Observer effect, observer bias, observation bias, etc. 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 Media "Observer Effect" (Star Trek: Enterprise), an episode of Star Trek: Enterprise, named after the effect in physics. See also Actor–observer bias Demonstration effect Uncertainty principle Meditation Personal equation, in experimental science Schrödinger's cat, a thought experiment, often described as a paradox, devised by Austrian physicist Erwin Schrödinger