Quanta Magazine

Decades of research and everyday experience offer striking examples of the interplay between mind and body. Around the time Pavlov was experimenting with drooling dogs, the American physician John Mackenzie watched one of his patients develop an itchy throat and struggle to breathe upon seeing an artificial rose — suggesting that the perception that pollen was present was enough to provoke her allergy symptoms. In the 1970s, scientists discovered a similar phenomenon while conducting taste-aversion experiments on rats: They repeatedly gave the animals an immunosuppressive drug along with the artificial sweetener saccharin; eventually, they found they could quell the animals’ immune activity with saccharin alone. Many of us can recall times when the mere scent of a food that once made us sick could trigger nausea anew.

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