Observer effect

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Observer effect, observer bias, observation effect, or observation bias may refer to a number of concepts, some of them closely related:

General experimental biases[edit]

  • Hawthorne effect, a form of reactivity in which subjects modify an aspect of their behavior, in response to their knowing that they are being studied
  • Observer-expectancy effect, a form of reactivity in which a researcher's cognitive bias causes them to unconsciously influence the participants of an experiment
  • Observer bias, a detection bias in research studies resulting for example from an observer's cognitive biases


  • Observer effect (physics), the impact of observing a physical system
  • Probe effect, the effect on a physical system of adding measurement devices, such as the probes of electronic test equipment


Other uses[edit]

See also[edit]

  • Actor–observer asymmetry, a bias one makes when forming attributions about the behavior of others or themselves
  • Demonstration effect, a effect on the behavior of an individual caused by observation of the actions of others and their consequences
  • Personal equation, the idea that different observers have different reaction times, which can introduce bias when it comes to measurements and observations
  • Placebo and nocebo effects, positive and negative effects autosuggested by a patient under an inert substance or treatment
  • Schrödinger's cat, a thought experiment that illustrates a paradox of quantum superposition, devised by Austrian physicist Erwin Schrödinger
  • Uncertainty principle, any of a variety of mathematical inequalities in quantum mechanics, introduced by German physicist Werner Heisenberg