Effects of Weapon Focus on Identification Accuracy in Super-recognisers and Controls

Amy Ailes: Third year project: BSc Psychology summary

Thanks to everyone who took part in Amy’s final year project which was supervised by Dr Josh P Davis. The weapon focus effect occurs when a weapon (in this case a knife) is present during a crime and it may prevent the witness from correctly remembering details about the crime, or the perpetrator of the crime leading to mistaken eyewitness identifications.

The aim of the current research was to examine whether accuracy of identification differed dependent on the face recognition ability of participants (super-recogniser vs. control), the retention interval between viewing a culprit committed a crime (1 day vs. 7 days) and whether identification was from a target-present or target-absent line-up.

In the current study, participants were super-recognisers invited from Josh’s database (n = 93, based on previous Cambridge Face Memory Test: Extended scores (Russell, Duchaine & Nakayama, 2009)[1] and controls, some of whom were students, while others were also invited from Josh’s database (n = 67).

All were randomly assigned to watch a video of a mock crime of a pub robbery in which the actor-culprit had a knife (weapon present) or not (weapon absent). They then waited either 1 day or 7 days (randomly assigned) to receive an e-mail to contribute to Part 2 of the study. In Part 2 they had to identify the perpetrator of the crime in either a target-present or target-absent line-up.

The data were analysed, and no significant results were found. This may be because participant numbers were low. However, it is likely due to the very fast action mock crime 20-second videos shown to participants at the start of the study only showed a couple of seconds of actor-culprit facial closeups. This was probably not sufficient for anyone (super-recogniser or not) to familiarise themselves with the actors for later identification from the line-up. Indeed, only 22% of participants correctly identified the actor-culprit from the six-person target-present photograph line-ups, which is just above chance (guessing rates 100%/6 = 16.67%).

Nevertheless, the wider implications are clear. It does not matter how good someone’s face recognition ability is if they do not get a good view of a suspect regardless of whether they carry a knife or not. They will be unlikely to identify them later.

[1] Russell, R., Duchaine, B., & Nakayama, K. (2009). Super-recognizers: People with extraordinary face recognition ability. Psychonomic Bulletin & Review, 16, 252-257. doi:10.3758/PBR.16.2.252