Definition of Heisenberg effect:
Observation that the very act of becoming a player changes the game being played. It is reflected in interviewing process where the interviewees tend to give answers they think interviewer wants to hear. Named after German Noble-laureate physicist Werner Karl Heisenberg (1901-76) whose uncertainty principle states that (in particle physics experiments) the very act of observing alters the position of the particle being observed, and makes it impossible (even in theory) to accurately predict its behavior. See also observer inseparability.
Meaning of Heisenberg effect & Heisenberg effect Definition