The Misleading Potential of Communicative Hand Gestures in a Forensic Interview
A wealth of research has highlighted the susceptibility of eyewitnesses to verbal influence. However, considerably less attention has been paid to the role of nonverbal influence in police questioning. The purpose of this thesis was to evaluate the extent to which gestures can exert an influence on witnesses and skew their responses when questioned. Study 1 initially investigated this by presenting participants with an on-screen 'police' interviewer who accompanied his questions with gestures conveying either accurate or misleading information about a piece of video footage they had witnessed. Results showed that, for one question in particular, participants' responses concurred with the information conveyed to them in gesture; accurate gestures led more participants to giving correct responses and misleading gestures led more participants to giving fabricated responses. Study 2 built on this by examining whether gestures could also affect the confidence attributed to their responses in order to give insight into whether gestures were knowingly processed for information. It was found that, in some cases, gestures were able to increase confidence in both accurate and misled responses. Study 3 examined participants' awareness of gesture further by studying their attention to gesture during its performance and ability to identify it retrospectively on a recognition task. A new set of questions confirmed that gestures could influence the responses of participants (including those working in the legal profession) and revealed that the influence of gesture appears to be at its strongest when unnoticed by participants. Finally, study 4 considered whether the results of the previous studies could be replicated in a more ecologically valid interview scenario and confirmed that gestures continued to be influential when performed face-to-face. Overall, it was concluded that gestures can impact accurate eyewitness testimony and can be a powerful influential tool in police interviews.