This is a situation I see my self first hand very often as someone who works in an IT related role. I also see it in other areas and experienced by seemingly everyone, but I don't know if there is a word for it. If not, I think we should make one!

For example: Your car is making a weird abnormal noise when you start it, and it predictably does this every single time you start it. However when you take it to a Mechanic and you start the car like any other time, and the noise is gone.

Maybe there's an idiom or proverb that describes this. I feel this is a common experience that should have more eloquent explaining what happened than saying "I swear I'm not crazy, it was just doing it before you came!"

marked as duplicate by tchrist single-word-requests Mar 6 at 15:54

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  • The same term is used across a wide range of contexts (including software support). What professional "fixers" really hate is intermittent faults. But there will be various alternatives (particularly, colloquial expressions, which may be domain-specific). – FumbleFingers Mar 6 at 15:22

In computer programming, we call this a "heisenbug"

In computer programming jargon, a heisenbug is a software bug that seems to disappear or alter its behavior when one attempts to study it. The term is a pun on the name of Werner Heisenberg, the physicist who first asserted the observer effect of quantum mechanics, which states that the act of observing a system inevitably alters its state.


I am not familiar with a more general term.

  • I wasn't familiar with the term, despite having spent many decades hunting this particular kind of bug myself. It raised a smile from me, but I wouldn't count on your average grease-monkey understanding it! (Dilbert's legendary garbage man certainly would though! :) – FumbleFingers Mar 6 at 15:28

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