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The Evolution of Communication
Marc D. Hauser.
Introduction
“Nothing would work in the absence of communication”
.- (Hauser)
• Flowers must communicate with bees for pollination
• Male songbirds must communicate with females if they are
to mate and rear young
• Lions on a cooperative hunt must communicate with each
other about how they will attack their prey
• A human infant must communicate with its parents so that
the needs of both are met
• Computer programmers must design software to
communicate their hardware
• Computer networks
Introduction
• But why do birds sing rather than speak
Mandarin? Why is this talk conveyed in English
and not by the blinking of eyes - Morse code
style?
• These are questions about design features of the
communication systems
• The design features of a communication system
are the result of a complex interaction between
the constraints of the system (cost) and the
demands of the job required
• What are the mandatory features?
Communication Definitions
• Sociobiology: Communication occurs when the action of or
cue given by one organism is perceived by and thus alters
the probability pattern of behavior in another organism in a
fashion adaptive to either one both of the participants
• Ethology: Communication is the transfer of information via
signals sent in a channel between a sender and a receiver .
The occurrence of communication is recognized by a
difference in the behavior of the reputed receiver in two
situations that differ only in the presence or absence of
the reputed signal . . . . the effect of a signal may be to
prevent a change in the receiver's output , or to maintain
specific internal behavioral state of readiness
Introduction
• Cognitive psychology: Communication is a matter of causal
influence. . .. the communicator [must] construct an internal
representation of the external world , and then . . . carry
out some symbolic behaviour that conveys the content of
that representation . The recipient must first perceive the
symbolic behaviour , i . e . construct its internal
representation and then from it recover a further internal
representation of the state that it signifies . This final step
depends on access to the arbitrary conventions governing
the interpretation of the symbolic behaviour
Introduction
• Linguistics: Human communication . . . includes forms of
verbal communication such as speech , written language and
sign language . It comprises nonverbal modes that do not
invoke language proper, but that nevertheless constitye
extremely important aspects of how we communicate . As
we interact, we make various gestures some vocal and
audible, others nonvocal like patterns of eye contact and
movements of the face and the body. Whether intentional
or not, these behaviors carry a great deal of communicative
significance
Introduction
•
•
Organisms differ with regard to what they can convey and
what they perceive . Consequently , there are a diversity of
communication systems the natural world.
Hauser uses 4 perspective to comparatively explore the
diverse animal communication systems:
Mechanistic - Understanding the mechanisms (neural ,
physiological , psychological ) underlying the
expression of a trait
Ontogentic - The genetic and environmental factors that
guide the development of a trait
Functional - Looking at a trait terms of its effects on
survival and reproduction
Phylogenetic - Unraveling the evolutionary history of the
species so that the structure the trait can
be evaluated in light of ancestral features
Talk Outline
• Introduction
• Approaches to study communication evolution
• Conceptional issues in communication
• Ontogeny
• Adaptive significance
Ethological Approach
Evolution
• Early ethologists focused on the
Non Signals
evolutionary origins of signals.
Breathing
Defensinve Posture
• The general view was that signals emerged
Preflight Movement
from nonsignals
Urinating
• Once nonsignals gain functionality (influence
the probability of survival and mating) , they
become ritualized , emerging as
communicative signals
• Once a ritualized signal evolved, its ultimate
form was designed for maximizing information
transfer.
• Selection operated on the sender to provide
recipients with signals conveying unambiguous
information.
• Rare signals and large repertoires were
selected against because they would lead to a
slowed in recipients
Ritualized Signals
Courtship song
Foraging display
Submissive signal
Territorial marking
Ethological Approach (70’)
• In contrast to the ambiguity reduction, the new view claimed
that ritualized signals were foils, designed increase ambiguity
by concealing the signaler 's " true " motivations
• selection should operate against individuals using displays that
are highly predictive of their subsequent behavior ( highly
informative)
• In some primates , individuals bristle their hair when they are
aggressive . This display is to make the signaling animal larger.
If an individual spots another with its hair bristled , it move
off in the opposite direction and thus avoid the attack
• Once the association between hair bristling and retreat is
established, an evolutionary option becomes available :
signalers can bypass the more costly attacks and simply hair
bristle in order to cause others to
Ethological Approach (70’)
• But what about cooperative interactions?
• Empirically, one tends to find that during
competitive interactions over valued resources
(food, mates ), signals are loud and exaggerated ,
consequently costly to produce
• Krebs & Dawkins have suggested that cooperative
signals should be quiet , subtle , produced with
minimal cost, and responded to with high
sensitivity (perceiver s threshold for responding
should be low )
Derek Bickerton
• Studied cases of language change that have occurred a
result of different cultures coming together
• When two communities lacking a common language are with a
situation that requires communication, Bickerton suggested
the emergence of protolanguage, or what is known as pidgin
• Relative to natural languages, the structure of a pidgin is
quite simple, often consisting of short strings and only a few
grammatical items .
• Over time, especially with the subsequent generation of
offspring , we see a refinement in the structure and usage of
language what is known as a creole
• How constrained will be the structure and usage of creole?
• Fundamental genetic changes were responsible for the
emergence of the first protolanguages
Charles Hockett
Peter Marler
• Marler's observations of avian vocalizations
produced in the context of predator led to a nonarbitrary acoustic features , maximize either silent
predator evasion or predator attack
• Birds use structurally different calls when they are
mobbing a predator (max localization) as opposed to
when they are warning group about presence of a
predator (min localization for predator)
• Marler suggested that the vervet monkey's alarm
call system represented a potential case of symbolic
signaling (not just changes in affective state).
Peter Marler
• Seeing predator or hearing a particular acoustically
distinctive alarm calls elicited a specific escape
response , and one that appeared to be designed to
maximize the probability of escape given the
predator's hunting strategy
• The definitive test of this hypothesis was carried
out several years later when Seyfarth Cheney, and
Marler playback experiments showing that the
acoustic features of each alarm call type were
sufficient to elicit the behaviorally appropriate
response
Peter Marler
• Also, Marler, pinpointed 7 parallels between birdsong and human
speech:
1 . Young learn the species typical repertoire from adult models
2. Dialects are formed as a result learning.
3. Experientially guided learning is most significant during a
critical period .
4. To develop a normal vocal repertoire , young must be able to
hear sounds from their species typical repertoire and to hear
themselves reproduce such sounds .
5. Like human infants , young also go through a series of
developmental stages , including a subsong phase that
resembles babbling .
6. Vocal imitation, in and of itself may be self reinforcing.
7. Left hemisphere is dominant for the control of sound
production (Chomsky combintorial organ)
Talk Outline
• Introduction
• Approaches to study communication evolution
• Conceptional issues in communication
• Ontogeny
• Adaptive significance
Ecology of Signal Transmission
• Studies strongly suggest that selection has favored signals
with particular design features, matched to achieve optimum
transmission in the species-typical environment.
• H . Brown and Waser's (1984, 1988) experimental results on
nonhuman primates indicate that calls that function in
intergroup interactions and require long distance
transmission are produced within a spectral range that
minimizes attenuation
• An individual may have the neurophysiological substrate
required to discriminate small differences in frequency , but
because of attentional distractors in the environment may
completely miss the signal conveyed.
• What can be discriminated under ideal conditions and what
is discriminated and acted upon under natural conditions?
Ecology of Signal Transmission
• A common methodological approach in
environmental acoustics involves the following
three steps :
1. Record a signal under relatively ideal conditions
or generate a computer synthesized signal .
2. Play the signal back under different ecological
conditions.
3. Record the signal played back and compare the
in acoustic morphology with the originally
emitted signal (subtract Fourier).
Signal detection theory
• Signal detection theory studies the cost relationship between
discriminability and attention
• Imagine a gazelle that must avoid prey to a predatory cheetah .
To avoid being eaten, the gazelle evolved an alarm call system.
• signal detection theory generates a series of probability curves
that reveal the trade off false alarms and misses , given the
signaltonoise ratio in the environment
• Gazelle’s optimum strategy requires a level of vigilance (sampling)
that will maximize hits and minimize misses (false alarms)
Similarity and Classification
• To respond to things appropriately , animals must
identify them as belonging to various categories :
potential mates , potential food items , potential
predators, and so on . All sentient animals therefore
simplify the world's diversity by imposing their own
categorical distinctions upon it.
• For the researcher interested in understanding a
species communication system , there is the daunting
task of cataloging representative exemplars into what
are putatively meaningful categories that is , of
determining characteristic (weighted) features
associated with particular contexts
Habituation-Dishabituation Paradigm
•
•
•
•
A1, A2 represent acoustic stimuli from the same category
B1 Comes from a different category
Response assay: amount of time looking at speaker after playback
Subjects habituate to repeated presentations of A1 but show
greater dishabituation to B1 than A2
Timing
• The timing of displays within a sequence represents
yet another problem.
• The analytical challenge lies in understanding whether
the signal delivered represents a directed response
to a prior signal or the initiation of a new bout .
• Studies of the squirrel monkey Symmes , Biben , and
Masataka (1993) , indicated that responses to " chuck
" vocalizations typically (with high probability) occur
in a O.5second period ; vocalizations occurring
outside of this time window are more likely to reflect
the initiation of a new vocal bout
Timing
• But, does response signals must occur within
restricted periods of time?
• Consider the following discussion:
– "Bert, let's have some chicken for dinner ?“
– "That sounds good, " says Ernie . " Let's have some
mushrooms as well and a salad."
– Bert and Ernie enter the kitchen and begin cooking.
– Five minutes later, Bert speaks to Ernie without making
eye contact :
"I think I will make a vinaigrette dressing to go along with
salad ."
Nonhuman Grammer
• For nonhuman animals we don't fully understand
what the relevant units of communication are, and
thus we are crippled in our ability to say, one way or
the other, whether grammatical structure
underlies their utterances
• In black chickadees and capuchin monkeys,
different call types within the repertoire are
strung together in sequences based on ordering (A
before B and C but never after B or C ). Missing
from analysis, however, is a clear description of
meaning or semantics of each call type
• Empirically build Markov sequence analysis
Talk Outline
• Introduction
• Approaches to study communication evolution
• Conceptional issues in communication
• Ontogeny
• Adaptive significance
Ontogeny
• Some organisms are born with the
essential mechanisms for responding
appropriately to biologically meaningful
stimuli in the environment. For others,
appropriate responses emerge over
time, shaped in part by maturation
and experience.
• Note that a behavior that emerged
without experience can be modified
by practice. On the other hand,
genetic factors determine the mode
of responsiveness to experience.
• Considering real world organisms ,
the notion of canalization tell us that during the course of
development, individuals will encounter a variety of
experiences that have the potential to throw them off of
their species typical trajectory
Vervet Monkey Alarm Call
• To determine when vervet monkeys begin to use alarm calls in
the appropriate context Seyfarth, Cheney & Hauser(1992)
analyzed of naturally occurring predator encounters and
infants vocal responses
• Results indicate that up until the age of two to three years ,
immatures produce alarm calls to both predatory and
nonpredatory species. With increasing age, the number of
species eliciting alarm calls diminishes to the point where
alarms are only given in response to predators
• We can interpret the developmental results as providing
evidence that infents make classification "mistakes" ,
producing alarm calls to inappropriate objects.
• Or infants may be using alarm calls to ask questions ("Is that
thing in the air something I should give an eagle alarm call
to?")
• when infants produce alarm calls , adults often follow with the
same type alarm call , if a vervet predator detected
Vervet Monkey Alarm Call
• When infants produce alarm calls , adults often follow
with the same type alarm call , if a vervet predator
detected (feedback)
• For correct feedback (equal), infants are more likely
to produce the correct alarm in the subsequent
encounter than mistaken infants (memory)
• Aggressive actions by mothers toward infants
producing the inappropriate alarm call - punishment!
• Since immature vervets produce alarm calls to the
same general kinds of stimuli as adults (e.g. eagle
alarm calls to “things” in the air), it appears that they
are born with an innate category for “context-thatelicit-eagle-sounding-alarm-calls”
Talk Outline
• Introduction
• Approaches to study communication evolution
• Conceptional issues in communication
• Ontogeny
• Adaptive significance
Adaptive significance
• When a squirrel gives an alarm call to a predator it does so
in order to protect its group. Why? given that alarm calling
is costly (increases the caller's probability of being
detected and eaten by the predator) what is the benefit ?
• Hamilton (1964) argued that individuals have been selected
to maximize their inclusive fitness : refers to the number
of genes one passes on to generations as a result of direct
reproduction (the number of offspring you produce who
survive and reproduce ) and indirect reproduction ( the
number of individuals you help survive and reproduce as a
function of your degree of genetic relatedness to them)
• But in a population where individuals always produce alarm
calls against predators, selection would favors a mutation
that caused an individual to withhold the alarm call , run for
cover, and save its own skin.
Adaptive significance
• Maynard Smith (1974) applied the logic and
mathematical tools of economic game theory to
problems in biology in an attempt to assess
whether evolutionarily stable strategies ESSs
existed
• Evidence for an ESS then comes from a set of
equations and conditions ( specified by the details
of the matrix ) which indicate that no mutational
strategy can invade a population X % of individuals
playing strategy 1 and Y% playing strategy 2
Zahavi Handicap Principle
• Zahavi (1975 ) argumented that signals are honest if and
only if they are costly to produce and maintain.
• Males with absurdly long tails or shockingly bright colors
would surely be more vulnerable to predation than males
with short tails or dull colors . Natural selection therefore
eliminate the showy males and favor the more cryptic ones .
But individuals who sport the exaggerated traits and live
tell the tale be truly extraordinary males genotypes that
can readily tolerate the survival costs of the trait
• Are honest signas are more or less likely to appear in
certain social situations?
• How much cost is either necessary or sufficient to both
generate and maintain an honest signal? (M.Smith 1994)