In France, we designate by "Bonaldi effect" a particular case of the Murphy's law which states that:

Any demonstration of any product that worked perfectly at the rehearsals will fail miserably during the public demonstration.

It takes its name from Jérôme Bonaldi, a television host who encountered many problems when he presented unusual objects and inventions.

How would you describe such a syndrome in English?

  • 3
    It seems to be correctly attributed (if rarely mentioned) in English also. Jun 25, 2017 at 22:26
  • @EdwinAshworth That article you linked to was quite entertaining.
    – Lawrence
    Jun 25, 2017 at 23:25
  • The exact term in French is L'effet Bobaldi (sometimes syndrome Bonaldi). Discussed on this thread on Linguaphiles: "Corollary on Murphy's Law", referred to by s.o. as the "demo effect".
    – None
    Jun 26, 2017 at 5:58

1 Answer 1


Urban dictionary suggests an appropriate term: demo effect.

Its downside term is that is typically connected with high-tech, and it has other meanings.

From another source:

Similar to [the bonaldi effect], the demo effect: an object, software, etc., used daily with no incident, would present a dysfunction during a demonstration, especially in public. exemple [sic] : bill gates' presentations of different windows, ending with a famous error on a blue screen.

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