The work had been inspired by observations the professor had made whilst in Mexico, when he noticed that -
“…virtually everyone in a Mexican village over 5 or 6 years of age liked the burn of chili pepper, but that none of the animals in the village showed a preference for it, even though they ate the pepper daily as they consumed the leftovers of the day in the garbage”
To find out why, the professor devised an experiment – along with chimp specialist Keith Kennel – in which two domesticated chimps at the University of Pennsylvania Primate Facility were offered -
“… a series of increasingly piquant crackers by their caretaker, and gradually came to prefer these crackers to unseasoned crackers. The preferences were stable over months, and generalized to a different piquant cracker.”
The chilli-loving chimps showed, possibly for the first time in a controlled experimental situation, that humans are not the only animals to develop likings for innately unpalatable substances.
“This nonobvious and previously unappreciated finding turns out to be important in understanding the conditions under which innate aversions are reversed.”
The paper was eventually published in the journal Appetite. 1983 Jun;4(2):69-77.