I feel the need to refer to this concept regularly in quite different situations, so I feel that there probably is a word.

Example 1 (silly engineering one)

I want to know how fast my paper aeroplane flies so I attach my smart phone to it with an app to measure speed. The plane does not fly any more because the measurement device is far too heavy; the plane's behaviour is altered by the measurement device.

The method suffered from X.

Example 2 (human one)

I want to know what people think about something at work so I ask a question. If I ask the same question but follow it with "I want to tell the management what people think" then in some situations this is likely to affect how people answer. The questioning suffers from X.

  • The result was compromised by the test method.
    – WS2
    Mar 10, 2015 at 16:19
  • Heisenberg Uncertainty Principle.
    – Hot Licks
    Mar 10, 2015 at 19:36

3 Answers 3


This is called the observer effect.

In science, the term observer effect refers to changes that the act of observation will make on a phenomenon being observed. This is often the result of instruments that, by necessity, alter the state of what they measure in some manner. A commonplace example is checking the pressure in an automobile tire; this is difficult to do without letting out some of the air, thus changing the pressure. This effect can be observed in many domains of physics.

(source: Wikipedia)

The observer effect can apply to your second example, as well, though often researchers will lean towards investigating the placebo effect or attempting to eliminate a cognitive bias when they believe that the subject's mental awareness may be a factor in the outcome.

(links: Wikipedia)


If the measurement device is heavier than the paper airplane, or the question is phrased in such a way that the answers are likely to be biased, your measurement process uses faulty methodology.


Surrogation: psychological phenomenon in which the measure of a construct of interest evolves to replace the construct itself (keeping score)

  • 2
    Thank you for your contribution. (I take it you do realise that this Q. is over 4 years' old.) In any case, please note that this site expects answers to be substantiated where appropriate, so it would be helpful if you were to provide, say, a dictionary link that supports your suggestion. Thanks.
    – TrevorD
    Apr 8, 2019 at 14:10

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