The effect of prior knowledge on open and closed question generation

Abstract

Given that eyewitness evidence is one of the most influential forms of courtroom evidence, and that eyewitness errors are a major contributor to wrongful conviction, it is paramount that investigators collect evidence from witnesses in a way that preserves accuracy. The best way to do this is to prioritise open questions (e.g., “what did you see?”) over closed questions (e.g., “did the man hit the woman?”). Yet despite comprehensive interview training protocols, police investigators continue to ask an inappropriately high number of closed questions during their interviews. We used a question generation paradigm to examine the ease with which lay participants generated open versus closed questions, and the role of prior knowledge on their performance. Participants (N = 287) were given two minutes to generate either open or closed questions for a hypothetical witness to an assault. Half of the participants were first provided with information about the crime—ostensibly from other witnesses. We expected that participants asked to generate open questions would generate fewer questions and make more errors than those asked to generate closed questions, and that exposure to prior information would make it harder to generate open—but not closed—questions. We also expected that participants provided with prior information would show evidence of using that information when asking closed questions. Each of these hypotheses was supported, suggesting that confirmation bias could play a role in question generation difficulty. These findings have important implications for the development of police protocols, and are also applicable to other professions, including healthcare and education.