Here is an excerpt from an article written by Justin Menkes for the Harvard Business Review series, “The Conversation.” To read the complete article, check out the wealth of free resources, and sign up for a subscription to HBR email alerts, please click here.

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Recently, I read an article in which a developmental psychologist cited a mountain of evidence showing that IQ was one of the most significant predictors of emotional resiliency in children. The same pattern has also long been seen in the military, where it has been conclusively shown that higher-IQ soldiers show fewer signs of long-term post-traumatic stress.

Why would cognitive ability predict emotional hardiness? In truth, it doesn’t. But the tests that measure cognitive ability do. When you tell people they have 12 minutes to show whether they are smart or dumb, the ability to stay calm and focused under duress has a huge impact on the scores.

Heightened anxiety has long been shown to dramatically impair people’s ability to think. It affects basic functions such as short-term memory and processing of simple information, as well as more complex thinking, where anxiety can aggressively interfere with the ability to differentiate between important and irrelevant tasks. In today’s business environment of unrelenting pressure, aspiring leaders must learn how to confront heightened levels of urgency without allowing the accompanying mental agitation to be disruptive.

About six years ago, I interviewed “Ollie,” the CEO of a consumer products company. I had been hired to evaluate Ollie by his parent company because his company had been doing poorly. In fact, it was the worst-performing brand in the parent conglomerate’s portfolio. I had just presented Ollie with a hypothetical crisis that threatened the survival of his business, and was asking him to evaluate data, along with suggestions from colleagues and his board of directors, and arrive at a sound conclusion about what to do.

Just a few minutes before, when I had asked Ollie about his history with the company, he had confidently articulated the direction in which he was taking the business. Now he was struggling to offer even the most basic sense of how to proceed in a hypothetical, but very plausible, real-world crisis. When I would ask Ollie a question, he would offer an answer that was virtually incoherent. I recognized the shift in eye movements, the slight rise in room temperature, and the slight increase in human body odor. These are all the physical responses of someone experiencing an adrenaline flood that is overloading their higher-order functions. When this happens, a person is prepared to run, not think.

Anyone witnessing Ollie’s answers to my questions would shudder at the thought that this person was responsible for a company with revenues over $1 billion, but Ollie was not nearly as incompetent as he appeared during the case study portion of our evaluation. Day-to-day, on the job, he appeared fine; it was when he was confronted with a high-stress crisis that his physical response overcame his mental processes. Ollie had been promoted to the CEO role at a time when the competitive environment was changing, and he had not been prepared to handle unfamiliar complexity. He had not yet learned to tame the cognitive overload that occurs for people in response to high levels of duress.

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Aspiring leaders must be taught how to manage their stress in such a way that it actually increases their focus and clarity. They need to gain experience in stressful situations where they get an elevated — but not overwhelming — sense of adrenaline and are set up for success. Confidence under pressure can be built like a railroad track in the brain through exposure to repeated experiences over time.

This capacity can be developed in many ways. One simple exercise involves memorizing something, be it a poem or the 50 states, and then reciting it before friends at a dinner party, while encouraging them to taunt you if you make mistakes. At first, you are more likely to have missteps in this context. Eventually, you will find that you can do the exercise faster, with more accuracy, in front of an audience than when you do it by yourself. Toastnasters uses the same concept, teaching people to do something they often fear — public speaking — by first exposing them repeatedly to speaking in a small, supportive environment before putting them in front of larger and larger groups.

Mentors can also nurture this quality in future leaders by creating similar experiences. For instance, if your next-in-line is slated to present before the board, don’t let him do so without preparation. Have him present first in front of a few colleagues, then at the Monday morning meeting, then before the management team, all before they present in the higher-pressure environment of the boardroom.

Once an executive learns how to manage adrenaline without panic, he or she can grow confident that the sensations that stress induces will not lead to collapse. While it is a noisemaker in the untrained mind, when channeled properly adrenaline can help people accomplish things that they never would have imagined possible. The ability to make adrenaline a friend is a necessity for executives in today’s environment of ongoing duress. Not surprisingly, it’s also a hallmark of the world’s best CEOs.

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Justin Menkes is an acclaimed author and expert in the field of C-suite talent evaluation. His latest book, Better Under Pressure, will be released by Harvard Business Review Press in May. I have read it, will soon review it, and highly recommend it ass well as his earlier work, Executive Intelligence.