The answer is simple: if you agreed to participate in an experiment, they are gleaning something about you, not just when you think they would, but all the time. Many experimental setups collect key information when the participants think that the experiment is over, or hasn't yet started.
So, relax and enjoy the quiet. They even likely paid you a small sum to do that!
So, relax and enjoy the quiet. They even likely paid you a small sum to do that!