It is that time of the year we've all been waiting for… pumpkin spice season. That means pumpkin spice pancakes, pumpkin spice snickerdoodles (seriously, you need to try them), and of course pumpkin spice lattes!

Now I'm not a regular at Starbucks most of the year, but when pumpkin spice is in the air, you can find me in line. This early in the season I order my lattes iced. “One grande iced pumpkin spiced latte with whip for ‘lil' mama.'” (I love to give Starbucks fake names!)

“And what can I get started for you?” the barista asks my boyfriend.

“A tall coffee please, black.”

Instant facepalm. I'm normally a tea drinker, but I take cream and sugar in my caffeinated beverages. The idea of drinking coffee black makes my stomach churn.

“How can you even drink that stuff? It's SO bitter.”

“No calories,” he says, “and I like it bitter.”

In case you're wondering, no, this is not normal. Not normal at all.

A preference for sweet flavors and an aversion to bitter and sour tastes have been demonstrated in primate infants and adults, including humans. In fact, even more distantly related organisms, like oysters, reject bitter tasting foods. The reason for this is evolutionary. Many, many moons ago, before our produce was picked and neatly labeled at the corner market, our ancestors had to depend on their senses to determine what was safe to eat. Survival depended on the consumption of sweet substances and rejection of bitter ones.

Sweet foods typically contain a lot of calories, a highly valuable resource when our species depended on foraging for survival. Bitter tastes, on the other hand, often indicate the presence of toxins, like cyanide  (for more on this check out this ASO blog about bitter foods!).   

So if we are evolutionarily primed to hate bitter tastes, why do some of us develop a ‘bitter-tooth'?

For one, we don't always use our taste preference to guide our diets. For example, we don't eat ice cream for dinner, because we care more about our health than we do about the near orgasmic explosion of cookies and cream in our mouths (most of the time). Additionally, there are many foods we acquire a preference for through repeated exposure, which is often reinforced by some other extrinsic factor. Nobody likes hot peppers the first time they try them. They just have such a good time eating spicy tacos with friends that the acquired taste is reinforced by a positive social experience.

Another factor that influences our taste preferences is personality. A few studies have shown that people who really enjoy and consume spicy foods often are typically more adventurous and willing to take risks. Those of us with a sweet tooth tend to have an equally palatable disposition. However, an individual's preference for bitter compounds has been shown to be the strongest overall predictor of personality. People who learn to really relish bitter substances tend to display psychopathic personality traits.

Yeah, my boyfriend might be a psychopath.

A study published in 2016 was the first to provide empirical evidence that bitter taste preferences are linked to malevolent personality traits known at the Dark Tetrad (Machiavellianism, psychopathy, narcissism, and sadism). In two separate surveys of ~ 1000 individuals, people answered 4 personality surveys (like this one) and 2 measures of food preference. The most robust associations found were for psychopathy and everyday sadism (YIKES!).

This study draws on previous work demonstrating that bitter taste experiences are causally linked to hostile thoughts and behavior. That's right, causally, as in the bitter taste experiences were shown to cause harsher moral judgements and interpersonal hostility. Participants in this study showed an increase in self-reported feelings of hostility, hypothetical aggressive behavior, and actual aggression. Further, this effect occurred whether or not the participants were provoked. Maybe this explains why bae gets so cranky sometimes…

The authors hypothesize that the  link between bitter taste preferences and psychopathic personality traits is related to the ‘repeated exposure and reinforcement' idea I mentioned earlier. Constant exposure to bitter tastes will likely lead to an eventual acquisition of bitter taste preference. Coupled with the power of bitter taste experiences to elicit hostile behavior, the constant exposure to bitter tastes can also lead to elevated levels of aggressive thoughts and behaviors. Eventually, this can lead to a pleasurable experience of bitter tastes that is systematically coupled with hostility.

Just because psychopaths like their coffee black doesn't mean you're going to turn into Norman Bates if you drink your coffee black (though it'll likely make you a little scrappy). Still, I'll be hiding the kitchen knives next time I step into the shower.

Featured Image Credit: Psyco via Wikimedia Commons

Michelle Ziadie is a Ph.D. student in the Department of Genetics at UGA working on the evolution of maternal effects and undergraduate evolution education. A native of Miami, Florida with Caribbean roots, Michelle never turns down an opportunity to engage with spicy food or spicy music. When she's not dancing the night away with friends or getting lost in the Georgia wilderness, Michelle can be found sipping a café Cubano and watching Teenage Mutant Ninja Turtles with her kitten, Thomas. More from Michelle Ziadie.