We explore the work of committees that aggregate private

information of their heterogeneous members under: (a) standard monotone preference; (b) non-monotones preferences reflecting fit between

The equilibria in case (a) have a partition structure but may be non-monotone, while in case (b) they can be either ``exclusive'' or ``overlapping.'' We provide a sufficient condition for uniqueness of equilibria with a fixed number of categories bunching the members private information.

More equilibrium categories imply ex-ante better decisions. Collective mistakes are possible even under the most informative equilibrium with the highest number of categories: The committee may make decisions to the contrary of the preferences of its members. The worst mistakes are made when the committee members observe opposite signals, confirming their inherent biases.