Group size, misinformation and unanimity influences on co-witness judgements

Researchers have typically observed the effects of co-witness influence on eyewitness pairs. However, research suggests that individuals are more likely to witness crimes in larger groups. Additionally, there is an abundance of evidence suggesting that social influence is heavily moderated by group size. Therefore, the present study aimed to gain a more accurate understanding of the risks of co-witness influence in relation to unanimity and group size effects. Participants (N=608) viewed and discussed a CCTV footage of a fight breaking out, with co-witnesses, before giving individual statements, where they were asked to identify which person had started the fight; confederates were used to suggest that the wrong man had started the fight. Results indicated that participants were vulnerable to co-witness influence, but only when exposed to misinformation from a majority of co-witnesses. Misinformation presented by an individual confederate did not have a significant influence over the participants’ responses. This study was the first to investigate the effects of group size on blame attribution. The findings suggest that the true risks of co-witness influence may not be as high as originally predicted from research on eyewitness pairs.