Tuesday, 9 April 2013

Head movements of police interviewers can influence confidence ofwitnesses

Guest blog by Dr Daniel Gurney, Department of Psychology

Dr Daniel Gurney
Simply nodding in response to a witness as they give their testimony can make them more confident in their story, regardless of whether it is accurate or not.

In my recent study, participants witnessed a piece of mock-up CCTV footage and were asked questions on this afterwards. As the participants gave their answers, the experimenter either nodded or shook their head deliberately in response to these. The head nods and shakes were only given during some of the questions and were given regardless of whether the witnesses were accurate or not.

The participants reported being significantly more confident in their answers if the interviewer nodded while those given head shakes were considerably less confident. These differences were found even when there were no differences in accuracy between the groups.

I found that people are very trusting of witnesses who claim to be very confident in their story.  However, in this research we show that a witnesses' confidence can be manipulated by a very simple nonverbal behaviour. Giving a witness a false sense of confidence in their story can have some big implications when obtaining accurate evidence.

This study adds to research showing that a police interviewer's nonverbal behaviour can influence the creditability of a witness. As simple head nodding and shaking are very common in everyday life, this research has implications for other social situations where individuals' confidence can be manipulated.

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