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Soldiers and marines were taught to observe rules of engagement, and throughout the video those in the helicopter call base for permission to shoot. But at a more primal level, fighters in a war zone must think of themselves as predators first, not bait, the report said. That frame of mind affects not only how a person thinks, but what he sees and hears, especially in the presence of imminent danger, it said. The fighters in the helicopter say over the radio that they are sure they see a "weapon", even though the Reuters photographer, Noor-Eldeen, is carrying a camera.

"It's tragic that this all begins with the apparent mistaking of a camera" for a weapon, David A. Dunning, a psychologist at Cornell University, told the paper. "But it's perfectly understandable with what we know now about context and vision. Take the same image and put it in a bathroom, and you swear it's a hair dryer; put it in a workshop, and you swear it's a power drill."

To a soldier or a pilot, it can look like life or death. "I worked with medivac pilots, and vulnerability is a huge issue for them," Dr Moore told the paper.
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