NewMexiKen posted this a year ago today, but it seems timely in light of the new season.
From Science Daily, Slow Balls Take The Swing Out Of Young Ball Players:
Exasperated parents practicing throw-and-connect skills with their young children will be relieved to know that their child’s inability to hit a slow-moving ball has a scientific explanation: Children cannot hit slow balls because their brains are not wired to handle slow motion.
“When you throw something slowly to a child, you think you’re doing them a favour by trying to be helpful,” said Terri Lewis, professor of psychology at McMaster University. “Slow balls actually appear stationary to a child.”
This explains why a young child holding a bat or a catcher’s mitt will often not react to a ball thrown toward her, prompting flummoxed parents to continue throwing the ball even slower. By adding a little speed to the pitch, Lewis and her team found that children were able to judge speed more accurately. There are several reasons for the phenomenon.