If one eyewitness to a crime recalls a rogue piece of information, it can seriously distort other witnesses' accounts of what happened, according to new research being led by the University of Aberdeen and being sponsored by the Economic and Social Research Council (ESRC).
A 13-month study, led by Professor Amina Memon of the Department of Psychnology, has investigated how the memories of pairs of witnesses can become distorted when they discuss what they believe to be the same event.
Professor Memon said: "It is human nature for people to discuss their shared experiences. Several high profile cases, such as the Oklahoma Bombing in 1995, have shown that even a single erroneous eyewitness can have a negative influence on the accuracy of another person's testimony if they come into contact and discuss the event. We call this phenomenon memory conformity."
Researchers from the University conducted two studies during the project. The first was to see whether wrong information provided during discussion with a fellow witness is more likely to influence memory than a misleading written narrative. Witnesses viewed a simulated crime and were then presented with a misleading account either verbally from another witness or in written form.
The other witness was in fact a stooge, instructed by the researchers to give a misleading account of the crime to their co-witness. The study found that misleading information from the stooge had more influence than a written report, with 44%of witnesses misled compared with 31% confused by the written report.
For the second study, witnesses were led to believe they had viewed an identical set of pictures, but in fact there were differences, or misinformation, in some critical details. Each person witnessed four critical items that were unique to their version of the event, and so had an opportunity to introduce unwittingly that number of items of misinformation.
Witnesses were asked to discuss what they had seen, and the discussions were tape-recorded. Researchers analysed transcripts of the recordings, noting who mentioned critical items first and whether or not this was disputed by the person being given the information.
Overall, they found that people were unlikely to challenge critical items of information brought up in discussion. The report says that 62.2% did not challenge these items when heard.
Importantly, whether or not a co-witness later influenced them was dependent on whether they had mentioned the item first themselves or not. For those who were the first to mention a critical item, there was only one instance out of 36 where the person later changed their mind about what they had seen, and reported what their co-witness had seen instead.
The analysis also showed that critical items were raised in conversation 37 times out of a possible 120, and that 20 of these later featured erroneously in individual recall tests.
Professor Memon added: "Our studies show that misinformation gained through talk can produce more errors than when it comes in, say, written form. This finding has implications both for forensic and theoretical understanding of eyewitness memory.
"Witnesses who have just seen a crime are highly likely to discuss their experience with one another. So if one witness recalls incorrect details this could negatively influence the other witnesses' memories of what actually happened."
For further information, contact:
Professor Amina Memon on 01224 272230 (work), or email: amemon@abdn.ac.uk
or Lesley Lilley or Anna Hinds at ESRC, on 01793 413119 /413122.
Note to Editors
1. The research report, Estimating and Understanding Memory Conformity Effects for a Simulated Crime, was funded by the Economic and Social Research Council (ESRC). Professor Amina Memon, who led the study, is based at the Department of Psychology, University of Aberdeen.
2. The ESRC is the UK's largest funding agency for research and postgraduate training relating to social and economic issues. It has a track record of providing high-quality, relevant research to business, the public sector and Government. The ESRC invests more than £53 million every year in social science research. At any time, its range of funding schemes may be supporting 2,000 researchers within academic institutions and research policy institutes. It also funds postgraduate training within the social sciences thereby nurturing the researchers of tomorrow. For further details visit: www.esrc.ac.uk
Issued by Public Relations Office, External Relations, University of Aberdeen, King's College, Aberdeen.
Tel: (01224) 272960 Fax: (01224) 272086. Contact: Angela Ferguson