Professor Deane Aikins, a psychiatrist at Yale University, said a small minority of individuals remain cool even in the most stressful circumstances.
His findings, based on research with the military, found that some individuals did not panic because their body naturally protected them.
Unlike the majority of people who were flooded with a stress hormone, they had much lower levels and also showed signs of another hormone that actually calmed them down.
He referred to Chesley Sullenberger, the pilot of the aeroplane that was successfully landed on the Hudson River in New York last month, as an example.
"There are some individuals who when confronted with extreme stress their hormone profile is rather unique," he said.
"It doesn't reach the same peak as the rest of us. So we're all ready to scream in our chairs, but there are certain individuals who just don't get as stressed.
"Their stress hormones are lower and the peptides that down-regulate that stress are higher, so you can see in action the hormonal regular system really hitting overdrive.
"Certain people are cooler under pressure and they perform very, very well during these periods of time."
Professor Aikins, who outlined his findings at the American Association for the Advancement of Science annual meeting, studied hormone stress levels during extreme training exercises like mock survival or combat swimming.
He said that while there was no such thing as a "man without fear" certain people were better equipped to deal with it.
"I think they were born with it," he said. "We started figuring out we can start predicting who are these individuals who are going to have this cooler hormonal profile under high stress."
He said the research could lead to new training programmes - mental therapies or "push-ups" or medications to make others just as good at dealing with extreme stress.
"So much so we're now getting to the point where we might be able to train people to do better under high stress and there might be ways to augment their hormonal system, mental health push ups might help to better deal with that stress."
He said that it was not that the "heroes" were not scared but they just did not exhibit signs of panic.
"They say wow that was a really miserable day," he said. "But when you say to them did your heart pound or your palm sweat they just say mm well, it was ok."
He said US special forces as a group tend to "run cooler" than non-special forces. He said it was too early to say what percentage of men were born heroes.
Meanwhile other researchers are developing drug therapies for people suffering from Post Traumatic stress Disorder (PTSD) that affects 20 per cent of the soldiers returning from Iraq.
Harvard University are testing a "beta blocker" style drug - often used to reduce blood pressure - to be taken immediately after the trauma that appears to dampen down future PTSD attacks.