Imagine yourself out on the golf course on a beautiful summer afternoon. You hit your best tee shot of the day, the second sails straight down the fairway, and your approach shot lands three feet from the cup. Just one smooth tap of the putter and you'll card a birdie.

You feel confident as you address the ball. But just as your putter is about to make contact with it, a hand and wrist spasm interrupts your calculated stroke — and your ball rolls past the cup.

You've just experienced the yips.

In up to 25 percent of serious golfers, the yips causes sudden, involuntary tremors, jerks or freezing in the hands and wrists that interrupts a putting stroke. To a casual observer, the yips might seem like a psychological issue — choking on a key putt. However, research has shown that sometimes there's more to it than that. Some cases of yips are related to a neurological dysfunction affecting specific muscles, called a focal dystonia.

Whatever the cause, the yips can add five strokes or more to an 18-hole game — making it a frustrating problem for affected golfers.