Effect of Question Type and Exposure to Prior Information on Question Generation in a Simulated Interview Task

Abstract

Given the key role that eyewitness evidence plays in criminal investigations, it is crucial that police investigators do not unduly constrain or contaminate witnesses’ reports. For this reason, best practice is to ask predominantly open questions during investigative interviews, resorting to more restrictive closed questions only when absolutely necessary. Yet despite the widespread introduction of evidence-based interview protocols and comprehensive training programmes to implement them, police investigators often struggle to adhere to open questioning when interviewing witnesses. Until now, however, researchers have only examined the extent to which interviewers favour one type of question over the other, rather than explicitly examining the ease with which questions are generated. Using a lab-based approach, we examined how well lay participants could generate open and closed questions for a hypothetical witness, and whether this was affected by exposure to prior information about the event in question. As expected, participants forced to generate open questions generated fewer correct questions and made more intrusion errors than those forced to generate closed questions. Furthermore, participants exposed to prior information generated fewer open questions than their naïve counterparts. Participants’ subjective experience of the task varied according to our manipulated variables as well as to participants’ own performance. Together, our findings underscore the difficulty that interviewers have generating open questions, and give some clues as to contributing mechanisms—in particular, the notion of confirmation bias. While continued research is necessary to further illuminate this effect, these findings could have important implications for both police training and practice.