Observer bias (or the Heisenberg and Hawthorne bias): Subatomic particles and humans have something in common. The act of observing them causes them both to change behavior. In 1927, the physicist Werner Heisenberg derived a formula showing that there is a limit to how much we can know about a particle’s position and velocity. When we observe particles, we have to interact with them (e.g., bounce light off them), causing their paths to change.
