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Animal Communication

They speak fish!

Cartoon by Dan Reynolds1 available at www.CartoonStock.com

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How Do Animals Communicate?

H umans are not the only creatures that communicate: in fact, almost all have some sort of communication system, sometimes a very elaborate these systems comparable to human language? From what we know about

mals communicate in the wild, it seems that no other animal uses a system that we "language." Human language has a number of characteristics that set it apart communication systems. For example, dogs cannot talk about what will happen or about the climate on another continent. Nevertheless, animal communication are interesting to study in their own right in order to understand how animals communicate in the wild.

Another question that has interested many researchers is whether humans animals to use language. A number of studies have been conducted to teach lartguagi variety of animals. The success of these attempts is still debated, but we can say that so animal has been taught human language to the same extent and degree of SO]phistiica· that a human child acquires it naturally without instruction.

Contents

14.1 Communication and Language Considers Hockett's design features for language with respect to animal communication.

14.2 Animal Communication in the Wild Describes aspects of how bees, robins, and some primates communicate in the wild, and their communication to the design features.

14.3 Can Animals Be Taught Language? Describes and evaluates attempts to teach animals to use human language.

14.4 Practice Provides exercises, discussion questions, activities, and further readings related to animal communication systems.

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mmunication and language

.1 Design Features Revisited The previous chapters have provided an introduction to various aspects of how humans use language to communicate. However, we are not the only species that communicates; most animals have some sort of communication system. All varieties of birds make short calls or sing songs, cats meow to be fed or let outside, dogs bark to announce the arrival of strang­ers or growl and bare their teeth to indicate their intent to attack, and so on. The fact that other animals send and receive messages is in evidence all around us. But can we call the communication systems of animals "language"?

Most people assume that only humans use "language"-it is something that sets us apart from all other creatures. But is it possible that when we examine animal communi­cation systems, we will discover that our assumption that only humans use language was wrong? The task of comparing human communication with various animal communica­tion systems is not an easy one. First, we need a suitable way to identify "language" on which to base our comparisons. Unfortunately, no definition seems to adequately define "language" or to be agreeable to everyone. One approach to getting around this problem, suggested by the linguist Charles Hockett, is that we identify the requisite descriptive char­acteristics of language rather than attempt to define its fundamental nature. Hockett iden­tified nine design features, introduced in File 1.4. Human language has all of these design features, but as far as we know, no animal communication system does. Therefore, if we define "language" as a communication system that possesses all nine of these features, we are correct in saying that only humans use language. The following sections discuss Hock­ett's design features with respect to animal communication systems.

1.2 Design Features Shared by All Communication Systems

All communication systems have the following features in common: Mode of communication refers to how a message is transmitted. Different animals

transmit messages via different media. Many animals-for example, birds, whales, frogs, rattlesnakes, and crickets-use their bodies to produce sound to communicate. In addition to the sounds we are familiar with, such as dogs barking and birds singing, some animals produce sounds that are not audible to humans. Elephants use infrasound-very low pitched sounds (less than 20 Hz)-to send messages. These sounds can travel several miles and allow elephants to communicate over long distances. Bats and whistling moths, on the other hand, use ultrasound-very high pitched sounds (over 20,000 Hz)-to communicate. Such sounds do not travel very far, but not much energy is needed to produce them. Other animals use objects to produce the sounds they use for communication. Kangaroos, hares, and rabbits thump their hind legs on the ground as a warning signal, while the death-watch beetle bangs its head against wood to communicate.

Some animals communicate using visual cues. For example, dogs and apes use certain facial expressions and body postures to express submission, threat, playing, desire, and so

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on. Female rabbits use the white of their tail as a flag to lead their young to the their burrows. Fireflies find mates by producing light, male spiders use elaborate inform a female that they are healthy and capable of mating, and fiddler crabs

claws to communicate. Animals may also use touch to communicate. Monkeys hug, big cats

nuzzle each other, and bees use touch to communicate the location of a food Other animals use odor to communicate. The best-known example

ical communication is the pheromones used by many insects to attract mates. In ants use scent trails in order to communicate which path other ants in the

travel along. Some fish and amphibians use electrical signals to communicate. These are

to identify mates, broadcast territoriality, and regulate schooling behavior. electrical signals don't get distorted when passing through different materials,

murky water. Semanticity and Pragmatic Function, respectively, refer to the fact that

communication systems have meaning and that all communication systems useful purpose. The previous paragraphs have already mentioned many of conveyed by their animal communication systems. Since survival is the animal communication systems, meaning of signals usually has to do with and other vital behaviors, such as deciding to fight or flee. In all of the tioned examples, such as bees communicating the location of a food source apes communicating submission or threat, the messages being purposes: helping others find food, and warning others of danger. In some matic functions are clearer than those commonly expressed in human tdnguio~

14.1.3 Design Features Exhibited by Some Animal Communication

Some, but not all, animal communication systems exhibit the following Interchangeability refers to the ability to both send and receive

ample, every elephant can use infrasound to send messages and can also sent this way from other elephants. But not all animals can both send and For example, the silkworm moth's chemical communication system does changeability with respect to mating. When the female is ready to mate, chemical that males can trace back to her. The males themselves cannot ical; they can only be receivers. On the other hand, for whistling moths, it send the signal (in this case to communicate messages about territory). moths have a rough edge on their wings that they can rub together to males and females can hear and react to these sounds, but only males can

Cultural transmission refers to the notion that at least some part of a system is learned through interaction with other users. In most organisms, code itself is innate, or genetically programmed, so an animal or insect a new signal code than it can grow an extra eye. For example, fireflies are to produce or interpret their light displays; they are born with these them naturally and instinctively at the appropriate time. Likewise, - ..... '"'·"' in other birds' nests and therefore are not raised around adult cow nevertheless grow up to produce cow bird calls and not the calls of the This means that their calls are fully innate.

However, for some animals, aspects of their communication learned. For example, regional dialectal variation (see File 10.3) has number of bird species' songs, in killer whales' communication, and gestures. Dialectal variation indicates that there has been cultural cases because the birds learn their dialect from hearing other birds

learn from hearing the clicking and whistling of other killer whales, and chimpanzees learn from seeing other chimpanzees using the specific gestures. These behaviors are not geneti­cally encoded: if a young killer whale is raised in a pod of whales it is not related to, it will learn the communication system of the pod it is living with, not the communication sys­tem of its mother's pod.

In some cases, the division between what is culturally transmitted and what is not is less clear. In experiments with finches, juvenile finches that were isolated until adulthood were able to make simple calls, indicating that finch calls are somewhat innate, but their calls were not as complex as those of finches raised in groups. These experiments suggest that finches have a critical period for song acquisition, indicating that some aspects of finch call making are transmitted culturally (see File 8.1 for critical periods in humans). Those finches that were not exposed to calls early in life exhibited the aspects of calls that are in­nate but did not exhibit the aspects of calls that are culturally transmitted.

Arbitrariness means that the form of a symbol is not inherently or directly related to its meaning or function. Since most animal systems use iconic signals that in some way directly represent their meaning, most animal signals are not arbitrary. For example, when a dog bares its teeth to indicate it is ready to attack, the signal (bared teeth) is directly related to its meaning ('I will bite you'). Likewise, a dog may roll over and show its belly in order to indicate submission; this is an iconic way for the dog to indicate that it is making itself vul­nerable. Many animals, including several species of snake, lizard, and frog, will stand up taller, puff out their features, or otherwise make themselves look larger in order to signify that they are making a threat; since larger individuals are often better able to win in a phys­ical confrontation, using size to indicate threat is also iconic.

However, not all of the signals animals use are iconic. For example, the dorsal region of the male western fence lizard turns different shades of blue to indicate territoriality. A darker blue indicates territorial ownership and the lizard's willingness to fight to keep its territory. A lighter blue indicates that the lizard does not consider a territory its own. It is used when walking across another male's territory to indicate that the lizard is not challeng­ing the other's territorial ownership. Here, the color blue does not iconically represent own­ing a territory. However, western fence lizards also use iconic signals to communicate; they

themselves look bigger (by turning sideways) to indicate threat. Another example of "Ombitrar'in<css in animal communication is the variety of alarm calls of primates, which will

discussed in the next file. Thus, animal communication systems can include both iconic and arbitrary signals.

Discreteness refers to the property of being able to construct complex messages that built up out of smaller discrete parts. The messages in most animal communication

that we are familiar with do not have this property. Each message is an indivisible However, limited discreteness can be found in some communication systems. One

.eX<lmiple is the way in which bees' dances are built up of smaller parts: the dance pattern, direction, and the vivacity of the dance, each of which contributes different informa­to the message. The bees' dance will be described in detail in the next file.

Features Not Found in Animal Communication Systems

human language exhibits the following features: Displacement refers to the ability to communicate about things that are not present

space or time. No animal communication system appears to display this feature. How­there is some debate as to whether bees (see File 14.2) and some apes exhibit it to a lim­degree. For example, Menzel and his colleagues (2002) studied spatial memory in

They used road signs with arbitrary symbols (lexigrams) that described where in food was hidden. The bonobo Kanzi could use the information on the sign to find

hidden food, even though it could not be seen from the location of the road sigu. Thus,

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572 Animal Communication

even though the food was not present in space, Kanzi used information on the

determine its location. This does seem to suggest that bonobos can understand messages about

present in their immediate environment. Thi~ is based ~n inte~preting the ro~d sages as something like There's a food source hidden at this location, though. This assumes a message about a distant, invisible object. But the message can be differently-and more simply-as Perform this behavior now, that is, Go to this This is no different from most messages sent in animal systems and does communicating about things that are not present. Thus, we don't know derstands the signs in terms of food being hidden somewhere, which would placement, or in terms of an order to perform a certain behavior. In other wcm1s t

know if Kanzi interprets the messages as representing objects that are not pr,esentc instruction to go somewhere. Thus, it is unclear whether bonobos exhibit lin1it<1d.di ment, or whether they do not possess this feature to any degree.

Productivity refers to the property of a language that allows for the rule-tms<1cl sion of an infinite number of messages, including the expression of novel ideas. terms, it refers to the ability of an individual to produce and understand the individual has not been exposed to before by applying rules and co1nbining discrete components of the language in new ways.

In all animal communication systems, the number of signals is fixed. Even signals in some animal communication systems are complex, there i~ no systematically combining discrete units in new ways to create new signals. some species of birds and whales have songs composed of differe:'t units that in various ways. However, it seems that regardless of the order m which the the song still has the same meaning. That is, while these birds and whalesdo combinations of discrete units, they do not seem to use the different comt>in,atiiJ~ to create signals with novel meanings or to convey novel ideas. These noll!:,mdl terns are thus called closed communication systems.

14-1.5 What the Design Features Show Us about Animal Commu

In the comparison of human language with animal communication systems, arisen over whether human language and other systems differ qtJtalitiltive:ly'Di tatively. If there were merely a quantitative difference, then we would animal communication system that possesses all nine of these features, but pressed to a lesser degree than in human language. If, on the other hand, and other communication systems differ qualitatively, we would not expect mal communication system that possesses each and every design feature. sometimes difficult to decide whether an animal communication system to a certain extent or not at all, as the displacement example above shows.

At any rate, no animal communication system has been identified to nine design features. If we agree that a communication system must have all features to be considered a language, we must conclude that animal

terns are not language.

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imal Communication in the Wild

1 Bee Communication

In File 14.1 we claimed that no animal communication system is qualitatively the same as human language because no animal system with which we are familiar possesses all of Hockdt's design features .. In this file we will investigate three animal communication sys­tems m a httle more detatl: that of an Italian species of honeybee (Apis mellifera ligustica), that of the European robin (Erithacus rubecula) and other bird species, and that of the rhesus monkey (Macaca mulatta). These investigations will describe how these species communi­cate in the wild and will provide further support for the claim that, although enormously complex, animal systems are quite different from human language.

We will begin by discussing honey bees. When a forager bee returns to the hive, if it has located a source of food, it does a dance that communicates certain information about that food source to other members of the colony. The dancing behavior may assume one of three possible patterns: round, sickle, and tail-wagging. The choice of dance pattern is determined by the distance of the food source from the hive. The round dance indicates locations near the hive, within 20 feet or so. The sickle dance indicates locations at an in­termediate distance from the hive, approximately 20 to 60 feet. The tail-wagging dance is for distances that exceed 60 feet or so.

. In all the dances, the bee alights on a wall of the hive and moves through the appro­pnate pattern. For the round dance, the bee's motion depicts a circle. The only semantic in­formation imparted by the round dance other than the approximate distance from the hive to. the food source is the quality of the food source. This is indicated by the number of rep­etitiOns of the basic pattern that the bee executes and the vivacity with which it performs the dance. This feature is true of all three patterns. To perform the sickle dance, the bee traces out a sickle-shaped figure eight on the wall. The angle formed by the open end of the sickle intersecting with an imaginary vertical line down the wall of the hive is the same angle as the angle of the food source from the sun. Thus, the shape of the sickle dance im­

information about the approximate distance, direction, and quality (see (1)).

The sickle dance. In this case the food source is 20 to 60 feet from the hive.

Reprinted with permission from Fromkin and Rodman, An Introduction to Langua(J"e 2nd edition (1978) p. 42. "''' }

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In the tail~ wagging dance, shown in (2), the bee's movement ag~in des~ribes a th' time the circle is interrupted when the bee cuts across the circle domg a taJJ-w•ai ac:~on. The tail-wagging dance imparts all the information of the sickle dance (in it is the angle between a vertical line and the tail-wagging path that . angle to the sun), with one important addition .. Th~ number of repet1t10ns per the basic pattern of the dance indicates the preCise distance: the slower the re(?etiti<JI the greater the distance.

(2) The tail-wagging dance. The number of times per minute the bee dances a co1nple tern (1-2-1-3) indicates the distance of the food source.

Reprinted with permission from From kin and Rodman, An Introduction to Language, 2nd

p. 43.

The bees' dance is an effective system of communication that is capable, in princ:ipli finitely many different messages. In this sense the bees' dan~es ~re infinitely human language. But unlike human language, the commumcatwn system of limited semantic value; the topics that bees can communicate about are lirnited. ample, an experimenter forced a bee to walk to a food source. When the bee hive it indicated a distance 25 times farther away than the food source acltually bee had no way of communicating the special circumstances or tak:ing them in its message. This absence of creativity makes the bees' dance from human language. . .

In the previous file, we discussed the design feature of arb1tranness. dance exhibit this feature? What are the forms of the signs, and to what m<,andnis~ correspond? Are the relationships arbitrary or non-arbitrary? In the ,tail-';agging form is the vivacity of the dance, with a correspondmg meanmg quality of The relationship is arbitrary, for there is nothing inherent ab~ut viVac~ty. that good or bad quality. Because the relationship is arbitrary, there IS no a pnon what the form means.

What about distance? The question here is more complicated. RE,memtber' slower the repetition rate, the greater the distance. On the surface this rela.ltio!1S seem arbitrary, but consider it this way: the longer it takes to complete the basiC longer it will take a bee to fly to the source. Thus, we see that this sign i~ in some arbitrary. Similarly, the direction-determining aspect of the dance 1s since the angle of the dance mirrors the angle to the food source. Therefore, we dances have both arbitrary and iconic (non-arbitrary) components.

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File 14.2 Animal Communication in the Wild 575 '---·- ---~-·······---··.:::. .. :.:.

Bird Communication

Birds communicate using both calls and songs. Calls are typically short, simple sounds that may warn of predators, express aggression, coordinate flight activity, or accompany feeding or nesting behavior. Flight calls, for example, are typically short sounds, and their place of origin is easy to pinpoint: they allow the bird flock to stay together more easily. Sounds warning of predators, on the other hand, are typically thin, high-pitched, and dif­ficult to locate. They allow birds to warn other members of the group of predators without giving away their location. We can see that these bird calls are not completely arbitrary; rather, the calls are functionally related to the meaning they convey: the calls that imply the meaning 'locate me' are easy to locate, whereas the calls that imply the meaning 'I don't want to be found' are difficult to locate.

Bird song is different from bird calls. In most species, only males sing, often to delimit their territory or attract a mate. Unlike calls, songs are largely seasonal. But like calls, the songs of certain species of birds have definite meanings. One song may mean 'let's build a nest together,' while another song may mean 'go get some worms for the babies.' But the bird cannot make up a new song to cope with a new situation.

Scientists who have studied the songs of the European robin found that the songs are very complicated indeed. But, interestingly, the complications have little effect on the message that is being conveyed. Scientists studied the song that signaled the robin's posses­sion of a certain territory. They found that rival robins paid attention only to the rate of alternation between high-pitched and low-pitched notes, but that which of the two tones came first didn't matter at all. A higher rate of alternation shows a greater intention to defend the territory. Thus, a robin's message varies only to the extent of expressing how strongly the robin feels about his possession and how much he is prepared to defend it and start a family in that territory. This means that the robin is creative in his ability to sing the same message in many different ways, but not creative in his ability to use the same units of the system to express many different tunes, each with a different meaning. In other words, there is evidence that certain birds combine parts of their songs in different orders, but there is no evidence that different meanings are associated with this recombination.

Similar patterns are seen in the songs of other songbirds, for example, the branded wren (Thryothorus pleurostictus). If we look more closely at the ways the songs can vary, some interesting patterns emerge. There are particular chunks or phrases that are the basis for song construction (rather than, for example, individual notes, as in human music). Let's suppose that the bird has four kinds of phrases, and we'll term them A, B, C, and D. Again, like the robin, the song of the branded wren does not change its meaning depending on how it is being sung. The components A, B, C, D and so on do not carry any meaning on their own (i.e., the song of the branded wren does not show discreteness). Unlike human language, there is no compositionality (see File 6.4). A possible form of a typical song is shown in (3).

(3) ABABABCCCCD ABABABABABABCCD ABCCCD

There are simple rules governing the constructions of these songs: start with A, go to B, and alternate between A and B as many times as you like; then go to C, and repeat that at least twice, before finishing with D. This rule-based system for the combination of sym­bols is very similar to syntax in human language (see Chapter 5). However, it is nowhere near as complex as the syntax of a human language-no human language works with rules this simple. The memory load for these rules is very low-the singer only needs to know what phrase it is singing at that very moment; it can forget whatever has come before. If a

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bird is singing A, it knows that the next phrase must be B, no matter what. ~uuuar i like structures can be found in the calls of gibbons, diana monkeys, and whales. of human languages cannot be explained with such a simple model: we can what word will come next based only on the current word.

14.2.3 Primate Communication

Many species of animals have communication systems that are much more cc,mple one might imagine, but they still appear to be very different from human 1dJ1tg11aE~e. : of non-human primates such as the vervet and rhesus monkeys, studied both in and in captivity, have revealed elaborate systems of vocal and facial co'mmtmilcatioi are almost invariably triggered by proximal external stimuli, such as the presence tors or food sources. Vervet monkeys have been observed to use a variety of alarm warn each other of different kinds of predators. A vervet monkey that emits a communicates to the rest of the group that a leopard has been spotted. This type call sends everybody up into the trees. A short, interrupted, usually two-part, sound means that an eagle is in the vicinity, and monkeys immediately look up hurry to take cover under thick bushes. If a snake has been seen by a member of the he or she will make a soft whirring noise that immediately prompts everybody to and look around the grass cautiously.

Other types of vervet monkey calls deal with social hierarchy arguments, rituals, and territorial disputes between different groups of monkeys. This limited lary" of monkey calls is rigid and fixed. There have been some claims that some ing" monkeys might emit an alarm call in the absence of a predator in order to a food source by sending everybody else to seek shelter. Such reports indicate that keys are able to use their limited array of calls for different purposes (either to give ine warning, or just to clear the area for selfish reasons). These instances of indicate that the monkeys are aware of the behavioral effects that their calls have members of the troupe. However, these cases do not represent novel utterances or nals. In fact, if we were to provide the gloss of 'Hey, everybody go climb a tree' 'Hey, everybody, there's a leopard,' then it would be totally reasonable to expect call to be used in two different sets of circumstances. Most animal communication do not have the sophistication to use the same signal for different purposes in but even a double usage like this doesn't come close to mirroring the complexity language.

A recent study of rhesus monkey calls has also revealed a human-like ability hance the auditory perception of vocal signals with visual cues. In (4), we can see ferent types of rhesus monkey calls and the accompanying facial expressions. The on the left represents a cooing call, and the picture on the right a threat call. Cooing are long tonal sounds, and threat calls are short and pulsating, cough-like sounds. revealed that rhesus monkeys are able to recognize the correspondence between ticular call and the appropriate facial expression. This is a very human-like ability.

The great apes (gorillas, chimpanzees, bonobos, and orangutans) also comrnunic with facial expressions, gestures, and calls to express anger, dominance, fear, dang·er;: ceptance in a group, and the like. These are also human-like behaviors. However, as plex and human-like as these systems may seem, they lack displacement and pnJdttctivi Apes do not communicate about things that are not physically present, nor can they bine their independent gestures or calls in novel ways to create new meanings.

File 14.2 Animal Communication in the Wild 577 ·······~~~·~-•<<~~•<•-~~--···~················-·~~~-

(4) Facial expressions, waveforms, and spectrograms of rhesus monkeys' cooing (left) and threat (right) calls

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Concluding Remarks

The philosopher and mathematician Rene Descartes pointed out more than three hundred years ago, in his 11 Discourse on Method," that the communication systems of animals are qualitatively different from the language used by humans:

It is a very remarkable fact that there are none [among people] 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.

Descartes went on to state that one of the major differences between humans and animals is that human use of language is not just an immediate response to external, or even inter­nal, emotional stimuli, as are the grunts and gestures of animals.

All the studies of animal communication systems provide evidence for Descartes's distinction between the fixed stimulus-bound messages of animals and the creative linguis­tic ability possessed by humans. Even though animal communication systems are not like human languages, they are nevertheless frequently very complex, interesting to study, and different from human languages in fascinating ways.

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Can Animals Be Taught language?

14.3.1 Attempts to Teach Animals Language

The previous file discussed how animals communicate in the wild. As far as we naturally occurring animal communication system is either qualitatively or equivalent to human language. But just because animals do not use or acquire naturally does not necessarily mean that they cannot be taught. This file · to teach animals language.

14.3.2 Primate Studies

The great apes (gorillas, chimpanzees, bonobos, and orangutans) are very tures and Homo sapiens' nearest relatives in the animal kingdom. Cttirrtp<mz.ee ample, share close to 99% of their genetic material with human beings. This similarity of ape and human, as well as the apes' intelligence, has prompted some to wonder if language could be taught to apes, even though they do not use rally (see File 14.2). Many such projects have been conducted, most in the or so. The ape used most often has been the chimpanzee, primarily because easily available than other primates. They are also considered to be one of the ligen! of the great apes. Orangutans, gorillas, and bonobos have also been studies.

These experiments have generated both exuberance and dh' ;ap•po·inltmenl:,:\ orous debate about the interpretation of their results continues to the present one hand, there are still some scientists who maintain that they have indeed to use human language. On the other hand, many scientists dispute this proposed alternative explanations for the behaviors other researchers assumed have been language use.

a. Early Projects. The first prominent experiment conducted on the · pacity of great apes in the United States took place in the 1930s. W. N. and · ·. wanted to raise a baby chimpanzee in a human environment to determine chimp would acquire language on its own, just as a human child does, posed to it. They decided not to give any training or "forcible teaching" to they acquired at seven and a half months, other than that which would be infant. Gua was raised alongside the Kelloggs' newborn son, Donald, and the of the chimp was compared to the boy's. W. Kellogg stated that his intent was how much of human language ability derived from heredity and how much tion. He reasoned, a bit naively in retrospect, that what the chimp could not be those aspects of language that a human inherently knows. Kellogg tion of this program when, at one point, he attempted to mold Gua's lips in an her to say papa. This effort, lasting several months, proved unsuccessful.

In the 1950s, Keith and Cathy Hayes decided to raise Viki, a female much like a human child as possible, believing that with a proper

578

could learn language. The Hayeses believed that they could teach Viki to speak, even though doubt was emerging at the time about whether the chimpanzee's vocal anatomy could even produce human speech sounds. The Hayeses, however, believed that the vocal tract of the chimp was similar enough to a human's for it to be able to articulate human sounds, and they had no aversion to "training." Their program included first teaching Viki to vocalize on demand (this took five weeks), and then shaping her lips with their hands into various configurations that yielded consonant sounds. After three years, Viki could "speak" three words-cup, mama, and papa-although they were accompanied by a "heavy chimp accent": it sounded as if Viki were whispering. The Hayeses reported that Viki could "understand" many words, but they offered no experimental proof of this. The Kelloggs' and Hayeses' experiments were not viewed by scientists as successful attempts to teach language to apes. Three words are not very many when one is trying to prove human language capability.

Allen and Beatrice Gardner believed, contrary to the Hayeses, that chimps were not capable of producing human speech sounds, so they felt that trying to teach a chimp to speak was fruitless. Since chimps are manually dexterous and use gestures to communicate naturally, the Gardners decided to teach American Sign Language (ASL) to a chimp they named Washoe. Their methods were quite different from those used with Gua and Viki. Washoe was not raised as a human infant but was brought up with minimal confinement in a stimulating atmosphere. Spoken English was not allowed in her presence because the Gardners feared she would come to understand spoken language first and not be moti­vated to learn ASL. Like Viki, Washoe also received deliberate training. Objects were pre­sented to her, and the trainers molded Washoe's hands into the shapes for their signs. Eventually, in order to be rewarded, she had to produce the signs herself and to produce them with greater and greater accuracy.

The experiment was considered at the time to be a great success. By the time Washoe was five years old, she had learned 132 signs; by the end of her life in 2007, she had learned over 250, not all of them in a training environment. More important, she supposedly ex­hibited some amount of productivity in her communication by inventing her own novel combinations such as dirty Roger, where dirty was used as an expletive, and water bird, up­on seeing a swan on a lake. There is some debate as to whether combinations such as water bird are compositional (see File 6.4) or whether Washoe was commenting on two separate things: she saw some water and she saw a bird. If the latter were true, the example would not show that Washoe had developed productivity in her language use.

Even more impressive, Washoe taught signs to her adopted son. Loulis was adopted by Washoe when he was 10 months old, and she taught him to sign in the same way she was taught: by molding his hands to make the signs. She taught him about 40 signs. This makes Loulis the first non-human to learn parts of a human language from a non-human! The Gardners and others, such as Robert Fouts, have continued the project with Loulis and other chimpanzees: Tatu, Dar, and Moja.

The Gardners' insight about the vocal limitations of the chimp has been noted by every researcher since. Consequently, subsequent endeavors have all involved simplified versions of either a signed language or visual signs such as lexigrams, symbols composed of geometric shapes used to represent words.

Anne and David Premack began in 1966 to work with a chimpanzee named Sarah. Like the Gardners, David Premack decided to try to find and use the best possible training procedure rather than raising Sarah as a child. The "language" used was also atypical. In­

of a simplified version of ASL, Premack used differently shaped and colored plastic He arbitrarily associated an English word with each chip. Communication between

· the trainers and Sarah involved placing these chips on the "language board." Sarah was how to do one type of "sentence" at a time. Typically, her task was to choose an ap­

propriate chip from a choice of two or to carry out a task indicated on the language board.

i.

580

Premack intended to teach Sarah the names of objects as well as the names of objects. He originally claimed to have taught her 130 symbols, including ca1:eg,0r such as color and concepts such as same and different. Premack also claimed learned the word insert. As proof of this, Premack offered the observation that when Sarah saw Sarah banana pail insert on her language board, she correctly task.

Duane Rumbaugh wanted to design an ape language experiment with as training taken out of the hands of human trainers as possible. He reasoned •w'l r<.tr ing were automated, one could avoid cueing the animal, and the training efficient and constant. So he and his associates designed a computer that training. The computer could execute certain commands, such as dispensing playing slides in response to an operator giving proper commands. Commands by lighting up symbols of an invented "language." Like the Premacks with baugh used lexigrams-in this case they were various combinations of nine metric figures, such as a big circle, a little circle, and a large X-as the Jar1g11a!~e 1:he of the machine would use. This operator was, of course, a chimp; her name was did learn to use the keyboard quite well and managed to make the computer commands, and Rumbaugh thought that he had succeeded in teaching a chimp• s man language.

In 1972 Francine Patterson began to teach ASL to a gorilla named Koko. has been one of the longest lasting of its kind, and Patterson has made some dramatic claims for such a project's success. According to Patterson, Koko hundred signs and has invented many of her own combinations, such as for 'ring.' Koko also supposedly uses her signs to insult people and things she After being reprimanded one day, for example, Koko called Patterson a dirty addition, Koko is reported to understand spoken English. The evidence given to support this claim is that Koko occasionally rhymes, putting together such and hair even though the signs themselves have no visual similarity to each also substitutes homophones for words when she cannot think of the sign, or know for no. Although Koko has exhibited a remarkable grasp of many linguisti ties, she does not yet seem to have displayed the abilities necessary to justify claim that "Koko is the first of her species to have acquired human language."

b. Criticisms of the Early Projects. The results and conclusions have been critically questioned; the first to do so was a researcher named His criticism was based on a critical review of his own project to teach a chi'r np•anz< of grammar. He then critically reviewed other projects and found similar smJWCO!

In the late 1970s, Terrace began his project, which was similar to that "fth,•f

with a chimpanzee he humorously named Nim Chimpsky (hoping that language, the joke would be on Noam Chomsky, the noted linguist who thing was impossible). Terrace's goal was to prove that a chimp could acquire some use of grammar. Terrace believed, as did most researchers at the time, dence of human language capability was the use of grammar and not just the By the time Nim was four years old, he had acquired 125 signs based on ASL bined them in various ways, and Terrace felt that Nim had acquired human ties as well.

This project was the first to videotape all interactions between chimp however, and it was on reviewing these tapes that Terrace decided he and instead acknowledge that the ape's use of signs was very different from guage. He noted that there were many dissimilarities between Nim's and a acquisition of "language." Nim, for example, almost never initiated signing. ing the tapes, Terrace found that only 12o/o of Nim's signs were 40o/o were mere repetitions of what the trainer had just signed. This subtle

File 14.3 Can Animals Be Taught Language? 581 '"••••----·-·••••·~~··•-~~--,,,_~m•---~--,..-m•---

never noticed by the trainer at the time. In addition, Nim's spontaneous signing was invari­ably a request for food or social reward; he never made unsolicited statements or asked questions. Quite unlike a human child, he did not display turn-taking behavior and was more likely to interrupt his trainer's signing than not. There was also no evidence that Nim knew any grammar. His combinations had variable word order, and, more importantly, Nim rarely went beyond two-word combinations. Even when he did, the additional signs added no new information. For example, Nim's longest utterance was give orange me give eat orange me eat orange give me eat orange give me you.

Terrace called into question the results of all previous experiments. He reviewed tapes of Washoe and Koko and concluded that they too had been cued by their trainers. He and others leveled even more serious criticisms of the Premack project, arguing that the train­ing procedure taught problem solving rather than language and that Premack's conclusions were not well founded, given his experimental design and his results. Consider Premack's claim that Sarah learned the word insert because she could correctly insert a banana into a pail when seeing Sarah banana pail insert on her language board. When the word insert was tested against the word give, however, Sarah could not distinguish the two. Premack like­wise claimed that Sarah knew the prepositions on and in but never administered a test where Sarah would have to distinguish one from the other. Following instructions did not necessarily involve Sarah's understanding a sentence on the language board, but rather her recognizing, for example, a banana chip and a pail chip and imitating what she had been trained to do in the first stage of the test-in this case, to insert the banana into the pail. (A banana couldn't go on an upright pail!)

c. More Recent Projects. Terrace's revelations had a great effect on the field of ani­mallanguage studies. Funding for projects was thereafter hard to come by, and many sci­entists responded with new cynicism to any and all claims of animal language researchers. Researcher Sue Savage-Rumbaugh maintains that both the initial easy acceptance of claims in this field and the post-Terrace cynicism are too extreme.

She has begun another project with several apes, but the focus of her work is quite different. She believes that looking for evidence of grammatical capabilities in apes asTer­race did was far too premature. She considers a more fundamental question: when apes use a sign, do they know what it means? This question is by no means easy to answer, and it is surprising in hindsight that the early researchers took it for granted that when an ape produced a sign, it was using it in the same way humans do; as a symbol with a mental representation as part of the meaning. A symbol is an arbitrary relationship between a form (the sound pattern or gesture) and its meaning (see Section 11.1.4). One aspect of meaning is the sense, or mental representation (see File 6.1). Mental representations have an exis­tence separate from their referents and can be manipulated independently of them. Thus we can think and talk about things that are not present; in fact, we can talk about things that don't even exist (e.g., unicorns).

Note that this approach represents a departure from the attempt to assess animal lan­guage capabilities in terms of the descriptive "design features," such as productivity and displacement, as discussed in File 14.1 by assessing how linguistic expressions are used. The use of a mental representation as part of a symbol is a separate characteristic that distin­guishes human language from the natural animal communication systems discussed in Files 14.1 and 14.2.

No one disputes that humans use their words in this way. Furthermore, no one dis­putes that, in many cases, animals have been able to associate a phonological or visual form of a sign with a referent. But how are we to know whether an ape, when it uses a sign in the same way we might, really has a mental representation for it? Savage-Rumbaugh has sug­gested that in all previous experiments, apes were not using their signs symbolically. She argues that apes had merely learned to associate certain behaviors (making or seeing a particular sign) with certain consequences (e.g., getting something to eat)-similar to a dog

582 Animal Communication ~---~--~··~~···········~·~·--·-~---·

which, upon hearing the word walk, knows it's going to get to go for a walk. tremely subtle distinction for humans to perceive, since the use of symbols coJme.sn, to us. We interpret other creatures' signals to us in the same way we interpret each other, but that doesn't necessarily mean they're intended in the same reason, Savage· Rumbaugh has pointed out the necessity of proper experiments that an ape has truly acquired a word in the same way a human has. She has claims made about previous projects either because they were not based on proper controls or because use of symbols had not been tested at alL In ad<iition) Rumbaugh reasoned that because apes had not learned to use symbols given techniques used previously (which had assumed that the symbol aspect of come naturally), apes must specifically and intentionally be taught to use before tests could be informatively administered.

How could Savage·Rumbaugh determine whether such instruction was How can one find evidence of a mental phenomenon? One must still look for havior of the animal or in the "processes of the exchange" with the trainer, be more discriminating about what counts as evidence. Savage-Rumbaugh leagues have worked extensively with two male chimpanzees, Sherman and tempting to teach them language skills with the computer and the lexigram.s '0 Lana. They have found that use of symbols by humans is not a single holistic but rather a complex of independent abilities and behaviors. For example, the duce a symbol was found to be composed of at least three separate abilities. dation of a lexigram and an object to request the object is only one of these of this ability does not prove the user has a mental representation for the ing is a second relevant behavior, which involves providing the lexigram associate object without the expectation of consuming or receiving that object. The valved in symbol use is called comprehension of the symboL It involves linking to its referent. One might find it difficult to separate these three, but they taught separately to the chimpanzee, and the presence of one ability could not because of the presence of another.

Savage-Rumbaugh also points out the extreme importance of a fourth bol use and human communication that had previously been overlooked: receiver or listener. This in itself was also found to comprise its own complex behaviors, each of which had to be taught separately to Sherman and Rumbaugh claims to have been successful at teaching the chimps these skills links between them (the coordination that occurs naturally in humans).

Furthermore, she has acknowledged Terrace's criticisms of other pn*'cts, tains that Sherman and Austin do not evidence Nim's shortcomings. ~ne 1nau they take turns, their utterances are not imitations of their trainers, and they sages not only when they are elicited, but at other times as well.

This project certainly has made real progress both in clarifying what skills are and in investigating our ability to teach them to apes. Criticisms eled, of course. Some suggest that, again, the apes have been skillfully train<edl[ll ther comprehend what they are saying nor use their signs symbolically. perhaps impossible to know whether another creature has a mental repres·ent word. Savage-Rumbaugh might respond that this criticism is a reflection of a tude rather than scientific considerations. However, given past experience dency to overinterpret results and behaviors, there is a need to scrutinize the field.

Savage-Rumbaugh's most recently begun project must be mentioned. to work with another species of ape, the bonobo, Pan paniscus, which she

File 14.3 Can Animals Be 583

telligent than the common chimpanzee, Pan troglodytes, which she had used in all of her other projects. She claims that the bonobo she has been working with, Kanzi, has learned to comprehend spoken English just by being exposed to it and has spontaneously begun to use the keyboard with lexigrams to make requests and comment on his environment. Savage-Rumbaugh reports both anecdotal observations and the results of tests that might substantiate these astonishing claims. Again, these newest claims are difficult to accept with­out further confirmation based on carefully controlled experimentation and the objective scrutiny that was advocated at the inception of the Sherman and Austin project.

While there are still some ways in which Kanzi's acquisition and use of English and lexigrams differ from the language acquisition of a human child, Savage-Rumbagh's work with Kanzi is the closest we have come to teaching a primate human language.

Non-Primate Studies

Primates have long been the focus of investigations into the linguistic capacity of animals, primarily because of their intelligence. However, attempts have also been made to teach small parts of language to non-primates.

a. Domestic Animals. Humans have always had close relations with domestic ani­mals, and many people anecdotally claim that their pet can understand what is being said to them. Is this simply because of a confirmation bias or an emotional connection or is

' there some truth to this claim? To what extent can domestic animals understand human language?

Wilhelm von Osten was a German math teacher and amateur horse trainer in the early 1900s. He owned a horse called "Clever Hans" who was claimed to be able to under­stand simple arithmetical questions and answer by tapping his hoof. For example, Wilhelm would ask "Hans, what is ten minus three?" The horse would then tap his hoof seven times. However, investigation by the psychologist Oskar Pfungst revealed that Hans was actually paying attention to the subconscious body language cues of his owner Wilhelm, who knew the answer. So Hans was not so clever after all-he was simply a keen observer of humans. This result highlights the importance of testing animals in a neutral environment, away from potential factors that may cue them to the answer.

Domestic dogs are well-known for their language ability, and many people train their dogs to respond to commands-for example, 11 Sit," 11fetch/' and '1beg." Herding dogs that work with farmers can learn many commands to help move herds of livestock. Is there a limit to this ability? Working with a border collie called Rico, Julia Fisher and colleagues investigated this question. They found that Rico was able to accurately retrieve over 200 different items by name, and was able to learn the names of new items with surprising speed. However impressive this is, though, the dog is most likely simply associating the sound of the word and the behavior of fetching with the reward; that is, the dog is simply giving a trained response. Thus, as with many of the primates, Rico is not using symbols. In addition, dogs and horses cannot respond with speech or signs-we cannot hold a conver­sation with them.

b. Alex the Parrot. Irene Pepperberg, an animal psychologist, bought a grey African parrot from a pet store in 1977 and attempted to teach him to speak. She named the parrot ((Alex/' which was an acronym for 11Avian Learning Experiment."

Alex was trained with the "model-rival" technique, where two trainers work with the animaL One trainer gives instructions, while the other trainer models correct and incor­rect responses. This way, the second trainer is competing with the animal for the attention of the first trainer. The trainers then swap roles and repeat the process. After observing, the animal then tries to model the correct behavior for the trainers. The following is an excerpt

584

of a training session using the model-riyal technique. lrene Pepperberg is trainer, with Kimberly Goodrich assisting as secondary trainer. In the excerpt in being taught to differentiate colors and shapes.!

(1) Irene: Kimberly: Irene:

Kimberly: Irene: Kimberly: Alex: Kimberly: Irene: Kimberly:

Irene: Alex: Irene: Alex: Irene:

(Holding up a green triangular piece of wood.) Kim, what color? Green three-corner wood. (Removes wood from sight and turns body slightly away from Listen! I just want to know what color! (Turns back to Kim and wood.) What color? Green wood. (Gives Kim the wood.) That's right, the color is green,. green wood. OK, Alex, now you tell me what shape. No. OK, Irene, yau tell me what shape. Three-corner wood. That's right, you listened! The shape is three-corner; it's tm'ee-mr," (Gives lrene the wood.) Alex, here's your chance. What color? Wood. That's right, wood; what colorwood? Green wood. Good parrot! Here you go. (Gives Alex the wood.) The color D >,'",n.

Alex was trained to identify four different shapes, five different colors, ferent materials. In a test where he was presented with both novel and fanailiari displayed at least 80% accuracy in description. Alex was also able to respond like "what is the same?" and "what is different?" between two objects, and order logical tasks. Pepperberg claims that this evidence supports the idea well-defined mental categories and conceptual representations. However, she that Alex knew language; instead, she called it "complex two-way cOlunlUIüc;ltiei!l

In light of Terrace's criticisms of primate language studies mentioned berg's work came under heavy scrutiny. How do we know that Alex wasn't phisticated mimic, learning what sound to make to correspond to a gjven object get some food? Were Pepperberg's experiments really testing for language they more related to the cognitive abilities of grey parrots? To what extent can utterances "Ianguage"? The same questions Savage-Rumbaugh asked of the asked of Alex: what kinds of mental representations does Alex have, and /(meaning" to thern?

Although grey parrots normally live for SO years, Alex died unexpectedly 31 in 2007. Pepperberg continues to work with grey parrots; but none yet aplPwia! ability. The demonstration of Alex-like ability in other parrots will be the validity of her findings.

'From Wise (2003), pages 103-4.

E 14.4 ...........................

14.1-Communication and Language

1. Refer to the cartoon at the beginning of this chapter to answer the following questions: i. Are the children actually 'speaking fish,' or speaking any language? Why or why

not? ii. Which of the design features does the children's use of "fish" show?

iii. Which of the design features does the fish's communication show?

2. The file mentions that when a dog bares its teeth, it indicates that it is ready to attack. Compare this with humans baring their teeth when they are smiling. What does it mean when we smile? Does it mean that we are ready to attack? ls this arbitrary or iconic? How do dogs probably interpret smiling in a person they don't know?

3. Many people insist that their dogs, cats, or other pets are able to understand what they want and to communicate with them. There is no doubt that our pets are often able to meld very weil into our lives. There is also no doubt that often there is at least some level of communication between people and their pets. Based on what you have read in File 14.1, however, how would you refute a person's claim that her dog or cat "knows exactly what I mean when I talk to hirn"?

4. Refer to the communication chain diagram in File 1.2. Although all animal communi­cation systems have a mode of communication, semanticity, and a pragmatic function, not all three of these are required to make the communication chain work. Which are, and which aren't? Explain your answers.

5. A wolf is able to express subtle gradations of emotion by different positions of the ears, the lips, and the tail. There are eleven postures of the tail that express such emotions as self-confidence, confident threat, lack of tension, uncertain threat, depression, defen­siveness, active submission, and complete submission. This system seems to be COffi­

plex. Suppose there were a thousand different emotions that the wolf could express in this way. Would you then say that a wolf had a language similar to a human's? Why or whynot?

uss,ion Questions

6. In File 14.1, many modes of communication are introduced. What are some reasons that a certain mode of communication might be weil suited to some species but not to others?

585

586 Animal Communication .. ~ ... "'~""~'~'

7. Think about the following situation: two male crayfish fight with each . them wins and a female crayfish chooses the winner as her mate. Who IS

cating with whom in this situation? Are the males communicating with each . are they using the other in order to communicate with the female? Explain

8. The male Tungara Frog (Physalaemus pustulosus), native to Central America, during the mating season described onomatopoeica11y as a "whine-chuck." serves to attract females, discourage nearby males from approachmg, and the frog's location to the predatory fringe-lipped bat (Trachops cirrhosus). tent can we say that the male frog intends for any of these consequences to

File 14.2-Animal Communication in the Wild

Exercises 9. Consider the bee communication system described in File 14.2 and an:sw'erlh

tions. Be sure to discuss a11 nine design features.

i. Which design features does the system display? Please explain.

ii. Which design features does the system elearly not display? Please eXlplain,

iii. For which design features does the file not provide you with enough information to decide whether the feature is present in the or not? What would you need to know about the system to make a would the system have to be like in order for the feature to be present?

10. Consider the bird communication systems described in File 14.2, and

and (ii) from Exercise 9.

11. Consider the primate communication systems described in File 14.2, and

(i) and (ii) from Exercise 9.

Activities 12. Male humpback whales (Megaptera novaeangliae) make Im~-f:requenCJ' v(xali"

ten referred to as songs (female whales do not sing, as far as we know). The the songs is not entirely elear, but they could be for foraging, mating and havior, long-range contact, assembly, sexual advertisement (male-male greeting, spacing, threat, individual identification, and/or sensmg ofthe Under optimal conditions, these songs can be heard hundreds of kilometers

The songs consist of aseries of notes organized into tunes, for example, a intonation fo11owed by several sharp drops. The tunes are repeated and archica11y, so that each song as a whole is a palindrome (it reads the same it does forwards). For instance, ifwe have tunes A, B, and C, a posslble song or C A B A C. This recursive organization is reminiscent of syntactic

language (see Chapter 5).

Which of Hockett's design features of language are present in humpback and which are not? For each feature, explain your reasoning in a sentence

13. Use the Internet, an encyclopedia, an animal behavior text, or other resoUlrCi tigate a natural animal communication system other than the o~es . 14.2. Describe this system relative to the design features outlmed m FIle 14.

File 14.4 Practice 587

14.3-Can Animals Be Taught Language?

14. There are transeripts of several "chats" with Koko the Gorilla available online. Pick a chat from the links on the Links pagefor Chapter 14 and answer the questions below.

i. What is Koko's longest utterance in the chat? What is Koko's average length of utterance; that is, how many words on average do Koko's utterances have? (You can estimate this.)

ii. About what percentage of the time did you understand Koko's utterances with­out any help from Dr. Patterson? About what percentage of the time did you need her to interpret for Koko?

iii. How relevant were Koko's utterances? Iv. Did Koko interrupt other speakers frequently or rarely? v. What are the main topics that Koko talks about? What, if anything, does this

reveal about her language use? vi. Does Koko ever seem to repeat or imitate Dr. Patterson's signs? About how fre­

quently does she do so? vii. Do you find evidence that Koko rea11y knows the meaning of the signs she uses?

If so, what kinds of evidence do you find? Please give specific examples. viii. Compare your answers to (i)-(vii) with the sorts of responses you would give after

reading the transcript of a conversation between humans. Based on this com­parison, do you think Koko can rea11y use language? ]ustify your answer. Explain both the things she does that do seem to model language use and the ways in which her behavior is dissimilar from human language use.

cussion Questions 15. Imagine that you wanted to teach language to an animalother than a primate or a

parrot. Consider how you would go about doing this, and then answer the questions

below. i. Which animal would you choose and why?

ii. What mode of communication would you choose to teach this animal? Why? iii. Ifyou tried to teach the animal symbols and a simple syntax, howwould you test

whether he had learned to combine the symbols to form different messages? Iv. Do you think the animal would be better at comprehending or producing both

symbols and simple syntax? Why do you think so?

16. In File 14.3, a distinction is olten drawn between teaching an animal language and teaching an animal to use language. However, the distinction between these two terms is never elearly defined. Based not only on what you have read in File 14.3 but also on your studies of language and linguistics throughout the book so far, what would you say the difference is between teaching an animal language and merely teaching an

animal to use language?

17. Throughout this book, we have presented both signed and spoken modalities of hu­man language. Both are equa11y authentie and natural modes of human communica­tion. Presumably, then, the choice of whether to train an ape using one or the other of these two types of language is not particularly relevant to whether we conelude that it has, in fact, learned language. Now consider the case oflexigrams. Does using lexigrams to communicate have any less authenticity than either speech or signing? Why do you

think so?

",~

588 Animal Communication

18. Suppose that animals can master some aspects of productivity (such as the word finger·bracelet for 'ring' and Washoe using water bird for 'swan.' If the cognitive capacity to put discrete units together in new ways, why do that we haven't found examples of productivity in apes' natural co:mnaur systems?

19. i. Savage-Rumbaugh claims that if we are able to teach an ape to use svrnbnl her three-part definition), it will be a more important indication of its language than would use of grammar. Do you agree?

ii. Suppose that we were able to teach a hypothetical animal-let's intelligent mutant guinea pig-to productively put together complex utterances using consistent word order, function words, and so on, guinea pig was unable to use signs symbolically. Would you say that the had a better command of language or a worse command of language who understood the symbolism of language but who did not have a grasp matical system?

20. Researchers have by and large concluded that -even if apes can be taught ments of human language-they cannot acquire human language naturally that human children do. Imagine that on some alien planet we were to species of animal. Further imagine that these animals never learned language (either growing up in communities with each other or growing up in a mans as a human child would) but that following instruction, the aliens language use completely. That is, they exhibited language use en•:ornpass:inl(t design features and full use of symbols: they could hold conversations, tell jokes, and so on. How would you describe the linguistic abilities of Would you say that their linguistic abilities (after training) were as genuine humans, or would you say that they were still lacking in some way? make this judgment?

21. The work that Terrace did and his interpretation of his results shed doubt on enterprise of trying to teach human language to animals. As a result, there grant funding for this sort of work. Such responses are very common in community: those who fund grants have only so much money to give, ably they generally try to underwrite projects that have a high level of the community. Suppose, though, that there were an unlimited amount funding. Do you think, following pronouncements such as Terrace's, that appropriate to reduce the amount of effort put into researching a particular

Further Readings

Hauser, M., & M. Konishi. (2003). The design of animal communication. Camt>ri<ige, Press.

Hillix, W. A., & D. Rumbaugh. (2004). Animal bodies, human minds: Ape, dolphin, language skills. New York: Springer.

Pepperberg, I. (1999). The Alex Studies: Cognitive and communicative abilities Cambridge, MA: Harvard University Press.

Savage-Rumbaugh, S., & R. Lewin. (1994). Kanzi: The ape at the brink of the human York: John Wiley and Sons.

Wise, S.M. (2002). Drawing the line: Science and the case for animal rights. New

CHAPTER

15 Writing Systems

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