Speranza
Conversational Implicatures
This paper introduces Paul Grice’s notion of conversational implicature.
The basic ideas — the cooperative principle, the maxims of conversation, and the
contrast between implicature and presupposition — make it clear that conversational
implicature is a highly contextualized form of language use that has a lot in common
with non-linguistic behavior. But what exactly is its role? Step by step, we invite
the reader to view conversational implicature as a way of negotiating meaning in
conversational contexts. Along the way, the reader will learn something about the
theoretical properties of implicatures, why they are tricky to work with empirically,
what can be done with them computationally, and (perhaps) where future research
on the topic may lead. But the basic message of the paper is actually quite simple:
context and conversational implicature are highly intertwined, and unravelling their
interactions is a challenging and worthwhile research goal.
1 Introduction
The notion of conversational implicature (CI) is important in both philosophy of
language [Grice, 1989; Davis, 2010] and pragmatics [Horn, 2004; Levinson, 1983],
the branch of linguistics which studies how human languages are actually used.
The key ideas were first presented in 1967 in Paul Grice’s William James lectures
at Harvard, and eventually appeared in the paper Logic and Conversation [Grice,
1975, p. 311]. The paper draws our attention to the fact that in typical linguistic
exchanges, many things are meant without being explicitly said, and attempts to
explain how this is possible. Let’s start with an example from Grice’s paper:
(1) Man standing by his car: I am out of petrol.
Passer-by: There is a garage around the corner.
Grice’s analysis runs as follows. The utterance made by the passer-by (let’s call
him B) wouldn’t have been relevant (to the conversational exchange) if B knew that
the garage was closed or that it had run out of petrol. If B is a local person who
knows about local garages, it is thus reasonable to assume that B is directing the
man standing by the car (let’s call him A) to a garage that is open and currently
selling petrol. That is, according to Grice, during the exchange (1), B made the
conversational implicature (2):
(2) The garage is open and has petrol to sell.
Well, so far, so good. But isn’t this just the sort of thing that goes on all the
time? Where’s the mystery? If this is all there is to conversational implicature, what
exactly requires explanation? What makes the concept so important? And why is it
considered difficult?
As we hope to make clear, even this little exchange conceals many problems.
Conversational implicature involves highly contextualized inferences that draw on
multiple sources of information. For instance, in the garage example, presumably
the visual information provided by A standing beside his stationary car plays an
important role in initiating the exchange. Moreover, by their very nature — we
will soon explain what we mean by this — implicatures tend to be resistant to
the usual tools of empirical linguistic investigation. Furthermore, they are ubiquitous:
get two people talking, and the conversational implicature flies thick and fast.
In short, Grice’s garage example is the tip of a large iceberg concerning meaning
and inference in context. In the pages that follow, we first show just how large the
iceberg is below the water’s surface, and then discuss recent attempts to reveal its
contours theoretically, empirically and computationally.
We proceed as follows. In Section 2 we present conversational implicature as a
form of contextualized inference, and make a first pass at explaining why it tends to
resist the usual tools of empirical linguistic analysis. In Section 3 we sketch some
of Grice’s ideas on the subject, notably his cooperative principle and his conversational
maxims. In Section 4 we note five key theoretical properties of conversational
implicature, and in Section 5 we discuss further difficulties with empirical
work. This leads us to one of the main points we wish to make: conversational
implicature is a form of negotiation. In Section 6, we sketch the relevance of clarification
requests to this conception, and in Section 7 we briefly note some recent
computational work. Section 8 concludes with a nod to the future.
Computational implicature is a huge subject, one that has been investigated from
many angles. We cannot hope to cover them all, and have opted instead to present a
birds-eye-view of relevance to researchers interested in context. But there are many
good points of entry to the topic. For a start, Grice’s own Logic and Conversation
is a must: it is clear, accessible and covers many topics we do not have space to
consider. Moreover, excellent surveys exist: we particularly recommend Chapter 3
of Levinson’s textbook Pragmatics [Levinson, 1983]. Furthermore, searching for
Conversational Implicatures 3
‘conversational implicature’ in the (free) online Stanford Encyclopedia of Philosophy
will lead to several informative and authoritative articles (for example, [Davis,
2010]) and detailed bibliographical information.
2 Implicature as contextual inference
In this section we have two main goals: to convince the reader that conversational
implicatures are a highly general form of contextualized inference, and to make a
first attempt to explain why conversational implicatures tend to be resistant to standard
empirical linguistic techniques. A good way into the discussion is to compare
conversational implicatures with what linguists call presuppositions.
Presuppositions are another ubiquitous form of inference, one that all known
human languages exploit. Consider the following sentence. Imagine it is uttered to
you out of the blue, with no prior conversational context:
(3) Anthony regrets that Brenda is pregnant.
Now, you know nothing about Anthony or Brenda or who they are or what their life
is like. But by reading this sentence, if you trust its source, you have internalized
one piece of information: namely, that Brenda is pregnant. But now consider the
following sentence:
(4) Anthony does not regret that Brenda is pregnant.
Once again, simply by reading this sentence, you have once again internalized
the information (or: accommodated the information, as a linguist would say) that
Brenda is pregnant. And this is surprising because it shows that we are dealing with
a very strange form of inference indeed. It is certainly not an ordinary logical inference.
In ordinary logical inference, replacing a positive premise with its negation
will typically destroy the inference. But here replacing ‘regrets’ with ‘does not regret’
has no effect: in both cases the (immediate and intuitive) inference to Brenda’s
pregnancy goes through.
Such presuppositions are ubiquitous, and their ability so survive negations is one
of their better known characteristics. Consider the following pair of sentences
(5) Candy knows that Dave is dead.
Candy does not know that Dave is dead.
Once again — positive or negative — we infer the same information, no matter the
context: Dave is dead.
Now, presupposition is an interesting phenomena. Like conversational implicature
it is a ubiquitous fact about language in action. But in at least one crucial
respect it is simpler than implicature: we can point to concrete linguistic triggers
that set the presuppositional process in motion, no matter the context. In the first
pair of examples, the trigger is the word ‘regret’. In the second pair of examples,
the trigger is the word ‘knows’. Part of the effect of using these words —
4 Luciana Benotti and Patrick Blackburn
part of their meaning — is that they induce presuppositional phenomena of this
sort, and every competent language user instinctively knows how to make good
use of this. Now, it should be stressed that presupposition is not a simple phenomena,
nonetheless, we now have detailed theoretical accounts of it [Beaver, 2001;
Geurts, 1999] and understand how to incorporate presuppositional phenomena into
computational work [Venhuizen et al., 2013; Bos, 2003; Blackburn et al., 2001].
And much of this understanding stems from the basic fact just noted: we can trace
presuppositions to specific linguistic locations, namely, certain trigger words (and
grammatical constructions).
But conversational implicatures can’t be linguistically localized in the same way.
As we said earlier, conversational implicatures are highly contextualized inferences,
capable of exploiting multiple information sources. Consider the garage example.
First, and most obviously, it rests on an assumed common knowledge context: both A
and B need to share the knowledge that “petrol can be bought at open garages which
have not run out of petrol”. Secondly, this example draws on the situational context,
most obviously on B knowing that the garage is around the corner and A can walk
there. But a lot also hinges on the fact that we are in a conversational context. It is
quite obvious that the implicature could not have been triggered without considering
the immediate conversational context: if A had said “Where do you come from?”
instead of “I am out of petrol”, B’s implicature would have been quite different. But
even more basic components of the interaction context are crucial: A and B take
for granted that the other is a language user, with intentions and goals, who may be
prepared to take part in a cooperative exchange in order to overcome undesired states
such as “being out of petrol”. In fact, as we shall soon discuss, Grice called one of
the central principles driving conversational implicature the cooperative principle.
Moreover, other contextual parameters may play a role in how the scenario unfolds,
such as information about race, gender and status (is A unshaven, sloppily dressed,
and standing by a beat-up old car, or is he wearing a suit and tie and standing by a
spiffy new Mercedes?).
So: Conversational implicatures are a highly contextualized form of inference.
Moreover (unlike presuppositions) there is no simple linguistic trigger with relatively
well defined rules which we can analyze to ‘solve the implicature problem’
in the general case. There is no linguistic trigger in the garage example that sets
the implicative process in motion. For example, it would be highly implausible to
claim that B’s behavior is induced by the word ‘garage’, on any other word in the
exchange for that matter. Words like ‘regrets’ and ‘know’ induce presuppositions,
but Grice’s little scenario has more complex origins. The same scenario would work
if we used the words ‘service station’ or ‘petrol station’ instead of ‘garage’. The
initial trigger may well have been non-linguistic: the sight of A (perhaps in his suit
and tie) standing forlornly by his new Mercedes may have been the spark that set
the little scene in motion.
Conversational implicatures are, in general, not closely tied to the inner-workings
of the lexical system in the way that presuppositions are. Rather, they are a type
of behavior exemplified by agents with intentions and goals — but special agents,
namely human beings, who have a highly refined form of behavior in their arsenal:
Conversational Implicatures 5
linguistic behavior. We might say: conversational implicature is a big share of the
meaning conveyed by goal seeking, linguistically competent agents when they interact
in contexts. Hopefully this goes some way towards explaining why conversational
implicatures are interesting and important — and why they are highly relevant
to the study of context. But note the downside: it also tells why they are likely to be
be resistant to straightforward empirical linguistic investigation. We can’t compile a
list of trigger words (as we can for presupposition) and explore their effects in a corpus
of example sentences. As we have said, in general, it is difficult or impossible
to point to critical lexical or grammatical triggers when it comes to conversational
implicature, because so much of what is going on in conversational implicature is
not specifically linguistic behavior; rather, it’s part of the general human behavior
displayed by linguistically adept agents. It spills over into, draws richly on, and is
guided by, the surrounding context in all its crazy variety. So empirical investigation
is a tricky business, a point we will return to later.
3 Grice on conversational implicature
We now outline Grice’s account of conversational implicature, and in particular his
cooperative principle and the conversational maxims. We draw attention to the
possibility of observing, flouting and violating maxims; these are not merely practical
distinctions, but are also helpful in understanding Grice’s motives. We further
note that the conversational maxims are linked to non-linguistic behavior, that they
can be used to classify conversational implicatures, and draw the reader’s attention
to both relevance implicatures, the conversational implicatures that embody
contextual inference in its most general form, and scalar implicatures, those that
probably embody it least. Our discussion will establish some standard ideas and terminology
and pave the way for our work in subsequent sections. Page references
here are to the version of Logic and Conversation in [Grice, 1989].
At the heart of Grice’s discussion lies the following principle (see page 26):
The cooperative principle: Make your contribution such as is required, at the stage at
which it occurs, by the accepted purpose or direction of the talk exchange in which you are
engaged.
In addition, he presents the following maxims (pages 26–27):
Maxims of Quantity:
(i) Make your contribution as informative as is required (for the current purposes of the
exchange).
(ii) Do not make your contribution more informative than is required.
Maxims of Quality: Try to make your contribution one that is true.
(i) Do not say what you believe to be false.
(ii) Do not say that for which you lack adequate evidence.
The Maxim of Relevance: Be relevant.
6 Luciana Benotti and Patrick Blackburn
Maxims of Manner: Be perspicuous.
(i) Avoid obscurity.
(ii) Avoid ambiguity.
(iii) Be brief (avoid unnecessary prolixity).
(iv) Be orderly.
Grice calls the cooperative principle a “rough general principle” and it is clear
from his discussion on pages 26–28 that the maxims are a tentative attempt to understand
how human beings interact in conversation. But at this point, the reader may
have doubts. Aren’t the cooperative principle and the maxims far too neat and tidy?
They seem to describe an ideal world of effective, rational, maximally cooperative
conversational interaction. And, all too obviously, real life just isn’t like that at all.
But it is a mistake to dismiss Grice and conversational implicature on these
grounds. Grice is not suggesting that all human conversational interactions live up
to these principles, or even that it would be better if they did. Rather, Grice is trying
to indicate the existence of deep-seated norms of conversational interaction. Humans
are social animals. They interact. Moreover they are social animals graced (or
cursed) with the power of speech. Grice is tentatively suggesting (see page 29) that
assumptions somewhat like the cooperative principle or the maxims must guide this
process. And of course — as Grice himself points out —- what is expected of others
swiftly becomes a resource to be exploited. We may communicate by observing
the maxims — but sometimes we can communicate more effectively by deliberately
flouting them; we will give examples of both strategies shortly. Indeed, sometimes
we may choose to distance ourselves still further from communicative norms and
deliberately violate the maxims: liars, tricksters, ironists and cheats thrive in the
ambience of the socially expected.
Grice views his conversational maxims as direct analogs of norms governing the
way we cooperate in non-linguistic settings. He is quite explicit on this point. As he
says on page 28:
[O]ne of my aims is to see talking as a special case of purposive, indeed, rational behavior. . .
and then lists analogies between the conversational maxims and physical actions.
For example, with regard to the Maxim of Quality which says we should seek to
be truthful, he points out that if we are cooperating to make a cake, and I need
sugar, then I expect you to pass me sugar, and not (say) salt, and that if I need a
spoon for stirring the cake mixture, I expect you to hand me a real spoon not (say) a
trick spoon made of rubber. The strong analogy that Grice draws between linguistic
and non-linguistic behavior is important, and we shall return to it when we discuss
implicature as negotiation.
The maxims are also useful in that they give us a (somewhat rough-and-ready)
way of classifying conversational implicatures. Consider, for example, the maxims
of quantity. This has given rise to an extensive literature on what are now called
quantity or scalar implicatures (see, for example, [Hirschberg, 1985; Geurts,
2011]). Let’s briefly consider an example which we will return to in more detail
when we discuss empirical work. Consider the following image:
Conversational Implicatures 7
B B B A A A C B C
Suppose I then say to you:
(6) Some of the B’s are in the box on the left.
then I would often be taken as having implicated that
(7) Not all of the B’s are in the box on the left.
Why? The point is this. If I am observing the maxims, and in particular the Maxim
of Quantity that tells us to make your contribution as informative as is required then
I must be making the strongest claim possible. Logically, the claim that some of the
B’s are in the box on the left is compatible with the (logically stronger) claim that
they all are. So why did I not make the stronger claim? Well, assuming that I am
observing to the maxims, this must be because I was not in a position to (truthfully)
do so (and looking at the image we see that I was not). Hence I implicated that
not all the items are in the box. In short, assuming that conversational agents are
observing to the maxims gives us explanatory power: in enables us to appeal to and
reason about communicative goals and intentions.
But so does flouting. Stephen Levinson has a nice example involving Maxims of
Manner (see page 104 of [Levinson, 1983]):
(8) A: Let’s get the kids something.
B: Okay, but I veto I-C-E-C-R-E-A-M-S
Why on earth would B spell out the word ice creams? This is not perspicuous presentation;
indeed it’s (deliberately) obscure and prolix! And of course, every parent
knows why: the maxim has been flouted because B’s message is not simply “Yes, I
agree we should get the kids something”, but the more desperate “For God’s sake
let’s not get them whining for ice creams!”, though truly experienced parents have
also learnt that the flouting-via-spelling strategy doesn’t work for very long. . .
The logic of flouting is interesting. Once again, it involves appealing to and reasoning
about communicative goals and intentions, but in a more subtle way: a flouting
seems to function as an invitation to look beyond the surface level of maxim
failure and to search for a deeper vein of cooperativity. Given such possibilities, it
is hardly surprising that many authors have found game theory (and related disciplines
which focus of strategic thinking) useful tools for exploring conversational
implicature; see [van Rooij, 2011] for a useful overview.
Finally, we remark that we can now see that conversational implicatures come in
all shapes and sizes. For example, the sort of scalar implicature involved in some
of the B’s are in the box on the left example is relatively specific, and closely tied
to the meaning of the word some — though as we shall learn later, even this seemingly
context independent example is not as innocent as it looks. Others, such as
the garage example, with which we started, are more general and commonplace.
This is because the garage example is a relevance implicature, governed simply by
the splendidly general: Be relevant! Some authors (notably Deirdre Wilson and Dan
8 Luciana Benotti and Patrick Blackburn
Sperber [Wilson and Sperber, 2004]) have insisted that the notion of relevance is the
real gold in Grice’s work. Indeed, Grice himself seems to be partly of this opinion.
As he remarks on page 27:
Though the maxim itself is terse, its formulation conceals a number of problems that exercise
me a good deal: questions about what different kinds and focuses of relevance there
may be, how these shift in the course of a talk exchange, how to allow for the fact that the
subjects of conversation are legitimately changed, and so on. I find the treatment of such
questions exceedingly difficult, and I hope to revert to them in later work.
The problems involving relevance implicature remain exceedingly difficult to this
day; some of the hardest problems of contextual inference live there.
4 A little theory
So far, our discussion has been relatively informal; in this section we make it more
precise. We first give a definition of conversational implicature; this won’t play a
role in our subsequent work, but it will give the reader a taste of the theorizing
typical of formal pragmatics and it constitutes a formal definition in which the role
of the context is made explicit. Following this, we will briefly discuss five basic
properties of conversational implicatures; three of them will play an important role
in the emergence of the concept of negotiability in the following section.
The following definition is adapted from [Hirschberg, 1985] by making explicit
the role of context and the role of the conversation participants as agents that can
modify context:
Definition 1. Proposition q is a conversational implicature of utterance U by agent
B in context C if and only if:
(i) B believes that it is mutual, public knowledge inC of all the discourse participants
that B is obeying the cooperative principle.
(ii) B believes that, to maintain (i) given U, the hearer will assume that B believes q
holds in C or can achieve q by modifying C.
(iii) B believes that it is mutual, public knowledge of all the discourse participants
that, to preserve (i), one must be assume that B believes q holds in C or can
achieve q by modifying C.
What does this mean? Let’s return to the garage example, where B implicated
The garage is open and has petrol to sell (that is, q) by uttering There is a garage
around the corner (that is, U). If B believes it is common knowledge to all the
participants (namely A and B) that B is obeying the cooperative principle, and B
further believes that A will assume, on the basis of B’s utterance, that the garage is
open and has petrol to sell and that A can get to the garage, then this implicature is
successful. It’s a tricky definition, and we won’t pause to discuss it further, but do
note the following: the form of the definition, with its explicit appeals to an agent’s
beliefs and what is mutual public knowledge make it clear that implicature is being
modeled as a form of epistemic reasoning that draws on contextual knowledge.
Conversational Implicatures 9
Now let’s examine the properties of conversational implicatures, for these will
play an important role in our discussion. Hirschberg argues that we need to insist
that conversational implicatures have the following five: 1) deniability, 2) reinforceability,
3) non-lexicality, 4) non-detachability, and 5) calculability. In the light our
previous discussion, many of these properties will probably appear familiar, or at
least natural.
First, conversational implicatures are deniable without contradiction. Let’s stick
with Grice’s garage example. B can append material that is inconsistent with the
implicature — for example, B can add but I don’t know whether it’s open — and the
resulting exchange will not be contradictory. Indeed, the resulting exchange would
be extremely natural: B would be implicating potentially useful information about
the garage, but then expressing some reservation. This is something that happens all
the time.
Second, note that B can also add material to the exchange that explicitly asserts
the implicature — and I know it’s open — without any sense that he is repeating
himself. That is, B can reinforce the implicature without redundancy. Indeed, once
again, this is very natural language use: we implicate the extra information and
then (if it seems important) ram the message home to make sure our conversational
partner gets the point.
Third, implicatures are non-lexical: they do not trace back to particular lexical
items. We have already mentioned this. For example, in Grice’s garage example,
the implicature is not triggered by any particular word in the exchange (such as
‘garage’) but is a result of the overall semantic content.
Fourth — again something we have discussed — since an implicature is attached
to the semantic content of what is said and not to the particular lexical items involved,
a conversational implicature cannot be detached from the utterance simply
by changing the words of the utterance by synonyms. B can replace each word in
his utterance with a word with the same meaning — he can say petrol station or
service station instead of garage — and the implicature will still go through. Note
that non-detachability and non-lexicality are not really two independent properties:
non-lexicality can only be tested by evaluating non-detachability. Basically, these
two properties are another way of getting at the basic point that conversational implicatures
are not part of the conventional meaning of the words uttered, but depend
on features of the conversational context.
Fifth and last, conversational implicatures are traditionally considered to be calculable.
Calculability means that the addressee should be able to infer the implicatures
of an utterance. For example, in in the garage example, A should be able to
infer that B conversationally implicates that the garage is open and has petrol to sell.
Three of these properties will shortly return in the guise of negotiability. But
to properly motivate this, we first need to take a closer look at some intriguing
empirical issues.
10 Luciana Benotti and Patrick Blackburn
5 Towards Negotiability
The empirical literature on conversational implicature is based almost entirely on
evidence obtained using the inference method [Chemla, 2009], a pragmatic-level
analog of the introspective method, which has been traditionally used in linguistics
and philosophy (in essence, the traditional approach is to obtain native-speaker
judgments on linguistic examples). However, Geurts and Pouscoulous [2009] have
shown that the inference method is a biased tool when it comes to gathering data
on conversational implicatures. Let’s briefly consider Geurts and Pouscoulous’s
(henceforth G&P) argument.
Consider the scalar implicature example we gave in Section 3. Experimenters using
the traditional inference paradigm might ask the experimental subjects whether
they think that sentence (9a) implies the sentence (9b):
(9) a. Some of the B’s are in the box on the left.
b. Not all of the B’s are in the box on the left.
Now, G&P argue that to ask oneself — or an experimental subject —- whether
or not (9a) implies (9b) is already to suggest that it might be implied. That is, the
experimenter’s question raises the issue of whether or not all of the B’s are in the
box on the left, and makes it relevant to establish whether this is the case. Indeed,
consider the image we used back in Section 3:
B B B A A A C B C
In order to explain the example, we carefully placed a B in the right-hand box. But
this makes the issue of whether all the Bs are in the box on the left very much at
stake. G&P claim that such inference experiments do not necessarily tell us anything
about how (9a) is interpreted in situations where (9b) is not at stake.
In order to support their claim, G&P compare the inference method with what
they call the verification method. In the verification version of the previous experiment,
subjects have to decide whether (9a) correctly describes the situation shown
below. Someone who interprets (9a) as implicating (9b) should deny that (9a) gives
a correct description of the picture (for note: no Bs in the right-hand box):
B B B A A A C C C
Intriguingly, participants derived conversational implicatures almost twice as frequently
given the inference condition (62%) as in the verification condition (34%)!
The inference task does increase the rate of detection of conversational implicatures,
and the effect is substantial. Moreover, G&P show that the effect is even more
evident in complex sentences such as (10a) describing the following situation:
Conversational Implicatures 11
Someone who interprets (10a) as implicating (10b) should deny that (10a) gives
a correct description of the picture (for note: one of the squares is connected to all
of the circles).
(10) a. All the squares are connected with some of the circles.
b. All the squares are connected with some but not all of the circles.
Studies carried out using these more complex sentences result in participants deriving
the conversational implicature (10b) from (10a) in 46% of the cases with the
inference method, and in 0% of the cases with the verification method!. As we have
said several times, the empirical study of conversational implicatures is not easy.
G&P’s work provides a useful warning of another source of error.
But what is the lesson we should draw? Is it simply that the verification method
is better than the inference method? We think not: if inference methods fail to tell us
anything about how utterances should be interpreted when the alleged implicature is
not at stake, the verification method used by G&P fails in the opposite direction; it
does not tell us anything when the issue is at stake. In our view, what G&P’s experiments
really show is that whether the issue is at stake or not is crucial. Moreover
their experiment is powerful because it involves scalar implicatures.
Scalar implicatures are usually considered ‘better behaved’ than (say) relevance
implicatures. Clearly the above inferences have something to do with how we interpret
the logical words ‘some’ and ‘all’, and such inferences are often felt to be ‘less
contextually sensitive’ than full-blown relevance implicatures such as the Grice’s
garage examples. And this makes G&P’s results even more fascinating: even allegedly
simply and well-understood implicatures such as scalar implicatures involving
‘some’ and ‘all’ can be dramatically manipulated by playing with the context.
G&P’s experiments simply change one pragmatic factor — whether something is
at stake or not — and the effects are plain to see. Conversational implicature really
does involve context — and this is true even of scalar implicatures.
And this brings us, at last, to the heart of the paper. In conversation, whether an
issue is at stake or not is naturally determined by what Grice calls “the accepted
purpose or direction of the talk exchange”. And the word that sums up best how
this is done is the word negotiation. Conversational implicature is not a museum
of dead examples that needs explaining — it is an practice, an activity, a way of
12 Luciana Benotti and Patrick Blackburn
interacting. Instead of asking (say) “How do we explain Grice’s garage example?”
we need to ask: how do we change it? How do we extend it? How do we see it as a
living, ongoing, conversational interaction?
Recall the implicature from the garage example — the garage is open and has
petrol to sell. Also recall the properties of deniability and reinforceability we isolated
in the previous section. Actually, these are not so much two independent properties
as two sides of the same coin: conversational implicatures are not explicitly
stated: they are not actual contributions to an exchange, but only potential contributions
that the speaker can either deny or reinforce. Moreover, if we also bring
calculability into the picture then we see that not only the speaker but also the hearer
can deny or reinforce the conversational implicatures. For instance, A can naturally
continue Grice’s garage example with — I went there, it’s closed — thereby denying
the conversational implicature. But A can also continue the exchange by reinforcing
the implicature — oh, and it must be open because it’s only 3pm!
That is, as promised, deniability, reinforceability and calculability can be summarized
by saying that computational implicatures are negotiable. Speaker and hearer
negotiate — they deny, reinforce, calculate, and switch roles as the conversation precedes.
In this fashion they explore the issue at stake until (all being well) they are
satisfied. Conversational implicature is truly conversational. In the following section
we will make these ideas concrete with the help of real conversational examples.
6 Conversational examples
In the previous section we argued that deniability, reinforceability and calculability
can be summed up by saying that conversational implicatures are negotiable. The
hearer can infer the implicatures of an utterance but cannot be 100% sure that the
speaker meant them (and the speaker knows this), so both the speaker and the hearer
can talk — negotiate — without redundancy or contradiction.
This account is theoretically satisfying, but it is of additional interest because it
suggests a novel empirical approach to conversational implicature. The idea, first
suggested in [Benotti, 2009], is to track the negotiation process by noting what linguists
call clarification subdialogues. Take, for instance, the clarification request
which can naturally follow Grice’s garage example:
(11) A: and you think it’s open?
B will have to answer and support the implicature (for instance with “yes, it’s open
till midnight”) if he wants to get it added to the common ground; otherwise, if he
didn’t mean it, he can well reject it without contradiction with “well, you have a
point there, they might have closed”.
Let’s see some examples of clarification, rejection and reinforcement of conversational
implicatures in real dialogues between two players of a multiplayer online
game [Stoia et al., 2008]. In this game, the player DF (Direction Follower) is collaborating
with the player DG (Direction Giver) in order to reach the goal of the game.
Conversational Implicatures 13
Since the DF knows how well the game world and how to reach the goal, most of
her contributions come in the form of instructions on how to perform actions in
the game world. Situated instructions are a kind of language that maintains a tight
link between physical actions and conversational maxims and, offer a concrete scenario
where to get strong intuitions about the mechanisms governing conversational
implicatures and how they interact with different kinds of contextual information.
Clarifying conversational implicatures.
In the dialogue below, the players are trying to move a picture from one wall to
another. The utterance being interpreted is the one uttered by the DG in (1). Using
the common knowledge context that “in order to put something somewhere you need
to have it in your hands first” and the situational context of “DF is not holding the
picture”, the DF infers a conversational implicature that involves picking up the
picture. This implicature, foreshadowed by (2) and (3), is finally made explicit as a
clarification request in (4):
DG(1): well, put it on the opposite wall
DF(2): ok, control picks the .
DF(3): control’s supposed to pick things up and .
DF(4): am I supposed to pick this thing?
Rejecting conversational implicatures.
Here, the players are trying to find a gun that is supposed to be hidden. As in the
previous example, the inference of the conversational implicature in (2) is allowed
by the common knowledge context that “in order to take something from a container
is has to be open”. However, the situational context of “the cabinet is closed” was
unknown by the DG and is an obstacle for carrying out instruction (1). As a result,
DF rejects the implicature “the cabinet is open” by uttering (2):
DG(1): take the gun from the cabinet .
DF(2): the cabinet is closed
Reinforcing conversational implicatures.
In this fragment, DG asks DF to go back where he started. This instruction relies
on its previous conversational context, in fact, it requires that the DF remembers
the beginning of the game that was also the beginning of the conversation. And the
DF remembers, and thus is able to infer a sequence of conversational implicatures
that he incrementally grounds making them explicit in (2), (4), and (6) while he is
executing it. Uttering the implicatures of an utterance is a frequently used method
for performing acceptance acts. As before, the conversational implicatures of (1) are
strongly dependent of the situational context. In particular, note that if the DF was
already near the steps at the moment of uttering (1), he would only need to infer (6),
not (2) and (4) as well.
14 Luciana Benotti and Patrick Blackburn
DG(1): let’s go back where you started . so
DF(2): ok . so I have to go back through here .
DG(3): yeah
DF(4): and around the corner .
DG(5): right
DF(6): and then do I have to go back up the steps
DG(7): yeah
DF(8): alright, this is where we started
Conversational implicatures are negotiable, and dialogue provides an intrinsic
mechanism for carrying out negotiations of meaning, namely clarifications. As these
examples show, conversational implicatures are a rich source of clarification subdialogues.
When talking, we do not make explicit all those things from the world that
serve “the accepted purpose or direction of the talk exchange in which we are engaged”,
but only those that are necessary for the addressees to fill in the details in the
way we intend them to. If the addressee is not sure that he has filled in the details
in the way we intended them to, if he is not sure he had interpreted our intended
conversational implicatures, a clarification subdialogue emerges.
A pleasant aspect of this approach is that it bring us to closer to standard linguistic
techniques: essentially the idea is to find conversational implicatures in corpora by
identifying clarification subdialogues. The characteristics and functions of clarification
subdialogues have been deeply studied by dialogue system researchers [Gabsdil,
2003; Purver, 2004; Rodr´ıguez and Schlangen, 2004; Rieser and Moore, 2005;
Skantze, 2007] and sociolinguists. In discourse analysis, this has been an even more
favored theme for almost three decades now; see [Schegloff, 1987] as a representative
example. This opens a myriad of possibilities for studying conversational implicatures
under a new light.
The approach has the additional merit of anchoring the study of conversational
implicatures in their natural habitat, that is, in natural occurring dialogue. As we
have seen, it is often controversial whether something is a conversational implicature
or not (people have different intuitions, which is not surprising given that people
often have different contexts in mind). But in naturally occurring dialogue, the follow
up conversational turns often provides good evidence of the implicatures that
have been made, simply because they make implicatures explicit.
7 Recent Computational work
Recall the five properties of conversational implicature we isolated in Section 4.
According to [Levinson, 1983], non-detachability (which is closely related to nonlexicality)
serves to distinguish conversational implicatures from presuppositions.
As we pointed out in Section 2, words like ‘knows’ and ‘regret’ carry, as a part of
their conventional meaning, the ability to trigger presuppositions. However conversational
implicatures are not part of the conventional meaning of the words involved
Conversational Implicatures 15
but depend on features of the conversational context — indeed (as the experiments
of G&P show) this is true even of seemingly-simple scalar implicatures.
But non-detachability (and non-lexicality) have a computational downside. While
progress has been made on computing presuppositions, computing implicatures is
a heavier task, for work that models the inference of conversational implicatures
has to model the (linguistic and extra-linguistic) conversational context. However,
in spite of the difficulties involved, there has been some recent work on the topic,
we shall briefly note here. These approaches differ not only on the conversational
context elements that they model but also on the inference techniques used.
First, [Vogel et al., 2013b] show that a team of interacting agents collaborating
to maximize a global reward using only local information reach implicature-rich interpretations
simply as a by-product of the way they reason about each other beliefs.
The technique used to model the interaction is multi-agent Decentralized POMDP
which only use local information to maximize joint utility. A similar approach is
taken by [DeVault and Stone, 2009] who instead of POMDPs use Maximum Entropy
models over abductive interpretations to model the maximization of interpretation
success. These two approaches provide a rich representation of the conversational
context and the goals shared by the agents. Using such techniques the cooperative
principle and the associated maxims of relevance, quality, and quantity have been
shown to emerge from agent interaction because they maximize utility. For instance,
agents do not lie to each other and do not give more information than necessary to
make collaboration more effective. The main problem of these two approaches is
their intractability, although [Vogel et al., 2013a] use cognitively-inspired heuristics
to simplify the otherwise intractable task of reasoning jointly about actions, the
environment, and the nested beliefs of other actors.
An alternative approach is not to explicitly reason about the nested beliefs but to
model and reason on the common ground using cheap causal reasoning techniques
such as classical planning [Benotti, 2010; Benotti and Blackburn, 2011]. Such have
been used to computationally explore the idea of conversational implicature as negotiation,
and have also proven to be useful in large scale practical applications [Smith,
2012]. The main problem with this approach is the limited expressive power offered
by the classical planing paradigm which is able to model only some kinds of conversational
implicatures. An interesting way around this problem would be to use
Dynamic Epistemic Planning [Bolander and Andersen, 2011], though, at least at
present, the additional expressivity this offers is likely to come with a hefty price in
terms of tractability.
8 Towards the future
In this paper we introduced conversational implicature, contrasted this notion with
presupposition, explained the cooperative principle and the maxims of conversation
on which it rests, and invited the reader to view conversational implicature as a way
of negotiating meaning in conversational contexts. We discussed recent theoretic,
16 Luciana Benotti and Patrick Blackburn
empirical and computational work, and hope it is now clear to the reader that context
and conversational implicature are deeply intertwined, and that unraveling their
interactions is a worthwhile research goal.
But what of the future? Where is research in this field likely to go? There has been
interesting recent work in pragmatics that points towards new research directions. In
this paper we simply contrasted conversational implicature with presupposition in
an attempt to make clear just how important context is to conversational implicature.
But presupposition and conversational implicature are only two of many phenomena,
and two strands of recent work are clarifying our understanding here. First,
in [Simons et al., 2011; Tonhauser et al., 2013] and related publications, a determined
attempt has been to make to more accurately map the contours of what are
called projectable inferences (presuppositions are an important example here, but
there are many others). On the other hand, in [Beaver and Zeevat, 2007] there are
signs that linguists are beginning to better understand the process of accommodating
new information that is inferred in context. These lines of work both hint at deeper
theoretical analyses of some of the key concepts in pragmatics, so the intellectual
landscape may well look very different from now.
Nonetheless, despite these new insights, it seems clear that Paul Grice got several
things right. We do use language in conversational contexts, this does involve reasoning
about the intentions and goals of those we interact with, and this may well
be a norm-governed process open to exploitation. And — above all — when we
negotiate with our conversational partners and adversaries, it seems that we draw
upon and reason about the information made available by the context in deep and
intriguing ways. Paul Grice: still relevant after all these years!
[Zeevat, 2014]
References
[Beaver and Zeevat, 2007] David Beaver and Henk Zeevat. Accommodation. In The Oxford
Handbook of Linguistic Interfaces, pages 503–539. Oxford University Press, 2007.
[Beaver, 2001] David Beaver. Pragmatics, and that’s an order. In Logic, Language and Visual
Information. CSLI Publications, 2001.
[Benotti and Blackburn, 2011] Luciana Benotti and Patrick Blackburn. Classical planning and
causal implicatures. In Michael Beigl, Henning Christiansen, Thomas R. Roth-Berghofer, Anders
Kofod-Petersen, Kenny R. Coventry, and Hedda R. Schmidtke, editors, Modeling and Using
Context, volume 6967 of Lecture Notes in Computer Science, pages 26–39. Springer Berlin Heidelberg,
2011.
[Benotti, 2009] Luciana Benotti. Clarification potential of instructions. In Proceedings of the
2009 SIGDIAL Conference on Discourse and Dialogue, pages 196–205, 2009.
[Benotti, 2010] Luciana Benotti. Implicature as an Interactive Process. PhD thesis, Universite´
Henri Poincare, INRIA Nancy Grand Est, France, supervised by Patrick Blackburn, 2010. ´
[Blackburn et al., 2001] Patrick Blackburn, Johan Bos, Michael Kohlhase, and Hans de Nivelle.
Inference and computational semantics. In Harry Bunt, Reinhard Muskens, and Elias Thijsse,
editors, Computing Meaning, volume 2, pages 11–28. 2001.
[Bolander and Andersen, 2011] Thomas Bolander and Mikkel Birkegaard Andersen. Epistemic
planning for single- and multi-agent systems. Journal of Applied Non-Classical Logics, 21:9–
34, 2011.
Conversational Implicatures 17
[Bos, 2003] Johan Bos. Implementing the binding and accommodation theory for anaphora resolution
and presupposition projection. Computational Linguistics, 29(2):179–210, 2003.
[Chemla, 2009] Emmanuel Chemla. Universal implicatures and free choice effects: Experimental
data. Semantics and Pragmatics, 2(2):1–33, May 2009.
[Davis, 2010] Wayne Davis. Implicature. In Edward N. Zalta (ed.), The Stanford Encyclopedia of
Philosophy, Stanford, CA: CSLI winter 2010 edn., 2010.
[DeVault and Stone, 2009] David DeVault and Matthew Stone. Learning to interpret utterances
using dialogue history. In Proceedings of the 12th Conference of the European Chapter of the
ACL (EACL 2009), pages 184–192, Athens, Greece, 2009. Association for Computational Linguistics.
[Gabsdil, 2003] Malte Gabsdil. Clarification in spoken dialogue systems. In Proceedings of the
AAAI Spring Symposium on Natural Language Generation in Spoken and Written Dialogue,
pages 28–35, Palo Alto, California, 2003.
[Geurts and Pouscoulous, 2009] Bart Geurts and Nausicaa Pouscoulous. Embedded implicatures?!?
Semantics and Pragmatics, 2(4):1–34, July 2009.
[Geurts, 1999] Bart Geurts. Presuppositions and Pronouns, volume 3 of Current Research in the
Semantics/pragmatics Interfaces. Elsevier, Amsterdam, 1999.
[Geurts, 2011] Bart Geurts. Quantity implicatures. Cambridge University Press, 2011.
[Grice, 1975] Paul Grice. Logic and conversation. In P. Cole and J. Morgan, editors, Syntax and
Semantics, volume 3, pages 41–58. Academic Press, New York, 1975.
[Grice, 1989] Paul Grice. Studies in the Way of Words. Harvard University Press, 1989.
[Hirschberg, 1985] Julia Linn Bell Hirschberg. A theory of scalar implicature. University of
Pennsylvania, 1985.
[Horn, 2004] Larry Horn. Implicature. In Handbook of Pragmatics, pages 3–28. Blackwell, Oxford,
2004.
[Levinson, 1983] Stephen Levinson. Pragmatics. Cambridge textbooks in linguitics, 1983.
[Purver, 2004] Matthew Purver. The Theory and Use of Clarification Requests in Dialogue. PhD
thesis, King’s College, University of London, 2004. Supervised by Jonathan Ginzburg.
[Rieser and Moore, 2005] Verena Rieser and Johanna D. Moore. Implications for generating clarification
requests in task-oriented dialogues. In Proceedings of the 43rd Annual Meeting on
Association for Computational Linguistics, ACL ’05, pages 239–246, Ann Arbor, Michigan,
2005. Association for Computational Linguistics.
[Rodr´ıguez and Schlangen, 2004] Kepa Rodr´ıguez and David Schlangen. Form, intonation and
function of clarification requests in german task oriented spoken dialogues. In Proceedings of
8th Workshop on the Semantics and Pragmatics of Dialogue (SEMDIAL), pages 101–108, 2004.
[Schegloff, 1987] Emanuel Schegloff. Some sources of misunderstanding in talk-in-interaction.
Linguistics, 8:201–218, 1987.
[Simons et al., 2011] Mandy Simons, Judith Tonhauser, David Beaver, and Craige Roberts. What
projects and why. In Proceedings of 20th Semantics and Linguistic Theory Conference (SALT
2010), volume 20, pages 309–327, 2011.
[Skantze, 2007] Gabriel Skantze. Error Handling in Spoken Dialogue Systems. PhD thesis, KTH
- Royal Institute of Technology, Sweden, 2007. Supervised by Rolf Carlson.
[Smith, 2012] Dustin Smith. Managing implicit assumptions in natural language interfaces. In
Proceedings of the 2012 ACM international conference on Intelligent User Interfaces, IUI ’12,
pages 383–388, New York, NY, USA, 2012. ACM.
[Stoia et al., 2008] Laura Stoia, Darla Magdalene Shockley, Donna K. Byron, and Eric FoslerLussier.
Scare: A situated corpus with annotated referring expressions. In Proceedings of the
6th International Conference on Language Resources and Evaluation (LREC 2008), Marrakesh,
Morocco, May 2008.
[Tonhauser et al., 2013] Judith Tonhauser, David Beaver, Craige Roberts, and Mandy Simons. Toward
a taxonomy of projective content. Language, 89(1):66–109, 2013.
[van Rooij, 2011] Robert van Rooij. Optimality-Theoretic and Game-Theoretic Approaches to
Implicature. In Edward N. Zalta (ed.), The Stanford Encyclopedia of Philosophy, Stanford, CA:
CSLI Dec 1, 2006, substantive revision Feb 17, 2011 edn, 2011.
18 Luciana Benotti and Patrick Blackburn
[Venhuizen et al., 2013] Noortje Venhuizen, Johan Bos, and Harm Brouwer. Parsimonious semantic
representations with projection pointers. In Proceedings of the 10th International Conference
on Computational Semantics (IWCS 2013) – Long Papers, pages 252–263, Potsdam,
Germany, 2013.
[Vogel et al., 2013a] Adam Vogel, Max Bodoia, Christopher Potts, and Dan Jurafsky. Emergence
of Gricean maxims from multi-agent decision theory. In Human Language Technologies: The
2013 Annual Conference of the North American Chapter of the Association for Computational
Linguistics, pages 1072–1081, Stroudsburg, PA, June 2013. Association for Computational Linguistics.
[Vogel et al., 2013b] Adam Vogel, Christopher Potts, and Dan Jurafsky. Implicatures and nested
beliefs in approximate Decentralized-POMDPs. In Proceedings of the 2013 Annual Conference
of the Association for Computational Linguistics, pages 74–80, Stroudsburg, PA, August 2013.
Association for Computational Linguistics.
[Wilson and Sperber, 2004] Deirdre Wilson and Dan Sperber. Relevance theory. In The Handbook
of Pragmatics, pages 607–632. Blackwell, Oxford, 2004.
[Zeevat, 2014] Henk Zeevat. Language Production and Interpretation: Linguistics meets Cognition,
volume 30 of Current Research in the Semantics/Pragmatics Interface. Brill Academic
Pub, 2014.
Subscribe to:
Post Comments (Atom)
Posts
No comments:
Post a Comment