The findings, which build on previous research showing improvements among soldiers and professional football players trained in mindfulness, are significant in part because members of the special forces are already selected for their ability to focus. The fact that even they saw improvement speaks to the power of the training, Dr. Jha said.

“They’re the best, and what they’re trying to do is the hardest,” she said.

Dr. Jha has spoken to the United States Army War College and the British Parliament, and she has been a consultant to New Zealand’s Defence Force and military officials in the Netherlands. “When the special forces do something,” she said, “not only does the rest of the U.S. military pay attention, but the rest of the world’s militaries pay attention.”

The science shows that techniques that focus and calm the mind allow people to perform better and make them less likely to overreact to incoming stimulation — whether a flash of movement, sound or an onslaught of information on a device.

The neuroscience of mindfulness involves, in part, strengthening a part of mental capacity known as “working memory” — a short-term, moment-to-moment catalog of tasks understood by scientists to effectively hold only a few pieces of information at one time.

As working memory clouds through overload, decisions become jumbled and reactions more impulsive. Breathing-induced focus lets people home in on the task at hand. But it does take practice.