This article proposes a new statistical method to measure persuasion within small groups, and applies this approach to a large-scale randomized deliberative experiment. The authors define the construct of ‘persuasion’ as a change in the systematic component of an individual's preference, separate from measurement error, that results from exposure to interpersonal interaction. Their method separately measures persuasion in a latent (left–right) preference space and in a topic-specific preference space. The model's functional form accommodates tests of substantive hypotheses found in the small-group literature. The article illustrates the measurement method by examining changes in study participants' views on US fiscal policy resulting from the composition of the small discussion groups to which they were randomly assigned. The results are inconsistent with the ‘law of small-group polarization’, the typical result found in small-group research; instead, the authors observe patterns of latent and policy-specific persuasion consistent with the aspirations of deliberation.
