This is one of the popular experiments mentioned in motivational books. Here is summary from a motivational webpage:

At the beginning of the experiment a number of fleas are placed in a jar. The natural reaction of the fleas is to jump out. After that a glass lid is placed on the top of the jar. Now the fleas fly high, hit the lid and fall back down into the jar. After a short time fleas adjust and begin jumping lower – until they start jumping slightly below the glass lid, in order not to hit it anymore. After three days the glass lid is removed. Since the fleas had already learnt to limit themselves from jumping high, they staid in the jar and there was no longer a lid needed to keep them inside. They have already been conditioned to the fact that they cannot escape from the jar and they have accepted that fact. Now no matter whether the lid is on or off the fleas will stay in the jar forever. Even more: when/if the fleas reproduce their offsprings will duplicate the behaviour and will not jump high either.

Now I've seen it cited many times, but without any proper background. There is one video on youtube presenting the experiment, but there is no source about how exactly it was conducted or proof about the behaviour of offspring.

To sum up, I have two questions:

  1. Do fleas really jump lower after being 'trained' in a lid? Does this behaviour persist?
  2. If so, is this behaviour passed onto next generations?
  • I expect that the only way to determine whether this is true is to try it and document the results. Feb 13, 2014 at 12:03
  • 2
    I am pretty sure that video is cgi. The link only references a fake video. I think this leaves us without a real claim
    – Andrey
    Feb 13, 2014 at 16:25
  • 3
    I'm not sure if either of your questions are true, but that video is from a Playstation 2 ad. youtube.com/watch?v=91JEZmVG2yM
    – Cruril
    Feb 14, 2014 at 22:11
  • I'm pretty certain that the answer to both your questions is "we don't know because no-one has done the experiments". Can't prove a negative though. Google Scholar searching on various combinations of "flea", "jump", "behavior", "evolution", "conditioning", all turn up dry. Most interesting result is this study (which won a 2008 IgNobel prize)" Cadiergues et al. “A Comparison of Jump Performances of the Dog Flea, Ctenocephalides Canis (Curtis, 1826) and the Cat Flea, Ctenocephalides Felis Felis (Bouché, 1835).” Veterinary Parasitology 92 (2000). doi.org/10.1016/S0304-4017(00)00274-0.
    – Ben Bolker
    Nov 5, 2022 at 20:53
  • (I don't know whether that comment should be an answer or not.)
    – Ben Bolker
    Nov 5, 2022 at 20:54


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