Why does public disagreement persist in the face of scientific data on best practices in disasters? Why are individuals more likely to accept or reject disaster guidelines that may contradict their political outlooks? Previous research on motivated reasoning finds that individuals are less likely to learn from data that contradicts their prior beliefs compared to congenial data, even among individuals highest in numeracy—a measure of the ability to make use of quantitative information. This paper asks whether individual differences in the motivation to engage in effortful cognitive thinking (NFC or Need For Cognition) is the likely mechanism that explains how individuals process uncongenial data. In the US, the issue of masking in public spaces during the COVID-19 pandemic generated a partisan divide in public opinion. We find via an experiment that involves data interpretation tasks on the effectiveness of masking that those high in NFC, as opposed to NFA (Need For Affect), are more likely to exhibit motivated reasoning when interpreting uncongenial data. The experiment was fielded online with adult US residents in the spring of 2021, when the issue of mask mandates was highly salient and politicized. This study contributes to the debate on the underlying psychological mechanisms that drive motivated reasoning.