Observer effect

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

General experimental biases

 * 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

Physics

 * 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

Computing

 * Heisenbug of computer programming, in which a software bug seems to disappear or alter its behavior when one attempts to study it
 * Observer effect (information technology), the impact of observing a process while it is running

Other uses

 * "Observer Effect" (Star Trek: Enterprise), an episode of Star Trek: Enterprise, named after the effect in physics