Animal Communication

Animal Communication Ling 001, Spring 2010

Starting Points • The idea that humans are biologically equipped for language… • How does “general intelligence” (however you would measure that) correlate with linguistic ability? • As we’ve seen at different points, intelligence and linguistic ability are dissociable in humans.

Starting Points, 2 • The same kind of question can be raised when we look across species • E.g., does general intelligence correlate with different abilities in different species? • In particular, do animals have “more language” to the extent that they are generally smarter than other animals, with humans being at the top of the chain?

Basic Answer • The basic answer: No. • Human language has syntax: it makes infinite use of finite means. This does not occur in the communication systems of other animals • In some domains, e.g. association a “sound” with a “meaning”, there might be some effects that correlate with general intelligence. In most cases, though, communication systems are tailored to very specific needs • There are some surprises; e.g. bees (not very sophisticated in terms of general intelligence) have real skills in communication

Three key points • Syntax: The ability to create infinite structures is only part of human language • Signals (words): Human language has a potentially unlimited (lexical) vocabulary • Reference: Human language is used to refer to things that are not present; among animals, bees have this ability, but it is otherwise not found

Two approaches (roughly) • Animal Communication: The study of what different species do under “normal” circumstances • Instructing Animals: The attempt to teach (aspects of) human language to a non-human species • We’ll see a nice analogy in the reading, where the former type of study is more like anthropology, the latter like missionary work…

Questions • Animal Communication studies in general ask things like • What is being communicated? • How does this relate to different properties in other systems? In human language? • What are the adaptive functions of communication in a particular species? • How does the communicative system relate to the environment, etc. • The last points have been applied to human language as well, from an “adaptationist” perspective, but this is controversial (Lewontin reading)

Questions, 2 • The teach human language to animals view is less clear in many ways. Assumptions: • Maybe animals don’t have language because they don’t happen to have invented it? • Maybe language is a facet of general intelligence, so smarter animals should get “more” language than animals that have lower general intelligence • Definitely better for headlines/PR. Cp. “bees show displaced reference property” vs. “Koko expresses grief about dead kitten”.

Reference (Signal Set) • Animal communication systems have a limited signal set: the inventory of things that are communicated about is very limited (e.g. food, sex, aggression, predators/threats) • Human language, recall, has the ability to incorporate new basic elements (typically words) in a way that is unlike what is found in animals • Moreover there is nothing like syntax for generating new ‘utterances’ in the animal kingdom (in some domains linear order is important, however, e.g. birdsong) • We’ll illustrate by looking at what animal calls ‘refer’ to, using some different case studies

Example: Stickleback • Male changes color (becomes red) • Swims in “zigzag” dance toward egg-laden female • Female approaches • Male heads towards his nest • Female follows • Male pokes head in nest entrance • Female enters, eventually lays eggs, which are fertilized

Introductory comments • Something is being communicated in the stickleback interaction • In the broadest sense, the male coloration/dance indicate the readiness to mate • But there’s no need to attribute “thinking” to the participants • It could be a stimulus/response chain • I.e., each action elicits a stimulus response from the other participant

General Question: Reference • Consider a simple example of communication: dog posture. In this case, the dog is communicating that it is ready to play (the following is a game)

Reference, II • The dog in the example above is communicating something, namely, something about its internal state • With reference, we mean roughly what it is that a signal in communication refers to • Most animal communication systems are limited in what their signals are capable of referring to; typically, an internal state, or an immediately present stimulus • We’ll see below various ways in which communicating about particular states/objects is useful, in the evolutionary sense

Basics: Displays • Returning to our first example… • Display: “…a conspicuous stereotyped movement performed in a special context with an apparent communicative function” • Example: Stickleback zig-zag dance • “normally occurring” behaviors evolve into exaggerated forms • Displays of this type are less ambiguous and more likely to provoke a response of the appropriate type • The idea is to make the display unambiguous enough so that it is functionally useful

Basics: Functions • Views on the evolutionary roles of communication • Mutual benefit: signaling systems exist because both the signaler and receiver benefit • E.g. dog displays, avoiding fights is “more efficient” • Sticklebacks: producing healthy, fertilized eggs is “good”

Functions, Cont. • The “Selfish” view: animal communication systems evolve because animals benefit from manipulating one another • Signals are evolved to increase the sender’s fitness (not the receiver’s) • A conspicuous display that attracts predators wouldn’t be selected for simply because it benefits others • Example: “Deception”; males attract mates not by being better, but simply by appearing to be healthier

Aspects of Communication • We’ll concentrate on what is transmitted, although how speaker/hearer effects are modeled will enter into this • I.e., focus on information transmission with the intent of informing or changing the cognitive state of receivers. • This gives us various things to look for in animal systems • Appropriate receiver response when stimulus is absent? • Communication suited to the audience? • Receivers generalizing properties of the caller?

Functional Reference • One property of interest is called functional reference; two parts • A signal is given in the presence of an appropriate stimulus; it is not just an indication of ‘general excitement’ • Conspecifics (animals of the same species) hearing the signal (receivers) behave consistently and appropriately, even in the absence of the stimulus triggering the signal. • The last part is important because we want to know if it is the signal that is causing some behavior, or the detection of the source of the signal…

An Example: The Chicken • Research using a variety closer to the ancestral type • Useful test case because • Chickens court/produce alarm calls in controlled conditions (lab) • Chickens respond to video/audio tape of predators or other chickens, so that controlled experiments can be set up without too many methodological difficulties

Alarms • Two kinds of alarm calls: • Aerial predators: shriek/whistle • Ground predators: series of pulses • Behavior to different types is matches as well (cover, looking at sky vs. standing and searching the ground level) • What about functioning like reference? How do signalers/receivers react?

Responses • Chickens seeing hawk/raccoon stimulus (simulated) behave appropriately • Importantly for “functional reference”, audience chickens show behavior appropriate to the call • The latter was tested with hens isolated from the stimulus viewed by the calling chicken; all they perceived was the alarm. Listening hens behaved according to the alarm type.

Audience Effects • Alarm calling has a cost for a single animal: it may attract attention of a predator • It might therefore be expected that there is an audience effect in such systems: aspects of the alarm calling depend on the receivers of the signal

Manipulating Audience Effect • Do chickens behave as if they intend to communicate to other chickens? • Roosters alarm call more when they see a live or video-taped hen • It’s not just any audience, it’s an audience of conspecifics (same species); the alarm call when other chickens are present is more than if e.g. a quail is present • This is interesting but it doesn’t mean that communication in chickens is intentional. Rather, it shows that both predator and audience play a role in some aspect of signaling

Some further examples • Two different communication systems; bees and vervet monkeys • Vervet Monkeys: different calls for different predators, which trigger appropriate behavior • Bees: Communicate distance and location (relative to the hive) of food sources

Vervet Monkeys • (multimedia from Hauser’s webpage, http://www.wjh.harvard.edu/~mnkylab/media/vervetcalls.html) • Snake Alarm: Hearers stand on hind legs and look on the ground • Leopard Alarm: Hearers run to the top of the nearest tree (where leopards can’t go) • Eagle Alarm: Vervets run under a bush/cover of tree branches

Function • The organization of the alarm system makes sense given the living conditions of the vervets • The predators are categorized in different ways: in particular, ways that require different responses • Categorization is acquired in the first four years of life; young vervets miscategorize, but eventually learn the correct association of calls with predators (without, apparently, any correction)

Vervets: Details • Further question: what kind of information is represented in the receiver? • (In particular…) Is something about the nature of the alarm caller represented by the listening vervets? I.e., do vervets show awareness of properties of the individual who is calling?

Outline • Habituation: Behavioral response decreases with repeated exposure to the same stimulus • Two additional calls (intergroup): • Wrrr: Approach of another group • Chutter: Approach of another group, with a more aggressive aspect

Set up • Vervets look toward a calling vervet • The situation can be filmed, and then the amount of time a listener spends looking at a “caller” can be measured • Recorded calls from one vervet; then • Baseline response • Eight habituating calls (30 min. apart) • Test call (30 min. later)

Tests Question : Would an unreliable wrrr-er be treated as unreliable for chuttering? • The test involves two cases: • One in which the baseline/test caller are identical to the habituating call: A A A chut. Wrr chut. • Another in which the habituating call is from a different vervet: A B A chut. Wrr chut.

Call Results (Habituation) • With habituation, the response goes down • The question is then for the last (“test”) call, is the habituation retained? • Habituation does not transfer from one individual’s wrrr’s to another’s chutters • Habituation DOES transfer from the same individual’s wrrr’s to that individual’s chutters • This seems to suggest that the unreliability of the individual can be extracted from the context independent of the specific call

That is… • Habituation transferred between two calls from the same individual • It appears that the vervets hearing the habituation sequence learned that the individual making the call was “unreliable” • What is learned is not “call specific”…

General Comments: Reference • What do the different alarm calls ‘mean’? • Note that there are several ways in which to interpret what the different calls might ‘mean’, if we approach it that way • ‘Leopard!’ • ‘Head for the trees!’ • Etc. • Even in systems of this type, which show some complexity because of the categorizations involved, we still seem to have calls made in the presence of some stimulus

Displacement • What the reading refers to as situational freedom or displacement involves referring to things that are not immediately present • This is an obvious property of human language; but with limited exceptions, this is clearly not the norm in animal communication

Bee Dancing • Honeybees forage for food sources and, upon returning from a successful trip (i.e. after finding a food source) they perform a dance • This dance is called the waggle dance because it involves this particular motion • The waggle dance conveys aspects of the journey the bee has completed– in particular, the location and distance of the food source • Other bees that have witnessed the dance then go to the food source (or a lot do, in any case)

The dance • The dance proceeds in a figure 8 pattern • The orientation of the dance with respect to either vertical or the position of a light indicates the direction (other factors indicate approximate distance)

Orientation • Dances oriented directly to vertical indicate that food is in line with the sun • Otherwise, the orientation of the dance indicates the angle of the food from the sun

Competing Hypotheses • One possibility with the bee dance is that it does not actually encode information • I.e. other factors, such as scent (which bees also use) were thought to be responsible for the fact that bees could find sources after a dance • An experiment designed to test this hypothesis versus the communication one involves making a bee ‘lie’ to others

Further facts • The experiment involves a further fact about the bee dance • When it is dark in the hive, the dance is oriented towards vertical • When there is a light source visible in the hive, the dance is oriented towards the light source • This provides the basis for a way to test what the bees witnessing a dance are actually doing

Making bees lie • Bees detect overall light with their ocelli, a set of photoreceptors on top of the head • Experiments can paint the ocelli of bees, so that bees with painted ocelli behave as if it is dark, whereas bees with unpainted ocelli act as if it is light • The experiment involves bees with painted ocelli dancing about the location of a food source; the dance is witnessed by bees with unpainted ocelli

Ocelli

The idea • Dancing Bees: The dancing bees orient with respect to vertical • Witnessing Bees: The witnessing bees interpret the dance with respect to a light source, which is not at vertical Result: Witnessing bees (the majority) went to the source that was indicated by the dance, not the source actually visited by the dancing bees (who were giving false information) This is consistent with the communication hypothesis, but not the odor-alone hypothesis.

Human language in non-humans • Another aspect of research on language in animals involves a different methodology than studying communications systems that are natural to non-human species • This involves trying to teach non-human animals (typically chimpanzees, bonobos, or e.g. gorillas in the case of Koko) human language

On the methodology • To some extent, studies of this type capture the popular imagination, often concentrating on the question of whether animals have ‘true language’ • The bulkpack reading quotes a paper by Snowdon (1993) with a perspective on this: “…ethologists who study natural communication differ from psychologists who try to teach human language to other species in the same way as anthropologists differ from missionaries. Anthropologists try to understand the natives whereas missionaries try to civilize them.”

Justification • One view (Rumbaugh/Savage-Rumbaugh), discussed in reading: results of language teaching to primates must be relevant to humans because chipmanzees and humans are clsoe (they are our closest relatives). • Counterpoint (Pinker and others): “closest relative” has no important status; if chimpanzees disappeared, some other animal would be our “closest relative”

Some facets of the program • In most of these cases, the primates were taught some version of sign language, such as with Washoe • In a few cases, the primates were taught visual symbols • There are some differences as well in the training situation (home, laboratory, etc.)

Constraints • Using sign language (e.g. ASL) is practical: chimpanzees don’t have the vocal system etc. of humans • In some early experiments, such as with Washoe, the experiment was “naturalistic”; I.e., the chimp lived with humans who were signing • The idea was that in this context, the chimpanzee would develop language like a human child does

Basic Results • In the basic case, it seems clear that the primates are able to associate signs (whether visual or manual) with a ‘meaning’ • This is unsurprising given that many species can associate a symbol of some type with something else (consider e.g. dogs) • Whether this amounts to the primates having a ‘vocabulary’ is a more difficult question

Harder questions • An additional question is whether the primates who have been studies are able to use new symbols in new combinations • This is, of course, a central facet of human language • In many cases, claims for new use of symbols or ‘proto syntax’ are taken from long sessions, and are not always representative • For instance, it has been claimed that Lana, upon encountering an orange for the first time, signed: “apple which-is orange-color”

More context Lana • Tim: What color of this ? Lana: Color of this orange Tim: Yes Lana: Tim give cup which-is red Tim: Yes Lana: Tim give which-is shut ?Shelley give ? Tim: No Shelley Lana: Eye // Tim give which-is orange? Tim: What which-is orange Lana: Tim give apple which-is green ? Tim: No apple which-is green Lana: Tim give apple which-is orange ? Tim: Yes Note the use of fixed expressions and the fact that the trainer introduced color into the conversation

Animal Communication