Apparent Bias: What Does Attitude Polarization Show?

Many, though not all, experiments have found that exposing groups of subjects who disagree to the same evidence may cause their initial attitudes to strengthen and move further apart, or polarize. Some have concluded that findings of attitude polarization show that people process information in a biased manner so as to support their initial views. We argue that, on the contrary, polarization is often what we should expect to find in an unbiased Bayesian population, in the context of experiments that find polarization.