The brain puts a great deal of effort into being able to recognise faces and the information they convey. Special areas of the brain deal in particular with facial expressions that convey fear and disgust.
There was most likely some evolutionary advantage to having such dedicated responses to the meanings behind the faces we observe, a session of the annual British Association taking place in Cardiff University was told yesterday.
Prof Andy Young, of the University of York, described how blood flow to parts of the brain changed on the basis of what a test subject saw when shown pictures of faces. The subjects were shown pictures that conveyed happiness, surprise, fear, sadness, disgust and anger.
One area responded when faces conveying fear were displayed and another to disgust. Anger seemed to be handled by the same location as fear, he said. These facial messages could have been a very important aid to survival, Prof Young suggested, with anger and fear conveying a "signal of threat" and disgust giving a "signal of illness".
Understanding the brain's response was valuable, he said, because it could help to overcome damage to perception and the ability to recognise facial features after a brain injury. Certain injuries left the patient "selectively blind to these features", he said.
Dr Peter Hancock, of the University of Stirling, described his research into how we assess age and gender from facial appearance. Composite images of faces could be assembled on a computer and then modified to assess how facial shape or colour changed the observer's view of age and gender.
Broader faces looked more male and narrower faces female, he said, but colour was also very important. Masculine shaped faces could be made to look feminine if a female colouring, dominated by reflected light from the cheekbones, was superimposed on the male shape.
Dr Hancock also showed how if the facial features were moved down the face it made a person look younger. These techniques were useful in forensic work, for example, altering the image of a missing child to approximate what they might look like years later. It was also valuable in predicting how facial changes after surgery might develop over time and what the impact of a progressive disease that affected the face might be.
Caricaturising a face made it much easier for an observer to recognise the caricatured person, according to research conducted by Dr Andy Calder of Applied Psychology Unit of the University of Cambridge. "Distorting a face in a particular way can improve recognition," he said. Tests showed that people recognised well known personalities much more quickly when exaggerated images emphasising their familiar features were displayed.
This technique was applied to facial expressions. When the telltale signs of fear were exaggerated in the picture, the subjects responded to the meaning behind the face much more quickly, he said.
