https://www.vice.com/en_us/article/pkgakv/why-does-thinking-hard-make-me-so-tired > In 1998, researchers baked chocolate chip cookies in order to fill a laboratory with the aroma of freshly made treats. Then, they brought people into the lab, and sat them in front a stack of aforementioned cookies, along with some chocolate candies, and a bowl of red and white radishes.  > People were put in either the radish group or the sweets group, and told to eat only the food that had been assigned to them, for the purposes of a “taste perception study.” Then an experimenter left the room, and watched the participants behind a one-way mirror.