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Animal Communication

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Title: Animal Communication


1
Animal Communication
  • Ling 001, Spring 2009

2
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 weve seen at different points, intelligence
    and linguistic ability are dissociable in humans.

3
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?

4
Basic Answer
  • The basic answer is 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

5
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
  • Well see a nice analogy in the reading, where
    the former type of study is more like
    anthropology, the latter like missionary work

6
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.

7
Questions, 2
  • The teach human language to animals view is less
    clear in many ways. Assumptions
  • Maybe animals dont have language because they
    dont 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.

8
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)
  • Well illustrate by looking at what animal calls
    refer to

9
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

10
Introductory comments
  • Something is being communicated in the
    stickleback interaction
  • In the broadest sense, the male coloration/dance
    indicate the readiness to mate
  • But theres 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

11
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)

12
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

13
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

14
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

15
Functions, Cont.
  • The Selfish view animal communication systems
    evolve because animals benefit from manipulating
    one another
  • Signals are evolved to increase the senders
    fitness (not the receivers)
  • A conspicuous display that attracts predators
    wouldnt be selected for simply because it
    benefits others
  • Example Deception males attract mates not by
    being better, but simply by appearing to be
    healthier

16
Aspects of Communication
  • Well 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?

17
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 hearing the signal (receivers)
    behave consistently and appropriately, even in
    the absence of the stimulus triggering the signal.

18
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

19
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?

20
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 they behaved according
    to the alarm type.

21
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

22
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
  • Its not just any audience, its 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 doesnt mean that
    communication in chickens is intentional. Rather,
    it shows that both predator and audience play a
    role in some aspect of signalling

23
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

24
Vervet Monkeys
  • (multimedia from Hausers webpage,
    http//www.wjh.harvard.edu/mnkylab/media/vervetca
    lls.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 cant go)
  • Eagle Alarm Vervets run under a bush/cover of
    tree branches

25
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)

26
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?

27
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

28
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)

29
Tests
  • Question Would an unreliable wrrr-er be treated
    as unreliable for chuttering?
  • The test involves two cases
  • One in which the baseline/test 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.

30
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
    individuals wrrrs to anothers chutters
  • Habituation DOES transfer from the same
    individuals wrrrs to that individuals chutters
  • This seems to suggest that the unreliability of
    the individual can be extracted from the context
    independent of the specific call

31
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

32
General Comments
  • 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

33
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

34
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)

35
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)

36
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

37
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

38
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

39
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

40
Ocelli
41
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.

42
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

43
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.

44
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 relativ

45
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.)

46
Constraints
  • Using sign language (e.g. ASL) is practical
    chimpanzees dont 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

47
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

48
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

49
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
50
More Success?
  • Kanzi the bonobo
  • Involved in language experiments from his early
    days noteworthy claims
  • Learned symbols from watching his foster mother
    being taught (I.e. without explicit training of
    him)
  • Supposedly has comprehension abilities of a
    two-year old, although under controlled
    circumstances
  • On some performance tests, like 1.5 year old
  • No explosion (vocabulary or utterance length)
    beyond this.

51
Synopsis
  • The idea that human language should be taught to
    non-humans involves several components
  • One the one hand, it is asking primates to do
    something that they do not by nature do
  • This seems to relate to a perspective on human
    language which we have found evidence against
    before if language is just general intelligence,
    then primates and other intelligent species
    should be able to learn some of it
  • Of course, we might learn something about primate
    intelligence in such projects, but what we learn
    about human language is limited

52
Conclusions
  • In complex systems of animal communication, there
    are questions about
  • What animal calls, etc. refer to (if they
    refer)
  • Whether or not they are used to influence the
    behavior of others, or are simply responses to
    stimuli
  • Some evidence exists for the encoding of
    information about stimuli that are not present
    (bees)
  • It is unclear what can be learned about language
    per se from experiments that try to teach human
    language to non-humans
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