Here's an easy question: If a person feels bitter, is he more likely to act with hostility toward others? Here's a tougher question: If a person tastes something bitter, is she more likely to be hostile?
The idea is less outlandish than you might think. A wide swath of previous research has shown how taste is linked to emotions, and therefore, behavior. Previous studies show that sweet tastes reduce stress and increase agreeableness. And watching happy video clips can make a sweet drink taste more pleasant than watching sad clips.
Bitter foods, on the other hand, have been linked with emotional reactivity and threat. And since bitterness has such strongly negative metaphoric meaning (think: bitter enemies, leaving a bitter taste in your mouth), researchers from the University of Innsbruck, Austria, predicted that bitter tastes might alter a person's emotions for the worse. In a paper published this week in Personality and Social Psychology Bulletin, they describe three experiments that showed how bitter tastes may cause people to act in aggressive and hostile ways.
A wide swath of previous research has shown how taste is linked to emotions, and therefore, behavior.
The first experiment showed that participants who drank "the bitterest natural substance currently known" (gentian root tea, in case you were wondering) felt significantly more hostile than those who drank sugary water, according to a self-reported mood survey. This effect remained even after accounting for the participant's perceived enjoyment of the beverage.
Next, researchers tested a more common bitter beverage, grapefruit juice, as compared to a neutral drink, water. After a taste test, participants completed a questionnaire that they were told was for another study. They read through a series of vignettes in which they could be provoked to anger, then rated how angry, frustrated, or irritated they would hypothetically be, and chose from five potential actions—one of which was directly aggressive. Those who drank grapefruit juice reported more anger and irritation and were more than twice as likely to choose the "direct aggression" option than those who drank water. For those who drank grapefruit juice, "when feeling angry, the option of acting out the anger was preferred over holding it back," the researchers write.
In the last experiment, researchers elicited actual aggressive behavior from participants, instead of using mood surveys or hypotheticals. Students in the study drank a shot of water or bitter gentian root tea. Then, as part of a supposed effort to determine a link between taste and creativity, an experimenter tested them on a filler task. Afterward, the subjects rated their experimenter. Those who drank the bitter tea were significantly more likely to give poor ratings to the experimenters—saying they were less competent, friendly, or good at their job—than those who drank water.
Taken together, these three experiments provide fairly strong evidence that bitter tastes can lead to hostility. And while you might plan to drink gentian root tea on a regular basis, other bitter foods and drinks have become more popular lately—like hoppy IPA beers or kale, for instance. Better watch out for aggressive behavior at your local organic bar.