Biased Belief Updating in Causal Reasoning about COVID-19

Abstract

In three experiments based on 977 participants, we investigated whether people would show belief bias by letting their prior beliefs on politically charged topics unduly influence their reasoning when updating beliefs based on evidence. Participants saw data from fictional studies and made judgments of how strongly COVID-19 mitigation measures influenced the number of COVID-19 cases (political problems) or a medicine influenced number of headaches (neutral problems). We predicted that liberals would overestimate and conservatives would underestimate causal strength on political problems relative to neutral problems. In Experiments 1 and 2, liberals showed this overestimation bias. Surprisingly, college-student conservatives in Experiment 2 showed the same overestimation as liberals. These findings made sense because all three groups who overestimated the strength of mitigation measures held prior beliefs that strongly favored use of these measures. In Experiment 3, conservatives' judgments of the strength of mitigation measures after seeing evidence increased as their degree of prior support for these measures increased. Furthermore, conservatives who strongly opposed the use of mitigation measures underestimated causal strength in the political problems. These results suggest that belief bias is driven more by specific beliefs relevant to the reasoning context than to general attitudinal factors like political ideology.