An Experimental Study of Collective Deliberation

We study the e¤ects of deliberation on collective decisions. In a series of experiments, we vary groups’preference distributions (between common and con‡icting interests) and the institutions by which decisions are reached (simple majority, two-thirds majority, and unanimity). Without deliberation, di¤erent institutions generate signi…cantly di¤erent outcomes, tracking the theoretical comparative statics. Deliberation, however, signi…cantly diminishes institutional di¤erences and uniformly improves e¢ ciency. Furthermore, communication protocols exhibit an array of stable attributes: messages are public, consistently reveal private information, provide a good predictor for ultimate group choices, and follow particular (endogenous) sequencing. JEL classi…cation: C92, D02, D72 Keywords: Jury Decision Making, Deliberative Voting, Strategic Voting. Goeree: Chair for Organizational Design, University of Zürich, Blümlisalpstrasse 10, CH-8006, Zürich, Switzerland. Yariv: Division of the Humanities and Social Sciences, California Institute of Technology, Mail code 228-77, Pasadena, CA 91125, USA. We thank the editor, Larry Samuelson, and three anonymous referees for very helpful comments. We also thank Gary Charness, Guillaume Frechette, Dino Gerardi, John Kagel, Alessandro Lizzeri, Tom Palfrey, and Lise Vesterlund for many useful conversations and suggestions. Lauren Feiler, Salvatore Nunnari, and Julian Romero provided us with superb research assistance. We gratefully acknowledge …nancial support from the National Science Foundation (SES 0551014) and the European Research Council (ERC Advanced Grant, ESEI-249433). An Experimental Study of Collective Deliberation 1