Spicy heat is popular in food worldwide, but how people react to it varies greatly.

Keely Richter eyes the sandwich with trepidation. It is just fried chicken topped by slaw and sauce between a bun – nothing unusual. But there is something menacing about the dish.

“It looks like it wants to hurt you,” Richter explains while keeping her distance.

The sandwich in question is a high-octane version of Nashville hot chicken not yet on the menu at Heatwaves, the Pacific Grove pop-up that occupies Rudolfo’s every Sunday. Richter is the Weekly’s business development director, part of a small staff gathering to gauge the differing perceptions of spicy heat.

As Oxford psychologist Charles Spence noted, there is greater individual variation in the reaction to fiery foods than perhaps any other type of cuisine. In a 2018 article published by the International Journal of Gastronomy and Food Science, “Why is Piquant/Spicy Food So Popular?” Spence observed that the question has not received the research interest it deserves, adding that a quarter of all people on the planet consume chiles on a daily basis.

“Man is the only animal that likes Tabasco sauce.”

Indeed, in his book How Pleasure Works, Paul Bloom pointed out, “Philosophers have often looked for the defining feature of humans – language, rationality, culture and so on. I’d stick with this: Man is the only animal that likes Tabasco sauce.”

There is an assumption that piling on heat smothers other flavors. Chef Rudolfo Ponce of Heatwaves pampers his chicken. It’s brined for 12 hours and dredged through two different seasoned flours. As our impromptu tasting panel agreed, the mild version is very good fried chicken. Things changed from that point, however. Richter bowed out when the medium flared beyond her threshold level. Reaching the hot, associate editor Erik Chalhoub reports that his palate still sensed chicken and the base seasonings – for a moment. Soon, however, his face took on a more than flushed hue.

“The mild and the medium I could do all day,” he says after a bit of recovery time.

Those who survived the hot version could pick out the fruity fire of habanero and the earthier bite of cayenne.

“Clucking hot” includes such fearsome chiles as the Carolina Reaper, approaching the surface of the sun at some 2.2 million Scoville Units. Jalapeños, by comparison, rate a relatively cool 8,000 or so. The off-menu (for now) chicken blasts the palate. Still, the creamy note of the meat itself hangs on, until it also is swept away in the inferno. Yet as graphic designer Kevin Jewell says, “I can distinctly taste different chiles.”

It’s an interesting observation. In fact, scientists tell us – or try to, anyway – that spices and chiles are not actually hot. Capsaicin, the ignition source in chiles, merely triggers receptors that intend to prevent us from scorching our mouths.

“This pain is nothing more than an illusory side effect of our confused neural receptors,” biologist Roberto Silvestro wrote in The Conversation.

Could have fooled several of the Weekly’s staff.

This mixed reaction has been observed by staff at Rudolfo’s and Heatwaves. Some guests come to the restaurant specifically for the experience. There is an aspect, researchers hypothesize, of thrill-seeking in the desire for hot stuff. Other diners struggle and sweat before succumbing.

Interestingly, studies suggest that tolerance of – and even craving for – spicy heat can be learned. An experiment with capsaicin on identical and fraternal twins published in Physiology & Behavior could not definitively settle whether DNA plays a role (genetics are responsible for between 18 and 58 percent of spice tolerance, according to the report), but research does indicate personality and environment are key.

As Spence observed, “No one, after all, is born liking spiciness. Rather, people learn to like the oral burn associated with eating moderately hot chile peppers.”

It should be noted that staff writer Celia Jiménez, who was raised in Mexico, sailed through all four heat levels. “When I was a kid we would play ‘who can eat more chiles,’” she recalls. After years of living north of the border, Jiménez admits to a changing palate. “I can’t handle the heat like I used to.”

Still, she was quick to snap up the last bite of “clucking hot” chicken.