Baseball has been dubbed “America’s favorite sport”,and many fans contend that there is no greater thrill than watching a good pitcher throw the ball skillfully in a series of expertly delivered “fast” and “curve” balls. Two such pitches, the “rising fastball” and the 5 “breaking curveball” are particularly exasperating to batters because these balls tend to veer in one direction or the other just as they reach home plate. The “rising fastball” zooms forward only to jump up and over the bat as the batter swings. The “breaking curveball” curves toward home plate, but plunges downward unexpectedly at the 10 last moment. Batters attempt to anticipate these pitches, and respond accordingly, while pitchers work at perfecting their “fast” and “curve” ball deliveries.

But, according to studies conducted by a team of engineers and psychologists, 15 the “rising fastball” and the “breaking curveball” do not actually exist; they are merely optical illusions. The studies revealed that batters perceive the ball as approaching more slowly or falling more quickly than it actually is, and it is this misperception that produces the visual illusion. Batters tend to have difficulty tracking a ball 20 continuously as it approaches and will briefly divert their eyes to the spot where they think the ball will cross the plate. When a batter has misjudged the speed or angle of a pitch, and shifts his or her gaze in this way, the ball will appear to suddenly rise or dip, and the batter will often miss.

25 How will this finding affect “America’s favorite pastime”? No doubt some will vehemently reject the notion that the “rising fastball” and the “breaking curveball” are mere illusions. But for others, the findings may imbue the game with a new level of intrigue as batters 30 attempt to respond to pitches that don’t exist.

what does the word the bold “they” refer to?