Sunday, January 13, 2019

Liberals & conservatives evaluate the logical structure of entire arguments based on the believability of conclusions, leading to predictable patterns of logical errors; detect better the others' failures than their own

Gampa, Anup, Sean Wojcik, Matt Motyl, Brian A. Nosek, and Peter Ditto. 2019. “(Ideo)logical Reasoning: Ideology Impairs Sound Reasoning.” PsyArXiv. January 13. doi:10.31234/osf.io/hspj

Abstract: Beliefs shape how people interpret information and may impair how people engage in logical reasoning. In 3 studies, we show how ideological beliefs impair people's ability to: (1) recognize logical validity in arguments that oppose their political beliefs, and, (2) recognize the lack of logical validity in arguments that support their political beliefs. We observed belief bias effects among liberals and conservatives who evaluated the logical soundness of classically structured logical syllogisms supporting liberal or conservative beliefs. Both liberals and conservatives frequently evaluated the logical structure of entire arguments based on the believability of arguments’ conclusions, leading to predictable patterns of logical errors. As a result, liberals were better at identifying flawed arguments supporting conservative beliefs and conservatives were better at identifying flawed arguments supporting liberal beliefs. These findings illuminate one key mechanism for how political beliefs distort people’s abilities to reason about political topics soundly.


General Discussion

In three high-powered studies (total N=2,898), we observed evidence that people’s political beliefs impact their ability to reason logically about political issues. Biased beliefs about political arguments’ conclusions caused liberals and conservatives to make predictable patterns of errors. Specifically, participants evaluated the logical structure of entire arguments based on whether they believed in or agreed with the arguments’ conclusions. Although these effects were modest in magnitude, they were persistent: we observed these biases in evaluations of both classically-structured logical syllogisms and conversationally-framed political arguments, across a variety of polarized political issues, and in large Internet and nationally representative samples.

These results demonstrate that belief bias is a pervasive problem in political reasoning that affects both liberals and conservatives. Participants failed to overcome ideological belief bias effects even after a training session on logical reasoning and explicit instructions on how to evaluate logical soundness. These studies also emphasize that belief bias can be particularly problematic in the political domain because of preexisting differences in partisans’ political beliefs. That is, political opponents’ judgments of logical soundness were biased in opposite directions, meaning that liberals and conservatives came to disagree not only about their political beliefs, but also in their perceptions of what it means to be logical at all.

Future research should examine whether and how individual differences might mitigate political belief bias. It is possible that indicators of cognitive ability, such as high numeracy, would improve overall performance. However, there is also evidence that enhanced cognitive abilities may exacerbate, rather than mitigate, our biases in a politically motivated setting (e.g., Kahan, Peters, Dawson, & Slovic, 2017).  Returning to our introductory question, is logical reasoning the antidote to political disagreement, or is it the poison? Our results suggest that it might be both. On the one hand, logical reasoning led participants to evaluate a majority of arguments in each study correctly, regardless of their political orientation. On the other hand, liberals and conservatives frequently and predictably disagreed in their evaluations of logical soundness. Conclusions and arguments that appear believable and therefore logically sound to liberals appear unbelievable and therefore unsound to political conservatives, and vice versa, regardless of the actual soundness of the arguments. While partisanship alone may push liberals and conservatives apart in their beliefs, ideological belief bias then pushes liberals and conservatives apart even in the perceived logic underlying those political beliefs.

Despite this, a more optimistic view of our results is that understanding these predictable biases could ultimately improve political reasoning. Consistent with bias blind spot research (Pronin et al., 2002), reasoners appear to be better at identifying biased reasoning in others than in themselves. That is, liberals were better at identifying flawed arguments supporting conservative beliefs and conservatives were better at identifying flawed arguments supporting liberal beliefs. A takeaway from this research, then, may be that reasoners should strive to be epistemologically humble. If logical reasoning is to serve as the antidote to the poison of partisan gridlock, we must begin by acknowledging that it does not merely serve our objectivity, but also our biases.

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