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Home , Mental model, Presupposition

Mental mo dels and the case of presupp ositions

Guido Bo ella Rossana Damiano and Leonardo Lesmo

Dipartimento di Informatica e Centro di Scienza Cognitiva

Universita di Torino

fguidorossanalesmogdiunitoit

Keywords Mental mo dels pragmatics and presupp ositions

Abstract The basic is that in order to understand an ut

terance one must build a of the

We claim mental mo dels are a framework that allows

describ ed situation it is clear eg that any representa

to shed light on the phenomenon of presupp ositi ons

tion of arrive must include that of leave The role played

A planbased lexical representation for verbs together

by mental models JohnsonLaird is to provide a

with the eect of conversational that dis

charge p ossible mental mo dels are the key features of

reasoning framework for these representations that al

this prop osal

lows to explain why presupp ositions survive in certain

contexts For instance these representations make it

p ossible to account for the that John didnt arrive

Intro duction

presupp oses John left as predicted by the pro jection of

Presupp ositions are what the utterance of a as

presupp ositions across moreover this

sumes to b e true or takes for granted They can b e

is correctly mo deled as a defeasible one since it is p os

triggered by dierent elements in sentences going from

sible to say John didnt arrive he didnt even leave

the use of denite NPs the King of France is bald pre

supp oses there is a unique King of France to the pres

The is carried out in the following way

ence of factive verbs he regrets that he has been impolite

rst of all the asp ectual features are accounted for

presupp oses he has been impolite These are

by means of a planbased representation of the lexical

characterized by resistance to negation eg he does not

moreover the temp oral features represented by

regret that he has been impolite presupp oses he has been

mental mo dels in the of Schaeken et al as

impolite and by cancellability in the presence of con

well as the interpretation of the negation and of the con

textual

text this amount to building one of more mental mod

This pap er addresses what may b e called lexical pre

els representing the describ ed event The information

supp ositions In particular the event structure as de

shared by all mo dels is what the sentence entails

scrib ed by certain verbs allows to draw some inferences

At this p oint p otential conversational implicatures are

ab out the describ ed situation These verbs are classied

applied their eect is to discharge those mental mo d

in Beaver as signiers of actions and temp o

els of the event that could have b een more precisely de

ralasp ectual mo diers most verbs signifying actions

scrib ed by alternative linguistic expressions In this way

carry presupp ositions that the preconditions for the ac

we gain more information since we are left with the

tion are met Beaver page

smaller of mental mo dels presupp ositions are the

We think that what accounts for preconditions for

information that b ecomes shared by all these remaining

the action still requires a more precise characterization

mo dels

Where do preconditions come from It seems rather

However can b e defeated in the presence

vague to state that leaving is a precondition for arriv

of further contextual information thus blo cking the dis

ing and climbing is a precondition for reaching the top

charge of mo dels presupp ositions cannot arise anymore

We claim that these presupp ositions arise naturally from

b ecause they do not o ccur in all event mo dels therefore

a representation of the of verbs in terms of ac

app earing defeasible to o

tions and plans describing the steps required to carry out

the activity referred to by the verb It may b e observed In the following we will describ e a planbased seman

that a planbased representation is complex and rather tic representation of action verbs and our treatment of

exp ensive to build However we have noticed elsewhere negation and of the temp oral expression before then

that it is indep endently required b oth for accounting for the conversational implicature mechanism will b e intro

the meaning of communication verbs Goy and Lesmo duced Next we face the problem of the pro jection of

and for the maintenance of coherence in dialogues presupp ositions Comparison with related approaches

Ardissono et al and conclusions close the pap er

d is not represented as a punctual event but

st et John arrive

as an instance of the action move that in this con

prec eff

sp ecializes into walk containing in its decomp o

at(a)walk(j,a,n) at(n) text

sition only the last steps of the plan plus the temp o

ral constraints sp ecifying that b oth the whole action of

...... step(i,l) step(m,n)

walking and its last steps happ ened b efore the

reference

time in Figure the decomp osition links are denoted by

the lines connecting the walkjan token to the tokens

Figure The mental mo del of John arrived to n The

representing the steps On the contrary if the sentence

stet line represents the event time of the action

to b e interpreted were John was arriving an instance

would b e built where the reference time o ccurs within

the sequence of steps that conclude the action In b oth

A planbased representation of verbs

cases the steps preceding the nal sequence are not rep

We will mainly consider verbs denoting actions that

resented but are assumed to exist on the basis of the

are intentionally executed by an agent The meaning

action instance inner relations and can b e consequently

of these verbs is represented by action schemata that

added to the representation if they b ecome relevant Ac

describ e how actions are carried out by a sequence of

cording to this representation the mental mo del of John

steps When a sentence is interpreted an action in

arrived entails the mo del of John left where in turn the

stance is built on the basis of the corresp ond

initial steps of the action walk are constrained to precede

ing to the main verb then a set of constraints express

the reference time

ing the temp oral and asp ectual information conveyed by

Therefore the presupp osition John left is not conned

the other linguistic elements asp ectual predicates ad

to a separate set of prop ositions that must b e accom

verbials verb and so on is added to this rep

mo dated in the representation as in Van Der Sandt

resentation by means of conditionaction rules Bo ella

moreover the requirement is satised that

and Damiano Temp oral constraints refer to the

presupp ositions are in some sense inserted at the

o ccurrence of the action instance with resp ect to sp eech

b eginning of the sentence interpretation Beaver

time and reference time following a reichenbachian tem

and not added or calculated afterwards as

p oral reference schema

in Karttunen Gazdar b

An action schema Act is comp osed of arguments among

On the other hand we do not face here the problem of

which the agent agt Act and the start and end time

the anaphorical character of presupp ositions exempli

of the action stAct and etAct resp ectively denot

ed in he left an hour ago but he didnt arrive where the

ing temp oral p oints the preconditions and eects of the

two clauses refer to two phases of the same underlying

action and the action decomp osition b o dyAct com

action of walking

p osed of steps the start and end time of the steps can

b e sp ecied to o

The representation of negation

Usually a mental mo del representing an action do es

We have adopted a p eculiar treatment of nega

not contain all the step instances tokens of the plan

tion in order to account for the fact that the

but only a subset of them Since steps express the fo

negated event was somehow exp ected to happ en

cused part of the action and its temp oral placement only

We interpret such exp ectations by representing them

the steps must b e included that are needed to represent

in terms of intentions attributed to the involved

the constraints resulting from the interpretation The

agent mental mo dels containing unexecuted action in

remaining steps can b e later inferred and added to the

stances can b e readily interpreted as an agents men

representation if they b ecome necessary for reasoning

tal of another agents intentional state

purp oses Moreover action schemata can b e only par

Bratman et al

tially instantiated to account for the fact that linguistic

The representation of John did not arrive includes the

expressions describ e an event by highlighting only cer

related plan instance of walking and its decomp osition

tain features of its that the sp eaker considers relevant

into steps the negation is not represented by lab eling

to his goals In our approach this corresp onds to build

the last steps in the plan instance as denied as men

ing mo dels in which only the currently relevant steps are

tal mo del theory prescrib es JohnsonLaird On

represented in order to fo cus on a sp ecic phase of the

the contrary starting from the that the walking

action or to represent the fact that the action has b een

1

action did not end b efore the reference time R all the

only partially executed

representations that include the plan instance act and

For example the interpretation of John walked to the

satisfy the constraint etact R are allowed Note that

store contains only the rst and the last steps of the plan

1

and constrains them to precede the reference time here

Otherwise we would have the representation of John ar

rived coinciding with the sp eech time on the other hand he didn’t leave he left

1 2start 3 start 4 start end walk walk walk walk

step ...step ...step step ...step ...step step ...step ...step step ...step ...step

ref time ref time ref time ref time

he didn’t arrive he arrived

Figure The relations among the mental mo dels concerning walk the thick line show whether the steps have b een

actually p erformed

this do es not imply that the walk action will necessarily The parallel b etween negation and before for what con

b e completed ie that John will arrive later cerns presupp ositions will b e examined b elow

By using mental mo dels it immediately b ecomes ap

Conversational implicature

parent that two pieces of information have to b e in

The gricean notion of conversational implicature is ex

cluded in any event description the fact that the end

ploited to explain why some of the mo dels are later dis

of the action necessarily follows the reference time and

charged In particular we will consider a particular in

given the internal constraints of the action schema the

ference licensed by the maxim of quantity the scalar

fact that the b eginning of the action precedes its conclu

implicature Gazdar a

sion Given these constraints two mo dels are p ossible

When an item b elongs to a salience order ie a scale

Schaeken et al in the former the whole action

the fact that the sp eaker has used this item instead of a

follows the reference time R in the latter some steps

dierent one in the scale causes the hearer to draw the of the action precede it

inference that the sp eaker was not in the p osition to use

mo dels

o

stact R etact

any of the higher elements of the scale see the mo del of

R etact

stact etact

Hirschb erg

R stact etact

For example from some composers died young it is p os

Actually we have to add another variable to the

sible to infer not al l composers died young even if some

mo del whether the action is conceived as partially

p er se do es not entail not al l But some b elongs to the

executed or not This concerns only the second

scale one a few some many most of al l where higher

mo delsince the part of an action preceding the reference

elements entail the lower ones If the sp eaker has used

time has certainly b een executed either the action has

some and at the same time he is assumed to resp ect the

b een or will b e executed after the reference time or it

gricean maxim of quantity this means that he cannot use

hasnt and it remains as a representation of the inten

the stronger element al l and therefore he intended to

tion of the agent

say that some comp osers last longer

So the interpretation of John did not arrive consists of

In our framework this means that an expression eg

the rst three mo dels in Figure

some is initially interpreted by means of a set of mental

Our representation of negative sentences is strictly re

mo dels and if some of them corresp ond exactly to the

lated to the meaning of the conjunction before Before

interpretation of another expression eg al l then they

do es not imply that the action in the sub ordinate clause

are discharged

actually happ ened as shown by Mozart died before n

Some A are B All A are B

ishing his Requiem As in case of negative sentences it

A

simply states an exp ectation again represented as in

A B

A B

tentions that the nish event was exp ected to o ccur at

B

a time which follows the death d

A B A B

d stact etact

A B A B

stact d etact

Mo dels discharged by

B B

the scalar implica

Note that for this before is not symmetric with

ture

A B A B

resp ect to after contrarily from what Asher and Las

A B A B

carides claim since the latter entails the execu

Arrive b elongs to a scale with resp ect to leave and the tion of b oth related actions Salieri nished Mozarts

same holds for nish and begin since in b oth cases the Requiem after he died in

former items entail the latter ones in fact the b eginning the mental mo del we have no explicit information ab out

of an action is present in every mo del representing its the conclusion of the action of writing the comp osition

conclusion The inference is then licensed by another kind of motiva

tion as we stated ab ove plan instances constitute a de

By reasoning with mental mo dels it is apparent why

scription of an agents intentions and the distinguishing

in case of negative sentences scales eg leave arrive

feature of intentions is their p ersistency Bratman et al

can b e reversed not arrive not leave The interpreta

if prevents him the agent will carry out

tion of John did not arrive pro duces three mental mo dels

his current intentions However this is a defeasible kind

see Figure two of them and also represent the

of reasoning and if more information is added the in

interpretation of John did not leave as only in stact

ference will b e canceled see Mozart died before nishing

R

his Requiem

But to describ e them the sp eaker would have more

appropriately used not leave a higher item in the scale

The pro jection problem

therefore we can discharge the rst two mo dels from the

The pro jection problem consists in explaining when and

interpretation and keep the last one

why the presupp ositions of a clause b ecome the presup

The presupp osition John left now emerges since it is con

p ositions of the whole sentence where it o ccurs

tained in all the remaining mental mo dels

We start from the pro jection problem in disjunctive sen

Note that we are assuming that the sp eaker knows

tences John has stopped smoking not only presupp oses

whether the higher elements of the scale not leave hold

John smoked but actually implies it In fact the in

or not otherwise this inference would not b e p ossible

terpretation of the asp ectual stop consists of a

Anyway the hearer usually knows whether the sp eaker

pro cess of smoking to which it is added the fact that the

has this kind of thanks to the in

agent has not b een smoking for a given p erio d of time

which the sentence is uttered

see Bo ella and Damiano

In this way the conversational implicature mechanism

Nevertheless in the sentence either John stopped smok

pro duces the presupp osition though in a rather indirect

ing or he never smoked this presupp osition do es not hold

way by deleting the mental mo dels that can b e b etter

anymore However since John smoked is implied by the

describ ed by other sentences Conversational implica

rst clause we cannot resort to the cancellability of pre

tures are a defeasible kind of inferences in presence

supp ositions

of contextual information they may disapp ear In our

A disjunction of clauses A B is represented by three

case the cancellation of the implicature prevents the re

2

mental mo dels

moval of the two mental mo dels representing the fact

A B

that John has not left therefore the presupp osition can

:A B

not b e drawn anymore In John did not arrive since he

A :B

did not leave the second clause reasserts the rst two

By substituting A with the interpretation of John

mo dels of Figure while it negates the third one

stopped smoking and B for that of John never smoked

that implies that John left In this way the basis for the

we obtain a set of p otential situations The interpreta

conversational implicature do es not hold anymore since

tion of the negated clause A consists of some mental

b oth items arrive and leave are denied

mo dels to which the interpretations of the clause B are

In case of p ositive sentences like John arrived the pre

added resulting in a set of integrated mo dels then the

supp osition b ecomes an since it is contained

conversational implicatures are applied nally the in

from the b eginning of the interpretation pro cess in the

consistent mo dels are discharged eg those in which is

only mental mo del representing the sentence interpre

asserted that John smoked and never smoked

tation in Figure and cannot b e cancelled John

John stopped smoking and never smoked

arrived but he didnt leave

John did not stop smoking and never smoked

Sentences involving before undergo the same reasoning

John stopped smoking and smoked

based on conversational implicatures From Mozart met

Now we add the entailments of the asserted rst clause

Casanova before nishing his Don Giovanni one can in

and the presupp ositions of the negated one underlined

fer that he met Casanova in the p erio d in which he was

writing his op era As stated ab ove before allows the

John stopped smoking and smoked and never smoked

construction of two mo dels One mo del represents the

and never smoked John did not stop smoking and smoked

interpretation of before he started writing his Don Gio

2

We directly esh out the explicit mo dels of the disjunc

vanni but since the sp eaker didnt use this sentence

tion in one should start from the implicit mo del

this mo del is discharged and the only mo del left is the

that contains only the p ositive information

A

one where the writing action contains the meeting event

B

Furthermore from this mo del it is p ossible to draw a

But in our example the negation conveys p ositive informa

tion ie the exp ectation that the action happ ens further inference Mozart actually nished his work In

John stopped smoking and smoked and smoked Finally we want to highlight how some inferences tra

ditionally classied as presupp ositions b ecause of their

The rst mo del is clearly contradictory and is dis

resistance to negation and cancellability can receive a

charged On the contrary in the mo del A B the pre

more accurate than as preconditions for ac

supp osition arising from a the negated disjunct has a de

tions Soames noticed the dierent b ehavior of

feasible character so it is canceled and the mo del kept

the factive verbs regret and realize in hyp othetical con

The third mo del is ne At the end of the interpretation

texts the former maintains its presupp osition that the

pro cess we have the following mental mo dels

sp eaker of the utterance b elieves that the content of the

John did not stop smoking and never smoked

sub ordinate clause holds while the latter do es not

John stopped smoking and smoked

If I regret that I told the false I wil l confess it

Do es this representation imply John smoked Certainly

If I realize that I told the false I wil l confess it

not as the two mo dels contain opp osite information

The dierence emerges when the corresp onding action

On the contrary in a sentence like either John stopped

denitions are examined In fact the precondition for

smoking or he is now il l the presupp osition that John

uttering the verb regret is that b oth the sp eaker and the

smoked is pro jected from the rst clause to the whole

describ ed agent at the event time b elieve that the sub

sentence In fact the interpretation pro duces the fol

ordinate clause p is true

lowing consistent mo dels

However on the contrary realize has the precondition

John stopped smoking and smoked and is il l

that p is true according to sp eakers b eliefs and that

and is il l John did not stop smoking and smoked

the agent who realizes do es not know it is rather the

John stopped smoking and smoked and is not il l

agents knowledge that p results from the action eect

Now all the mo dels contain the information that John

When these verbs are asserted in past tense they share

smoked so from the disjunctive sentence it is p ossible

the presupp osition that the sp eaker b elieves p in fact

to draw the inference that John smoked

the action preconditions must b e true Moreover if re

Note that the presupp ositions of the two clauses are in

alize is asserted in the rst p erson the sp eaker and the

dep endently added to the interpretation of the whole

describ ed agent coincide In the past tense this means

sentence and the single mo dels containing them are

that only after the realize event happ ened the sp eaker

discharged if inconsistent Therefore dierently from

came to know that the event preconditions were true ie

Karttunen s approach we are able to cop e with

p was true and he didnt know p Were the sentence ut

cases in which the two clauses convey contradictory pre

tered in a hyp othetical context some mental mo dels of

supp ositions as in either Fred knows hes won or hes

the description would represent the realize event as not

upset that he hasnt Beaver

happ ened in some mo dels the agent do es not come to

A linguistic context where presupp ositions do not sur

know that p has b een true from the start and that he

vive is represented by verbs like say and tel l they prevent

was not aware of it thus blo cking the conclusion that in

the pro jection of the presupp ositions of the sentential

all mo dels he is currently aware of ps

ob jects Bil l says he is not guilty do es not presupp ose

he is inno cent Karttunen has classied these

Comparison with related works

verbs as plugs in order to account for their b ehavior In

Many approaches to presupp ositions have a logical

our mo del such verbs are semantically interpreted as in

the presupp osition is interpreted as a function trans

stances of the action schema of the corresp onding sp eech

forming contexts represented as set of sets of p ossi

acts see Ardissono et al from the precondi

ble words Beaver However as JohnsonLaird

tion of the action of informing and under the sincerity

claims is not a candidate for building cogni

assumption it is p ossible to infer only that Bill b elieves

tively plausible solutions to reasoning In this work we

the prop osition he uttered while no information is given

have shown how mental mo dels can b e exploited to give

ab out the sp eakers b eliefs Therefore the semantic rep

an explicative solution to the problem of presupp ositions

resentation consists in a mental mo del of the action that

that b e also cognitively plausible

contains an emb edded mental mo del representing Bills

b elief that he is not guilty Marcu and Hirst prop ose a treatment of prag

Similarly a question p erformed by a sp eaker provides matic inferences which aims at accounting for b oth con

a context in which the presupp ositions may b e cancelled versational implicatures and presupp ositions in a single

even if there is no negation in fact the representation way They intro duce two dierent notions of satisfaction

of Did John arrive contains an instance of the linguis of a formula where the rst one is preferred in case of

tic action representing since it has the pre conicts This mechanism allows to distinguish b etween

condition that the questioner do es not know whether pragmatic inferences that can b e canceled ie conver

the prop ositional content is true two mental mo dels are sational implicatures and presupp ositions from negative

p ossible one in which John arrived and another repre sentences and those that cannot b e removed felicitously

senting John didnt arrive presupp ositions from p ositive sentences For these rea

sons dierent rules referring to dierent satisability cognitive plausibility Here we tried to show how mental

notions are needed to express the fact that the same mo dels can b e exploited to provide natural and general

presupp osition is triggered by the same lexical item in for linguistic phenomena

p ositive and negative sentences Action verb presupp ositions are ruled out as an in

Moreover they argue that a default based formalism dep endent phenomenon to reapp ear as an opp ortunis

cannot explain pragmatic inferences b ecause they are tic phenomenon stemming from the interaction of many

not always cancellable On the contrary we keep apart other factors In the rst place conversational implica

the treatment of conversational implicatures from that of ture and in the second place the reasoning on a mental

presupp ositions We exploit a single nonmonotonic form mo del representation This representation in turn re

of reasoning for mo deling implicatures while presupp o lies on a plan formalism to represent actions mental

sitions are explained by the interaction of mental mo dels mo dels oer a natural way to exploit action plans and

with scalar implicatures Furthermore we need no rules to reason on them Defeasibility of implicatures com

for deriving presupp ositions even in p ositive sentences pletes the framework causing presupp ositions to lo ok

since presupp ositions emerge from the planbased repre cancelled under certain circumstances

sentation of action verbs

Many approaches relate presupp ositions

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