Here's how it happens, and how you can deal with it. Our brains are structured so that when we have practiced something really well, we no longer need to think about it. Our subconscious processing systems are at work. But when we slow down to focus on our automatic actions, we screw up the processes, and tie ourselves in knots. Jordan Spieth choked on the 12th hole at Augusta, not when he hit his first ball into the creek, but when he hit his second. Psychologist Sian L. Beilock of the University of Chicago says well-meaning experts often encourage performers to take their time-slow down, think things over-but the evidence suggests that it's actually better just to get on with things. Beilock divided novice and professional golfers into two groups and instructed them to perform a series of golf putts. The novices performed poorly when asked to putt quickly, and better when asked to slow down. But the pros showed exactly the opposite result: they performed better when putting quickly, and more poorly when asked to take their time. Spieth may have had a case of the yips-muscle tremors or freezing up-that some golfers get when they take too long pondering a shot. Beilock speculates that taking time to think about what you've already practiced thousands of time triggers too much conscious thought. Self-monitoring hinders performance. The cerebral cortex is good for learning new tasks, and dealing with novel situations. But when we practice something over and over, we transfer control of that activity from the cerebral cortex to the cerebellum, which provides the greased-lightning capabilities needed to execute complex actions. When people are learning something new, they show high levels of activity in the cerebral cortex. But when they're doing something they've already mastered, they show greater activity in the cerebellum. The problem is-and it's a big one-the cerebellum is not consciously accessible. Nobody has the key to consciously unlock its power. Spieth got locked out of his cerebellum and began to self-monitor, which crippled his ability to perform. The question is, how much conscious thought is too much? You can't consciously check every muscle in your body when swinging a golf club, but you can't be fantasizing about the blue-jay on the limb of a near-by pine tree either. The answer is: give yourself one-word instruction. Studies show that "holistic, single word cues," are best for high stakes situations. "Using one word prevents you from regressing into conscious thought, but is still enough to activate a schematic cue to start the motor program running," said psychologists Daniel Gucciardi and James Dimmock. Jordan Spieth is a great player and a brave person. He will certainly learn something having had such a humbling experience. Let's hope you never choke. But if you do, perhaps this short exploration of the psychology of choking will serve you well in your moment of need.