Heisenberg Effect

Observer Effect

The observer effect can be found in almost any scientific discipline. A commonplace example is taking the temperature of a liquid. This measurement might occur by inserting a mercury-bulb thermometer into the container and then reading the outcome on the instrument. Yet unless the thermometer has exactly the same temperature as the liquid, this act will alter the liquid's post-measurement temperature. If the thermometer's temperature is warmer, then the liquid will be warmed, but if the thermometer's temperature is cooler, then the liquid will be cooled. Of course, the magnitude of the measurement contamination will depend on the temperature discrepancy between the instrument and the liquid. The contamination also depends on the relative amount of material involved (as well as on the specific heat capacities of the substances). The observer effect of measuring the temperature of saline solution in a small vial is far greater than using the same thermometer to assess the temperature of the Pacific Ocean.

As the last example implies, the observer effect can be negligible and, thus, unimportant. In some cases, it can even be said to be nonexistent. If a straight-edge ruler is used to measure the length of an iron bar, under most conditions, it is unlikely that the bar's length will have been changed. Yet even this statement is contingent on the specific conditions of measurement. For instance, suppose that the goal was to measure in situ the length of a bar found deep within a subterranean cave. Because that measurement would require the observer to import artificial light and perhaps even inadvertent heat from the observer's body, the bar's dimension could slightly increase. Perhaps the only natural science in which observer effects are completely absent is astronomy. The astronomer can measure the attributes of a remote stellar object, nebula, or galaxy without any fear of changing the phenomenon. Indeed, as in the case of supernovas, the entity under investigation might no longer exist by the time the photons have traveled the immense number of light years to reach the observer's telescopes, photometers, and spectroscopes.

Observer effects permeate many different kinds of research in the behavioral and social sciences. A famous example in industrial psychology is the Hawthorne effect whereby the mere change in environmental conditions can induce a temporaryand often positivealteration in performance or behavior. A comparable illustration in educational psychology is the Rosenthal or “teacher-expectancy” effect in which student performance is enhanced in response to a teacher's expectation of improved performance. In fact, it is difficult to conceive of a research topic or method that is immune from observer effects. They might intrude on laboratory experiments, field experiments, interviews, and even “naturalistic” observationsthe quotes added because the observations cease to be natural to the extent that they are contaminated by observer effects. In “participant observation” studies, the observer most likely alters the observed phenomena to the very degree that he or she actively participates.

...