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 used as a measure of stress levels, and to monitor recovery.

Thermal imaging, according to the psychologists behind the study could be a "game changer" in stress research.

The experimental stress test that I subjected myself to is carefully controlled and deliberately designed to be an unpleasant surprise. I arrived at the university with no idea what I was in for.

First, I was asked to sit, relax and listen to white noise through a set of headphones.

So far, so calming.

Then, the researcher who was running the test invited a panel of three strangers into the room. They all stared at me silently as the researcher informed that I now had three minutes to prepare a five minute speech about my "dream job".

As I felt the heat rise around my neck, the scientists captured my face changing colour through their thermal camera. My nose quickly dropped in temperature - turning blue on the thermal image - as I considered how to bluster my way through this unplanned presentation. (I decided I would take the opportunity to make my pitch to join the astronaut training........

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