In the past two years, an Army researcher, Steven Burnett, has overseen a study into human perception and bomb detection involving about 800 military men and women. Researchers have conducted exhaustive interviews with experienced fighters. They have administered personality tests and measured depth perception, vigilance and related abilities. The troops have competed to find bombs in photographs, videos, virtual reality simulations and on the ground in mock exercises.

The study complements a growing body of work suggesting that the speed with which the brain reads and interprets sensations like the feelings in one’s own body and emotions in the body language of others is central to avoiding imminent threats.

“Not long ago people thought of emotions as old stuff, as just feelings  feelings that had little to do with rational decision making, or that got in the way of it,” said Dr. Antonio Damasio, director of the Brain and Creativity Institute at the University of Southern California. “Now that position has reversed. We understand emotions as practical action programs that work to solve a problem, often before we’re conscious of it. These processes are at work continually, in pilots, leaders of expeditions, parents, all of us.”

Seeing What Others Miss

The patrol through Mosul’s main marketplace never became routine, not once, not after the 10th time or the 40th. A divot in the gravel, a slight shadow in a ditch, a pile of discarded cans; any one could be deadly; every one raised the same question: Is there something  anything  out of place here?

Clearing a road of bombs is one of the least glamorous and most dangerous jobs on the planet. It is also one of the most important. In May, coalition forces found 465 of them in Afghanistan and 333 in Iraq. The troops foiled more than half the traps over all  but about 10 percent of the bombs killed or maimed a soldier or a Marine.

“We had indicators we’d look for, but you’d really have to be aware of everything, every detail,” said Sergeant Tierney, whose unit was working with the Iraqi police in that summer of 2004.