Many years ago, my college chemistry teacher squeezed an orange peel in the front of the auditorium asking us to raise our hands when we smelled it. Hands rippled through the auditorium (at least 40 rows) very quickly.

I am trying to replicate this but it is not working. I've tried scrubbing the oranges in case they had been heavily waxed but without no luck.

How can I replicate this? Anything else with a strong (but pleasant) odor that can travel through a large theater almost very quickly?

  • $\begingroup$ I have done this experiment many times. The smell has always taken some seconds and minutes to diffuse through the auditorium up to the highest row. It was fast, but never instantaneous. Your auditorium must have had some strange technical way of mixing the air. $\endgroup$
    – Maurice
    Feb 16 at 20:55
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    $\begingroup$ Well, either the smell was already dispersed beforehand, or there was a strong updraft of air, or people were less than truthful. BTW smells travel mostly disperse via convection, diffusion itself is much slower. $\endgroup$
    – Mithoron
    Feb 16 at 21:57
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    $\begingroup$ Aside of possible artificial air convection, I would not underestimate subjective factor. When people are told what they are expected to smell, they have tendency to smell it in advance. $\endgroup$
    – Poutnik
    Feb 17 at 12:53
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    $\begingroup$ Perhaps the prof had some dedicated fans in that room. $\endgroup$ Feb 18 at 1:54
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    $\begingroup$ One part of doing good repeated experiments is to control the environment. A large classroom or theatre has many elements that will influence this result so just because it worked somewhere, doesn't mean it will work for you. Perhaps the incoming air in the original theatre was behind the lecturer and blew the scent towards the audience? Perhaps it was a much smaller room? To know how fast the smell travels, you need to control those factors. $\endgroup$
    – matt_black
    Feb 19 at 11:36

1 Answer 1


The setup confounds chemistry and physics on side (transport of molecules by «normal» air flow because a door/window, sash of a hood is open; convection by a radiator, diffusion by concentration gradient) on one side, with psychology on the other. The former can be monitored by organisms, and machines.

The later may be more complex. Over time, we are primed for instance by the taste of a lemon, can develop a response expectancy about the scent associated by other stimuli e.g., sound and sight. Say you were a sparring partner for the uneven bars; after some training together, don't you equally move while the other performs the exercise -- not only for safety to promptly catch him/her if necessary? If you usually play an instrument and go to a concert, knowing some of the passages by heart, isn't your brain equally similarly engaged except for the actual play of the instrument, too?

Placebos play a role in medical research -- even to the degree that there are active placebos intentionally containing ingredients e.g., to cause dizziness in order to prevent de-blinding medical studies because patients can be conditioned to the presence of typical side effects the verum generates -- by the talk with the physician, the leaflet in the package, hearsay. Why else running blinded and even double-blinded studies where neither patient, nor physician know the content of the box until the end? Their role is even more prominent (or better, more important) in treatments which are less (or not) evidence based.

And group dynamics like «well if my dear neighbor feels sickened...» You equally might repeat the experiment, unveil a beautiful container of tap water «I'm so glad to present you a new, exquisite parfum; the first to sense it, gets it for free».

  • $\begingroup$ This is a great exaplanation of how and why the effect works, both physically and psychologically. What I am really after is how to get the audience to smell oranges within, say, 10 seconds of planting the seed in their minds that "I can get them to think of oranges". (This is for a high school magic show.) $\endgroup$
    – Greg
    Feb 22 at 20:19

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