There are techniques that can speed your response and improve your score:
- lay the iPhone or Touch flat on a table, near the edge
- hold your finger as close to the screen as possible without accidental touches
- you want to tap with only your finger tip, not moving your whole hand or even your whole finger, so rest the palm of your hand on the edge of the table or on your other hand so that you can tap with a flick of your fingertip, rather than a downward tap.
One of my beta testers (Ainsley, 5) insisted on holding her hand at her side while waiting for the target button to turn green. Her times were not good.