Episode 28: Is Yawning Contagious?

Air Date: March 9, 2005

Over a ¼ mile long down-hill course a toy car can beat a full size Dodge Viper powered only by gravity.


The toy car was able to beat the Viper over 100 feet (30 metres) but over the full length of the course the Viper won by an extremely wide margin.

A person can be subconsciously influenced into yawning if another person near them yawns.


In a test pool of 50 people those who were influenced into yawning by the MythBusters yawned 29% of the time. However, those who were not influenced yawned only 25% of the time. Despite this supportive evidence, the 4% difference between the experimental and control groups was not large enough to constitute a statistically significant difference (at alpha = 0.05), and therefore no definitive conclusion could be reached based on these results.

Toast is more likely to land buttered side-down when dropped.


In an extensive and highly objective test the toast showed no statistical preference for landing buttered side-down or up when dropped. It was an even 50-50 split when the final results were compared. However, when pushed off the side of a table, toast showed preference to flip once and land buttered side down.


  1. isa says:

    whether toast lands buttered side-down is to do with the height of the table it’s being pushed off…

    • ty says:

      Its just like a penny, it’s a 50:50 chance. It’s obvious there is no way to prove it no matter how manny times you test it.

      • tyler says:

        my names tyler not ty

  2. TC says:

    “A person can be subconsciously influenced into yawning if another person near them yawns. – Plausible.”

    You say that the results were not statistically significant. In that case, you can’t draw any conclusions (pro or con) about the myth. You certainly can’t conclude (from those results) that it is “plausible” – that would be a positive finding.

    For example, say I said that a person can be subconsciously influenced into yawning if another person near them “thinks of a cauliflower”. You do some tests, and find that the results are not statistically significant. You would not conclude (from those results) that what I said was “plausible”.

    Yes? No?

    • JasonD says:

      I fully agree. Perhaps the problem is that the Mythbuster categorization system (Confirmed, Plausible, Busted) does not include ‘No Result’ label, as such would admit defeat.

      Although, in this case, the lack of statistical significance should have indicated ‘Tentatively Busted’.

    • Barking says:

      Wrong – an unconfirmed hypothesis can still be WAY more plausible than another unconfirmed hypothesis. Sometimes it’s just waiting for the right experimental deign.

      I politely suggest, look up the definition of plausible. Then find out if the experiment has been repeated. Then try to understand the difference between proof of absence and absence of proof. Then get a life.

  3. Buster says:

    I agree with your logic, but ‘Plausible’ is what the MythBusters reported, so I will leave it. Here is an article discussing the MythBusters’ flawed statistics in this myth: http://www.omninerd.com/2007/04/19/articles/75

    • Dendrite says:

      Actually, I just watched the episode, and the verdict given by the MythBusters was, in fact, not “Plausible” as stated above but “Confirmed” – which, of course, is total bollocks. The link above is not working, but a two-proportion z-test with H0: p1=p2 for a sample that size gives P=0.38 (single-tailed test) which is nowhere near P=0.05. Such a small difference in proportion would require a sample size of over 1500 to become statistically significant, i.e., the original MythBusters verdict is definitely busted.

  4. Ray says:

    Plausible is plausible. It means that it ‘could’ happen. This is true. It could happen. Goodness me, maybe there should be a ‘grammar-busters’ article, but then again, that would be for solicitors, lawyers and politicians. I hope I said this in the correct grammatical context, if that makes sense. Sometimes I yawn when I have to listen to some people with cauliflower ears. Only joking mate.

  5. Bekaak says:

    Where did the cauliflowr idea come out of? the fact that you used cauliflower as an example makes me laugh!


  6. sprucebranch says:

    falling toast:

    I didn’t see this episode; how high were you guys willing to go? Did you do toast from an aeroplane?

  7. suzanne says:

    I saw the butter portions being used to butter the toast and I know from experience there isn’t enough butter in those portions for this butter lover. I was laying on my butter, cashew spread and jam this morning and I reckon if I dropped it it would definitely have landed on the buttered side because it was so heavy. I could test this theory but I don’t want to waste all that yummy toast. So maybe the issue is not just buttered toast but toast with butter and spreads.

  8. paul Malley says:

    Buttered Toast

    You demonstrated in the first five minutes that buttered toast when SLID of a table
    would land buttered side down.
    That was the myth and you proved it.

    Dropping butterd toast on edge falls randomly, OK but that wasn’t the MYTH.

    With regard to the Science of the phenomenon some Engineering type produced
    the maths to show that the incrementally
    increasing rotational moment caused by the self weight of the toast as it slid over the edge of the table, being resisted by the toast’s torsional moment of inertia,was
    only sufficient to rotate the toast through
    an angle >180degrees but

  9. paul malley says:


    through an angle >90 degrees

  10. Bria says:

    This i think is a very plausible topic. I did it an more than 80 percent of the people were influenced to yawn!

  11. angie says:

    i just yawned and now my dog wont stop!

  12. lizzie says:

    i am doing a report on this i need all the help i can get

    • ashley says:

      i yawned and 60% of my class yawned it was halarious

  13. Ray says:

    Yawning is a way for the brain to cool it self down.Seeing someone yawn might trigger what you brain is going to do sooner or later anyways

  14. Julian says:

    How do I get a copy of this episode? I am doing my science fair project on the buttered toast problem. Thanks.

  15. Pat says:

    in the toy car vs the viper race down a 1/4 mile track i think you have a big problem. the size of the bumps on the road and in effect on the track that the toy car is on will have a much bigger impact on the 1/64th scale car than the full size viper. the road that was used was not smooth. a 1 inch change or bump in the road would be like the full size car hitting a 64 inch speed bump. even a 1/4 inch change for the toy would be like hitting and 16 inch speed bump. this is probably why Adam’s car kept jumping the track. you can even hear them say in the episode that it jumps the track at the same spot. you need to build an equally scaled smooth track for the toy car.

  16. Ward says:

    It is common knowledge that the chances of toast landing butterside down is inversley perportional to the value of the carpet.

  17. mythbustersrule7 says:

    I never saw the buttered toast one but i tried 20 times and the results were 11 butter side down and 9 butter side up.

  18. MB2008 says:

    I would try a different approach to testing this myth. If I remember correctly, Tory would yawn (or not) before showing the subjects to a small room which had nothing to do in it. I think that would make most people yawn period.

    My idea is this: Record an episode of MB (one with and one without yawning) and see how many yawn while watching the show.

  19. jaryd says:

    i yawned just reading that.

  20. mojoe44 says:

    I suspect you might be wrong on
    Why Toast Falls Butter Side Down.

    Please Read…

    Table of Contents: December 1995 Volume 273 Number 6

    Mathematical Recreations
    Murphy’s Law demystified: why toast falls butter-side down.

  21. Natas M. says:

    i think yawning is contagious, i yawn and then maybe look across the room and someone else has already been yawning and i didnt know about it.

  22. KS says:

    So if toast with a heap load of butter will be more likely to fall buttered side down I cant help but wonder that if a cat is supposed to always lands on it’s feet, what if you slid a cat off the edge of a building with a slice of toast strapped to it’s back buttered side up ????

  23. sarah to the michelle says:

    hmm.. it seems to me that after reading this i yawned about 10 times!! Oops 11! =)

  24. Matt says:

    Butter toast IS more likely to land butter side down. This is because when butter toast is knocked off a table it has to complete almost a complete 360 spin to be butter side up when it lands, while it only needs to spin at least 90 degrees to be butter side down on landing.

    Since the average table/counter/etc is half the height of an adult, there is not much distance to allow a full 360 spin during fall unless the toast is knocked off at a weird angle or fumbled.

    I suppose that doesn’t mean however that is ALWAYS lands butter side down. Just more often then not.

  25. Chris says:

    Matt you have it precisely right.

    If you place the toast on the table butter side down and push it off what do you think will happen?

    The reason it spins is because one side of it will give way to gravity and turn, flipping the slice! I guess its chaotic how many more spins it will do with a given height, probably got something to do with the initial resultant force which causes the spin. i.e. if you forcably pushed down on the side slid out from under the table.

  26. Justin says:

    In regards to yawning was the mental state of the test subjects considered? Ive noticed if your in a group of tired people the phenomenon of yawning being contagious is much more likely to happen than if one person is tired and the others are rested. Was this taken into consideration?

  27. Tim says:

    In regards to yawning; In my case, I can make my wife yawn at will. I can make her continue to yawn until her jaw cramps up if I want to.

  28. Chamon says:

    You guys all made me yawn while i was eating my toast butter side up i fell off a table, but my toast was already digested, which way do you think the toast was when i landed on my back?

  29. felixnoir says:

    Guys. Leave the science to the scientists. Every time New Scientist needs a filler they reprint some piece of research that proves that yawning is catching.

    The wonder is not that yawning is catching. The wonder is that we focus on that to the exclusion of other behaviours. Humans are primates and pack animals. We unconsciously copy each other. Sneezing is catching. Scratching yer bum is catching. Believing that there are aliens lurking outside the office door is catching. Watching Mythbusters is, fortunately for you, catching if you consider yourself to be a member of that particular pack.

    You guys are not scientists. You are inventor-engineers. Like most inventor-engineers, you have a zest for practical fun, a theoretical side that has some gaping holes, and a somewhat limited grasp of history and culture. Because these cause you to fit well into your pack they are your strengths .

  30. dave says:

    Yawning is caused by a small rise in carbon dioxide in the blood stream. When this occurs in a (semi enclosed) area to a level where one person starts to yawn, this cue can illicit a response from others also being effected by the CO2 level in the room, but they would eventually yawn anyway once their personal CO2 level threshold was reached. So it is contageous? No, but it could appear to be if one only looks at the effect of suggestion, not that there is a cause too and it need not be a room low in CO2, it could be something as simple as an inactive, tired person has decreased breathing rate.

    As for felixnoir’s suggestion that humans are pack animals, no they are not to this extent. You may find that within a group that if one or more members of the group doesn’t something of questionable social grace, it puts the others more at ease about doing similar things but they don’t do it to be conformist, the copying of each other is not a conscious or subconscious decision, it is merely that being genetically near identical and being in the same environment, they are effected to similar extends and exhibit similar responses to that environment.

  31. Beni says:

    On the small car experiment, I saw you had problems with the track, because the sun kept dilating the track, and the cars would fall out. Maybe the experiment would have had better chances in the evening, since then the track would contract, and make the track more straight, exactly opposite as the morning effect.

  32. Tony says:

    I definitely yawned a number of times through this episode…any not once through many others. I think it’s plausible.

  33. Sariah says:

    Scientific American reported on studies about yawning a few months ago. The findings suggested that contagious yawning was influenced by empathy, of all things.

    I think this myth should be retested using complete strangers vs. close friends vs. family members and see if that makes a difference.

  34. Jack says:


  35. Gerard says:

    Sorry, just caught this episode. I’m probably not adding anything new here, but the Fisher’s exact test for the yawn test is p=1.0. The result is indistinguishable from that expected by chance.

    While it is true that this means the ‘myth’ is ‘plausible’, it is wrong to say that yawns being contagious has been proven by this experiment.

    Very large numbers would need to be tested (in far more rigorous conditions) to obtain p < 0.05.

    Perhaps MB could consider engaging the services of a statistician to comment before judging their own results.

  36. keyur says:

    i was yawning the whole episode. .so yes it is contagious..

  37. whoa says:

    Can anybody tell me what breed is the dog shown in this episode ? the black one ? the yawning one ?

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