Faces of fear. Six images of a man's face showing progressive stages of fear in his expression. At top left is a neutral face; at bottom centre is a prototype fear expression. From the neutral face, fear is progressively added by 25% (top centre), 50% (top right) and 75% (bottom left). Enhanced fear 25% beyond the prototype is seen at bottom right. These faces were used in a study to test the response of the left amygdala in the brain to facial expressions of fear (see photo P335/032). With increased fearful expression the amygdala shows increased activity, suggesting this part of the brain recognises and responds to facial fear.