Polarization and extremism emerge from rational choice: Estimation as a solution to biased sampling

Polarization is often described as the product of biased information search, motivated reasoning, or other psychological biases. However, polarization and extremism can still occur in the absence of any bias or irrational thinking. In this talk, we show that polarization occurs among groups of decision makers who are implementing rational choice strategies (specifically, random walk / relative evidence choice strategies) that maximize decision efficiency. This occurs because extreme information enables decision makers to make up their minds and stop considering new information, whereas moderate information is unlikely to trigger a decision and is thus under-represented in the sampled information. Furthermore, groups of decision makers will generate extremists – individuals who stop sampling after examining extreme information. In re-analyses of seven empirical studies spanning perceptual and preferential choice, a series of simulations manipulating threshold, bias, and drift rates, and a new study examining politically and affectively charged decisions, we show that both polarization and extremism manifest when decision makers gather information to make a choice (choice task). Polarization did not occur, however, when participants made an inference about the difference between two quantities (estimation task). Estimation therefore offers a theoretically-motivated intervention that can increase the amount of information people consider and reduce the degree of polarization and extremism among groups of individuals.