The Evolution of Communication

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 traitOntogentic - 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 Non Signals Breathing Defensinve Posture Preflight Movement Urinating • Early ethologists focused on the evolutionary origins of signals. • The general view was that signals emerged from nonsignals • 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 Evolution 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 non-arbitrary 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)

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

Ontogeny • Some organisms are born with theessential mechanisms for responding appropriately to biologically meaningfulstimuli in the environment. For others, appropriate responses emerge overtime, shaped in part by maturationand experience. • Note that a behavior that emergedwithout experience can be modifiedby practice. On the other hand, genetic factors determine the modeof 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-that-elicit-eagle-sounding-alarm-calls”

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)

The Evolution of Communication