Final answer:
The problem in which participants change their behavior due to the awareness of being observed is known as the Hawthorne effect.
Step-by-step explanation:
Participants who modify their behavior because they know they are being observed as part of an experiment are experiencing the Hawthorne effect. This term specifically refers to the alteration of behavior by the subjects of a study due to their awareness of being observed. The Hawthorne effect was named after a series of experiments that took place at the Western Electric Company's Hawthorne Works, where researchers discovered that any change in a work environment variable led to changes in worker productivity simply because the workers knew they were being observed.