Lisa is participating in a psychology experiment. She is seated in a dimly lit room and is told to look straight ahead at the blank screen. Lisa's task is to detect points of light as they appear on the screen, and Lisa will be paid $10 for every point of light she correctly detects. Several minutes into the experiment, Lisa is discouraged by how few light points she is seeing, so she changes her strategy and starts focusing off to the side of the screen rather than in the middle of the screen as she had been. Sure enough, by the end of the experiment, Lisa has enough money to buy the pizza for tonight's study group. Lisa's new strategy worked because: