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arxiv: 2605.28265 · v1 · pith:36SONXZZnew · submitted 2026-05-27 · 💰 econ.TH

Robustness of Persuasion to Receiver Preferences

Pith reviewed 2026-06-29 09:26 UTC · model grok-4.3

classification 💰 econ.TH
keywords Bayesian persuasionrobustnesscontinuityKnightian uncertaintypreference uncertaintygenericityinformation design
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The pith

Bayesian persuasion is continuous and robust to small preference uncertainty exactly when the two properties coincide, and both hold generically.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper distinguishes two responses to uncertainty about the receiver's preferences in Bayesian persuasion. Continuity means the modeler's predictions remain accurate even without precise knowledge of preferences. Robustness means the sender's chosen outcome stays the same despite the sender's own ignorance. Modeling this uncertainty as infinitesimally small Knightian uncertainty and letting the sender either minimize regret or maximize minimum utility, the authors establish that the two properties are logically equivalent and that each holds for a generic set of persuasion problems. This matters because it separates atypical fragile cases from the typical ones that remain stable under minor ignorance.

Core claim

We show that continuity holds if and only if robustness holds, and that both notions are generic. Thus, while some instances of Bayesian persuasion are fragile, typical instances are both continuous and robust with respect to a small amount of ignorance.

What carries the argument

The logical equivalence between continuity and robustness under infinitesimal Knightian uncertainty about receiver preferences, together with the genericity of both properties in the space of persuasion problems.

Load-bearing premise

Preference uncertainty is modeled as infinitesimally small, non-probabilistic Knightian uncertainty, with the sender either minimizing regret or maximizing minimum utility.

What would settle it

A concrete Bayesian persuasion instance in which continuity holds but robustness fails, or a demonstration that the set of problems satisfying both properties fails to be dense.

Figures

Figures reproduced from arXiv: 2605.28265 by Fengming Hu, Rann Smorodinsky, Ronen Gradwohl.

Figure 1
Figure 1. Figure 1: Example 1, sender’s indirect utility as a function of [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Example 2, utilities of the receiver. at which the receiver is indifferent among three actions, a1, a2, and a3 (the red solid point in Figure 2b). Moreover, this posterior is the unique belief at which a2 is a best response. Finally, the viability of action a2 is fragile: for some of the utility realizations of the receiver it is never played. A naive modeler, working under complete information (δ = 0), pr… view at source ↗
Figure 3
Figure 3. Figure 3: Example 2, sender’s indirect utilities under two realizations [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Partition of the simplex at θ0 and its three perturbations. In the next step, we use a reusable technical device—the adjustment signal policy— which will also play a role in proving later results (detailed in Appendix A). The intuition is as follows. In general, an optimal policy for one type of receiver may be suboptimal for 6Throughout, we use the terms upper and lower semicontinuous for real-valued func… view at source ↗
Figure 5
Figure 5. Figure 5: Partition of the simplex at (a) Original type: [PITH_FULL_IMAGE:figures/full_fig_p016_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Motivation for the adjustment signal policy [PITH_FULL_IMAGE:figures/full_fig_p026_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: lower-dimension set in R 2 (a): A point, the 0-dimensional case (b): A segment, the 1-dimensional case. Among the implicit equalities, those defining the simplex, are therefore linear indepen￾dent. By Corollary 1, the implicit equalities are linear dependent. Thus, at least one of the equality defines the best-response constraints. For that equality, we find the other action b, satisfying B∗ θ (a) ⊂ B∗ θ (… view at source ↗
read the original abstract

We study the robustness of Bayesian persuasion to uncertainty about the receiver's preferences. We analyze two conceptually distinct notions: continuity, in which only the modeler lacks precise knowledge, but where the model's predictions are nonetheless accurate; and robustness, in which the sender also lacks precise knowledge, but where the outcome is insensitive to this ignorance. We model preference uncertainty as infinitesimally small, non-probabilistic (Knightian) uncertainty, and the sender's behavior as either minimizing the regret or maximizing the minimum utility. We show that continuity holds if and only if robustness holds, and that both notions are generic. Thus, while some instances of Bayesian persuasion are fragile, typical instances are both continuous and robust with respect to a small amount of ignorance.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The paper claims that in Bayesian persuasion, two notions of robustness to receiver preference uncertainty—continuity (accurate predictions despite modeler ignorance) and robustness (sender outcomes insensitive to sender ignorance)—are equivalent, and that both hold generically, when preference uncertainty is modeled as infinitesimally small Knightian uncertainty and the sender either minimizes regret or maximizes minimum utility. Thus typical instances are both continuous and robust.

Significance. If the equivalence and genericity results hold under the stated assumptions, the paper provides a positive characterization showing that fragility is nongeneric in Bayesian persuasion. This is a clean mathematical contribution; credit is due for establishing the if-and-only-if link and the genericity argument in an appropriate topology on preference spaces.

major comments (1)
  1. [Introduction and §3 (main result)] The central equivalence and genericity claims are derived under the specific modeling of infinitesimal non-probabilistic uncertainty together with min-regret or max-min sender behavior. The manuscript should explicitly state whether the equivalence is an artifact of this behavioral assumption or holds more broadly; if the former, the scope of the 'typical instances are robust' conclusion needs to be qualified in the introduction and conclusion.
minor comments (2)
  1. [§2 (model)] Clarify the precise topology used to define 'generic' in the space of receiver preferences; this is essential for interpreting the genericity claim.
  2. [§2] Ensure that the definitions of continuity and robustness are stated formally before the equivalence theorem, with explicit reference to the sender's objective functions.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive comment on clarifying the scope of our results. We address the point below and will incorporate a minor revision to qualify the claims in the introduction and conclusion.

read point-by-point responses
  1. Referee: [Introduction and §3 (main result)] The central equivalence and genericity claims are derived under the specific modeling of infinitesimal non-probabilistic uncertainty together with min-regret or max-min sender behavior. The manuscript should explicitly state whether the equivalence is an artifact of this behavioral assumption or holds more broadly; if the former, the scope of the 'typical instances are robust' conclusion needs to be qualified in the introduction and conclusion.

    Authors: The equivalence between continuity and robustness, as well as the genericity result, are derived specifically under infinitesimal Knightian uncertainty together with the sender's min-regret or max-min behavior; these are the modeling choices adopted throughout the analysis. We do not claim the equivalence holds for arbitrary sender objective functions, and we will revise the introduction and conclusion to state this limitation explicitly, qualifying the conclusion that typical instances are both continuous and robust. revision: yes

Circularity Check

0 steps flagged

No circularity; equivalence is a direct proof under explicit modeling assumptions

full rationale

The paper proves that continuity holds iff robustness holds (and both are generic) by modeling preference uncertainty as infinitesimal Knightian uncertainty with the sender using min-regret or max-min utility. This is a standard mathematical derivation under stated assumptions; the equivalence does not reduce to self-definition, fitted parameters renamed as predictions, or load-bearing self-citations. The modeling choices are declared upfront and are not smuggled in via prior work. The result is self-contained as a theorem in the given framework.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The paper relies on standard mathematical continuity concepts and domain-specific behavioral assumptions for the sender under Knightian uncertainty; no free parameters or new entities are introduced.

axioms (2)
  • standard math Standard mathematical definitions of continuity and robustness applied to Bayesian persuasion outcomes.
    Invoked to define the two notions whose equivalence is proven.
  • domain assumption Sender behavior is either regret minimization or max-min utility under Knightian uncertainty.
    This behavioral model is used to formalize robustness.

pith-pipeline@v0.9.1-grok · 5647 in / 1198 out tokens · 27780 ms · 2026-06-29T09:26:00.079736+00:00 · methodology

discussion (0)

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Reference graph

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    Now he knows that the receiver is indeed ofθ 2, and he knows that there existµ ′ 1 = 0.49 andµ ′ 2 = 0.501, which are very close toµ 1 andµ 2, and satisfyv(µ i, θ) =v(µ i, θ2),∀i≤2

    His expected utility here is 1 4 ×1 + 3 4 ×0.97 = 0.9775. Now he knows that the receiver is indeed ofθ 2, and he knows that there existµ ′ 1 = 0.49 andµ ′ 2 = 0.501, which are very close toµ 1 andµ 2, and satisfyv(µ i, θ) =v(µ i, θ2),∀i≤2. If he neither chooses to deduce the new optimal signal policy, nor applies the adjustment signal policy, but just upd...

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    X ω∈Ω v(a, ω)µk j (ω) # ≥ X j≤I k X ω∈Ω v(ak, ω)βk j µk j (ω) = X ω∈Ω v(ak, ω) X j≤I k βk j µk j (ω) = X ω∈Ω v(ak, ω)µk(ω) = max a∈optA(µk)

    There exists aγ-adjustmentbπ θ′ ofπ θ′—the optimal signal policy atθ ′—with the fol- lowing properties: Evθ′(πθ′)≤Ev θp(bπθ′) +D(γ)≤Ev θp(optΠ(θp)) +D(γ). Proof.Note thatθ 0 is an interior type of theδ-BP model wrapping it. For anyδ >0 and anyδ-BP model, chooseδ ∗ >0 small enough so that the typeθ ′ defined below belongs to theδ-BP model. Sincev(a, ω)∈[0,...

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    Letθ 1 andθ 2 be two types such thatB θ1(a), Bθ2(a)̸=∅, ifmax x∈B∗ θ1(a) miny∈B ∗ θ2(a) ||x− y||2 ≤γ, thenmax x∈Bθ1(a) miny∈Bθ2(a) ||x−y|| 2 ≤(1 + √ N−1)γ. 14For any setBand anyx 0 ∈B, define the linear subspaceL:= span{x−x 0 :x∈B}. The dimension of Bis defined by the linear dimension ofL, dim(B) := dim(L). This definition is independent of the choice of ...

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    Third,we establish the stability of contracted system

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    If the first one is true, there existsδ 1 such that theδ 1 ball aroundx 1 satisfies that for anyx∈B δ1(x1),⟨c, x⟩< d

    there exists a pointx 2 ∈ {C =,−1x=D =,−1}such that⟨c, x 2⟩=d. If the first one is true, there existsδ 1 such that theδ 1 ball aroundx 1 satisfies that for anyx∈B δ1(x1),⟨c, x⟩< d. Notice thatx 1 ∈B δ1(x1)∩ {x|C =,−1x=D =,−1}, and so we have B δ1(x1)∩ {x|C =,−1x=D =,−1}is theδ 1 ball aroundx 1 in the subspace defined by {x|C=,−1x=D =,−1}. Also, B δ1(x1)∩ ...