When strong evidence has less impact than weak evidence: Bias, adjustment, and instructions to ignore

Results from three experiments show that individuals who are asked to ignore a strong testimony "overadjust" their judgments relative to those asked to ignore testimony with a milder persuasive impact. Participants made jury decisions after reading several testimonies, one of which provided either strong or weak evidence for the defendant's guilt. Relative to the weak testimony, the strong testimony led to higher judgments of guilt when participants were instructed to use it, but lower judgments of guilt when participants were instructed to ignore it. Strength of the critical testimony was manipulated through the confidence of the witness (Experiment 1), linguistic cues to the witness's age (Experiment 2), and the abnormality of the defendant's actions (Experiment 3). Results are interpreted as supporting previous theories about awareness of cognitive processes and how individuals adjust beliefs.