Pragmatic insights Pragmatic insights on the evolution of language - - PowerPoint PPT Presentation

Dan Sperber

www.dan.sperber.fr

Pragmatic insights Pragmatic insights

• n the
• n the

evolution of language evolution of language

Summer Institute in Cognitive Science 2010: The Origins of Language - UQUAM June 27, 2010

Collaborators: Deirdre Wilson Gloria Origgi

Two models of communication

• The code model
• The inferential model

The code model

• A code is a set of <signal, message> pairs
• Communication is achieved by the

communicator encoding a message into a signal and the receiver decoding the signal back into the message

signal decoding message encoding message

The code model

• f linguistic communication
• A human language is a complex code, the

<sound, meaning> pairs of which are sentences generated by a grammar with recursive capacities and a rich lexicon

• Linguistic communication consist in a speaker

encoding her meaning into the sound structure paired with it in the language, and in the hearer retrieving this meaning through decoding

utterance decoding meaning encoding meaning

The proximal function of language

• For the code model: To provide the means for

the speaker to encode her meaning into an utterance and for the addressee to decode this utterance

The bootstrapping problem

in explaining the evolution of language

Two types of adaptations

• Hetero-adaptations
• Homo-adaptations

Hetero-adaptations

• Hetero-adaptations are adaptations to an aspect of the

environment that predated the adaptation

• Most specialized cognitive abilities have a specific

domain of information available in the environment well before the ability develops. They are adaptations to this aspect of the environment. Examples: – 3D perception – Detection of a given kind of predator

Homo-adaptations

Some specialized cognitive abilities have a domain of information that is initially empty and that gets filled only by the behavior of individuals already equipped with this ability. Examples:

– Cognitive bases of reciprocal altruism

– biologically evolved signals – language faculty

A possible explanation of the emergence of homo-adaptations

– Every homo-adaptation starts as a side-effect

• f an other adaptation, or is neutral enough

not to be selected out. – It becomes positively selected as an homo- adaptation when the offsprings of the initial mutant are sufficiently numerous to benefit from the trait in their interactions

The biological evolution of codes

Compare:

• The emergence one by one of atomic

signals, each conveying a complete message

• The evolution of a repertoire of signals into

a system of complex expressions

Moreover, in the case of language,

• what has biologically evolved is not a language,

but the ability to learn a language (a ‘language faculty’)

• it is not enough to have a sufficient number of

people sharing such an ability for them to find in their environment a language to acquire

• Coded communication works best when the

interlocutors share exactly the same code

• Differences in the codes of the communicators

typically cause failures in communication

• The biological or cultural emergence of codes

must secure their quasi-identity across communicators

With the code model,

• A change in the language faculty of an individual

either will be without effect on languages, or will cause her to acquire a language different from that of others on the basis the same linguistic evidence

• If the code model of linguistic communication is

right, this mismatch between languages will impair the individual’s abililty to communicate. It will be anti-adaptive.

• A change in the language faculty of an individual

either will be without effect on languages, or will cause her to acquire a language different from that of others on the basis the same linguistic evidence

• If the code model of linguistic communication is

right, this mismatch between languages will impair the individual’s ability to communicate. It will be anti-adaptive.

• The evolution of small repertoires of

signals is not too hard to understand.

• The evolution of a capacity to acquire

culturally variable systems with a rich lexicon and complex syntax is quite paradoxical

With the code model,

Anyhow, is linguistic communication a matter of coding and decoding?

• Human languages are incomparably richer

than the codes of other animals both syntactically and lexically

• Human languages are grossly defective

qua codes: sentences massively underdetermine their interpretation.

Examples

• It is late
• Henry’s car is too big
• I have eaten

Two models of communication

• The code model
• The inferential model

The inferential model

• In inferential communication, the communicator

helps the addressee by giving evidence of her meaning and the adressee infers the meaning from this evidence and the context

• Anything can serve as evidence provided

meaning can be inferred from it

• Example:

– Peter: Do you want to come for a walk? – Mary hold up the book she is reading

Communicative behaviour communicator’s meaning contextual information memory perception Pragmatic inference perception environment

What kind of inference?

• A communicator’s meaning is a complex intention

(Grice)

• Understanding such meaning consists in inferring

a mental state of the communicator

• It is a special case of ToM or ‘mindreading’

inference

Peter: Do you want to come for a walk? Mary hold up the book she is reading

Peter must infer that, in ostensively holding up her book, Mary has 1.The communicative intention to inform Peter

• f her informative intention,

2.the informative intention to inform Peter that she wants to go on reading rather than go for a walk

The inferential model

• f linguistic communication
• The speaker helps the addressee by giving as

evidence of her meaning an utterance and the adressee infers the speaker’s meaning from this utterance – and in particular its semantic properties – and the context

• Example:

– Peter: Do you want to come for a walk? – Mary: I want to read

speaker’s meaning contextual information memory perception Pragmatic inference environment utterance Perception and linguistic decoding semantic structure

Peter: Do you want to come for a walk? Mary: I want to read

Peter must infer that, in saying “I want to read,” Mary has 1.The communicative intention to inform Peter

• f her informative intention,

2.the informative intention to inform Peter that she wants to go on reading rather than go for a walk

The proximal function of language

• For the code model: To provide the means for

the speaker to encode her meaning into an utterance and for the addressee to decode this utterance

• For the inferential model: to provide the means

for encoding precise and structured evidence of the speaker’s meaning

Inferential communication is an exploitation of mindreading and hence can only evolve in a species capable of mindreading

The evolution of mindreading

Facts:

• Other primates (chimpanzees in particular) have at most rudiments
• f a mindreading
• Modern humans are virtuoso mindreaders

Questions:

• Is mindreading an evolved adaptation or an acquired skill?
• If an evolved adaptation, what drove its evolution?

Standard hypothesis:

• The evolution of metarepresentational ability was driven by

selection for social competence (“Machiavellian intelligence hypothesis”)

A mindreading ability does not have communication as a primary function, but it makes inferential communication possible

Inferential comprehension

• More complex inference than ordinary

mindreading

• But the communicator helps the addressee read

her mind

• Hence, possibly specific, relevance-based

heuristics

• A distinct adaptation?

• For communication to succeed, it is not

necessary that the communicator and the addressee decode the sentence uttered in exactly the same way

• It is enough that they see the utterance, however

decoded, as evidence for the same conclusion regarding the speaker’s meaning.

With the inferential model…

Examples:

Peter: I am exhausted Mary: Then let’s go home Your glass is full! Don’t you like Chardonnay? Peter: I love you! Mary: I love you too!

• A richer decoding of linguistic evidence

may actually facilitate inference

• A language faculty that leads to the

acquisition of a grammar that attributes to utterances more structure than they superficially realize may be advantageous

With the inferential model…

Unexpressed constituants

Atomic symbols: “drink”, “water” Language: S NP VP V NP «water»

Unexpressed constituants

Atomic symbols: “drink”, “water” Language: S NP VP V NP water

Unexpressed constituants

Atomic symbols: “drink”, “water”

Unexpressed constituants

Atomic symbols: “drink”, “water” Language: S NP VP V NP drink water

• Individuals sharing a grammar richer than that

indicated by the surface structure of utterances may converge towards novel forms of expression for unexpressed constituents, and thus enrich their language.

• This is also the case for the very emergence of a

linguistic ability: To be disposed to process a non-coded communicative act as if it were a coded sign may facilitate the discovery of the informative intention of the communicator.

With the inferential model…

Mindreading ability

Mindreading ability Inferential communication

Mindreading ability Inferential communication languages language faculty Verbal communication

Mindreading ability Inferential communication languages language faculty Verbal communication

Code vs. inference in evolution

• In coded communication, any shared

<signal, message> pair is a strong local

• ptimum, with very little possibility of

evolution

• In inferrential communication, there is

much more slack, and hence more possibility of evolution towards structural complexity.

Conclusions

• Human languages are adaptive only in a

species capable of inferential communication

• They are adaptive by making make inferential

communication hugely more effective

• The way this function is fulfilled does not put

an absolute premium on symmetry between interlocutors, and therefore provides the slack for the biological evolution of a language faculty and the cultural evolution of languages