  Phenomena which involves collective choice of many agents who are interacting
with each other and choosing one of several alternatives, based on the limited
information available to them, frequently show switching between two distinct
phases characterized by a bimodal and an unimodal distribution respectively.
Examples include financial markets, movie popularity and electoral behavior.
Here we present a model for this biphasic behavior and argue that it arises
from interactions in a local neighborhood and adaptation & learning based on
information about the effectiveness of past choices.
