Documentation

Studies.Warstadt2022

Warstadt (2022): Presupposition Triggering Reflects Pragmatic Reasoning About Utterance Utility #

Warstadt derives soft presupposition triggers from a listener's inference about the common ground the speaker assumed. The model is Qing, Goodman and Lassiter's. Within a context set the literal listener conditions the prior on the utterance and answers the question under discussion (L0), the speaker is informative about the answer at her world and says nothing false there (speaker), and the pragmatic listener inverts the speaker jointly over worlds and context sets (listener).

Main results #

Implementation notes #

TODO #

References #

The model (3) #

def Warstadt2022.weight {W U Q : Type} [DecidableEq W] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) [(u : U) → DecidablePred fun (x : W) => x ∈ sem u] (C : Finset W) (q : Q) (u : U) (w : W) :
ℕ × ℕ

The speaker's weight on an utterance at a world before the rationality exponent (3c), as a numerator and a denominator. Where the utterance is true it is the literal listener's probability of the world's answer, the prior weight of the context-set worlds that make the utterance true and share the answer over that of those that make it true. Where it is false it is 0 over 1.

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  • Warstadt2022.weight P cell sem C q u w = if w ∈ sem u then (∑ v ∈ {x ∈ C | x ∈ sem u} with cell q v = cell q w, P v, ∑ v ∈ C with v ∈ sem u, P v) else (0, 1)
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    noncomputable def Warstadt2022.pairPrior {W : Type} [DecidableEq W] [MeasurableSpace W] (P : W → ℕ) :
    MeasureTheory.Measure (W × Finset W)

    In the prior over pairs of a world and a context set (3d), a world's weight within a context set is its prior share of the set, and context sets are equally likely.

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    • Warstadt2022.pairPrior P = MeasureTheory.Measure.count.withDensity fun (p : W × Finset W) => if p.1 ∈ p.2 then ↑(P p.1) / ∑ v ∈ p.2, ↑(P v) else 0
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      theorem Warstadt2022.pairPrior_singleton {W : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] (P : W → ℕ) (w : W) (C : Finset W) :
      (pairPrior P) {(w, C)} = if w ∈ C then ↑(P w) / ∑ v ∈ C, ↑(P v) else 0
      theorem Warstadt2022.pairPrior_singleton_le_one {W : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] (P : W → ℕ) (w : W) (C : Finset W) :
      (pairPrior P) {(w, C)} ≤ 1
      theorem Warstadt2022.pairPrior_real {W : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] (P : W → ℕ) (w : W) (C : Finset W) :
      (pairPrior P).real {(w, C)} = if w ∈ C then ↑(P w) / ∑ v ∈ C, ↑(P v) else 0
      instance Warstadt2022.instIsFiniteMeasureProdFinsetPairPrior {W : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] (P : W → ℕ) :
      MeasureTheory.IsFiniteMeasure (pairPrior P)
      noncomputable def Warstadt2022.L0 {W U Q : Type} [Fintype W] [MeasurableSpace W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (C : Finset W) (q : Q) :
      ProbabilityTheory.Kernel U (Finset W)

      The literal listener within a context set (3a) conditions the prior on the context set and on the utterance, and answers the question.

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        instance Warstadt2022.instIsFiniteKernelFinsetL0 {W U Q : Type} [Fintype W] [MeasurableSpace W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (C : Finset W) (q : Q) :
        ProbabilityTheory.IsFiniteKernel (L0 P cell sem C q)
        noncomputable def Warstadt2022.speaker {W U Q : Type} [Fintype W] [MeasurableSpace W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (C : Finset W) (q : Q) (α : ℝ) (w : W) :
        MeasureTheory.Measure U

        The speaker within a context set (3b) is informative about the answer at her world, with no cost, and says nothing false there (3c).

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          instance Warstadt2022.instIsFiniteMeasureSpeaker {W U Q : Type} [Fintype W] [MeasurableSpace W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (C : Finset W) (q : Q) (α : ℝ) (w : W) :
          MeasureTheory.IsFiniteMeasure (speaker P cell sem C q α w)
          noncomputable def Warstadt2022.share {W U Q : Type} [Fintype W] [MeasurableSpace W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (C : Finset W) (q : Q) (u : U) (w : W) (α : ℝ) :
          ℝ

          The share of an utterance at a world within a context set, on reals.

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            noncomputable def Warstadt2022.listener {W U Q : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (q : Q) (α : ℝ) :
            ProbabilityTheory.Kernel U (W × Finset W)

            The pragmatic listener (3d) inverts the speaker jointly over worlds and context sets, given the question.

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              def Warstadt2022.worldEvent {W : Type} [DecidableEq W] [Fintype W] (w : W) :
              Finset (W × Finset W)

              The pairs whose world is w.

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                theorem Warstadt2022.listener_worldEvent_lt_iff {W U Q : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] (P : W → ℕ) (cell : Q → W → Finset W) (sem : U → Set W) (q : Q) {α : ℝ} {u : U} (w₁ w₂ : W) :
                ((listener P cell sem q α) u).real ↑(worldEvent w₁) < ((listener P cell sem q α) u).real ↑(worldEvent w₂) ↔ ∑ C : Finset W, (pairPrior P).real {(w₁, C)} * share P cell sem C q u w₁ α < ∑ C : Finset W, (pairPrior P).real {(w₂, C)} * share P cell sem C q u w₂ α

                The listener's preference between two worlds, marginalizing the context set, is the comparison of prior-weighted speaker shares summed over context sets.

                theorem Warstadt2022.L0_apply {W U Q : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] {P : W → ℕ} {cell : Q → W → Finset W} {sem : U → Set W} {C : Finset W} {q : Q} [(u : U) → DecidablePred fun (x : W) => x ∈ sem u] [DiscreteMeasurableSpace W] {u : U} {w : W} (h : w ∈ sem u) :
                ((L0 P cell sem C q) u) {cell q w} = ↑(weight P cell sem C q u w).1 / ↑(weight P cell sem C q u w).2
                theorem Warstadt2022.L0_apply_eq_one_iff {W U Q : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] {P : W → ℕ} {cell : Q → W → Finset W} {sem : U → Set W} {C : Finset W} {q : Q} [(u : U) → DecidablePred fun (x : W) => x ∈ sem u] [DiscreteMeasurableSpace W] {u : U} {w : W} (h : w ∈ sem u) (hC : w ∈ C) (hP : P w ≠ 0) :
                ((L0 P cell sem C q) u) {cell q w} = 1 ↔ (weight P cell sem C q u w).1 = (weight P cell sem C q u w).2

                At a context-set world of positive prior where the utterance is true, the literal listener is certain of the answer exactly when the two components of the weight agree.

                theorem Warstadt2022.share_eq {W U Q : Type} [DecidableEq W] [Fintype W] [MeasurableSpace W] [MeasurableSingletonClass W] [Fintype U] [MeasurableSpace U] [MeasurableSingletonClass U] {P : W → ℕ} {cell : Q → W → Finset W} {sem : U → Set W} {C : Finset W} {q : Q} [(u : U) → DecidablePred fun (x : W) => x ∈ sem u] [DiscreteMeasurableSpace W] {u : U} {w : W} {α : ℝ} (hα : 0 < α) :
                share P cell sem C q u w α = (↑(weight P cell sem C q u w).1 / ↑(weight P cell sem C q u w).2) ^ α / ∑ u' : U, (↑(weight P cell sem C q u' w).1 / ↑(weight P cell sem C q u' w).2) ^ α

                The share of an utterance is its weight, raised to the rationality, among those of all utterances.

                The green card scenario (Table 1) #

                Tom is a US citizen, a green card holder, or a non-US citizen without a green card.

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                  @[instance_reducible]
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                  def Warstadt2022.instReprWorld.repr :
                  World → ℕ → Std.Format
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                    @[instance_reducible]
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                    @[instance_reducible]
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                    Silence, US citizen, not US citizen, green card, not green card.

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                      • One or more equations did not get rendered due to their size.
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                        Does Tom need a visa? Can Tom get a free drink?

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                          @[instance_reducible]
                          instance Warstadt2022.instDecidableEqQUD :
                          DecidableEq QUD
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                          def Warstadt2022.instReprQUD.repr :
                          QUD → ℕ → Std.Format
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                            The answer of a world to a question.

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                              def Warstadt2022.QUD.cell (q : QUD) (w : World) :
                              Finset World

                              The cell of a world holds the worlds with the same answer.

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                                def Warstadt2022.nonUSSets :
                                List (Finset World)

                                The context sets containing the non-US world, and those containing the US-citizen world.

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                                • One or more equations did not get rendered due to their size.
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                                  def Warstadt2022.usSets :
                                  List (Finset World)
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                                  • One or more equations did not get rendered due to their size.
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                                    The uniform world prior.

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                                      Not green card settles the free-drink question in every context set, since at a world where it is true the literal listener is certain of the answer.

                                      It does not settle the visa question. In the universe the literal listener gives the US-citizen world's answer probability one half, while within the context set that Tom is not a US citizen he is certain of the non-US world's answer.

                                      Shares #

                                      The listener over worlds #

                                      noncomputable def Warstadt2022.gcListener (q : QUD) (α : ℝ) :
                                      ProbabilityTheory.Kernel Utterance (World × Finset World)

                                      The joint listener of the green card scenario.

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                                        With the question whether Tom needs a visa, not green card makes the listener favour the non-US world over the US-citizen world at every rationality. Within the context set that Tom is not a US citizen the utterance answers the question, whereas at the US-citizen world US citizen always answers it at least as well (Figure 1).

                                        With the question whether Tom gets a free drink, not green card is an exhaustive answer in every context set, yet the listener still favours the non-US world. At the US-citizen world US citizen is an equally good answer, so the utterance's share there never exceeds a half (Figure 2 reports the two posteriors as nearly equal).

                                        The family-genus-species scenario (Table 2) #

                                        Tom is an Olympic sprinter, another runner, another athlete, or none of these.

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                                          def Warstadt2022.instReprHobby.repr :
                                          Hobby → ℕ → Std.Format
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                                            The three predicates, affirmed or negated, and silence.

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                                                def Warstadt2022.which :
                                                Unit → (w : Hobby) → Finset Hobby

                                                Under the question which world it is, every cell is a singleton.

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                                                  Not an Olympic sprinter settles the question at the runner world exactly within context sets that exclude the athlete and the non-athlete world, so the accommodation the paper describes is of a common ground in which Tom is a runner or a sprinter.

                                                  Not a runner settles the question at the athlete world exactly within context sets that exclude the non-athlete world.

                                                  At the non-athlete world in the universe, not an Olympic sprinter is produced more often than silence but less often than not a runner, which loses to not an athlete. Olympic sprinters are rare, so denying that Tom is one says little (4).