Extremely Partisan Samples Distort Perceptions of Group Beliefs

How do we infer the beliefs of an entire group (e.g., Democrats) after being exposed to the beliefs of only a handful of group members? What if we know that the beliefs we encountered were selected in a biased manner? Across two experiments, we recruited 640 U.S. residents and assessed whether they could correct for known sample bias. Some participants viewed biased samples that exclusively presented the political beliefs of extreme partisans while others viewed representative samples free from selection biases. We find evidence that people correct for known sample bias, but do so insufficiently, leading them to make inaccurate inferences that are aligned with sample bias. Specifically, participants overestimated the ideological extremity of Democrats and Republicans to a greater extent when exposed to explicitly biased—compared to representative—samples. We discuss how peoples’ tendency to insufficiently adjust from transparently biased samples leads to partisan misperceptions that amplify political polarization.