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Linglib.Phenomena.Presupposition.Studies.ScontrasTonhauser2025

@cite{scontras-tonhauser-2025} #

Projection emerges from RSA over speaker's private assumptions, not lexical presupposition. L1 jointly infers world state and speaker's belief state.

The Model (Section 3) #

Domain: 6 utterances × 4 worlds × 15 belief states × 2 QUDs. α = 10.

Section 3 Parameters (fn. 12) #

Cost (complex = 2×simple) is omitted: exp(−αC) with α = 10 introduces irrational numbers incompatible with ℚ arithmetic. Cost omission affects S1's normalization even for same-cost comparisons, reversing the direction of prediction (2a); the full model with cost predicts know > think (Figure 7a). Predictions (2b) and (2c) are robust to cost omission.

Factive Semantics #

Literal truth conditions derive from Semantics.Attitudes.Factivity: know = factivePos (BEL ∧ C), think = nonFactivePos (BEL).

Key Structural Insight #

Under QUD=BEL?, L1's world-marginal P(C|u) = P(C) for all utterances — a mathematical identity. S1 scores depend on w only through w.bel, so the complement dimension washes out in the marginal. Prediction 2b (prior effect) therefore comes from the C? QUD condition; prediction 2c (QUD effect) compares the uninformative BEL? marginal against the C? marginal.

BToM Connection #

This is a BToM model: L1 inverts S1's generative model to jointly infer the speaker's belief state and the world state.

Experimental Results #

Exp 1 confirms (2a) utterance effect (β = 0.35, p < .001) and (2b) prior effect (β = 0.16, p < .001). The QUD manipulation was not significant (β = 0.009, p = .75). Exp 2 confirms (2a) utterance effect (β = 0.34, p < .001) and (2c) QUD effect (β = 0.14, p < .001) with a stronger QUD manipulation. Exp 2 did not manipulate prior probability.

Connection to @cite{degen-tonhauser-2021} #

The prior effect (prediction 2b) replicates the core finding of @cite{degen-tonhauser-2021}: higher prior probability of complement content leads to stronger projection. D&T 2021 demonstrate this across 20 predicates with β = 0.14 (categorical) / β = 0.28 (individual-level). S&T 2025's RSA model provides the theoretical explanation: L1's Bayesian inference naturally incorporates prior beliefs, so higher priors yield higher posteriors.

World state: (BEL, C) where BEL = Cole believes C, C = complement is true. Flat inductive for tactic enumerability.

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      Attitude verb utterances about Cole's mental state, plus bare complement assertions.

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          Speaker's private assumptions: all 15 non-empty subsets of W. Section 3 follows @cite{qing-goodman-lassiter-2016}: A ranges over all non-empty subsets of the world space.

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              Membership in belief state. Boolean operations on WorldState fields reduce cleanly for rsa_predict.

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                QUD aggregation: sums L0 probabilities over the QUD equivalence class of w. Named qudAggregate to distinguish from Factivity.qudProject (the equivalence relation, not the aggregation).

                • BEL? QUD: partitions by BEL → sums over same-BEL worlds
                • C? QUD: partitions by C → sums over same-C worlds
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                  RSA model for Section 3: uniform prior over all 15 belief states, QUD-projected rpow scoring, α = 10.

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                    @[reducible, inline]

                    QUD=BEL?, P(C)=2/3.

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                      @[reducible, inline]

                      QUD=BEL?, P(C)=1/3.

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                        @[reducible, inline]

                        QUD=C?, P(C)=2/3.

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                          QUD=C?, P(C)=1/3.

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                            Under BEL? QUD, L1's world-marginal for C equals the prior P(C) for every utterance. S1 scores depend on w only through w.bel, so the complement dimension washes out in the marginal:

                            L1_marginal(C|u, BEL?) = Σ_{w:C(w)} P(w)·f(u,w.bel) / Σ_w P(w)·f(u,w.bel) = (pC/2)·(f₁+f₀) / ((1/2)·(f₁+f₀)) = pC.

                            Same identity for the low-prior configuration: P(C|u, BEL?) = P(C) = 1/3.

                            Under C? QUD, knowNeg is evidence AGAINST C: ¬(BEL∧C) is literally compatible with C-false worlds, so an informative speaker uses knowNeg more often when C is false. Thus thinkNeg preserves P(C) better.

                            Prediction 2a: Utterance Effect (know > think) #

                            The paper predicts stronger projection for factive know than non-factive think (Figure 7a). The full Section 3 model — including utterance cost (complex = 2×simple) — produces this direction via the world-marginal. Our cost-free model does not:

                            The reversal is due to cost omission, which changes S1's normalization. With cost, simple utterances (cPos, cNeg) dominate S1's softmax via exp(−α·C_simple) ≫ exp(−α·C_complex), altering which (world, belief state) combinations favor knowNeg vs thinkNeg in L1's posterior.

                            The paper also notes (fn. 11) that projection can be measured via the A-marginal P(A ⊧ C | u) — the probability that the speaker's inferred belief state entails C. This measure may capture the utterance effect even without cost, since the mechanism works through belief state inference rather than world-marginal.

                            Prediction 2b (prior effect): higher prior increases projection. Under C? QUD, L1 assigns higher probability to C with P(C) = 2/3 than with P(C) = 1/3.

                            Prediction 2c (QUD effect): BEL? QUD increases projection over C? QUD. Under BEL? QUD, C is not at-issue and L1_marginal(C) = P(C) = 2/3. Under C? QUD, the literal semantics of "doesn't know C" (= ¬(BEL∧C)) lowers P(C) from the prior, so BEL? > C?.

                            knowNeg is compatible with strictly more worlds than thinkNeg (3 vs 2), making it the weaker (less informative) negation.

                            Exactly 3 of 15 belief states assume C: onlyW11, onlyW01, cTrue.

                            Effect size from a linear mixed-effects model. p values are upper bounds (paper reports "< .001").

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                                Exp 1: Prior effect (higher > lower).

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                                  Exp 1: QUD effect (NOT significant — manipulation too weak).

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                                    Exp 2: QUD effect (significant with stronger manipulation).

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                                          Belief states that don't assume C have indicator 0.

                                          The prior effect found by S&T 2025 (β = 0.16) replicates the prior effect found by @cite{degen-tonhauser-2021} (β = 0.14 categorical, β = 0.28 individual). Both find that higher prior probability of the complement content leads to stronger projection. The RSA model's prediction_2b provides the theoretical explanation for this empirical finding.