First pitch begins an at-bat with Tableau Rasa, a Latin phrase that means clean slate. It begins with the pitcher and it ends with the batter. What the batter does with the pitch adds color to the slate that endures the entire at-bat.
The batter has a big decision – usually made as the first pitch approaches the plate - swing or take? That decision certainly has impact.
The batter can look for a specific pitch type in a specific location, and only swing if he sees what he is looking for (although he could be fooled).