Transcript Chapter 1
大學部 生態學與保育生物學學程 (必選)
2010 年 秋冬
溝通的演化
(The Evolution of Communication)
─動物行為學 (Ethology)
鄭先祐(Ayo)
國立 臺南大學 環境與生態學院
生態科學與技術學系 教授
Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/
Part 3. 個體間的互動
生殖行為 (Reproductive Behavior)
親代照顧與交配體系 (Parental Care and Mating
Systems)
溝通:管道與功能 (Communication: Channels and
Functions)
溝通的演化 (The Evolution of Communication)
衝突 (Conflict)
團體生活,利他和合作 (Group Living, Altruism,
and Cooperation)
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15b 溝通的演化
Communication: Evolution
The changing views of communication
Sharing information
Manipulating others
Signals and honesty
The evolutionary origins of signals
Retualization
Receiver-bias mechanisms
By Goodenough, McGuire, and Jakob
Selective forces that shape signals
Language and apes
What is language?
Ape language studies
Communication and animal cognition (認知)
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Views about communication are changing
We can answer the questions of who, what, where, and
when of the communication process
But it is difficult to answer questions of how and why have
signals taken various forms that they have
Communication involves the transmission of information
from one animal to others
A cooperative view of communication: both sender and
receiver benefit from the accurate transfer of information
Selection should make signals efficient, reliable, and
unambiguous
Dishonest or inaccurate signaling was thought to be unlikely
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Animals manipulate other animals
The cooperative view of communication does not fit
every situation
A sender might gain by sending an inaccurate signal
In a territorial dispute, the sender might bluff by sending
signals that exaggerate its willingness to escalate the
contest
A male competing for a female’s attention might
exaggerate his qualities
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Dishonesty may benefit an animal
An animal that gives a dishonest signal gains an
advantage
Over animals that honestly communicate their abilities or
intentions
So, animals don’t communicate to convey information
But to manipulate the behavior of others to their own
advantage
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Signals: normally reliable, occasionally
deceptive
An animal produces a signal when, on average, it
increases its own reproductive success
By influencing the behavior of others
For signals to evolve, they must benefit senders overall
Senders may not be trustworthy
If signals are potentially dishonest, why not just
ignore them?
On average, the receiver must benefit from responding
to signals
Even if it is sometimes deceived
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When are honest signals likely?
Four circumstances under which we expect to see
honest signals:
When senders and receivers share overlapping goals
When signals indicate something about the sender that
cannot be faked
When signals are costly to produce
When dishonest signalers can be identified
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Honest signals: senders and receivers share
goals
Natural selection favors unambiguous, honest signals for
coordination of mating activities
The sexes share overlapping goals in the relationship
between parent and offspring
But even this relationship can entail significant conflict
Altricial baby bird s(幼鳥) beg their parents to feed them
Baby birds stand, gape, flap their wings, and call
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Honest communication
Begging chicks are obvious to predators
Begging too much, when food is not needed, is a poor
strategy
Parents provide food to chicks that beg most vigorously
Parents respond because their own fitness depends on the
survival of their offspring
Communication between baby birds and parents is honest
Other examples of similar goals of the sender and receiver
Belding’s ground squirrels call to warn relatives of a
predator
Every bee benefits when scouts convey the location of a
patch flowers
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Honest signals: signals cannot be faked
Signals are honest because they are tightly linked to a
trait of the sender
The sender simply cannot fake the signal
Size is a good predictor of fighting success
Displays allow opponents to judge one another’s size
Combatants(戰鬥人員) enhance their apparent size
Puffing up their feathers
Fluffing out their fur
Assuming an upright posture
In other species, size is not so easily faked
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Male stalk-eyed flies send honest signals
During an aggressive display, these flies strike a pose
that
Allows each competitor to compare the length of its
eyestalks
Males with shorter eyestalks usually retreat without a
fight
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Honest signals are linked to an animal’s
health
Bright red and yellow feathers, scales, or fleshy necks
or combs of some birds
Depend on chemicals called carotenoids
Carotenoids must be obtained in the diet
These bright colors honest signal of foraging ability
and health
Female house finches prefer brighter, redder males
Females benefit from their choice
Brighter males are better parents
Bringing more food to the nestlings.
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Honest signals: are costly to produce
What prevents a male from exaggerating his qualities?
Handicap principle (障礙原則): reliable signals are
favored when signals are costly to the sender
Their very extravagance indicates the owner’s qualities
These signals are handicaps
Their owners are perceived as doing well
In spite of the handicap of investing in the signal
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Criteria for a signal to evolve as a
handicap
The signal must be costly
It must relate to the quality of the sender
The receiver must be interested in the quality of the
sender that is being signaled
And must benefit from attending to an honest signal
Receivers benefit from correctly assessing the quality
of a signaler
Especially in the context of sexual selection
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Signals may be costly
Energetic costs are the most common measurements
Oxygen consumption increases in insects and frogs
Male red deer lose weight during the rut cost (發情代價)
Other costs: decreased ability to move, escape, or forage
Long tail feathers of male birds serve as sexual ornaments
And impair their ability to fly
Higher-quality senders can pay the cost of higher-quality
signals
Brighter colors, vigorous displays
Only male red deer in top physical condition can continue
roaring (咆嘯) to win the vocal duel (聲音對抗)
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Honest signaling in the blue-footed booby
Seabirds with brightly colored feet
During their courtship ritual, boobies stand facing one
another
The male lifts his feet to display them to the female
Males in good condition have bright blue-green feet
Unfed males have dull blue feet
Females prefer males with brightly colored feet
藍腳鰹鳥
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blue-footed booby (藍腳鰹鳥)
blue penguins : Few penguin
interactions end in fighting
because they suffer flesh
wounds and sometimes eye loss
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Signal costs also affect receivers
In the form of the response of receivers to the signal
Little blue penguins have aggressive displays that
differ in
Cost (risk of injury)
Effectiveness in deterring an opponent
Ability to predict an attack
A penguin conveys information about its willingness to
sustain injury while performing the display
And its willingness to fight
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Penguin displays are honest
Because aggressive encounters are potentially costly
Attempting to intimidate (威嚇) an opponent into
retreat could be costly
If the rival called the bluff (嚇唬)
Penguin encounters begin with low-risk displays
They escalate until one opponent retreats or a fight
occurs
One “bidder” decides that the territory is not worth the
risk
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Honest signals: dishonest signalers can
be identified
A stable social unit favors honest communication
Individuals both send and receive signals at different
time
The advantages of sending dishonest signals would be
reversed
When the animal is the receiver
So honesty predominates in the population
Members of social units recognize one another
And learn whether a particular individual is honest
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Vervet monkeys don’t believe dishonest
signalers
Members of a social group stop believing an individual
that gives unreliable signals
Vervet monkeys have two different calls that warn of
another group of monkeys on their territory
Monkeys stopped responding and no longer believed a liar
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Vervet monkey alarm calls that alert group members
of the approach of a neighboring troop are of two
types. The “chutter” warns that another group is
nearby. The “wrr” is given when another group is
spotted in the distance.
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Dishonest signals: senders and receivers
have different goals
Different goals set the stage for deception (欺騙)
A father bird and his chick share the goal of the
chick’s survival
But the chick may want more parental investment than
the father would like to give
At the cost of his other chicks or his future reproduction
Signals between parents and chicks are essentially
honest
But with some attempt by the chick at manipulation
and deceit
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Some signals are bluffs (嚇唬)
Honest signals can be corrupted by dishonest bluffs
Stomatopods (mantis shrimps)蝦蛄 ferociously
defend their burrows
Stomatopods have two appendages used in prey
capture and territorial defense
Combatants may be injured or killed during battles
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Stomatopods
(mantis shrimps)
蝦蛄
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Mantis shrimp (蝦蛄) signal their
readiness to attack
Readiness to attack is signaled by a threat display
(meral spread)
A newly molted stomatopod is defenseless
But still gives the meral spread display
Its opponent is deceived and retreats
A stomatopod can get away with the bluff
The receiver would pay dearly (付出昂貴代價) if it
tested the honesty of the signal
The signal is stable because, on average, it is honest
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Honest and dishonest signals coexist
The costliness of signals can reinforce honesty
When signals are generally honest
A low level of deceit is stable and is expected to evolve
Populations are in flux
At any time dishonesty may spread
A signal may be perceived by different receivers
Some have the same goals as the sender (i.e. prospective
mate)
Some have different goals (a competitor)
A mixed signaling strategy, sometimes honest and
sometimes deceptive, may be best
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The evolutionary origins of signals
Two approaches may explain the evolutionary origins of
signals
Identifying the behaviors of the senders that form the raw
material for signals
Ritualization
Focusing on how signals exploit the receiver’s sensory
biases
Ability to detect some information better than others
These two evolutionary pathways are not mutually
exclusive
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Ritualization
Many signals get their start as part of another behavior
Or as a physiological response
That takes on a signaling function later
Ritualization: evolution favors modification of the
incipient signal
It becomes more stereotyped and unmistakable
The three sources of raw material for signals are
1. Intention movements
2. Displacement activities
3. Autonomic responses
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1. Intention movements
Animals begin behavior patterns with characteristic
movements
That prepare them for action
It is possible to judge what the animal intends to do
A wolf pulls back its lips and bares its teeth before
biting
It improves another wolf’s fitness if he correctly
interprets the bared teeth
Rather than waiting to get bit
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Avian displays originated with intention movements
For flight or walking
A bird about to fly crouches, points its beak, raises its
tail, and spreads its wings
Components of the takeoff leap have been ritualized
into communicative signals
The blue-footed booby incorporates “sky pointing”
into its courtship dance
This display originated in flight
But changed during ritualization
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2. Displacement activities
Irrelevant actions performed in situations in which an
animal has conflicting motivations and is thus
indecisive (無法決斷)
Faced with an aggressor, an animal may have
conflicting motivations
To fight and to flee
So it may instead preen itself (鳥)用喙理(毛);
Displacement activities are often incomplete actions
Courtship is a time of conflicting tendencies
Sexual partners must come together to mate
In spite of aggressive tendencies that keep them apart
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Displacement activities in male ducks
Mock preening of the courtship displays of male ducks
Originated in displacement preening
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3. Autonomic responses
The autonomic nervous system (自主神經系統)
regulates many basic body functions
Digestion, circulatory activities, heart rate, diameter of the
blood vessels, thermoregulation
Displays may have originated from autonomic functions
At times of stress or conflict
The naked head or neck skin of turkey, jungle fowl, and
bateleur flush (發紅) and swell (腫脹)during stress
because of vasodilation
These changes are now part of signaling during courtship
and aggressive encounters
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Evolution of signals from the respiratory system
Modifications of the respiratory system
produce sound signals
And visual signals
In inflation displays of birds, males fill
pouches with air to attract mates
The male frigate bird’s throat pouch
inflates to an enormous size and brilliant
color to attract females
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Evolution of signals from thermoregulation
Piloerection (erection of feathers and hair) traps heat
It is also a part of aggressive(攻擊) and appeasement(緩和)
displays
A zebra finch that cannot escape from a dominant individual
Fluffs its feathers as an appeasement signal
Feather position can be part of courtship displays
Tail-raising courtship display of the peacock (孔雀)
In mammals the message’s meaning varies with the part of the
body on which hair is erected
If all the hair is erect on tamarins (狨猴) : attack or be
indecisive
If only the tail hair is erected: flee (逃走)
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zebra finch
tamarins (狨猴)
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Other behaviors as raw materials for displays
Ritualization is a highly opportunistic evolutionary
process
It can be launched from almost any behavior pattern,
anatomical structure or physiological change
Predatory behaviors have been ritualized in the male
gray heron (灰鷺)
During courtship, he erects his crest and body feathers
Points his head downward and snaps his mandibles
closed
Movements are similar to those used during fishing
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Masked lovebirds
gray heron (灰鷺)
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Food exchange has also been ritualized
The touching of bills is derived
from the parental feeding
Is common in courtship and
appeasement display
Establishes or maintains bonds
Masked lovebirds bill during
greetings and after a spat
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Flight can also be ritualized
Yellow-headed blackbirds and red-winged blackbirds
perform aerial displays to entice(誘惑) females
Ritualized flight is more conspicuous than normal flight
Movements are accentuated and reveal plumage patterns
Courtship displays of the fiddler crab evolved from the
movement of the male while entering his burrow
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Ritualized flight in blackbirds.
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The ritualization process
During the evolutionary process of ritualization
Signaling behaviors become more stereotyped
They may also change
Slow down, speed up, become more exaggerated
Anatomical features (colors, claws) might evolve to draw
attention to the display
Emancipation (解放): behaviors that become freed from
the internal and external factors that originally caused them
The original triggers no longer cause the behavior to occur
The behavior has only a communicative function
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Evolution of the whistle-shake in ducks
The body-shake is the evolutionary precursor of the
whistle-shake in ducks
Serves to dry and rearrange the feathers
Whistle-shakes resemble body shakes
But are ended by the duck tilting(翹起) back its head and
emitting a trill (顫音)
And are given in social situations
Some signals are not completely emancipated from their
original causes
Whistle shakes are still given in response to water
sprays
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Receiver-bias mechanisms
Ritualization focuses on characteristics of the sender
Sensory exploitation hypothesis: the receiver has a
preexisting preference for a particular signal
Features of the receiver’s nervous system makes it more
responsive to a particular form of stimulus
The sender takes advantage of the receiver’s preexisting
sensory biases when new signals are evolving.
Evolution of swordtails (劍尾魚) in fish
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Sensory bias in frogs
Female túngara frogs prefer males with lower frequency
chuck calls
Female túngara frogs benefit from their preference
Low-frequency chucks are produced by larger males
Resulting in more fertilized eggs
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Sensory bias in water mites
Male courtship signals have exploited the females’
sensory adaptations for prey detection
Water mite hunts by ambush
When a courting male detects a female he moves his
legs
These vibrations mimic prey
Leading the female to grab him
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Sender characteristics shape signals
Anatomical structures form the foundation for
producing signals
i.e. sensory organs of electric fish
Body form (i.e. size) influences signal design
Small species not be visible, so other sensory modalities
are favored for long-distance communication
Physical characteristics may evolve that enhance visual
signals (i.e. facial expression, erection of hair)
Smaller species give more acrobatic (特技的) displays
In vertebrates it influences vocalizations
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Signal evolution does not happen in a vacuum
Many signals are produced by structures that have other
functions
Body size, hair, beaks, and respiratory tracts are under
selection for other reasons
Besides their role in producing signals
For example, beak shape in Darwin’s finches is
important in
Feeding behavior
Song production
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Environmental characteristics affect the
choice of communication
The habitat helps determine which channel of
communication (sound, chemical, visual, etc.) a
species uses
Visual signals are not much use in the ocean’s depths
So whales rely on sound for long-distance
communication
The habitat affects sound transmission
Attenuation (weakening): how far the sound will carry
Degradation: how distorted the signal becomes during
transmission
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The acoustic adaptation hypothesis
Acoustic properties of bird song are shaped by habitat structure
Songs attenuate and degrade differently in different
environments
Songs are more attenuated and degraded in dense foliage
Lower frequencies become less distorted in dense foliage
In habitats with complex vegetation structure
Songs should have low frequencies, narrow bandwidths
Whistles and long notes
In open habitat (i.e. grasslands)
Songs should have high frequencies and broad bandwidths
Trills and short notes
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Habitat structures influence bird songs
Great tits have a large geographic distribution
Forest dwellers sing songs with a lower pitch
A narrower range of frequencies
Fewer notes per phrase than open woodland birds
No differences were found between other species in
different habitats
But a review of the literature (meta-analysis) shows that
Habitat structure weakly influences acoustic properties
of bird songs
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Displays vary according to the background
The environment influence transmission of other
channels of communication
Visual signals differ in visually “noisy” versus plain
environments
Many lizard species rely on visual displays
Head bobs, push-ups, back arching, extension of the
dewlap and tail flicks
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Lizard displays and background motion
Jacky lizard species that live in trees display faster and
flick their tails more
When it is windy and the vegetation moves
Senders of signals may change their behavior when the
environment changes
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Jacky lizard
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Habitat changes caused by humans
Human activities alter the environment in which animals
communicate
And alter selection pressures on signal form
Great tits do well in both urban and rural environments
Urban birds sing shorter, faster songs with higher
minimum frequencies
Most likely due to competition with the noise of the urban
background
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Human-induced environmental changes
affect visual signals
Visual signals can be impeded (阻礙)
The Baltic Sea has grown turbid (cloudy)
Making it harder for female stickleback fish to see
males
Males have to court much more vigorously to get the
female’s attention
The honesty of male signals is reduced because males
are not as likely to see each other
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Receiver characteristics: sensory drive
Sensory drive: the environment shapes receiver
characteristics
Surfperch (海鯽) are marine fish that live in a variety of
habitats
Differing in light intensity and variability
The retinas of surfperch species differ
They are good at detecting differences in color contrast
Or differences in brightness
But not both
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Different optical habitats of related surfperch species.
(left) live in an environment that is highly variable in light intensity.
Striped surfperch (right) live in deeper water in the kelp forest where
the background light is more even.
Deepwater surfperch are better at detecting brightness differences
Species living in shallow water can better see color differences
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Language and apes
Humans are very interested in what separates us from
other species
Tool use was thought to be confined to humans
But this is not the case
Language seems to clearly be a talent confined to
humans
Which elements of language are unique to humans
Which are more broadly shared?
Are differences a matter of kind or degree?
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True language has four elements
Words or signs must be used as true symbols
That stand for, or take the place of, a real object, event,
person, action, or relationship
2. Symbols should permit reference to objects or events
That are not present
3. There should be some elements of grammar (rules)
That determine the relationship between words
Changing the order of symbols alters the meaning of the
message
4. Words or signs should be combined to form novel phrases
Or sentences that are understandable to others
1.
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Early studies taught chimps to talk
Researchers have studied the ability of great apes
(chimpanzees, western (lowland) gorillas orangutans,
bonobos) to learn language
A chimp named Viki was taught to say three words
“Mama,” “papa,” and “cup”
These attempts failed
Chimpanzees lack the vocal apparatus to make the
range of sounds of human speech
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Studies taught chimps nonverbal languages
Washoe, a young chimpanzee, was taught American Sign
Language (ASL)
Washoe and other chimps were reared like human
children
Spoken English was not allowed
Washoe had a vocabulary of 132 signs
Her signs were not restricted to requests
She applied them correctly to a wide variety of referents
She extended the sign for dog from a picture to all pictures
of dogs, living dogs, and even the barking of an unseen dog
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Washoe signs with ASL
Washoe combines signs to denote “water bird” for a
swan
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Stop and think:
Do you agree that the best way to test whether apes
have linguistic skills is to incorporate them into human
society as much as possible?
What are the advantages and disadvantages of this
approach?
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Koko, Chantek and Nim Chimpsky
A gorilla named Koko and an orangutan named Chantek
were taught ASL
Spoken English was permitted
Emphasized the production of language (the use of signs)
Not comprehension (understanding the meaning of signs)
Nim Chimpsky a young male chimp, was accused of
imitating his trainers
But Nim’s language abilities were stunted(受礙) by the
operant-conditioning procedures used in his training
And Nim’s trainers changed so often that he could not form
the relationships essential for language development
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It was accepted that chimpanzees could
not learn language
But when other trainers worked with Nim
His language skills improved
Chantek’s signs were more spontaneous
Could not be attributed to imitation
Washoe and the other language-trained chimps
Signed to other animals and objects
And frequently to themselves
Washoe adopted a ten-month-old infant named Loulis
Loulis learned his first 55 signs by observing other chimps
Washoe and her family signed to one another their daily
activities (playing, eating, family fights)
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Sarah used plastic chips as words
The chimpanzee Sarah used a particular
plastic chip as a word
To complete a preformed statement
She arranged four to five words into a
sentence
Sarah named many objects and used
complicated relationships
Such as if-then and same-different
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The LANA Project
A chimpanzee named Lana was trained to use a
computer to communicate
Eliminating social cueing and the difficulty of
interpreting symbols
Lana communicated in Yerkish, a symbolic language
Yerkish words (lexigrams) are geometric figures
Pressing a computer key labeled with the lexigram
selects words
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The LANA Project
Lexigrams had to be used
in an appropriate order
Lana had to learn syntax rules governing word order
She developed a large
vocabulary and mastered
grammar
She also coined new words
She called an orange soda a
“Coke-which-is-orange”
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Apes learn words in various forms
To refer to objects not present
Stringing words together in short sequences
Follow rules of grammar
They coin new words
But do apes use words as symbols?
When a chimp uses a “word” (sign, plastic chip, or
lexigram) to name an object
Is it used as a symbol that stands for the object
Or is it a label that is associated with the object through
a reward system?
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Using “words” as true symbols
Two chimpanzees, Sherman and Austin communicated
with each other symbolically
By pressing computer keys with lexigrams
The emphasis was on interanimal communication,
They were not taught to produce strings of lexigrams
Or to adhere to grammatical rules
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Chimps communicate with each other
Sherman and Austin specify foods to one another using
lexigrams
They communicate with each other
Regardless of which of them is the observer
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Chimps use symbols in communication
To inform each other of the appropriate tool to use to
solve a problem
Clearly using words as symbols and not simply labeling
objects
This shifted the emphasis from demonstrating that apes
can produce language
To showing that they can understand symbols or words
of language
It also showed how important the learning environment
is in developing language comprehension
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Kanzi and Panbanisha
Bonobo (pygmy) chimpanzees
Kanzi was adopted and raised by Matata
And was always present during Matata’s training
sessions
After Kanzi was separated from Matata
He used symbols on the keyboard that they had tried to
teach to Matata
Not only did he know the lexigrams
He also knew the English words that the lexigrams
represented
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Kanzi has a large vocabulary
Kanzi learned communication skills by observing his
mother’s training
Much the same way as a child would
Panbanisha, Kanzi’s half-sister
Was reared in the same learning environment as Kanzi
She, too, shows remarkable comprehension of spoken
English
Reward-based language training was stopped and
replaced with conversation
Kanzi’s human companions served as communicative
models
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Kanzi learned symbols through observation
• Kanzi observed and interacted with humans who used
gestures and lexigrams to communicate
Kanzi communicates using a board with 256 lexigrams
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Kanzi and others understand spoken
English
Besides being able to produce language
Kanzi was not trained to vocalize
But spontaneously makes sounds with different content
Chimpanzees utter natural sounds when they find food
Producing distinct grunts when encountering different
foods
This skill is found in other animals besides apes
Including vervet monkeys and even chickens
Ape communication fulfills the four requirements of
language
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Communication and animal cognition
Do nonhuman animals have thoughts or subjective
feelings?
Are they are aware of other animals’ feelings?
Are they cognitive, conscious, aware beings?
Tapping animals’ communication lines can indicate
whether animals have conscious thoughts or feelings
If nonhuman animals thoughts and feelings
They probably communicate them to others through
their communication signals
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Evidence of cognition: forming mental
representations
Of objects or events that are out of sight
Some animal signals are symbolic
They refer to things that are not present
Some animals learn a language that uses symbols
i.e. apes
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Other species understand symbols
Alex the parrot could vocally request more than 80 items
Even if they were out of sight
He could quantify and categorize these objects
He understood the concepts of color, shape, and same versus
different for both familiar and novel objects
Bottlenosed dolphins also understand symbolic languages
“Words” are gestures or are generated by a computer
They can refer to objects, actions, and relationships
Dolphins understand experimenter’s references to objects that
are not present
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Evidence of cognition(認知): natural
communication systems
Language involves the ability to relate words to
meanings
In some species, individuals classify signals by their
meaning
Not by some obvious physical property (the way a signal
sounds)
When a rhesus monkey finds food
It announces this with one or more of five different food
calls
A different type of call announces if the item is of high
quality or rare
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Classifying calls by meaning or sound
Animals habituate (gradually stop responding) to a
stimulus that is repeated many times without
consequence
If monkeys classify a food call by its sound
After habituating to one type of call they still respond to
any other type of call because it sounds different
If they classify a food call by its meaning
They will be unresponsive to a call in the same category
But remain responsive to a call in a different category
Rhesus monkeys classify calls by their meaning.
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Evidence of cognition: understanding
mental states of others
Does a communicating animal understand what
potential receivers know?
Vervet monkeys apparently do not
Mother vervet monkeys give alarm calls when they
sense a predator
But do not take into account whether their offspring
are ignorant or knowledgeable about the predator
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Langurs call to their audience
Male Thomas langurs give alarm calls
But only if there is an audience
Males call persistently after spotting a predator
Stopping only when every other member in the group
also gave an alarm call
Callers seem to keep track of all the other members in
their groups
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Ethical ramifications of cognition in
animals
The question of animal awareness is difficult to answer
scientifically
The answer has ethical ramifications
If the line between animals and humans is erased or even
smudged a bit, should we rethink the way we treat animals?
Should we keep them in zoos?
Should great apes be used for language studies?
What about dolphins?
So what’s your opinion?
Are animals aware, cognitive beings? All of them?
Where do we draw the line?
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Summary
Signals should be honest, unambiguous and informative
Sometimes the sender of a signal benefits from being dishonest
On average, a sender manipulates the behavior of others to its
own advantage
Receivers should respond to signals when they benefit from
them, on average, even if they are sometimes deceived
Conditions for honest signals (1) senders and receivers share
overlapping goals, (2) they cannot be faked, (3) they are costly
to produce, and (4) dishonest signalers can be identified
Conditions that favor dishonest signals (1) senders and receivers
have different goals, (2) they are costly to assess or to challenge
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Summary
Honest and dishonest signals can coexist in a population
Signals originate through ritualization and sensory exploitation
Evolutionary sources of ritualization (1) intention movements,
(2) displacement activities, and (3) autonomic responses
The design of the signal may be influenced by the anatomy and
physiology of the sender and the habitat
Most animal communication signals are not true language
They do not use symbols that can replace their referent
They do not string signals together to form novel sentences
Researchers have attempted to teach apes language
Some animals understand signals that represent unseen items
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問題與討論
[email protected]
Ayo 台南 NUTN 站
http://myweb.nutn.edu.tw/~hycheng/
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