The amygdala is activated by angry faces

A group of scientists from Dartmouth College in the US scanned the brains of volunteers to see which parts of their brains were activated when confronted with photographs of men showing either fear or anger in their facial expressions.

Other research has already established that a region of the brain called the amygdala seems to play a key role when the brain is trying to "read" emotions such as these from faces.

However, the latest research, published in the journal Science, looked at what happened in the brain when the picture showed angry faces - but with the gaze averted so that they no longer looked the volunteers directly in the eye.

Images of angry or fearful faces were used

The researchers found that, when viewing pictures of angry expressions, there was far more activity in the amygdala when the gaze is averted.

However, the reverse appeared to be true when viewing pictures of fearful people - direct eye contact led to much more amygdala activity.

The researchers suggested that both of these were suggestive of danger - but of an uncertain source, which could mean that the brain has to work harder to process them.

Dr Reginald Adams, who led the research, said: "It highlights the need for including eye gaze direction in future research examining how emotion is processed and perceived."

Complex subject

Dr Andrew Calder, from the University of Cambridge, UK, said other research had indicated that a direct gaze seems to produce more amygdala activation than an averted gaze.

"Our work uses individuals who have suffered some damage to the amygdala - some of whom have difficulty in recognising fear and anger.

"But we know there are many other areas of the brain which are involved with the processing of emotion."