Here's an old study I came across while reading this very interesting and disturbing book on electronic drugs: Addiction By Design: Machine Gambling in Las Vegas, Natasha Dow Schüll, Princeton University Press, 2012. [link]
Effects of Ambient Odors on Slot-Machine Usage in a Las Vegas Casino.
Alan R. Hirsch. Smell & Taste Treatment and Research Foundation, Ltd. Psychology & Marketing Vol. 12(7):585-594 (October 1995). John Wiley & Sons, Inc. [link]
Our data show that the amount of money gambled in the slot machines surrounding Odorant No. 1 during the experimental weekend was greater than the amount gambled in the same area during the weekends before and after the experiment by an average of 45%.
- The odor was noticeable (suprathreshold levels)
- It showed a dose-response relationship because they emitted less on Sundays, and people spent less on Sundays (yet still more than the other days)
- I don't see any description of how they ensured the emitted smell actually accumulated in the targeted area instead of getting blown away by ventilation or occupant circulation, but that's a minor criticism
- Although both odorants were described as pleasant by a panel, I don't see any other information about them, although it should be pointed out that only one of the odorants had an effect;
- On multi-modal stimulation and hijacking your hindbrain, he reminds us, "In casinos it is common to incite patrons to gamble by directly appealing to their senses: the exciting sounds of coins jingling, sirens screaming when someone hits the jackpot, intense lighting, plush carpets, luxurious surroundings, and controlled temperature."
*Wordplay, not to be taken seriously; hindbrain refers to the cerebellum and below, whereas the limbic system, which is where smell happens, is located above, in the midbrain
Note on the Author: Alan R. Hirsch was the Neurological Director of the Smell & Taste Research and Treatment Foundation in Chicago.