Belief in the Claim of an Argument Increases Perceived Argument Soundness

Abstract

We examined subjects' ability to judge the soundness of informal arguments. The argument claims matched or did not match subject beliefs. In all experiments subjects indicated beliefs about spanking and television violence in a prescreening. Subjects read one-sentence arguments consisting of a claim followed by a reason and then judged the soundness of the argument. Signal detection theory analyses were used to examine discrimination performance and response bias. In Experiment 1 discrimination was not predicted by beliefs, but subjects were biased in favor of rejecting arguments as unsound when the claim was inconsistent with their beliefs compared with when it was consistent. In Experiments 2 and 3 we replicated these effects and examined neutral subjects and reasoning ability as factors. The results suggest that belief or disbelief in an argument claim biases students' judgments of the argument's soundness.

Acknowledgments

We thank Andrew Taylor and Jazzmine Carrol for assistance with the research and Todd Williams for comments on an earlier draft of the manuscript.

Notes

¹ We use the terminology “sound” and “unsound” arguments in the Introduction and Discussions to refer to arguments in which the reason is relevant or is not relevant to the claim. We use “acceptable” and “flawed” to refer to actual subject responses in the task because this terminology was used in the instructions.

² We collected measures of subjects' prior knowledge of the research related to spanking and television violence to assess whether performance on the argument evaluation task may be related to levels of prior knowledge. In Experiments 1 and 2 prior knowledge did not predict d’ or C for any group on either topic. In Experiment 3 there was a significant correlation between level of prior knowledge and d' for arguments with belief inconsistent claims. No other variables were related to prior knowledge in Experiment 3. Because of the overall lack of relationship between prior knowledge and any measure of interest in these experiments, we do not discuss prior knowledge further.