concept
Observer Effect
The act of measuring something changes the thing being measured.
Origin
Strict version: in quantum physics, observing a particle's state forces it to take one. Loose version: putting a thermometer in a small glass of water cools it slightly; surveying employees about morale changes morale. Routinely conflated with the (unrelated) Heisenberg uncertainty principle.
Modern usage
Used in physics, social science, management ('the metric becomes the target'), and journalism. 'Observer effect' is a polite way of saying your investigation has contaminated its subject.
Tags
measurement
physics
social-science