For decades after the first sports psychology lab was established in 1920 in Germany, mental coaches have been the water boys of sports science, viewed by their colleagues as not quite good enough to make the first-string team.
That has changed. Virtually every top professional team and elite athlete has a psychologist on speed dial for help conquering the yips - when stress makes crucial muscles jerk and ruins, say, an archery shot - marshal the power of visualization, or just muster the confidence that can mean the difference between medaling or just muddling through.
But a more important reason for the improved reputation of sports psychology is the solid science demonstrating the effect of the mental game on athletic performance.
A 2011 study, for instance, examined U.S. National Basketball Association players' free throws. Their success rate is 6 to 9 percentage points lower when their team trails by a point or two with 15 seconds or less left on the clock. Researchers at Oregon State University reported the findings in the Journal of Sports Economics.
When free throws can mean the difference between a win and a loss - that is, when it's clutch time - the resulting stress makes many players choke.
But the power of the mind is sufficiently great that it can even trump reality.
Scientists have known since the 1990s that athletes who look at a target without moving their eyes have better success making soccer penalty kicks, basketball free throws, golf putts and other challenges where aim is crucial. But why does "quiet eye," as it's called, help?
One idea was that by keeping the gaze fixed on the target the athlete could better ignore distractions. But scientists led by Purdue University's Jessica Witt, a psychology professor and 2005 Ultimate Frisbee team gold medalist, had a different hunch. They asked whether quiet eye changes how a target looks: objects seen in the centre of the eye, called the fovea, appear larger than those seen in peripheral vision. Could that improve aim?
For a 2012 study, Witt and her colleagues made golf holes seem bigger by projecting five large or 11 small circles around them, creating what's called the Ebbinghaus illusion: see graphic.
In this illusion, large circles make a target look smaller and small circles make it look larger. Volunteers sank more putts when the hole looked larger, Witt's team reported in the journal Psychological Science. The most likely explanation: believing the target was larger increased people's confidence in their skill, which improves performance.
Confidence also seems to explain the power of sports superstitions, from lucky underwear to game-day rituals.
To test the power of superstitions, scientists led by Lysann Damisch of the University of Cologne in Germany ran several experiments. In one, they gave participants either a "lucky ball" or an ordinary one before they tried to sink a golf putt. In another, they had people bring their own lucky charms. The researchers let half of them keep the rabbits feet and the like, but confiscated the rest.
Superstition triumphed in both cases. People given a "lucky ball" sank more putts than those with an ordinary one, and performed much better if they kept their lucky charms than did people whose talismans were confiscated, the scientists reported in 2010 in Psychological Science.
How does superstition work? The scientists found that people who thought that luck was smiling on them felt more confident and competent. That inspired them to try harder and keep at it.
Which is not to say athletes can talk themselves into better performance with any old mantra. Nearly three dozen studies have analyzed sports "self-talk," in which athletes tell themselves variants of "I've got this!" or "I can beat this guy!" But not all of it, found sports psychologist Antonis Hatzigeorgiadis of the University of Thessaly in Greece and colleagues.
In general, self-talk worked better for fine motor movements such as those involving the fingers, as in archery, rather than for gross motor skills using the large muscles of the legs and arms, as in track. And what the scientists call "instructional self-talk" was more effective than "motivational self-talk": "raise the elbow," "keep the head down," or "follow through" rather than pep talk like "I can do it!"
The reason, they suggested in a 2011 paper in Perspectives on Psychological Science, is that instructional self-talk can sharpen focus on, say, what that elbow is supposed to be doing in archery. It can increase confidence - "I know what movements are crucial to nail this" - and trigger the automatic brain program that executes the task.
The more an athlete can off-load that brain program to automatic rather than conscious circuits, the better the performance.
Other scientists, have found that benching part of the brain can sharpen performance. Recreational athletes who practised bench presses hoisted a couple of kilograms more when they were blindfolded, found kinesiologist Ali Boolani of the University of Georgia. "When you're not seeing, your proprioception," or sense of where each part of your body is in space, "improves," he said. That seems to allow weight-lifters to position their hands and arms in a way that maximizes lift.
Boolani has also found that when athletes listen to music they like, their performance improved, whether they were shooting baskets, hitting baseballs or competing in track events.
"We think it's because of dissociation," he said. "If you don't think so much about what you're doing, which happens when you're listening to music, muscle memory takes over."
For all the importance of mind games, it seems, less thinking can be better than more.