An Investigation of the Role of Confirmation Bias in the Evaluation of Informal Reasoning Fallacies

Abstract

A total of 168 undergraduate students at Temple University provided a measure of their prior beliefs and measures of attitude strength on three topics and then attempted to identify and explain informal reasoning fallacies based on the same topics. Contrary to the hypothesized predictions, prior beliefs and measures of attitude strength did not have a significant effect on participants' ability to accept informal reasoning fallacies consistent with their beliefs based on that topic, although agreement with the topic demonstrated modest effects. Furthermore, this research demonstrated that participants have significant difficulty identifying and explaining informal logical fallacies. Ability to identify and explain one informal fallacy is not a significant predictor of the ability to identify and explain other fallacies. Also, ability to identify and explain one fallacy in a topic is a poor predictor of the ability to identify and explain that fallacy in another topic. This research indicates that formal fallacy syllogism scores were the best predictor of the ability to identify and explain informal logical fallacies, and that agreement with the topic and willingness to act on those beliefs demonstrated modest effects. Consistent with studies on dual-processing theory, in informal logic the individual is forced to examine the information presented in the statement and the structure of the statement and then relate it to their prior opinions and attitudes about the topic, and therefore, the acceptance of the fallacy is a matter of motivated reasoning bias or self-deception instead of an error in analytical reasoning. Informal reasoning fallacies represented an error in judgment, or a misunderstanding of the validity of an argument. Practical implications for school psychologists, limitations of this research, and directions for future research were discussed.