Cass Sunstein (with Harvard's Edward L. Glaeser) recently posted a new paper to SSRN, entitled "Extremism and Social Learning." The abstract is below, and the whole paper is available here.
Extremism and Social Learning
EDWARD L. GLAESER
Harvard University - John F. Kennedy School of Government - Department of Economics; Brookings Institution; National Bureau of Economic Research (NBER)
CASS R. SUNSTEIN
University of Chicago - Law School December 2007
U of Chicago Law & Economics, Olin Working Paper No. 375
U of Chicago, Public Law Working Paper No. 193
When members of deliberating groups speak with one another, their predeliberation tendencies often become exacerbated as their views become more extreme. The resulting phenomenon - group polarization - has been observed in many settings, and it bears on the actions of juries, administrative tribunals, corporate boards, and other institutions. Polarization can result from rational Bayesian updating by group members, but in many contexts, this rational interpretation of polarization seems implausible. We argue that people are better seen as Credulous Bayesians, who insufficiently adjust for idiosyncratic features of particular environments and put excessive weight on the statements of others where there are 1) common sources of information; 2) highly unrepresentative group membership; 3) statements that are made to obtain approval; and 4) statements that are designed to manipulate. Credulous Bayesianism can produce extremism and significant blunders. We discuss the implications of Credulous Bayesianism for law and politics, including media policy and cognitive diversity on administrative agencies and courts.