example, she used the word "more" in a wide variety of contexts (not just for more tickling, which was the first referent) (Gardner & Gardner 1979: 190). The Gardners noted that "Washoe has transferred the DOG sign to the sound of barking by an unseen dog" (191). They also reported that Washoe began to use combinations of signs spontaneously after learning only about eight or ten of them. The Gardners soon extended their experiments to several other chimpanzees: Moja, Pili, Tatu, and Dar. They needed to replicate their success with Washoe, and they did. All of these chimpanzees "signed to friends and to strangers. They signed to each other and to themselves, to dogs and to cats, toys, tools, even to trees" (Gardner & Gardner 1989: 24). Private signing by the chimpanzees has recently been studied systematically the study confirmed that private signing is robust (Bodamer, Fouts, Fouts & Jensvold 1994). One of the most remarkable developments in this research occurred when Washoe adopted an infant named Loulis. For the next five years, no sign language was used by humans in Loulis' presence however, Loulis still managed to learn over 50 signs from the other chimpanzees. Bob Ingersoll, who studied Washoe and Loulis during this time, believes that there wasn't much active teaching going on, but rather Loulis picked up the signs from the other apes' use of them. The learning of signs from other chimpanzees meets Hockett's criterium of cultural transmission. Because the chimpanzees continued to use sign language without any input from humans, the Gardners concluded that "once introduced, sign language is robust and self-supporting, unlike the systems that depend on special apparatuses such as the Rumbaugh keyboards or the Premack plastic tokens" (Gardner & Gardner 1989: 25).

In the year after Project Washoe began, David Premack started an experiment with a different kind of language. The above-mentioned plastic tokens are those which Premack used to train a chimpanzee named Sarah. These tokens represented words, and varied in shape, size, texture, and colour. Sentences were formed by placing the tokens in a vertical line (an orientation which Sarah favoured). This language differs from sign language in that "the permanence of the sentence not only makes it possible to study language without a memory problem, but to study memory in the context of language by regulating the duration for which the sentence remains on the board" (D. Premack 1979: 233). Sarah was taught nouns, verbs, adjectives, pronouns, and quantifiers she was also taught same-difference, negation, and compound sentences. The earliest words named "various interesting fruits, so that Sarah . could both solve her problem and eat it" (A. Premack 1976: 79). Sarah exhibited displacement, the ability to think of something (in the following case, chocolate) when it is not immediately present. Presented with the sentence "Brown color of chocolate" without any chocolate present, and later presented with "Take brown," Sarah took a brown object (A. Premack 1976: 89). When a trainer put a question on Sarah's board and walked away, Sarah showed little interest in answering it--"in somewhat the way a conversation falters when one person ceases to pay attention to the other" (D. Premack 1971: 821). To show that Sarah was not merely responding to cues from her human trainers, she was adapted to a new trainer that did not know her language. When this trainer presented her with questions, she gave the correct answers less frequently than usual, but still well above chance. Ann Premack remarked that "it would be interesting to see how well a child at this language stage of about 150 words would do in a simple language test with a virtual stranger" (A. Premack 1976: 103). To test Sarah's view of words, Premack presented her with an apple and a set of features (for example, round vs. square and red vs. green). Then she was presented with her word for apple, and the same set of features. She choose the correct features for both the real apple and her word for apple, a light-blue plastic triangle (A. Premack 1976: 104). This demonstrates Hockett's property of arbitrariness the symbol for apple is arbitrary (that is, there is no similarity between an apple and a light-blue plastic triangle).

The chimpanzee Lana learned to use another language system, an electronic keyboard. The Lana Project was headed by Duane Rumbaugh, who wanted to create a situation which would "allow for the systematic variations of training procedures that would differentially influence the course of acquiring and using linguistic skills" (Rumbaugh, Warner & von Glasersfeld 1977: 87). The language of lexigrams, each of which represented one word, was called Yerkish. When Lana pressed a key with a lexigram on it, that key would light up and the lexigram would appear on a projector. When keys were pressed accidentally, Lana used the PERIOD key (end of sentence) as an eraser so that she could restart the sentence Lana did this on her own before it occurred to the researchers (Rumbaugh & Gill 1977: 167). Lana also started using NO as a protest (for example, when someone else was drinking a Coke and she did not have one) after having learned it as a negation ("it is not true that. ") (Rumbaugh & Gill 1977: 169-170). Lana acquired "many linguistic-type skills for which she had received no specific training" which showed her ability to abstract and generalize (Rumbaugh & Gill 1977: 190). For example, she spontaneously used THIS to refer to things for which she had no name, and she invented names for things by combining lexigrams in new ways. Lana's trainers admit that

Herbert S. Terrace was skeptical of the reported success of the chimpanzees Washoe, Sarah, and Lana. He believed that there were simpler explanations for many of the reported interpretations of these apes' language use. Although Terrace admitted that the apes had achieved something significant, he compared their behaviour to that of pigeons who are taught to peck different colours in a certain order (Terrace 1979: 20). He also believed that the apes used signs only to receive rewards from their human trainers. When Terrace set up his own experiment with the chimpanzee Nim, "Nim's main reward for learning to sign was our approval and being able to sign about something that was important to him" (Terrace 1979: 145). Nim was raised like a human child and taught sign language in similar ways to those of Washoe. He was observed practicing his signs in the absence of their referents (Terrace 1979: 143). Nim often signed DIRTY (used when he had to go to the toilet) or SLEEP when he was bored and wanted a change. He used the signs BITE and ANGRY to express his feelings, and he tended not to attack if he perceived that his warning was heeded this is an important substitution of an arbitrary word for a physical action, displaying Hockett's property of specialization (the speaker does not act out messages). Although Nim learned many words, Terrace concluded that Nim could not combine words to create new meanings on his own. He believed, from viewing videotapes, that the combinations of words that Nim used were prompted by prior utterances from his trainers. The other thing Terrace discovered from the videotapes was that Nim interrupted his trainers more than human children interrupt their parents. Terrace has a good point: if we are going to say that apes can create a sentence, we must eliminate the other possible explanations for the utterances (Terrace 1979: 219). Terrace is not as much of a skeptic as some others make him out to be, though he believed that the conditions under which Project Nim were operated were not ideal, and future projects might have more success if they were able to instill a greater motivation to sign in their subjects (Terrace 1979: 223).

Other Ape Language Experiments: Sherman & Austin, Chantek, Kanzi, Koko

Many other ape language experiments were done other than the four described above I will briefly list several of these. Sherman and Austin were two chimpanzees who were able to communicate specific information to each other through the use of symbols, information that they could not communicate without the symbols (Savage-Rumbaugh, Rumbaugh & Boysen: 1978). Chantek, an orangutan, learned about 150 different signs, and used them spontaneously and without undue repetition. Chantek internalized a minimal value system, using signs for GOOD and BAD in appropriate contexts (Miles 1993: 47, 52). A bonobo named Kanzi learned at a faster rate than the chimpanzees he learned his first words by merely watching lessons directed at his mother. Sue Savage-Rumbaugh describes Kanzi as "the ape at the brink of the human mind" in her book of that title. Savage-Rumbaugh asserts that Kanzi uses sentences that is, he follows structured rules in his multi-word utterances (showing the property of duality). He even makes up his own rules, such as first using a lexigram to specify an action and then using a gesture to specify an agent (Savage-Rumbaugh & Lewin: 1994: 161). Francine Patterson has been raising Koko, a gorilla, since 1972 and teaching her sign language. Koko has learned a greater vocabulary than Nim, uses more words per utterance on average, and "a great deal of creativity, spontaneity, and structure characterize her utterances" (Patterson & Linden 1981:116). Koko also rhymes and jokes on one occasion she used a metaphor of an elephant to refer to herself when she pretended a long tube was her "trunk" (Patterson & Linden 1981: 143). These characteristics of Koko's utterances show the property of productivity, in which a speaker says something never heard or said before and is understood by the audience. (It is interesting how one automatically uses the language of speech when describing any form of language use, including those which are not spoken. Many of my sources also exhibit this trait.) The Nova program Can Chimps Talk? did a good job of exploring the various experiments and issues involved in ape language.

Dichotomy in the Scientific Community

Scientists seem to be divided into two camps on the subject of ape language research. In the one camp are the researchers who treat their apes more like children these people tend to focus on the accomplishments of their subjects, and the similarities between ape and human language. In the other camp are the researchers who treat their apes more like experimental subjects these people tend to focus on the failures of their subjects, and the differences between ape and human language. Both groups have problems with the research methods of the other. Francine Patterson, Koko's trainer, believes that "one cannot really understand the mental workings of other animals or bring them to the limits of their abilities unless one first has true rapport with them" (Patterson & Linden 1981: 211). Herbert Terrace and others believe that the accomplishments of apes who are taught language are less than what is reported because the apes' utterances are cued by humans. Sue Savage-Rumbaugh characterizes this difference of opinion as sometimes generating "more heat than light" she believes that people accepted the results of the early ape language experiments too readily, and rejected them too readily after Project Nim (Savage-Rumbaugh 1986: 398, 10). George Johnson summarizes the views of both sides in his article Chimp Talk Debate: Is It Really Language?.

This dichotomy in the scientific community still exists today. It is exemplified by Joel Wallman's recent book, Aping Language, and the responses to it. In his book Wallman states that he does "not believe that any of the ape-language projects succeeded in instilling even a degenerate version of a human language in an ape" (Wallman 1992: 109). Whether the point of the ape language research is specifically to teach apes a human language is questionable. In her review of Aping Language, Patricia Greenfield argues that Wallman exaggerated differences between ape and human language, used human language as a standard to measure ape language by, ignored published results that did not agree with his thesis, and used unscientific evidence to discuss accomplishments by apes (Greenfield 1994: 940-942). In another review, Justin Leiber concludes that "Wallman has written a clear, helpful, even definitive, book" (Leiber 1995: 374). Ironically, it seems that scientists involved in the study of ape language need to communicate better among themselves.

Ethical implications of ape language research

In addition to the disagreements about what apes have learned, there are disagreements about the ethical implications of ape language research. Although not a primatologist, author Douglas Adams has some perceptive comments about "this business of trying to teach apes language" (Adams & Carwardine 1993: 23). While sitting four feet away from a wild silverback mountain gorilla, he asks

Although it might not seem like it to their trainers (who are biased towards any semblance of "humanity" in apes), apes who are domesticated may be less intelligent than their wild counterparts. De Luce and Wilder point out that "while most investigators have assumed that the primate language experiments develop and enhance the intelligence and linguistic abilities of the apes, just the opposite may be the case" (de Luce & Wilder 18). One problem is that we have no way of communicating with apes unless we teach them some language that humans also know the only other possibility is them teaching us their code. Roy Harris speculates that "human infants would fare no better at the language game if subjected to comparably bizarre experiments (involving removal from natural habitat, control by members of another species, . )" (Harris 1984: 204). Perhaps further study of apes in the wild (while there are still some left) would be more profitable.

Are you responsible for what you tame?

Shirley Strum asks the question "are you responsible for what you tame?" and answers in the affirmative (Strum 1987: 199). Apes are cute and cuddly when they are small, but they get rather large and strong as they mature. One problem with apes raised by humans is that it is very difficult to teach them how to survive in the wild. I wonder what their trainers will do when Kanzi and Koko themselves start demanding more rights--we certainly cannot let a bonobo or a gorilla walk around town on its own in today's society.

The best interests of the apes

There is an interesting paradox in ape language research: the more successful the findings are, the better the case for not doing the research at all. If language use gives beings rights and freedoms, we should ask the apes' permission before experimenting on them--of course, it is difficult to see a situation in which an ape would understand the experiment before it was undertaken. Some scientists may claim that it is in the apes' best interests to teach them language, but Thomas Simon points out that we do not even know what is in the best interests of humans when it comes to language (Simon 1983: 106). Simon believes that the use of computer models, human subjects, and field studies are more appropriate than ape language research (Simon 1983: 108).

Basic rights for all great apes

If apes can use language, in some sense, then what is the significance of this? The collaborators of The Great Ape Project declare that apes should be included in a community of equals with humans: each member of this community should have the right to life, liberty, and freedom from torture (Cavalieri, Singer et al. 1993). This declaration may seem radical to many (and not radical enough for a few), but the trend has been for people to agree with more and more rights for animals. The contributors to The Great Ape Project argue from various viewpoints that apes and humans should be classified together at some level. James Rachels argues that Darwinism implies that we should treat the other great apes (we are also great apes) as equals (Rachels 1993). Christoph Anstotz compares the linguistic competence of apes favourably with that of profoundly mentally disabled humans (Anstotz 1993). Ingmar Persson argues that the same basis on which we justify equality among humans can be applied to other species (Persson 1993). In their epilogue, Cavalieri and Singer compare our treatment of nonhuman animals to that of slaves in former times (Cavalieri & Singer 1993). Even disregarding the apes who use language, "the behavior of wild chimpanzees is not so different from that of non-technological groups of humans" (Fouts & Fouts 1993: 39). What all of these people are saying is that there should not be an arbitrary line drawn between humans and other great apes.

What do the apes say? Eugene Linden reported that Viki and Washoe thought of themselves as human when categorizing humans and animals, they placed themselves with humans and other chimpanzees with animals (Linden 1974: 50). The problem of interpreting apes' signs will always be that we really do not know what they are thinking of course, we can say the same for humans. The philosopher and mathematician Descartes believed that language separated humans who have souls from animals who do not (de Luce & Wilder 1983: 13). If it is language that makes us human, then surely at some level apes are human too. Many ape language researchers hope, as do I, that this research will lead to a better understanding of the relationships among all animals, including humans, and that we will work harder at giving the other animals their space on this earth.

For further information, here are a few web sites related to this topic.

Adams, D. and Carwardine, M. "Meeting a Gorilla," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 19-23. New York: St. Martin's Press, 1993.

Anstotz, C. "Profoundly Intellectually Disabled Humans and the Great Apes: A Comparison," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 158-172. New York: St. Martin's Press, 1993.

Bodamer, M.D., Fouts, D.H, Fouts, R.S. and Jensvold, M.L.A. "Functional Analysis of Chimpanzee (Pan troglodytes) Private Signing." Human Evolution, 9:4, 1994. pp. 281-296.

Cavalieri, P., Singer, P. et al. "A Declaration on Great Apes," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 4-7. New York: St. Martin's Press, 1993.

Cavalieri, P. and Singer, P. "The Great Ape Project--and Beyond," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 304-312. New York: St. Martin's Press, 1993.

de Luce, J. and Wilder, H.T. "Introduction," in Language in Primates: Perspectives and Implications. Ed. J. de Luce and H.T. Wilder, pp. 1-17. New York: Springer-Verlag, 1983.

Diamond, J. The Third Chimpanzee: The Evolution and Future of the Human Animal. New York: HarperCollins Publishers, 1993.

Fouts, R.S. and Fouts, D.H. "Chimpanzees' Use of Sign Language," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 28-41. New York: St. Martin's Press, 1993.

Gardner, R.A. and Gardner, B.T. "Teaching Sign Language to a Chimpanzee," in Language Intervention from Ape to Child. Ed. R.L. Schiefelbusch and J.H. Hollis, pp. 171 - 195. Baltimore: University Park Press, 1979.

Gardner, R.A. and Gardner, B.T. "A Cross-Fostering Laboratory," in Teaching Sign Language to Chimpanzees. Ed. R.A. Gardner, B.T. Gardner and T.E. Van Cantfort, pp. 1-28. Albany: State University of New York Press, 1989.

Gardner, R.A., Gardner, B.T. and Drumm, P. "Voiced and Signed Responses of Cross-Fostered Chimpanzees," in Teaching Sign Language to Chimpanzees. Ed. R.A. Gardner, B.T. Gardner and T.E. Van Cantfort, pp. 29-54. Albany: State University of New York Press, 1989.

Greenfield, P. "Book Review: 'Aping Language'." International Journal of Primatology, 15: 6, 1994. pp. 939-943.

Harris, R. "Comment: 'Language in apes' by H.S. Terrace," in The Meaning of Primate Signals. Ed. R. Harre and V. Reynolds, pp. 204-205. Cambridge: Cambridge University Press, 1984.

Hewes, G.W. "Language Origin Theories," in Language Learning by a Chimpanzee: The Lana Project. Ed. D.M. Rumbaugh, pp. 3-53. New York: Academic Press, 1977.

Jolly, A. The Evolution of Primate Behavior. 2nd ed. NewYork: Macmillan, 1985.

Leiber, J. "Apes, Signs, and Syntax." American Anthropologist, 97:2, 1995. p. 374.

Linden, E. Apes, Men, and Language. NewYork: Saturday Review Press, 1974.

Miles, H.L.W. "Language and the Orang-utan: The Old 'Person' of the Forest," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 42-57. New York: St. Martin's Press, 1993.

Patterson, F., and Linden, E. The Education of Koko. New York: Holt, Rinehart and Winston, 1981.

Persson, I. "A Basis for (Interspecies) Equality," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 183-193. New York: St. Martin's Press, 1993.

Premack, A.J. Why Chimps Can Read. New York: Harper & Row, 1976.

Premack, D. "Language in Chimpanzee?" Science, 172, 1971. pp. 808-822.

Premack, D. "A Functional Analysis of Language," in Language Intervention from Ape to Child. Ed. R.L. Schiefelbusch and J.H. Hollis, pp. 229-259. Baltimore: University Park Press, 1979.

Rachels, J. "Why Darwinians Should Support Equal Treatment for Other Great Apes," in The Great Ape Project: Equality Beyond Humanity. Ed. P. Cavalieri and P. Singer, pp. 19-23. New York: St. Martin's Press, 1993.

Rumbaugh, D.M. "The Emergence and State of Ape Language Research," in Progress in Ape Research. Ed. G.H. Bourne, pp. 75-83. New York: Academic Press, 1977a.

Rumbaugh, D.M. "Preface," in Language Learning by a Chimpanzee: The Lana Project. Ed. D.M. Rumbaugh, pp. xix-xxii. New York: Academic Press, 1977b.

Rumbaugh, D.M., and Gill, T.V. "Lana's Acquisition of Language Skills," in Language Learning by a Chimpanzee: The Lana Project. Ed. D.M. Rumbaugh, pp. 165-192. New York: Academic Press, 1977.

Rumbaugh, D.M., Warner, H. and von Glasersfeld, E. "The LANA Project: Origins and Tactics," in Language Learning by a Chimpanzee: The Lana Project. Ed. D.M. Rumbaugh, pp. 87-90. New York: Academic Press, 1977.

Savage-Rumbaugh, E.S. Ape Language: From Conditioned Response to Symbol. New York: Columbia University Press, 1986.

Savage-Rumbaugh, E.S., Rumbaugh, D.M., and Boysen, S. "Symbolic Communication Between Two Chimpanzees (Pan troglodytes)." Science, 201, 1978. pp. 641-644.

Savage-Rumbaugh, S. and Lewin, R. Kanzi: The Ape at the Brink of the Human Mind. New York: John Wiley & Sons, 1994.

Simon, T.W. "Limits of Primate Talk," in Language in Primates: Perspectives and Implications. Ed. J. de Luce and H.T. Wilder, pp. 97-111. New York: Springer-Verlag, 1983.

Strum. S.C. Almost Human: A Journey into the World of Baboons. New York: W.W. Norton, 1987.

Terrace, H.S. Nim. New York: Alfred A. Knopf, 1979.

Wallman, J. Aping Language. Cambridge: Cambridge University Press, 1992.

Copyright © 1995 by Dave Switzer. Return to Dave Switzer's Home on the Web.
Last modified: November 23, 1999.

Animals laugh too, analysis of vocalization data suggests

“This work lays out nicely how a phenomenon once thought to be particularly human turns out to be closely tied to behavior shared with species separated from humans by tens of millions of years,” said UCLA professor Greg Bryant. Credit: Unsplash/CC0 Public Domain

Human laughter is common, but it's a somewhat mysterious part of our evolution. It's clear to evolutionary scholars that we laugh as a part of play, signaling our cooperation or friendliness. But how did laughter evolve? And are humans the only ones who do it?

Not a chance: Animals laugh too, researchers have observed.

In a new article published in the journal Bioacoustics, primatologist and UCLA anthropology graduate student Sasha Winkler and UCLA professor of communication Greg Bryant take a closer look at the phenomenon of laughter across the animal kingdom.

The pair combed through the existing scientific literature on animal play behavior, looking for mentions of vocal play signals—or what might be thought of as laughter.

They found such vocal play behavior documented in at least 65 species. That list includes a variety of primates, domestic cows and dogs, foxes, seals, and mongooses, as well as three bird species, including parakeets and Australian magpies.

"This work lays out nicely how a phenomenon once thought to be particularly human turns out to be closely tied to behavior shared with species separated from humans by tens of millions of years," Bryant said.

The researchers looked for information on whether the animal vocalizations were recorded as noisy or tonal, loud or quiet, high-pitched or low-pitched, short or long, a single call or a rhythmic pattern—seeking known features of play sounds.

There's much existing documentation of play-based body language among animals, such as what is known as "play face" in primates or "play bows" in canines, the researchers noted.

Since what constitutes "play" in much of the animal kingdom is rough-and-tumble and can also resemble fighting, play sounds can help emphasize non-aggression during such physical moments, the article suggests.

"When we laugh, we are often providing information to others that we are having fun and also inviting others to join," Winkler said. "Some scholars have suggested that this kind of vocal behavior is shared across many animals who play, and as such, laughter is our human version of an evolutionarily old vocal play signal."

While Winkler and Bryant say that further observation and research into vocalizations would be fruitful, they also note that such observations can be hard to come by in the wild, especially for animals whose play sounds might be quieter.

Paying attention to other species in this way sheds light on the form and function of human laughter, the researchers write, and helps us to better understand the evolution of human social behavior.

The Main Differences: In Depth

While many scholars may add to this list, this article will examine seven properties that are largely unique to human language: duality, creativity, displacement, interchangeability, cultural transmission, arbitrariness, and biology.

Duality of patterning: Distinctive sounds, called phonemes, are arbitrary and have no meaning. But humans can string these sounds in an infinite number of ways to create meaning via words and sentences.

The primary difference is known as duality of patterning, or structure. Each human language has a fixed number of sound units called "phonemes." These phonemes are combined to make morphemes, the smallest unit of sound that contains meaning. Thus, language has got two levels of patterning that are not present in other animals&apos communication.

Yet another distinctive feature is creativity. Human beings use their linguistic resources to produce new expressions and sentences. They arrange and rearrange phonemes, morphemes, words, and phrases in a way that can express an infinite number of ideas. This is also called the open-endedness of language. Animal communication is a closed system. It cannot produce new signals to communicate novel events or experiences.


Displacement: Human language can talk about things that aren&apost happening here or now. Other animals react only to stimuli in the present.

Human beings can talk of real or imaginary situations, places, or objects far removed from their present surroundings and time. Other animals, on the other hand, communicate in reaction to a stimulus in the immediate environment, such as food or danger. Because of this, human language is considered context-free, whereas animal communication is mostly context bound.


Human language is interchangeable between sexes. But certain communications in animal world are performed only by one gender. For example, bee dancing is only performed by worker bees, which are female.

Cultural Transmission

Cultural Transmission: Human language is culturally transmitted, or taught. Other animals communicate largely with signs they are born knowing.

Another important difference is that human language is culturally transmitted. Human beings brought up in different cultures acquire different languages. Man can also learn other languages via the influence of other cultures. Animals lack this capacity. Their communication ability is transmitted biologically, so they are unable to learn other languages.


Human language is a symbolic system. The signs, or words, in language have no inherent connection to what they signify, or mean (that&aposs why one object can have so many names in different languages). These signs can also be written with the symbols, or alphabet, of that language. Both verbal and written language can be passed down to future generations. Animal communication is not symbolic, which means ideas cannot be preserved for the future.

Biological differences also play a vital role in communication. Human vocal cords can produce a large number of sounds. Each human language uses a number of those sounds. Animal and birds have entirely different biological structures, which impact the way they can form sounds.


Domestication is the process of adapting wild plants and animals for human use. Domestic species are raised for food, work, clothing, medicine, and many other uses. Domesticated plants and animals must be raised and cared for by humans. Domesticated species are not wild.

Plant Domestication

People first domesticated plants about 10,000 years ago, between the Tigris and Euphrates rivers in Mesopotamia (which includes the modern countries of Iran, Iraq, Turkey, and Syria). People collected and planted the seeds of wild plants. They made sure the plants had as much water as they needed to grow, and planted them in areas with the right amount of sun. Weeks or months later, when the plants blossomed, people harvested the food crops.

The first domesticated plants in Mesopotamia were wheat, barley, lentils, and types of peas. People in other parts of the world, including eastern Asia, parts of Africa, and parts of North and South America, also domesticated plants. Other plants that were cultivated by early civilizations included rice (in Asia) and potatoes (in South America).

Plants have not only been domesticated for food. Cotton plants were domesticated for fiber, which is used in cloth. Some flowers, such as tulips, were domesticated for ornamental, or decorative, reasons.

Animal Domestication

About the same time they domesticated plants, people in Mesopotamia began to tame animals for meat, milk, and hides. Hides, or the skins of animals, were used for clothing, storage, and to build tent shelters.

Goats were probably the first animals to be domesticated, followed closely by sheep. In Southeast Asia, chickens also were domesticated about 10,000 years ago. Later, people began domesticating larger animals, such as oxen or horses, for plowing and transportation. These are known as beasts of burden.

Domesticating animals can be difficult work. The easiest animals to domesticate are herbivores that graze on vegetation, because they are easiest to feed: They do not need humans to kill other animals to feed them, or to grow special crops. Cows, for instance, are easily domesticated. Herbivores that eat grains are more difficult to domesticate than herbivores that graze because grains are valuable and also need to be domesticated. Chickens are herbivores that eat seeds and grain.

Some animals domesticated for one purpose no longer serve that purpose. Some dogs were domesticated to assist people in hunting, for instance. There are hundreds of domestic dog species today. Many of them are still excellent hunters, but most are pets.

Throughout history, people have bred domesticated animals to promote certain traits. Domestic animals are chosen for their ability to breed in captivity and for their calm temperament. Their ability to resist disease and survive in difficult climates is also valuable.

Over time, these traits make domestic animals different from their wild ancestors. Dogs were probably domesticated from gray wolves. Today, dogs are a distinct species from gray wolves.

Domesticated animals can look very different from their wild ancestors. For example, early wild chickens weighed about two pounds. But over thousands of years of domestication, they have been bred to be larger. Larger chickens yield more meat. Today, domestic chickens weigh as much as 17 pounds. Wild chickens only hatched a small number of eggs once a year, while domestic chickens commonly lay 200 or more eggs each year.

Effects on Humans

Domesticating plants marked a major turning point for humans: the beginning of an agricultural way of life and more permanent civilizations. Humans no longer had to wander to hunt animals and gather plants for their food supplies.

Agriculture&mdashthe cultivating of domestic plants&mdashallowed fewer people to provide more food. The stability that came with regular, predictable food production led to increased population density. People were able to do more than hunt for each day&rsquos food&mdashthey could travel, trade, and communicate. The world's first villages and cities were built near fields of domesticated plants.

Plant domestication also led to advances in tool production. The earliest farming tools were hand tools made from stone. People later developed metal farming tools, and eventually used plows pulled by domesticated animals to work fields.

Dogs and Wolves
Though today's dogs were likely domesticated from gray wolves, they are now a distinct species. Dogs' scientific name is canis lupus familiaris, while the scientific name for gray wolves is canis lupus.

Wild Horses
The process of domestication continues. Cowboys and other horse experts train horses. Sometimes, this is called "breaking" a horse. Training a horse to allow a saddle and rider requires an enormous amount of physical work, training, and patience. Horses that are born on ranches or in stables still need to be trained, although training a young horse is easier than domesticating a horse caught in the wild.

Can Animals Acquire Language?

Human intelligence, even in its most basic forms, is expressed in our language, and is also partly dependent on our linguistic capacity. Homer, Darwin and Einstein could obviously not have achieved what they did without language&mdashbut neither could a child in kindergarten. And this raises an important question about animal intelligence. Although we don&rsquot expect a chimpanzee to write an epic or a dolphin to develop a scientific theory, it has frequently been asked whether these or other animals are close in intelligence to young children. If so, we must wonder whether animals can acquire a language.

In the last half century, much effort has been put trying answer that question by teaching animals, primarily apes, a basic language. There have been some limited successes, with animals using signs to obtain things in which they were interested, for instance. But no animal has yet acquired the linguistic capability that children have already in their third year of life.

This is a question children start asking by the age of three at the latest. No animal has yet asked anything. &ldquoWhy?&rdquo is a very important question: it shows that those asking it are aware they don&rsquot know something they wish to know. Understanding the why-question is also necessary for the ability to justify our actions and thoughts. The fact that animals don&rsquot ask &ldquowhy?&rdquo shows they don&rsquot aspire to knowledge and are incapable of justification.

Children start saying no before they are two years old. No animal has yet said no. In order to master basic logic, one must understand negation. The inability of animals to use negation shows they lack basic logical abilities.

If a person knows that either A or B, and later learns that A isn&rsquot the case, he&rsquoll infer that B holds. This is called a disjunctive syllogism or inference. Are animals capable of such an inference? In 2001 Watson, Gergely et al. published the results of the following study, conducted on dogs and on four- to six-year-old children (Journal of Comparative Psychology. The dogs and children were first shown a desirable object in a container next, a person holding the container passed behind three screens and then the container was shown to be empty. The dogs and children were then allowed to search for the object behind the screens.

While children tended to increase their speed of checking behind the third screen after failing to find the object behind the first two, dogs tended to significantly decrease their speed of checking behind the third screen after thus failing. We know that children of this age are capable of a disjunctive inference, and this explains their search pattern. The contrasting dogs&rsquo search pattern is explained if the dogs did not think logically but were motivated by mere association, and then each failure to find the object amounted to an extinction trial for the association. &lsquoThere is as yet no compelling evidence for successful logical reasoning using the disjunctive syllogism in nonhuman animals&rsquo (Mody & Carey, Cognition 2016).

Another essential characteristic of our language is its normativity&mdashnamely, the fact that there are right and wrong uses of a word or phrase. We understand, for instance, that we used a certain word wrongly, or that we don&rsquot yet know how to use it. Animals&rsquo use of language does not have this aspect. An animal might use a sign the way we intended it to be used, or it might not yet use the sign that way. But the animal itself cannot understand that it doesn&rsquot know how to use the sign or that it has used it incorrectly. Understanding the idea of a mistake or of normativity depends on the ability to understand that something is not right, and since animals cannot understand negation they cannot understand normativity.

Since normativity is essential to our language, animals don&rsquot have a language in the sense we do. Animals produce sounds that express their emotions, and some can use signs in a Pavlovian way, as a result of an association between previous uses and succeeding events. But without &ldquoWhy?&rdquo and &ldquoNo!&rdquo there&rsquos nothing resembling human language.

And the distinctions don&rsquot stop there. To ascribe a mistake to another is to ascribe him a belief which is not true. Accordingly, the inability to understand negation makes animals incapable of understanding that someone has a false belief. Indeed, a study recently published in Science claimed apes can ascribe a mistake to others. But empirical issues, as well as faulty analysis of the findings (see my response in Science) make the study&rsquos conclusions unsupported.

Some emotions also depend on the understanding of negation, possibility, and other logical concepts. For instance, you hope that something will happen if you want it to happen but understand that it might not happen. And since animals cannot understand the notions of negation or of possibility, they cannot hope. Your dog expects you to take it out for a walk when you take the leash off the hook, and that is why it gets excited. But when you take a nap it cannot hope that you will take it out once you get up.

Ethics involves normative concepts, of what is right, just or fair to do, and of their contraries. And since animals do not understand such concepts, they are incapable of anything like human moral behaviour or related feelings. For instance, if Alice clearly gave Bob more than she did Charlie, although it was equally clear that Bob did not deserve more, Charlie will get upset: it&rsquos not fair! Such moral emotions, the result of injustice or lack of equity, are beyond the purview of animals.

Several studies have been conducted in order to show that animals do have such emotions, the best known probably being that of Frans de Waal and his colleagues with capuchin monkeys. One monkey gets furious when it continues to receive cucumbers after it sees the other monkey receiving grapes for the same task. However, the monkey gets upset not because it thinks it was treated unjustly, but because it expects grapes and receives cucumbers. The monkey doesn&rsquot initially get upset when it sees the other receiving a grape after it received a cucumber Charlie, by contrast, will remonstrate when he sees Alice giving Bob more than she earlier gave him. Rather, the monkey gets upset only later, when it doesn&rsquot receive what it expects. It cries in frustration, not with moral indignation.

We shouldn&rsquot immediately interpret behaviour that with us would be the result of a specific feeling or belief as resulting, in similar circumstances, from the same feeling or belief in animals. We should rather first examine the animals in other circumstances as well, to determine the limits of their capacities.

Animals can suffer, enjoy, be angry, surprised or afraid. Some are also sad when they lose their young. These and similar feelings bring us to love them, pity them and try to prevent them from suffering. But their resemblance to humans stops there. Human beings, as Aristotle observed and Descartes reiterated, are animals with a language. And language here is also logos, that is, logic or rationality. And experience teaches us that these are absent from the rest of the animal kingdom.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

Emotion and cognition

Perhaps the most difficult unanswered question about animal emotions concerns how emotions and cognition are linked, how emotions are felt, or reflected on, by humans and other animals. Researchers also do not know which species have the capacity to engage in conscious reflection about emotions and which do not. A combination of evolutionary, comparative, and developmental approaches set forth by Tinbergen and Burghardt, combined with comparative studies of the neurobiological and endocrinological bases of emotions in various animals, including humans, carries much promise for future work concerned with relationships between cognition and individuals' experiences of various emotions.

Damasio (1999a, 1999b) provides a biological explanation for how emotions might be felt in humans. His explanation might also apply to some animals. Damasio suggests that various brain structures map both the organism and external objects to create what he calls a second-order representation. This mapping of the organism and the object most likely occurs in the thalamus and cingulate cortices. A sense of self in the act of knowing is created, and the individual knows “to whom this is happening.” The “seer” and the “seen,” the “thought” and the “thinker” are one and the same.

Clearly, an understanding of behavior and neurobiology is necessary to understand how emotions and cognition are linked. It is essential that researchers learn as much as possible about animals' private experiences, feelings, and mental states. The question of whether and how animals' emotions are experienced presents a challenge for future research.

Both elephants and killer whales are suffering dramatic losses in their population. Connect these two creatures for us and what challenges they face in the modern world?

I tried to take a break from writing about conservation to write about what animals do in their natural lives. I focused on three of the most protected populations of animals in the world—elephants in national parks in Kenya, wolves in Yellowstone National Park, and killer whales in the Pacific Northwest in all three cases I found that these protected animals are still being killed by people.

Elephants have been undergoing a tremendous slaughter since 2009, when the powers that be decided China could import ivory from dead elephants. As a result, elephant populations are being devastated by poachers throughout Africa and Asia.

In the case of the wolves in Yellowstone National Park, the U.S. removed endangered species status from wolves outside the parks. So, when wolves from the parks stray outside, they’re often shot and it is usually the alpha pack leaders who are killed. When wolf packs lose their alpha male or female, they often break up. The younger wolves don’t have the knowledge to survive that adults have.

Killer whales have very poor reproduction because the salmon stock they depend on is so depleted that they don’t get enough food and are not in good enough condition to bear young. The young don’t survive well, either. Killer whales are full of toxic chemicals that they get from their food and the polluted waters where they swim around Washington State and West Coast of the United States. Even though they’re endangered and they’re supposed to be afforded the strictest protections, the Navy also continues to test live bombs in areas where these whales swim.

One pod that desperately needed a young, healthy female had their only young female killed by massive hemorrhaging in her ear canals. A Navy bomb explosion was recorded on the listening devices of the whale researchers the day she died. It’s very distressing that even when we are supposedly protecting these animals they’re not being protected by our own government.


By examining the scientific literature regarding stereotypic behaviour in laboratory macaques, it is possible to move towards an understanding of this abnormal behaviour. Experimental evidence seems to indicate that environmental factors such as cage size, housing type, stress and boredom which are often cited as the "causes" of stereotype in laboratory animals, do not necessarily cause the behaviour. Not all monkeys that experience these environmental conditions develop stereotypic behaviour . However, in animals which already exhibit the behaviour, these conditions will tend to accentuate it. Thus, these environmental components appear to influence the frequency of established stereotypic behaviour but do not cause it.

There is experimental evidence to suggest that intrinsic factors determine whether or not an individual animal will develop stereotypic behaviour. Factors such as rearing history, breed or genotype, and individual disposition will all contribute to the psychological makeup of an animal. Animals which are separated from their mothers early in life seem to be more prone to developing abnormal or stereotypic behaviour. The different breeds of macaques respond differently to stressful stimuli and situations, including maternal separation. Finally, an animal's individual personality appears to contribute to the likelihood of it exhibiting stereotypic behaviour.

Stereotypic behaviour is believed to signify poor psychological well-being and constitute a welfare problem in laboratory macaques. However, this behaviour is extremely complex and is not completely understood in animals or humans. Although it cannot be argued that stereotypic behaviour is not a welfare problem, this author believes that it is not enough simply to conclude that stereotypic behaviour is a sign of poor welfare in laboratory macaques. That conclusion, in the absence of a fundamental understanding of the behaviour, may lead to condemnation of research - facilities, animal care providers, and biomedical research in general. None of these may be directly responsible for the development of stereotypic behaviour in laboratory primates. It is crucial to determine why these animals exhibit stereotypic behaviour and to address the underlying causes, which may relate to experiences years before. Only in this way can we move towards an effective method of completely eliminating this behaviour in laboratory macaques.



Members: Drs Cecilia Baxter, Edmonton, Alberta Fabian P Gorodzinsky, London, Ontario Denis Leduc, Montrບl, Qu󩯬 (chair) Paul Munk, Toronto, Ontario (director responsible) Peter Noonan, Charlottetown, Prince Edward Island Sandra Woods, Val-d’Or, Qu󩯬

Consultant: Dr Linda Spigelblatt, Montrບl, Qu󩯬

Liaison: Dr Joseph Telch, Unionville, Ontario (Canadian Paediatric Society, Community Paediatrics Section)

Principal author: Dr Cecilia Baxter, Edmonton, Alberta

The recommendations in this statement do not indicate an exclusive course of treatment or procedure to be followed. Variations, taking into account individual circumstances, may be appropriate.

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