Bayesian Non-Persuasion -- by Joshua S. Gans

Rules against persuasion often focus on beliefs: an institution should not manipulate the information on which a decision rests. We show that such rules can miss a distinct source of directional influence. An institution can steer an outcome without changing beliefs by selecting among authorised procedures that translate the same belief into different actions. Jury instructions provide the leading example: a judge may alter no juror’s assessment of the facts yet still affect the verdict through the permissible formulation of the law. The gap is sharpest near a decision threshold. There, the scope for belief movement that preserves the default action vanishes, while procedural steering can remain maximal whenever authorised procedures disagree near the boundary, even with genuinely informative communication. In general, exposure to procedural steering is the concavification of a local steering score. The geometry of Bayesian persuasion thus reappears in reverse: it measures not the value of manipulating beliefs, but the directional discretion left open by institutional rules.