On average how much time does a Major League Baseball batter have to decide to swing at a pitch?

In baseball, a hitter has approximately 0.125 seconds to decide whether or not to swing.

As Yogi Berra said (or is said to have said, anyway), you can’t think and hit at the same time. Once it leaves the pitcher’s hand, the ball, typically traveling 85 to 95 mph, takes 400 to 500 milliseconds to reach home. But hitters have much less time than that to decide what to do. Information about the pitch — its speed, trajectory and location — takes about 100 milliseconds, or a tenth of a second, to go from eye to brain. It takes another 150 milliseconds for the batter to start a swing and get the bat over the plate. This leaves 150 to 250 milli­seconds — a quarter of a second at most — for the hitter to decide whether to complete the swing and, if he opts to do so, where to place the bat.