Lessons In Survival

With so much more NPY in their systems, the Special Forces soldiers were much more clearheaded under interrogation stress and performed better according to the trainers. Special Forces soldiers really are special and different from the rest of the Army. They stay more focused and engaged in a crisis and bounce back faster afterward because their bodies produce massive amounts of natural anti-anxiety chemicals. In the fog of war—and everyday life for that matter—that's a major advantage. (Article continued below...)

At the elite Navy Diving and Salvage Training Center in Panama City, Fla., they know how to figure out quickly who will be capable of accomplishing extremely dangerous underwater missions. They take young sailors and tie their hands behind their backs and bind their feet. They put the strap of a dive mask between the sailors' teeth and then throw them in the Olympic-size pool. The challenge is to stay afloat and live. "The more someone struggles," Morgan tells me, "the harder it is to get air and the more tired they get. You just have to inhibit the powerful, incredible instinct to breathe and your anxiety and alarm." Morgan knows how scary it is because they also tied him up and threw him in so he could understand what the sailors were going through. Most trainees quickly realize that the only way to avoid drowning is to relax and sink to the bottom of the pool, kick off powerfully toward the surface, gasp for a little bit of air through clenched teeth and then fall back into the water and drop down to the bottom again.

During this testing, a lot of sailors black out. They simply don't get enough oxygen and lose consciousness. Morgan has watched many of them sink to the bottom of the pool before divers pull them to the surface. On the deck, the unconscious sailors are rolled on their sides, and as soon as they revive, an instructor shouts again and again: "Are you gonna quit? Are you gonna quit?" Sailors are given 30 seconds to answer or they're kicked out of the program. If they say they want to keep going, they're given another 30 seconds to recover and then they're thrown back into the pool. It may sound sadistic, but the Navy is simply trying to identify who will survive the most dangerous missions and who won't. Through this grueling test, it finds soldiers and sailors who refuse to give up, who can suppress the need to breathe, who trust that they'll be rescued if something goes wrong and who are prepared to lose consciousness—or even die—following orders.

In another arduous test, sailors are taken three miles off the Gulf Coast at night and are given a target destination on the beach. Dumped in the water, the students submerge and are not allowed to surface until they reach their objective. To make the challenge even more stressful, a clock is running and the divers aren't allowed to go deeper than 25 feet. Despite the tides and currents, they're also forbidden to swim parallel to the beach looking for their target. The penalty for breaking any of the rules is immediate expulsion from the course. Speed, efficiency and accuracy are a critical part of their grade.

In this underwater navigation test as well as the exercise in the pool, Morgan found again that brain chemistry makes a big difference. The amount of NPY you pump is closely connected to your success—the more, the better. Morgan also found that the best underwater navigators release a lot of a natural steroid called DHEA, which buffers the effects of the stress hormone cortisol and helps the brain's hippocampus with spatial relationships and memory. Divers with the most NPY and DHEA graduated at the top of the class. Those with the lowest amounts did poorly.

At POW camp and dive school, Morgan has discovered a simple and accurate way of predicting who will survive and perform the best under extreme stress. You might call it the telltale heart. It starts with something called heart-rate variability, or HRV, the variations between beats. Healthy people have a lot of variability in the intervals between their beats, with their tickers speeding up and slowing down all the time.

It turns out that the best survivors don't have a lot of heart-rate variability. Instead, they've got "metronomic heartbeats"—their hearts thump steadily like metronomes—with almost no variability between beats. That is, the intervals between the beats are evenly spaced. Morgan believes that a metronomic heartbeat is an easy way to detect good survivors and high neuropeptide Y releasers. It makes sense biologically because your brainstem, which controls your heartbeat, has a high density of neuropeptide Y.