The myside bias in written argumentation entails excluding other side information from essays. To determine the locus of the bias, 86 Experiment 1 participants were assigned to argue either for or against their preferred side of a proposal. Participants were given either balanced or unrestricted research instructions. Balanced research instructions significantly increased the use of other side information. Participants' notes, rather than search patterns, predicted the myside bias. Participants who defined good arguments as those that can be “proved by facts” (...) were more prone towards the myside bias. In Experiment 2, 84 participants of high and low argumentation ability read a text called “More Than Just the Facts” designed to contradict this fact-based argumentation schema. For high argumentation ability participants, the intervention reduced the myside bias, but for low ability participants it increased. The roots of the myside bias are underdeveloped argumentation schemata leading to misconceptions about research and argumentation. (shrink)

Homo sapiens have evolved a dual-process cognitive architecture that is adaptive but prone to systematic errors. Fuzzy-trace theory predicts that nested or overlapping class-inclusion relations create processing interference, resulting in denominator neglect: behaving as if one ignores marginal denominators in a 2 × 2 table. Ignoring marginal denominators leads to fallacies in base-rate problems and conjunctive and disjunctive probability estimates.

The empirical research on the psychology of argumentation suggests that people are prone to fallacies and suboptimal performance in generating, comprehending, and evaluating arguments. Reasoning and argumentation are interrelated skills that use many of the same cognitive processes. The processes we use to convince others are also used to convince ourselves. Argumentation would be ineffective if we couldn't reason for ourselves.