When I was asked to give an impromptu five-minute speech and then to count backwards in intervals of 17 - all in front of a panel of three strangers - the acute stress was written on my face. That is because psychologists from the University of Sussex were filming this somewhat terrifying experience for a research project that is studying stress using thermal cameras. Stress alters the blood flow in the face, and scientists have discovered that the drop in temperature of a person's nose can be