A response to

Joshua Dever ’s

“Living the Life Aquatic”

and some open questions about accommodation,

from a generation perspective

Presupposition and the problem with other minds

Kees van DeemterComputing Science Department

King’s CollegeUniversity of Aberdeen

Scotland, UK

We tell our students:

– Formal semantics/pragmatics has taken a “dynamic turn”

– Meanings of sentences used to be viewed as a (static) proposition, but

– they are better viewed dynamically, thus embracing the notion of change

Motivating phenomena include anaphora and presupposition

Dever asks excellent questions:

1. What exactly does it mean for a theory to be static/dynamic?

2. Where does dynamism leave the proposition (which we know and love)?

3. Does presupposition (accommodation) force us to be dynamic?

– His question is not whether a dynamic theory is more elegant, economical, etc.

Dever’s answers (very globally)

• Interesting static reconstructions of dynamic proposals

• Cautious discussions of drawbacks that these static reconstructions might have

• As far as I can see: nothing that forces us to go dynamic

Let’s briefly revisit questions (1)-(3) above.

1. What does it mean for a theory to be static/dynamic?

STATIC (Dever): ()= [[]] for every sentence and state

• STATIC is very specific. Imagine a theory saying ()= [[]] (forgetting everything that went on before ). – This would be static but not STATIC.– INTERSECTIVE might be a better word

STATIC or static?

• Later on, Dever will effectively widen the concept of staticism, exploring some of STATIC’s close relatives.

• In some cases, one wonders whether a purely STATIC approach would have been possible. (E.g. below, point 3; the problem of gimcracks; and the treatment of accommodation)

2. Where does dynamism leave the proposition?

• Propositions won’t go away: they are what remains when is given:

[[]] is not a proposition but () is

• E.g., in Groenendijk & Stokhof’s DPL all of these survive:– proposition– truth– entailment

I agree with Dever:

Dynamism is not suspect: it’s the natural way to formalise action. Compare Hoare’s logic for programming, with rules like

(p cond){S}q (p ¬cond)→q p{if cond then S}q

3. Does presupposition accommodation force us to be dynamic?

a. “Can presupposition projection be modelled statically?”

Saul does not regret that p

presupposes

p

Dever’s response to (a)

• projection can be handled statically if the meaning of the sentence distinguishes between assertion () and presupposition () : [[]] = [[]] [[]]

[[ ]] = [[]] [[]]

• Dever views this as noncompositional

• But is this analysis not compositional in every important sense?

b. The problem of gimcracks

• Saving staticism by elaborating on it

• Example: pronominal anaphora

Dever: an attempt to treat anaphora statically:

– Lifting sets to sets of sets . Example:‘John came in’ intersects the context with the set of those sets of Reference Markers that have John as an element

Dever: this adds a nontruthconditional component to the semantics. • Not clear how bad this is• But how to link the two components?

(More work seems to be needed)

Can this approach be made STATIC?

• This is not purely STATIC, because it involves 2 intersection operations, not 1.

• Perhaps the same effect can be achieved using one intersection operation, e.g. modelling a state as a sets of pairs of the

form w, set of RMs• Plenty of room for further work

Conclusion (Part I)

• It is not obvious how to define staticism/dynamism

• A lot depends on “how compositional” we want our semantic theories to be

• It’s not clear whether truth-conditional and “binding” can be treated in one STATIC operation (i.e. based on just one intersection)

Questions to Dever:

• Q1: On balance, does presupposition (accommodation) mandate dynamism?

• Q2: What would happen if the same questions were asked about dynamic analyses of imperatives such asx:=0 (ok, that’s easy)

Questions to Dever:

• Q1: On balance, does presupposition (accommodation) mandate dynamism?

• Q2: What would happen if the same questions were asked about dynamic analyses of imperatives such asx:=0 (ok, that’s easy)x:=x+1Eat an apple a day

How crucial is accommodation to Dever’ story?

• I’ve mentioned anaphora and presupposition• But how about accommodation? Consider

an utterance . Two options:

1. Don’t accommodate. (Dever)– test whether holds in – if not then CRASH,

else interpret according to STATIC

Dever’s verdict: this is only a mild deviation from STATIC

2. Second option: Accommodate.

a. If is consistent with thenperform STATIC, computing [[]] [[]]

b. Otherwise perform belief revision, throwing away enough of , until ’ is consistent with , then compute ’ [[]] [[]]. My verdict: This does look seriously non-static.

If accommodation involves belief revision then maybe this is a knock-down argument for dynamics. (But if so, then note that the assertion can also be inconsistent with , which would also trigger belief revision.)

Question to Dever:• Q3: Is accommodation more of a challenge to

staticism than presupposition? Does belief revision play a role in your answer?

Reconciliation between staticism and dynamism raises questions:

• Should we stop worrying about the distinction?

• Problems about accommodation that existing theories do not help us with:– When is it ok for a speaker to rely on

accom? – Why is accom not marked explicitly?

A (much too naive!) generation perspective

• Suppose Speaker believes A. S wants A’ A to be known by Hearer– What parts of A’ should be asserted?

– Which presupposed?

• Heim 1992: “assumptions to be accommodated are supposed to be uncontroversial and unsurprising”1. Too restrictive: why exclude belief revision

(see above)?

2. Too liberal:

• S= ‘It was John who borrowed my bicycle’ p= borrowed my bicycle. Can I say S if ...

– I believe you believe p? No– I believe you do not know whether p? No– I don’t know whether you know whether p? No

• Some thoughts, focussing on generation of referring expressions

1. Knowing something in principle

• The dychotomy between knowing and not knowing hides some important issues

Example: reference

Suppose we’re having a conversation.

Suppose I see a football while you don’t.

Example: reference

I see a football while you don’t.

Can I say Please give me the football? No

Can I say Please give me the football behind you ?Yes

• Ivandre Paraboni et al. (e.g., INLG-2002, INLG-2006): empirical/algorithmic investigation into the effects of adding “redundant” information on– acceptability of a referring expression– effort involved in finding the referent

Lack of Orientation (LO)

Univ. of Aberdeen

Meston building Taylor building

North Wing South Wing North West South

library libraryauditorium

“the West Wing”

Dead End (DE)

Univ. of Aberdeen

Meston building Taylor building

North Wing ? South Wing North West South

library libraryauditorium

“the library in the North

Wing”

• Paraboni et al. experimentally explore how much “redundant” information is optimal

• Corollary: Sometimes it’s less egocentricto let the hearer accommodate more!

( pace Evans 2005, cf. Lyn Frazier’s paper )

• Presuppositions are expressed for a purpose (e.g., allowing hearer to find the referent)

2. Egocentricity

• Children can reason about other minds from at least age 6

• Yet even adults often do not use this ability (experiments by Keysar et al.)

• The simplest experiment:– hearer sees three candles of different sizes– speaker does not see the largest one– hearer knows this– speaker says “Pick up the large candle”

This candle not seen by speaker

This candle not seen by speaker

“Pick up the large candle”

Egocentricity

• Results (Keysar, Barr, Balin and Brauner 2000)

– hearers often grab the largest of the three, even though they know the speaker cannot see it

– hearers’ interpretation of these utterances is delayed

• Similar in other experiments (Keysar, Lin, and Barr 2003)

Egocentricity

• Accommodation may result from speaker’s egocentricity

• Need to understand when and why speakers are egocentric. – e.g., addressing a varied audience?

• Formal models of shared information (as used in NLG) need to become more sophisticated

3. Handling uncertainty

• Jean Carletta (1992) “Risk-taking and recovery in task-oriented dialogue”

• MAPTASK experiment: Dialogues between two people looking at a map with landmarks (e.g., ‘the swamp’, ‘the cactus’)– Route giver: map with route– Route follower: map without route

• Task: giver lets follower draw the route• One version of experiment lets them have

different sets of landmarks!

Carletta’s observations

• Speakers use different “gambling” strategies

• One strategy: High risk posture: – assume that partner has same information– specify referents minimally– rely on follow-up dialogue

• mismatches trigger negotiations, e.g. replanning (cf. J.Moore 1990).

Conclusions (Part II)

• The main gaps in our understanding of presupposition and accommodation now involve generation

• Issues:– The concept of knowledge (Paraboni et al.)– Egocentricity (Keysar et al.)– Handling uncertainty and “gambling”

(Carletta, based on Maptask)

Back to Josh Dever

• Ice-age semantics

Back to Josh Dever

• Ice-age semantics

• permafrost semantics

Back to Josh Dever

• Ice-age semantics

• permafrost semantics

• aquatic semantics

What next?

Back to Josh Dever

• Ice-age semantics

• permafrost semantics

• aquatic semantics

What next? Global warming might cause ...

• steamy semantics

Over to others ...

additional slides

• (to be kept in reserve)

dynamics in adjectives

• Dever observes that few people are scared of dynamism as a theory of adjectives:

[[large N]] [[large]] [[N]]

• A static account: [[large]] is initially determined by some “general-purpose” comparison set. Later material (such an N) changes this general-purpose interpretation.

• Empirical support: Sedivy et al. 1999’s attempt to reconcile English word order with incremental interpretation

Treating RMs declaratively

[ 2. Making the existence of a reference marker explicit, restricting to states in which there exists a peg for an individual called John.

Dever: This fails to account for the fact that claims of this kind have to be true.

E.g.: You cannot respond to ‘John is tall’ saying ‘No’ , meaning ‘There is no peg for a person named John.’ ]

Illustrating Heim’s qualification

• My cousin is talking to me about a camera once owned by her brother (whom I believe to be alive and well): “I inherited this camera from Jaap”

• ‘inherit’ can be taken literally or figuratively• In both senses, it presupposes that Jaap

once owned the camera, but ...• ... the literal interpretation could not have

been intended!