Tendency for people to evaluate evidence, generate evidence, and test hypotheses in a manner biased toward their own prior opinions and attitudes.
Perkins, D. N. (1989). Reasoning as it is and could be: An empirical perspective. In D. M. Topping, D. C. Crowell, & V. N. Kobayashi (Eds.), Thinking across cultures: The third international conference on thinking (pp. 175–194). Hillsdale, NJ: Erlbaum.
Participants first respond to a questionnaire item, embedded in a series of other items, that probes the participant's position on the issue of abortion ("I believe that abortion should be legal in this country"). Then, each participant grades four paragraphs: two two-sided paragraphs and two one-sided paragraphs (one on each side of the abortion issue).
Not provided by the authors.
Each participant receives four scores:
the rating (numerically transformed grade) they gave their 4anti/0pro paragraph
the rating they gave their 0anti/4pro paragraph
the rating they gave their 2anti/2pro paragraph
the rating they gave their 2pro/2anti paragraph
Each participant's myside bias is indexed by a difference score whose calculation depends on their prior opinion (e.g., for the anti-abortion participants, the myside bias score is derived by subtracting their 0anti/4pro score from their 4anti/0pro score).
Stanovich, K. E., & West, R. F. (2008). On the failure of cognitive ability to predict myside and one-sided thinking biases. Thinking & Reasoning, 14(2), 129–167.