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
Related
Science & Thought Experiments
Schrödinger's Cat
Something held in two contradictory states at once until you actually check.
Science & Thought Experiments
Hawthorne Effect
People behave differently when they know they're being studied.
Science & Thought Experiments
Pavlov's Dogs
An automatic, conditioned response to a cue — usually one you didn't choose.