How to distinguish Blair from Bond and Maggie from Marilyn

13 December 2004

By morphing the faces of state figures such as Margaret Thatcher into those of famous actors like Marilyn Monroe, University College London (UCL) scientists have discovered how our brains process and identify people from their faces.

In a study published in the latest online issue of Nature Neuroscience , UCL researchers showed that people use three different parts of their brain in a step-by-step process to analyze a face: the first scrutinizes its physical aspects, the second forces it into a known or unknown category and the third retrieves facts about a known face such as a name.

If just one of these steps breaks down, which can happen in some forms of dementia, people can lose their ability to identify others. The findings might help scientists to explore interventions for people with 'face-blindness' who are unable to recognize others from their faces.

Pia Rotshtein of UCL's Institute of Neurology says: "Recognizing people is an essential social skill that we often take for granted. Most of us are gifted with this incredible skill of being able to recognize someone even if the lighting is poor, their hair-style is drastically different, we haven't bumped into them for ten years or we're looking at a grainy image of them on CCTV footage!

"Our brains have in-built mechanisms for 'reading' faces which we use all the time. When you go home for Christmas and your mum studies you as you walk through the door, one part of her brain will be analyzing different bits of your face (are your cheeks fat, do you look well?), while other parts will be comparing the current image of your face to memories from the last time she saw you - the whole process leading her to declare that you have gained or lost weight.

"When a face in a crowd gives you a nagging feeling that you know this person, one part of your brain has made a match between the face you are seeing and stored memories, prompting another part to try to put a name to the face.

"Our study also shows that the brain tries to force us to pin a single identity to a face, even if it looks like a mix of two people we know. So a face that is 60 per cent Marilyn Monroe and 40 per cent Margaret Thatcher will be identified as an older version of Marilyn Monroe, while an image which is 40 per cent Marilyn Monroe and 60 per cent Margaret Thatcher will be seen as the sexier side of Margaret Thatcher."

UCL researchers prepared a series of images starting with the face of one celebrity that in incremental steps, transformed into the face of another. For example, Tony Blair became Pierce Brosnan and Margaret Thatcher became Marilyn Monroe. Volunteers were then shown pairs of morphed faces and asked to identify each face within the sets.

When shown the faces, volunteers' brains were found to be primarily active in three areas. The inferior occipital gyri (IOG) at the back of the brain were found to be particularly sensitive to slight physical changes in the morphed faces, as if picking out the smallest details such as the number of wrinkles.

The right fusiform gyrus (RFG), located just behind the ears, was more active for images that significantly changed the identity of the face. This area of the brain generalizes across different images of the same face and compares images to stored memories, which can give rise to a feeling of familiarity e.g. 'I think I know this person'.

The third activated region, the anterior temporal cortex (ATC), is believed to store facts about people we know and is thought to be an essential part of the identifying process. This area was more active when volunteers knew the celebrities well, and was barely active when the face was unknown to the volunteer, for example when a Polish volunteer was presented with the face of John Major.

Professor Jon Driver of UCL's Institute of Cognitive Neuroscience says: "Previous studies have found that damage to these areas of the brain can result in the loss of one's ability to identify people. Some autistic people also struggle with this ability. Dementia patients with damage to the ATC can find it difficult to correctly name someone, while people with a form of epilepsy triggered by the RFG might struggle to distinguish between faces, mistakenly believing different faces to belong to the same person.

"Prosopagnosia or 'face-blindness' is a rare condition where the brain is unable to process faces normally, and is linked to damage in some or all of these brain regions. Someone with prosopagnosia will have difficulty recognizing people from their faces and may have to rely on other cues such as hairstyle, clothes, hand gestures or voice. Some sufferers may not even be able to recognize their own spouse or their own face in a mirror."

Notes for Editors

For more information or to set up an interview, please contact Jenny Gimpel at the UCL Media Relations Office on +44 (0)20 7679 9739, mobile: + 44 (0)7990 675 947 or e-mail j.gimpel@ucl.ac.uk.

'Morphing Marilyn into Maggie: dissociated physical and identity face-representations in the brain', by Rotshtein, P., Henson RNA., Treves , A., Driver, J. and Dolan, RJ, is published online on Sunday 12 December 2004 on the Nature Neurosci ence website at http://www.nature.com/neuro/index.html .

Images of the following are available from the UCL Media Relations Office: Tony Blair morphing into Pierce Brosnan, Margaret Thatcher morphing into Marilyn Monroe. Please acknowledge Nature Neuroscience for any images used.