(In Mind and
Language, 2002, 17. 3-23)
Pragmatics,
Modularity and Mind-reading
DAN SPERBER AND DEIRDRE
WILSON
___________________________________________________________________________
Abstract
The central problem for
pragmatics is that sentence meaning vastly underdetermines speaker’s meaning. The
goal of pragmatics is to explain how the gap between sentence meaning and
speaker’s meaning is bridged. This paper defends the broadly Gricean view that
pragmatic interpretation is ultimately an exercise in mind-reading, involving
the inferential attribution of intentions. We argue, however, that the
interpretation process does not simply consist in applying general mind-reading
abilities to a particular (communicative) domain. Rather, it involves a
dedicated comprehension module, with its own special principles and mechanisms.
We show how such a metacommunicative module might have evolved, and what
principles and mechanisms it might contain.
___________________________________________________________________________
We would like to thank the
participants in the Mind & Language Workshop on Pragmatics and
Cognitive Science, and in particular Robyn Carston and Sam Guttenplan, for
valuable comments and suggestions.
Address for
correspondence: Deirdre
Email: deirdre@ling.ucl.ac.uk
1. Introduction
Pragmatic studies of verbal
communication start from the assumption (first defended in detail by the
philosopher Paul Grice), that an essential feature of most human communication,
both verbal and non-verbal, is the expression and recognition of intentions
(Grice, 1957; 1969; 1982; 1989a). On this approach, pragmatic interpretation is
ultimately an exercise in metapsychology, in which the hearer infers the
speaker’s intended meaning from evidence she has provided for this purpose. An
utterance is, of course, a linguistically-coded piece of evidence, so that
verbal comprehension involves an element of decoding. However, the decoded
linguistic meaning is merely the starting point for an inferential process that
results in the attribution of a speaker’s meaning.
The central problem for
pragmatics is that the linguistic meaning recovered by decoding vastly
underdetermines the speaker’s meaning. There may be ambiguities and referential
ambivalences to resolve, ellipses to interpret, and other indeterminacies of
explicit content to deal with. There may be implicatures to identify,
illocutionary indeterminacies to resolve, metaphors and ironies to interpret. All
this requires an appropriate set of contextual assumptions, which the hearer
must also supply. To illustrate, consider the examples in (1) and (2):
(1) (a) They gave him life.
(b) Everyone left.
(c) The school is close to the hospital.
(d) The road is flat.
(e) Coffee will be served in the lounge.
(2) (a) The lecture was as you would expect.
(b) Some of the students did well in the exam.
(c) Someone’s forgotten to take out the rubbish.
(d) Teacher: Have you handed in your essay?
Student: I’ve had a lot to do recently.
(e) John is a soldier.
In order to decide what the
speaker intended to assert, the hearer may have to disambiguate and assign
reference, as in (1a), fix the scope of quantifiers, as in (1b), and assign
appropriate interpretations to vague expressions or approximations, as in
(1c-d). In order to decide what speech act the speaker intended to perform, he
may have to resolve illocutionary indeterminacies, as in (1e) (which may be
interpreted as an assertion, a request or a guess). Many utterances also convey
implicit meaning (implicatures): for example, (2a) may implicate that the
lecture was good (or bad), (2b) may implicate that not all the students did
well in the exam, (2c) may convey an indirect request and (2d) an indirect
answer, while (2e) may be literally, metaphorically or ironically intended. Pragmatic
interpretation involves the resolution of such linguistic indeterminacies on
the basis of contextual information. The hearer’s task is to find the meaning
the speaker intended to convey, and the goal of pragmatic theory is to explain
how this is done.
Most pragmatists working
today would agree with this characterisation of pragmatics. Most would also
agree that pragmatic interpretation is ultimately a non-demonstrative inference
process which takes place at a risk: there is no guarantee that the meaning
constructed, even by a hearer correctly following the best possible procedure,
is the one the speaker intended to convey. However, this picture may be fleshed
out in several different ways, with different implications for the relation of
pragmatics to other cognitive systems. On the one hand, there are those who
argue that most, if not all, aspects of the process of constructing a
hypothesis about the speaker’s meaning are closely related to linguistic
decoding. These code-like aspects of interpretation might be carried out within
an extension of the language module, by non-metapsychological processes whose
output might then be inferentially evaluated and attributed as a speaker’s
meaning. On the other hand, there are those who see pragmatic interpretation as
metapsychological through and through. On this approach, both hypothesis
construction and hypothesis evaluation are seen as rational processes geared to
the recognition of speakers’ intentions, carried out by Fodorian central
processes (Fodor, 1983), or by a ‘theory of mind’ module dedicated to the
attribution of mental states on the basis of behaviour (Astington, Harris and
Olson, 1988; Davies and Stone, 1995a; 1995b; Carruthers and Smith, 1996). Both
positions are explored in the papers in this volume.
We want to defend a view of
pragmatic interpretation as metapsychological through and through. However,
departing from our earlier views (Sperber and Wilson, 1986/1995; Wilson and
Sperber, 1986), we will argue that pragmatic interpretation is not simply a
matter of applying Fodorian central systems or general mind-reading abilities
to a particular (communicative) domain. Verbal comprehension presents special
challenges, and exhibits certain regularities, not found in other domains. It
therefore lends itself to the development of a dedicated comprehension module
with its own particular principles and mechanisms. We will show how such a
metacommunicative module might have evolved as a specialisation of a more
general mind-reading module, and what principles and mechanisms it might
contain; we will also indicate briefly how it might apply to the resolution of
linguistic indeterminacies such as those in (1) and (2) (for fuller accounts,
see Sperber and Wilson, 1986/1995; Carston, forthcoming; Wilson and Sperber,
forthcoming).
2. Two Approaches to
Communication
Before Grice’s pioneering
work, the only available theoretical model of communication was what we have
called the classical code model (Sperber and Wilson, 1986/1995, chapter 1,
sections 1-5; Wilson, 1998), which treats communication as involving a sender,
a receiver, a set of observable signals, a set of unobservable messages, and a
code that relates the two. The sender selects a message and transmits the
corresponding signal, which is received and decoded at the other end; when all
goes well, the result is the reproduction in the receiver of the original
message. Coded communication need involve no metapsychological abilities. It
clearly exists in nature, both in pure and mixed forms (in which coding and
inference are combined). Much animal communication is purely coded: for
example, the bee dance used to indicate the direction and distance of nectar
(von Frisch, 1967; Hauser, 1996). It is arguable that some human non-verbal
communication is purely coded: for example, the interpretation by neonates of
facial expressions of emotion (Fridlund, 1994; Sigman and Kasari, 1995;
Wharton, 2001). Human verbal communication, by contrast, involves a mixture of
coding and inference. As we have seen, it contains an element of inferential
intention-attribution; but it is also partly coded, since the grammar of a
language just is a code which pairs phonetic representations of sentences with
semantic representations of sentences.
In studying such a mixed
form of communication, there is room for debate about where the borderline
between coding and inference should be drawn. One way of limiting the role of
metapsychological processes in verbal comprehension would be to argue for an
extension in the domain of grammar, and hence in the scope of
(non-metapsychological) linguistic decoding processes. This is sometimes done
by postulating hidden linguistic constituents or multiple ambiguities;
approaches along these lines are suggested by Millikan (1984, 1988) and Stanley
(this volume) (for discussion, see Origgi and Sperber, 2000; Carston, 2000; and
Breheny, this volume). But however far the domain of grammar is expanded, there
comes a point at which pragmatic choices – choices based on contextual
information – must be made. An obvious example of a pragmatic process is
reference resolution, where the hearer has to choose among a range of
linguistically possible interpretations of a referential expression (e.g. ‘I’,
‘now’, ‘this’, ‘they’) on the basis of contextual information. Here, too, it is
possible to argue that code-like procedures play a role in determining how
pragmatic choices are made.
Many formal and
computational approaches to linguistics suggest that certain aspects of
pragmatic interpretation may be dealt with in code-like terms. One way of
handling reference resolution along these lines is to set up contextual
parameters for the speaker, hearer, time of utterance, place of utterance, and
so on, and treat the interpretation of referential expressions such as ‘I’,
‘you’, ‘here’ and ‘now’ as initially determined by reference to these (e.g. Lewis,
1970; Kaplan, 1989). There are also code-like (‘default-based’) treatments of
generalised conversational implicatures (e.g. the implicature regularly carried
by (2b) above that not all the students passed the exam) (see for example
Gazdar, 1979; Lascarides and Asher, 1993; Levinson, 2000). These formal
accounts might be combined with an inferential approach by assuming that the
output of these non-metapsychological pragmatic decoding processes is
inferentially evaluated before being attributed as a speaker’s meaning.
Grice himself seems to have
seen explicit communication as largely a matter of linguistic and contextual
decoding, and only implicit communication as properly inferential (Grice 1989:
25), and many pragmatists have followed him on this (Searle, 1969; Bach and
Harnish, 1979; Levinson, 1983; Bach, 1994; for discussion, see the papers by
Breheny; Carston; Recanati; and Stanley, this volume). However, the code-like
pragmatic rules that have been proposed so far do not work particularly well. For
example, even if ‘now’ refers to the time of utterance, it is still left to the
hearer to decide whether the speaker, on a given occasion, meant now this
second, this minute, this hour, day, week, year, etc. (Predelli, 1998). For
other referential expressions (e.g. ‘he’, ‘they’, ‘this’, ‘that’), and for
disambiguation and the other aspects of explicit communication illustrated in
(1) above, it is hard to think of a code-like treatment at all. Similarly,
default-based accounts of generalised conversational implicatures typically
over-generate (Carston, 1997), and it is widely acknowledged that
particularised implicatures (which depend on special features of the context)
are not amenable to code-like treatment at all (Levinson, 2000).
What the available psycholinguistic
evidence shows is that, other things being equal, from a range of
contextually-available interpretations, hearers tend to choose the most salient
or accessible one, the one that costs the least processing effort to construct
(Gernsbacher, 1995). This is also what many theoretical accounts of pragmatic
interpretation (e.g. Lewis, 1979; Sperber and Wilson, 1986/1995) predict that
hearers should do. The question is whether they do this because they are
following a conventional, code-like procedure that children have to learn (as
they have to learn that ‘I’ refers to the speaker, ‘now’ to the time of
utterance, and so on), or because this is a sound way of inferring the
speaker’s intentions, independently of any convention. If it is such a rational
procedure, then it falls outside the scope of a decoding model and inside an
inferential account. We will argue that, within the specifically communicative
domain, it is indeed rational for hearers to follow a path of least effort in
constructing a hypothesis about the speaker’s meaning, and that the pragmatic
interpretation process is therefore genuinely inferential (for discussion, see
Origgi and Sperber, 2000; Carston, this volume; Recanati, this volume).
Inferential comprehension,
then, is ultimately a metapsychological process involving the construction and
evaluation of a hypothesis about the communicator’s meaning on the basis of
evidence she has provided for this purpose. It clearly exists in humans, both
in pure and mixed forms. As we have seen, verbal communication involves a
mixture of coding and inference, and there is room for debate about the
relative contributions of each. By contrast, much non-verbal communication is
purely inferential. For example, when I point to the clouds to indicate that I
was right to predict that it would rain, or hold up my full glass to indicate
that you need not open a new bottle on my account, there is no way for you to
decode my behaviour, and no need for you to do so. You could work out what I
intend to convey by a straightforward exercise in mind-reading, by attributing
to me the intention that would best explain my behaviour in the situation
(though if we are right, you can actually do it even more directly, via a
dedicated comprehension procedure). Thus, metapsychological inference plays a
central role in human communication, both verbal and non-verbal.
These theoretical arguments
are confirmed by a wealth of experimental evidence linking the development and
breakdown of general mind-reading abilities and communicative abilities, both
verbal and non-verbal. In autism, both general mind-reading and non-verbal
communication are impaired (Baron-Cohen, 1995; Perner, Frith, Leslie and
Leekam, 1989; Sigman and Kasari 1995; see also Langdon, Davies and Coltheart,
this volume). There are also links between the development and breakdown of
general mind-reading and verbal communication (Happé 1993; Wilson 2000; and the
papers in this volume by Bloom; Happé and Loth; Langdon, Davies and Coltheart;
and Papafragou). For example, normal word learning involves the ability to
track speakers’ intentions, and correlates in interesting ways with the ability
to pass the false-belief tasks used in the study of general mind-reading
(Bloom, 2000, this volume; Happé and Loth, this volume). Reference resolution
is another pragmatic ability that correlates in interesting ways with the
ability to pass false-belief tasks (Mitchell, Robinson and Thompson, 1999); and
there seems to be a well-established correlation between the interpretation of
irony and second-order mind-reading abilities, (Happé, 1993; Langdon, Davies
and Coltheart, this volume). However, there are different ways of analysing
both general mind-reading abilities and their links to specifically
communicative abilities. In the next section, we will consider some of these.
3. Two Approaches to
Inferential Communication
Grice was rather
non-committal on the source of pragmatic abilities and their place in the
overall architecture of the mind. He wanted to be able to show that our communicative
behaviour is rational:
I am enough of a rationalist to want to find a basis that underlies these facts, undeniable though they may be; I would like to be able to think of the standard type of conversational practice not merely as something that all or most do in fact follow but as something that it is reasonable for us to follow, that we should not abandon. (Grice, 1989b, p. 29)
However, he was prepared to
retreat, if necessary, to the ‘dull but, no doubt at a certain level, adequate
answer’ that ‘it is just a well-recognized empirical fact that people do behave
in these ways; they learned to do so in childhood and have not lost the habit
of doing so’ (Grice, 1989b, p. 28-9).
He was equally
non-committal on the form of the comprehension process. What he clearly
established was a link between pragmatic abilities and more general
mind-reading abilities. But mind-reading itself can be analysed in rather
different ways. It may be thought of as a conscious, reflective activity,
involving Fodorian central processes, and many of Grice’s remarks about the
derivation of implicatures are consistent with this. For example, his rational
reconstruction of how conversational implicatures might be derived is a
straightforward exercise in ‘belief-desire’ psychology:
He said that P; he could not have done this unless he thought that Q; he knows (and knows that I know that he knows) that I will realise that it is necessary to suppose that Q; he has done nothing to stop me thinking that Q; so he intends me to think, or is at least willing for me to think, that Q. (Grice, 1989b, p. 30-31)
For Grice, calculability
was an essential property of implicatures, and he gave several examples of how
particular implicatures might be derived using a ‘working-out schema’ like the
one given above. But there are several reasons for thinking that the actual
comprehension process should not be modelled along these lines.
In the first place, it is
hard to imagine even adults going through such lengthy chains of inference in
the attribution of speaker meanings. Yet preverbal infants already appear to be
heavily involved in inferential communication, and they are surely not using
the form of conscious, discursive reasoning illustrated in Grice’s ‘working-out
schema’ (see the papers by Bloom; Happé and Loth; and Papafragou, this volume).
In the second place, we have argued above that Grice substantially
underestimated the amount of metapsychological inference involved in
comprehension. Given the failure of the non-metapsychological pragmatic
decoding account, his ‘working-out schema’ for implicatures would have to be
supplemented with further schemas designed to deal with disambiguation,
reference assignment, and other inferential aspects of explicit communication. While
reflective inferences of this type do occur when spontaneous inference fails to
yield a satisfactory interpretation, inferential comprehension is in general an
intuitive, unreflective process which takes place below the level of
consciousness.
All this is more consistent
with a view of inferential comprehension as falling within the domain of an
intuitive ‘theory of mind’ module. This view is tacitly adopted in much of the
literature on mind-reading, and explicitly defended by Bloom (2000, this
volume). Grice himself makes remarks indicating that he might not have been
averse to a modularised implementation of his approach, in which the recovery
of implicatures was treated as an intuitive rather than a reflective process:
The presence of a conversational implicature must be capable of being worked out; for even if it can in fact be intuitively grasped, unless the intuition is replaceable by an argument, the implicature (if present at all) will not count as a conversational implicature; it will be a conventional implicature. (Grice, 1989b, p. 31)
There is thus no
requirement in the Gricean framework that implicatures should actually be
recovered by reflective reasoning. A modular view is also possible.
There has been a strong
(though by no means unanimous) trend in the development of the cognitive
sciences, and in particular in developmental and evolutionary psychology and in
neuropsychology, towards a more modular view of the mind. (We use ‘module’ in a
looser sense than the one suggested by Fodor, 1983, to mean a domain- or
task-specific autonomous computational mechanism; see Sperber, 1996, chapter 6;
forthcoming.) One reason for this trend is that a general-purpose inferential
mechanism can only derive conclusions based on the formal (logical or
statistical) properties of the input information it processes. By contrast, a
dedicated inferential mechanism or module can take advantage of regularities in
its specific domain, and use inferential procedures which are justified by
these regularities, but only in this domain. Typically, dedicated modules
exploit the relatively ‘fast and frugal heuristic’ (Gigerenzer et al., 1999)
afforded by their special domain.
A cognitive ability may
become modularised in the course of cognitive development, as in the case of
reading or chess expertise. However, it is reasonable to assume that many
modular structures have a strong genetic component. The selection pressures
which lead to the emergence of cognitive systems over evolutionary time must
also tend to make these systems more efficient, and in particular to attune
them, via dedicated mechanisms, to the specific problems and opportunities it
is their function to handle. Much developmental evidence also suggests that
infants and young children come equipped with domain-specific cognitive
mechanisms (Hirschfeld and Gelman, 1994; Barkow, Cosmides and Tooby, 1995). Mind-reading
is one of the best-evidenced cases in this respect.
Most theories of
mind-reading do assume that it is performed not by a general-purpose reasoning
mechanism, which takes as premises a number of explicit hypotheses about the
relationships between behaviour and mental states, but by a dedicated module. What
is still open to debate is how this module exploits the regularities in
intentional behaviour. According to the rationalisation (or ‘theory-theory’)
account, the mind-reading module carries out a form of belief-desire reasoning
which differs from the ‘folk-psychology’ of philosophers not so much in its
logic as in the fact that it is modularised: that is, performed automatically,
unconsciously, and so on. On this approach, mind-reading is a form of automatic
inference to the best rationalisation of behaviour. It involves, in particular,
the attribution to the agent of beliefs and desires that would make her
observed behaviour rational given its actual or likely effects. Another
possibility (proposed by the 'simulation theory') is that mind-reading succeeds
by exploiting similarities between the interpreter and the agent whose behavior
is being interpreted, and amounts to a form of simulation. However, while it is
true that an utterance is a type of action, and a speaker's meaning is a type
of intention, we want to argue that neither the rationalisation nor the
simulation view of mind-reading adequately accounts for the hearer’s ability to
retrieve the speaker's meaning.
According to the
rationalisation account (e.g. Davies and Stone, 1995b; Carruthers and Smith,
1996), the procedure for inferring the intention behind an action should be as
follows: first, decide what effect of the action the agent could have both
predicted and desired; second, assume that this was the effect the agent
intended to achieve. In most cases of utterance interpretation, this
rationalisation procedure would not work, because the desired effect just is
the recognition of the speaker’s intention. As we have seen, the gap
between sentence meaning and speaker's meaning is so great (going well beyond
the standard ambiguities normally considered in the literature) that there may
be no way of listing the possible speaker's meanings without some advance
knowledge – however sketchy – of what she might want to convey. Moreover, the
range of possible speaker's meanings that the hearer is able to reconstruct may
include several candidates that, to the best of his knowledge, the speaker
might have wanted to convey. In other words, only a hearer with some advance
knowledge of at least the gist of what the speaker might have wanted to convey
would find it relatively easy to reconstruct the intention behind her utterance
using a rationalisation procedure. But we often say or write things that our
hearers or readers did not anticipate, and we have no particular reason to
doubt that we will be understood. In such cases, the standard procedures for
inferring intentions do not help with identifying the speaker's meaning. Unlike
what happens in regular cases of intention attribution, hearers cannot first
identify a desirable effect of the utterance, and then infer that
the speaker’s intention was precisely to achieve this effect.
According to the simulation
account (e.g. Davies and Stone, 1995a), we attribute intentions by
imaginatively simulating the action we are interpreting, thus discovering in
ourselves the intention that underlies it. As an account of comprehension, this
is not too promising either. Since the same sentence can be used to convey
quite different meanings in different situations, a hearer who is simulating
the speaker's linguistic action in order to retrieve her meaning must provide a
considerable amount of contextualisation, based on particular hypotheses about
the speaker's beliefs, preferences, and so on. Again, this would only work in
cases where the hearer already has a fairly good idea of what the speaker is
likely to mean. On this approach, the routine communication of genuinely
unanticipated contents would be difficult or impossible to explain.
More generally, the problem
of applying a general procedure for inferring intentions from actions to the
special case of inferring speaker's meanings from utterances is that speaker's
meanings typically carry a vastly greater amount of information than more
ordinary intentions. This is true whether information is treated in
quantitative probabilistic or qualitative semantic terms. In the repertoire of
human actions, utterances are much more differentiated than other types of
actions: many utterances are wholly new, whereas it is relatively rare to come
across actions that are not reiterations of previous actions. While
stereotypical utterances ('Nice day, isn't it?') make up a significant
proportion of all uttered sentence tokens, they are only a minute
proportion of all uttered sentence types. Leaving stereotypical
utterances aside, the prior probability of most utterances ever occurring is
close to zero, as Chomsky pointed out long ago. Semantically, the complexity of
ordinary intentions is limited by the range of possible actions, which is in
turn constrained by many practicalities. There are no such limitations on the
semantic complexity of speaker's meanings. Quite simply, we can say so much
more than we can do. Regular intention attribution, whether achieved via
rationalisation or simulation, is greatly facilitated by the relatively narrow
range of possible actions available to an agent at a time. There is no
corresponding facilitation in the attribution of speaker's meanings. It is
simply not clear how the standard procedures for intention attribution could
yield attributions of speaker's meanings, except in easy and trivial cases.
Add to this the fact that,
on both Gricean and relevance-theoretic accounts, there are always several
levels of metarepresentation involved in inferential comprehension, while in
regular mind-reading a single level is generally enough (Grice, 1989b; Sperber
and Wilson, 1986/1995, chapter 1). It is hard to believe that two-year-old
children, who fail for instance on regular first-order false-belief tasks, can
recognise and understand the peculiar multi-level representations involved in
communication, using nothing more than a general ability to attribute
intentions to agents in order to explain their behaviour. All this makes it
worth exploring the possibility that, within the overall ‘theory of mind’
module, there has evolved a specialised sub-module dedicated to comprehension,
with its own proprietary concepts and mechanisms (Sperber 1996, 2000).
Given the complexity of
mind-reading, the variety of tasks it has to perform, and the particular
regularities exhibited by some of these tasks, it is quite plausible to assume
that it involves a variety of sub-modules. A likely candidate for one
sub-module of the mind-reading mechanism is the ability, already present in
infants, to infer what people are seeing or watching from the direction of
their gaze. Presumably, the infant (or indeed the adult) who performs this sort
of inference is not feeding a general-purpose inferential mechanism with, say,
a conditional major premise of the form ‘If the direction of gaze of a person P
is towards an object O, then P is seeing O’ and a minor premise of the form
‘Mummy's direction of gaze is towards the cat’ in order to derive the
conclusion: ‘Mummy is seeing the cat.’ It is also unlikely that the infant (or
the adult) rationalises or simulates the observed eye-movement behaviour. In
other words, the inference involved is not just an application of a relatively
general and internally undifferentiated mind-reading module to the specific
problem of inferring perceptual state from direction of gaze. It is much more
plausible that humans are equipped from infancy with a dedicated module, an Eye
Direction Detector (Baron-Cohen, 1995), which exploits the de facto strong
correlation between direction of gaze and visual perception, and directly
attributes perceptual and attentional states on the basis of direction of gaze.
This attribution may itself provide input for other dedicated devices, such as
those involved in word learning (Bloom, 2000; this volume). In infants at
least, such attributions need not be available at all for domain-general
inference or verbal expression.
Similarly, for reasons
given above, we doubt that normal verbal comprehension is achieved either by
wondering what beliefs and desires would make it rational for the speaker to
have produced a given utterance, or by simulating the state of mind that might
have led her to produce it. The question is: Are there regularities specific to
the production of utterances (or of communicative behaviour more generally)
which might ground a more effective dedicated procedure for inferring a speaker's
meaning from her utterance? If there are, they are not immediately obvious,
unlike the strong and simple correlation between gaze direction and visual
attention. Nevertheless, we have argued (Sperber and Wilson, 1986/1995;
Sperber, 2000; Wilson, 2000) that human communication exploits a tendency of
human cognition to seek relevance in a way that narrowly constrains the
interpretation of utterances, thus providing inferential comprehension with a
strong regularity in the data which justifies a dedicated procedure. In the
next section, we will outline these claims, adopting an evolutionary
perspective.
4. Relevance, cognition
and communication
Two kinds of evolutionary
transformation may be distinguished. Some are continuous, and involve the
gradual increase or decrease of a variable such as body size or visual acuity. Others
are discrete, and involve the gradual emergence of a new trait or property,
such as eyes or wings. We claim that relevance has been involved in two
evolutionary transformations in human cognition: one continuous, and the other
discrete. The continuous transformation has been an increasing tendency of the
human cognitive system to maximise the relevance of the information it
processes. The discrete transformation has been the emergence of a
relevance-based comprehension module.
Cognitive efficiency, like
any other kind of efficiency, is a matter of striking the best possible balance
between costs and benefits. In the case of cognition, the cost is the mental
effort required to construct representations of actual or desired states of
affairs, to retrieve stored information from memory, and to draw inferences. The
benefits are cognitive effects: that is, enrichments, revisions and
reorganisations of existing beliefs and plans, which improve the organism's
knowledge and capacity for successful action (Sperber and Wilson, 1986/1995).
In most animal species, the
function of cognition is to monitor quite specific features of the environment
(or of the organism itself) which enable it to exploit opportunities (for
feeding, mating, and so on) and avoid dangers (from predators, poisonous food,
and so on). For these animals, cognitive efficiency is a matter of achieving
these benefits at the lowest possible cost. When the environment of such a species
has remained stable enough for long enough, there is likely to have been a
continuous transformation in the direction of greater efficiency, involving, in
particular, a reduction in the costs required to achieve the given range of
benefits. In some cases, this increase in efficiency may also have involved the
emergence of cognitive mechanisms attuned to specific aspects of the
environment, which provide new cognitive benefits: this would be an example of
a discrete transformation.
In humans, a considerable
amount of cognitive activity is spent in processing information which has no
immediate relevance to improving the organism's condition. Instead, a massive
investment is made in developing a rich, well-organised data-base of
information about a great many diverse aspects of the world. Some—though not
all—of these data will turn out to be of practical use, perhaps in unforeseen
ways. As a result, humans have an outstanding degree of adaptability to varied
and changing environmental conditions, at the cost of a uniquely high
investment in cognition.
Human cognition has three
notable characteristics: it involves the constant monitoring of a wide variety
of environmental features, the permanent availability (with varying degrees of
accessibility) of a huge amount of memorised data, and a capacity for effortful
attentional processing which can handle only a rather limited amount of
information at any given time. The result is an attentional bottleneck: only a
fraction of the monitored environmental information can be attentionally
processed, and only a fraction of the memorised information can be brought to
bear on it. Not all the monitored features of the environment are equally worth
attending to, and not all the memorised data are equally helpful in processing
a given piece of environmental information. Cognitive efficiency in humans is
primarily a matter of being able to select, from the environment on the one
hand, and from memory on the other, information which it is worth bringing
together for joint – and costly – attentional processing.
What makes information
worth attending to? There may be no general answer to this question, but merely
a long list of properties – practical usefulness, importance to the goals of
the individual, evocative power, and so forth – that provide partial answers. We
have argued instead that all these partial answers are special cases of a truly
general answer, based on a theoretical notion of relevance. Relevance, as we
see it, is a potential property of external stimuli (e.g. utterances, actions)
or internal representations (e.g. thoughts, memories) which provide input to
cognitive processes. The relevance of an input for an individual at a given
time is a positive function of the cognitive benefits that he would gain from
processing it, and a negative function of the processing effort needed to
achieve these benefits.
With relevance
characterised in this way, it is easy to see that cognitive efficiency in
humans is a matter of allocating the available attentional resources to the
processing of the most relevant available inputs. We claim that in hominid
evolution there has been a continuous pressure towards greater cognitive
efficiency, so that human cognition is geared to the maximisation of relevance
(we call this claim the First, or Cognitive, Principle of Relevance). This
pressure has affected both the general organisation of the mind/brain and each
of its components involved in perception, memory and inference. The result is
not that humans invariably succeed in picking out the most relevant information
available, but that they manage their cognitive resources in ways that are on
the whole efficient and predictable.
The universal cognitive
tendency to maximise relevance makes it possible, at least to some extent, to
predict and manipulate the mental states of others. In particular, an
individual A can often predict:
(a) which stimulus in an
individual B’s environment is likely to attract B's attention (i.e. the most
relevant stimulus in that environment);
(b) which background information
from B’s memory is likely to be retrieved and used in processing this stimulus
(i.e. the background information most relevant to processing it);
(c) which inferences B is
likely to draw (i.e. those inferences which yield enough cognitive benefits for
B’s attentional resources to remain on the stimulus rather than being diverted
to alternative potential inputs competing for those resources).
To illustrate: suppose that
Peter and Mary are walking in the park. They are engaged in conversation; there
are trees, flowers, birds and people all around them. Still, when Peter sees
their acquaintance John in a group of people coming towards them, he correctly
predicts that Mary will notice John, remember that he moved to Australia three
months earlier, infer that there must be some reason why he is back in London,
and conclude that it would be appropriate to ask him about this. Peter predicts
Mary’s train of thought so easily, and in such a familiar way, that it is not
always appreciated how remarkable this is from a cognitive point of view. After
all, there were lots of other stimuli that Mary might have noticed and paid
attention to. Even if she did pay attention to John, there were lots of other
things she could have remembered about him. Even if she did remember that he
had left for Australia, there were lots of other inferences she could have
drawn (for example, that he had been on a plane at least twice in the past
three months). So why should it be so easy for Peter to predict Mary's train of
thought correctly? Our answer is that it is easy for two reasons: first,
because attention, memory retrieval and inference are guided by considerations
of relevance, and second, because this regularity in the data is built into our
ability to read the minds of others.
Most studies of
mind-reading have focused on the attribution of beliefs and desires. There has
also been a lot of interest in joint attention, and particularly its role in
early language acquisition. However, the understanding that we have of others routinely
extends to an awareness of what they are attending to and thinking about even
in situations where we ourselves are attending to and thinking about other
things. There is no rich body of evidence on the development of these aspects
of mind-reading. However, it would be possible to set up, as a counterpart to
the famous false-belief task, a ‘disjoint attention task’ in which the
participant has to infer what a certain character is paying attention to in a
situation where there is a discrepancy between (a) what is relevant to the
participant and (b) what is relevant to the character. We predict that children
will succeed on well-designed tasks of this kind long before they succeed on
false-belief tasks. After all, children try to manipulate the attention of
others long before they try to manipulate their beliefs.
This ability to recognise
what other people are attending to and thinking about, and to predict how their
attention and train of thought are likely to shift when a new stimulus is
presented, may be used in manipulating their mental states. An individual A may
act on the mental states of another individual B by producing a stimulus which
is likely:
(a) to attract B’s
attention;
(b) to prompt the retrieval
of certain background information from B's memory;
(c) when jointly processed
with the background information whose retrieval it has prompted, to lead B to
draw certain inferences intended by A.
A great deal of human
interaction takes this form. Individual A introduces into the environment of another
individual B a stimulus which is relevant to B, and which provides evidence for
certain intended conclusions. For example, Peter opens the current issue of Time
Out, intending not only to see what films are on, but also to provide Mary
with evidence that he would like to go out that evening. Mary chooses not to
stifle a yawn, thereby providing Peter with evidence that she is tired. In this
interaction, each participant produces a stimulus which is relevant to the
other, but neither openly presents this stimulusas manifestly intended to
attract the other’s attention. These are covert – or at least not manifestly
overt – attempts at influencing others.
However, many attempts to
influence others are quite overtly made. For example, Peter may establish eye
contact with Mary and tap the issue of Time Out before opening it,
making it clear that he intends Mary to pay attention to what he is doing and
draw some specific conclusion from it. Mary may not only choose not to stifle
her yawn, she may openly and deliberately exaggerate it, with similar results. By
engaging in such ostensive behaviour, a communicator provides evidence not only
for the conclusion she intends the addressee to draw, but also of the fact that
she intends him to draw this conclusion. This is ‘ostensive-inferential’
communication proper: that is, communication achieved by ostensively providing
an addressee with evidence which enables him to infer the communicator's
meaning.
Ostensive-inferential
communication is not the only form of information transmission. A great deal of
information is unintentionally transmitted and sub-attentively received. Some
is covertly transmitted, particularly when it would be self-defeating to be
open about the fact that one intends the other participant to come to a certain
conclusion, as when wearing a disguise. However, ostensive-inferential
communication is the most important form of information transmission among
humans. In a wide range of cases, being open about one’s intention to inform
someone of something is the best way – or indeed the only way – of fulfilling
this intention. For example, if Peter wants to go out with Mary, Mary will want
to know about it; similarly, if Mary is too tired to go out, Peter will want to
know about it. By being open about their intention to inform each other of
something – that is, by drawing attention to their behaviour in a manifestly
intentional way – each elicits the other’s co-operation, in the form of
increased attention and a greater willingness to make the necessary effort to
discover the intended conclusion.
Notice that
ostensive-inferential communication may be achieved without the communicator
providing any direct evidence for the intended conclusion. All she has to do is
provide evidence of the fact that she intends the addressee to come to this
conclusion. For example, Peter might just tap the cover of Time Out
without even opening it. This is not normally part of the preparations for
going out, and provides no direct evidence of his desire to go out. Still, by
ostensively tapping the magazine, he does provide Mary with direct evidence
that he intends her to come to the conclusion that he wants to go out. Similarly,
when Mary ostensively imitates a yawn, this is not direct evidence that she is
tired, but it is direct evidence that she intends Peter to come to the
conclusion that she is tired. The same would be true if Peter said, ‘Let's go
out tonight!’ and Mary replied, ‘I’m tired.’ Utterances do not provide direct
evidence of the state of affairs they describe (notwithstanding some famous
philosophical exceptions).
The fact that
ostensive-inferential communication may be achieved simply by providing
evidence about the communicator’s intentions makes it possible to use symbolic
behaviours as stimuli. These may be improvised, as when Peter taps the cover of
the magazine, standardised, as in a fake yawn, or coded, as in an utterance. In
each case, the symbolic stimulus provides evidence which, combined with the
context, enables the audience to infer the communicator's meaning. How is this
evidence used? How can it help the hearer discover the communicator's meaning
when it never fully encodes it, and need not encode it at all? What procedure
takes this evidence as input and delivers an interpretation of the
communicator's meaning as output? This is where considerations of relevance
come in.
5. Relevance and
pragmatics
When it is manifest that
individual A is producing an ostensive stimulus (e.g. an utterance) in order to
communicate with another individual B, it is manifest that A intends B to find
this stimulus worth his attention (or else, manifestly, communication would
fail). Humans are good at predicting what will attract the attention of others.
We have suggested that their success is based on a dedicated inferential
procedure geared to considerations of relevance. These considerations are not
spelled out and used as explicit premises in the procedure, but are built into
its functioning instead. So when B understands that A intends him to find her
ostensive stimulus worth his attention, we can unpack his understanding in
terms of the notion of relevance (terms which remain tacit in B's own
understanding): A intends B to find the stimulus relevant enough to
secure his attention.
Thus, every utterance (or
other type of ostensive stimulus, though we will talk only of utterances from
now on) conveys a presumption of its own relevance. We call this claim the
Second, or Communicative, Principle of Relevance, and argue that it is the key
to inferential comprehension (Sperber and Wilson 1986/1995, chapter 3). What
exactly is the content of the presumption of relevance that every utterance
conveys? In the first place, as we have already argued, the speaker manifestly
intends the hearer to find the utterance at least relevant enough to be worth
his attention. But the amount of attention paid to an utterance can vary: it
may be light or concentrated, fleeting or lasting, and may be attracted away by
alternative competing stimuli. It is therefore manifestly in the speaker’s
interest for the hearer to find her utterance as relevant as possible, so that
he pays it due attention. However, in producing an utterance, the speaker is
also manifestly limited by her abilities (to provide relevant information, and
to formulate it in the best possible way) and her preferences (and in
particular her goal of getting the hearer to draw not just some relevant
conclusion, but a specifically intended one). So the exact content of the
presumption of relevance is as follows:
Presumption of relevance
The utterance is presumed to be the most relevant one compatible with the speaker's abilities and preferences, and at least relevant enough to be worth the hearer's attention. (Sperber and Wilson, 1986/199595, p. 266-78)
The content of this
presumption of relevance may be rationally reconstructed along the lines just
shown, but there is no need to assume that hearers go through such a rational
reconstruction process in interpreting utterances. Our suggestion is, rather,
that the presumption of relevance is built into their comprehension procedures.
The fact that every
utterance conveys a presumption of its own relevance (i.e. the Communicative
Principle of Relevance) motivates the use of the following comprehension
procedure in interpreting the speaker’s meaning:
Relevance-theoretic comprehension procedure
(a) Follow a path of least effort in computing cognitive effects. In particular, test interpretive hypotheses (disambiguations, reference resolutions, implicatures, etc.) in order of accessibility.
(b) Stop when your expectations of relevance are satisfied.
The hearer is justified in
following a path of least effort because the speaker is expected (within the
limits of her abilities and preferences) to make her utterance as relevant as
possible, and hence as easy as possible to understand (since relevance and
processing effort vary inversely). It follows that the plausibility of a
particular hypothesis about the speaker’s meaning depends not only on its
content but also on its accessibility. In the absence of other evidence, the
very fact that an interpretation is the first to come to mind lends it an
initial degree of plausibility. It is therefore rational for hearers to follow
a path of least effort in the particular communicative domain (though not, of
course, in other domains).
The hearer is also
justified in stopping at the first interpretation that satisfies his
expectations of relevance because, if the speaker has succeeded in producing an
utterance that satisfies the presumption of relevance it conveys, there should
never be more than one such interpretation. A speaker who wants to make her
utterance as easy as possible to understand should formulate it (within the
limits of her abilities and preferences) in such a way that the first
interpretation to satisfy the hearer’s expectations of relevance is the one she
intended to convey. It is not compatible with the presumption of relevance for
an utterance to have two alternative co-occurring interpretations, either of
which would be individually satisfactory, since this would put the hearer to
the unnecessary extra effort of trying to choose between them. Thus, when a
hearer following the path of least effort arrives at an interpretation which
satisfies his expectations of relevance and is compatible with what he knows of
the speaker, this is the most plausible hypothesis about the speaker’s meaning
for him. Since comprehension is a non-demonstrative inference process, this
hypothesis may well be false; but it is the best a rational hearer can produce.
(Note, incidentally, that the hearer's expectations of relevance may be
readjusted in the course of comprehension. For example, it may turn out that
the effort of finding any interpretation at all would be too great: as a
result, the hearer would disbelieve the presumption of relevance and terminate
the process, with his now null expectation of relevance trivially satisfied.)
Here is a brief
illustration of how the relevance-guided comprehension procedure applies to the
resolution of linguistic indeterminacies such as those in (1) and (2) above. Consider
the following dialogue, in which Mary’s utterance ‘John is a soldier’
corresponds to (2e):
(3) Peter: Can we trust John to do as we tell him and defend the interests
of the Linguistics Department in the University Council?
Mary: John is a soldier!
Peter's mentally
represented concept of a soldier includes many attributes (e.g. patriotism,
sense of duty, discipline) which are all activated to some extent by Mary's use
of the word ‘soldier’. However, they are not all activated to the same degree. Certain
attributes also receive some activation from the context (and in particular
from Peter’s immediately preceding allusions to trust, doing as one is told,
and defending interests), and these become the most accessible ones. These
differences in accessibility of the various attributes of ‘soldier’ create
corresponding differences in the accessibility of various possible implications
of Mary's utterance, as shown in (4):
(4) (a) John is devoted to his duty
(b) John willingly follows orders
(c) John does not question authority
(d) John identifies with the goals of his team
(e) John is a patriot
(f) John earns a soldier's pay
(g) John is a member of the military
Following the
relevance-theoretic comprehension procedure, Peter considers these implications
in order of accessibility, arrives at an interpretation which satisfies his
expectations of relevance at (4d), and stops there. He does not even consider
further possible implications such as (4e)-(4g), let alone evaluate and reject
them. In particular, he does not consider (4g), i.e. the literal interpretation
of Mary's utterance (contrary to what is predicted by most pragmatic accounts,
e.g. Grice, 1989b, p. 34).
Now consider dialogue (5):
(5) Peter: What does John do for a living?
Mary: John is a soldier!
Again, Mary’s use of the
word ‘soldier’ adds some degree of activation to all the attributes of Peter’s
mental concept of a soldier, but in this context, the degree of activation, and
the order of accessibility of the corresponding implications, may be the
reverse of what we found in (3): that is, (g) may now be the most accessible
implication and (a) the least accessible one. Again following the
relevance-theoretic comprehension procedure, Peter now accesses implications
(g) and (f) and, with his expectations of relevance satisfied, stops there. Thus,
by applying exactly the same comprehension procedure (i.e. following a path of
least effort and stopping when his expectations of relevance are satisfied),
Peter arrives in the one case at a metaphorical interpretation, and in the
other at a literal one. (For interesting experimental evidence on depth of
processing in lexical comprehension, see Sanford, this volume. For a fuller
relevance-theoretic account of lexical comprehension, and in particular of the
relation between literal, loose and metaphorical uses, see Sperber and Wilson,
1998; Wilson and Sperber, 2000.)
6. Conclusion
We have considered two
possibilities. First, comprehension might be an application of a general
mind-reading module to the problem of identifying the speaker's meaning (a
neo-Gricean view). Second, it might involve a sub-module of the mind-reading
module, an automatic application of a relevance-based procedure to ostensive stimuli,
and in particular to linguistic utterances. We have argued that, given the
particular nature and difficulty of the task, the general mind-reading
hypothesis is implausible. We have also argued that the tendency of humans to
seek relevance, and the exploitation of this tendency in communication, provide
the justification for a dedicated comprehension procedure. This procedure,
although simple to use, is neither trivial nor easy to discover. So how can it
be that people, including young children, spontaneously use it in communication
and comprehension, and expect their audience to use it as a matter of course? Our
suggestion has been that relevance-guided inferential comprehension of
ostensive stimuli is a human adaptation, an evolved sub-module of the human
mind-reading ability.
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