In reading a web page on increasing word power, there was a German word with the definition that means:

It only works when I try to show you how it does not work.

Is there a single word in German to describe that situation?

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    "… there was a German word with the definition …" What was that word? Or did you mean that you a) only remember the definition or b) the word was in another language?
    – l0b0
    Oct 6, 2019 at 19:14
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    BTW in English that is called a "demo effect". Using this name could shorten your Q's title substantially. Oct 7, 2019 at 7:01
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    If this happens systematically with a specific observer, one also speaks of the Pauli effect or Pauli-Effekt. Oct 7, 2019 at 13:32
  • I tend to confuse the Pauli effect with the Peter principle that everybody climbs the career ladder until they reach their personal levels of incompetence. Oct 10, 2019 at 22:39

2 Answers 2


there was a German word with the definition that means:

It only works when I try to show you how it does not work.

What you are probably looking for is called the Vorführeffekt.

It's used like

Die öffentliche Präsentation der Anwendung scheiterte leider am Vorführeffekt.1

It basically means that you try to give some evidence in public while showing how something works (or doesn't work), but you fail because it just gives evidence to present the opposite.

1)That's why we prefer to use power point presentations and (maybe even faked) screen shots to present software in early stages of development, instead of really running a live installation of the program.

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    In computer terms, the small but relevant part of the computer responsible for this Vorführeffekt behaviour is sometimes called die Admin-Diode. As soon the computer administrator arrives to confirm the problem, it's not there.
    – Janka
    Oct 4, 2019 at 11:58
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    @Janka: In English, a software defect that cannot be seen when you are specifically looking for it is sometimes called a "Heisenbug" after German physicist Werner Heisenberg, who discovered that you lose information about the position of a particle when you try to measure its velocity. I'd be curious to know if this jargon exists in German as well. Oct 4, 2019 at 19:14
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    @EricLippert Of course Heisenbug is used in German as well. Oct 4, 2019 at 19:39
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    That word isn't that specific, I have heard the phrase "demo effect" in French and English as well.
    – Relaxed
    Oct 5, 2019 at 6:15
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    The Vorführeffekt can be thought of as a special case of Murphy's Law: if something can go work, it will go wrong during a demo.
    – miw
    Oct 5, 2019 at 7:04

The word is "Vorführeffekt", which translates to "presentation effect". It's used in both cases. Something works fine all the time until you show it your boss / parents / friends. Or something broken magically works again when you are showing it the technician.

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    Hi, did you check the other answer before writing yours? Oct 6, 2019 at 18:39
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    @EricDuminil This answer adds information that the other one does not, so I don't see a problem. Oct 7, 2019 at 11:49

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