Public Release: 

People can 'beat' guilt detection tests by suppressing incriminating memories

University of Cambridge

New research published by an international team of psychologists has shown that people can suppress incriminating memories and thereby avoid detection in brain activity guilt detection tests.

Such tests, which are commercially available in the USA and are used by law enforcement agencies in several countries, including Japan and India, are based on the logic that criminals will have specific memories of their crime stored in their brain. Once presented with reminders of their crime in a guilt detection test, it is assumed that their brain will automatically and uncontrollably recognise these details, with the test recording the brain's 'guilty' response.

However, research by psychologists at the universities of Kent, Magdeburg and Cambridge, and the Medical Research Council, has shown that, contrary to this core assumption, some people can intentionally and voluntarily suppress unwanted memories - in other words, control their brain activity, thereby abolishing brain activity related to remembering. This was demonstrated through experiments in which people who conducted a mock crime were later tested on their crime recognition while having their electrical brain activity measured. Critically, when asked to suppress their crime memories, a significant proportion of people managed to reduce their brain's recognition response and appear innocent.

This finding has major implications for brain activity guilt detection tests, among the most important being that those using memory detection tests should not assume that brain activity is outside voluntary control, and any conclusions drawn on the basis of these tests need to acknowledge that it might be possible for suspects to intentionally suppress their memories of a crime and evade detection.

Dr Zara Bergstrom, Lecturer in Cognitive Psychology at the University of Kent and principal investigator on the research, said: 'Brain activity guilt detection tests are promoted as accurate and reliable measures for establishing criminal culpability. Our research has shown that this assumption is not always justified. Using these types of tests to say that someone is innocent of a crime is not valid because it could just be the case that the suspect has managed to hide their crime memories.'

Dr Michael Anderson, Senior Scientist at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, commented: 'Interestingly, not everyone was able to suppress their memories of the crime well enough to beat the system. Clearly, more research is needed to identify why some people were much more effective than others.'

Dr Anderson's group is presently trying to understand such individual differences with brain imaging.

Dr Jon Simons, of the Department of Psychology at the University of Cambridge, added: 'Our findings would suggest that the use of most brain activity guilt detection tests in legal settings could be of limited value. Of course, there could be situations where it is impossible to beat a memory detection test, and we are not saying that all tests are flawed, just that the tests are not necessarily as good as some people claim. More research is also needed to understand whether the results of this research work in real life crime detection.'

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'Intentional retrieval suppression can conceal guilty knowledge in ERP memory detection tests' (Zara M. Bergström, Michael C. Anderson, Marie Buda, Jon S. Simons and Alan Richardson-Klavehn) will be published by Biological Psychology in September 2013 (Volume 94 issue 1).

It is currently online at http://dx.doi.org/10.1016/j.biopsycho.2013.04.012

For further information or interview requests with Dr Zara Bergstrom contact Gary Hughes in the University of Kent

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Tel: +44 (0) 1227 823100/823581
Email: g.m.hughes@kent.ac.uk

News releases can also be found at http://www.kent.ac.uk/news

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For University of Cambridge contact:

Genevieve Maul, Communications Officer, Science Research, Office of External Affairs and Communications
Tel: +44 (0) 1223 765542
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Email: Genevieve.Maul@admin.cam.ac.uk

Notes to editors

(1)

The University of Kent - the UK's European university - was established at Canterbury in 1965. It has almost 20,000 students and operates campuses or study centres at Canterbury, Medway, Tonbridge, Brussels, Paris, Athens and Rome. It has long-standing partnerships with more than 100 major European universities and many others across the world, including institutions in Argentina, China, Japan, USA, Canada, Malaysia and Peru.

Kent is one of the few universities to be consistently rated by its own students as one of the best in the UK for the quality of its teaching and academic provision. This includes its 3rd place for overall student satisfaction in the 2012 National Student Survey. It was also ranked 22nd in the 2013 Guardian University Guide, 28th in the Sunday Times University League Table 2013, and 28th in the Complete University Guide 2014.

In the 2008 Research Assessment Exercise, Kent placed 24th out of 159 participating institutions in the UK for its world-leading research, while 97% of its academic staff work in schools or centres where the research is rated as either internationally or nationally excellent.

It is worth £0.6 billion to the economy of the South East, with its students contributing £211 million to that total. The University also supports directly or indirectly almost 6,800 jobs in the South East (source: Viewforth Consulting, 2009-10).

In 2012, Kent launched a campaign to celebrate its 50th anniversary.

(2)

Established as the Applied Psychology Unit by the Medical Research Council in 1944, the Cognition and Brain Sciences Unit at Cambridge is one of the largest and most enduring contributors to the understanding of human cognition and its disorders. Its research investigates fundamental human cognitive processes such as attention, language, memory, and emotion. It does this using a combination of behavioural experiments, neuroimaging, and computer modeling.

For further information go to http://www.mrc-cbu.cam.ac.uk

(3)

University of Cambridge: The University of Cambridge's mission is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence.

Cambridge's reputation for excellence is known internationally and reflects the scholastic achievements of its academics and students, as well as the world-class original research carried out by its staff. Some of the most significant scientific breakthroughs occurred at the University, including the splitting of the atom, invention of the jet engine and the discoveries of stem cells, plate tectonics, pulsars and the structure of DNA. From Isaac Newton to Stephen Hawking, the University has nurtured some of history's greatest minds and has produced more Nobel Prize winners than any other UK institution with over 80 laureates.

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