In 2015, the psychologists Christina Sagioglou and Tobias Greitemeyer ran two studies with a combined total of 953 American adults, asking each person to rate how much they liked a range of bitter, sweet, salty, and sour foods and drinks, black coffee and tonic water among them, and then measuring their personality across several established scales. The result, published in the journal Appetite, was a consistent positive association between liking bitter tastes and scoring higher on Machiavellianism, narcissism, everyday sadism, and psychopathy, with the strongest links to sadism and psychopathy specifically.
Before going further, it is worth being precise about what that finding actually says, because it is not what a headline like “black coffee drinkers are more likely to be psychopaths” implies. This was a correlational study measuring existing taste preferences and existing personality traits in the same people at the same time. It did not test what happens to someone’s personality if they switch from a milky, sweetened drink to an unsweetened black one. Nothing in this research supports the idea that changing your order at a coffee shop changes who you are.
What the finding actually is, and its replication problem
Even the narrower, correlational version of this claim comes with a real complication. In 2017, an undergraduate researcher at Rollins College, Lauren Waymire, ran a partial replication of the original study with 40 participants, using laboratory taste testing rather than self-reported preference alone. That replication failed to find the specific link between bitter taste preference and psychopathy that the original study reported, though it did find a separate, unexpected correlation between psychopathy scores and extraversion. The sample was small and the study was a single undergraduate thesis rather than a large peer-reviewed follow-up, so it does not overturn the original finding on its own, but it is a legitimate reason for caution rather than treating the original 2015 result as settled fact.
A broader picture comes from a 2025 systematic review led by Ziang Li and colleagues that pulled together 24 studies on the relationship between taste preference and personality traits more generally. That review reported that preferences for bitter and sour tastes were, across the body of research it examined, still associated with antisocial personality traits, while a preference for sweetness tracked with neuroticism and agreeableness, and a preference for spiciness tracked with sensation-seeking and extraversion. Taken as a whole, the association between bitter taste and darker personality traits has more support behind it than a single failed student replication would suggest, but the review authors themselves called for more standardized measurement and more diverse samples before treating any of these associations as fully settled.
What might actually explain the correlation
Sagioglou and Greitemeyer’s own explanation for their finding was cautious rather than dramatic. They proposed that a general tolerance for unpleasant or aversive sensations, whether a bitter taste on the tongue or a harsh social interaction, might be the underlying trait connecting the two, rather than bitterness itself somehow shaping personality. Under that account, someone does not become more callous by drinking black coffee; someone who already tolerates unpleasant sensations more easily than average may be more likely to end up liking black coffee and, separately, to score higher on traits involving reduced sensitivity to others’ distress. The shared root, on this account, is a general trait of aversion tolerance, not a causal arrow running from the cup to the personality.
What this means, and does not mean, for a latte drinker
None of this research treats taste preference as fixed or innate in a way that would make “switching to black coffee” meaningless as a life change; people’s preference for bitterness can and does shift over time, often through repeated exposure, which is a well-documented phenomenon in taste research separate from the personality question. But shifting a taste preference is not the same claim as the research tested. The Sagioglou and Greitemeyer study measured people who already preferred bitter tastes, not people who had recently started drinking their coffee differently, and no study in this area has tracked what happens to someone’s Machiavellianism or sadism scores after they change their order.
It is also worth noting that a latte and a black coffee are not simply a sweetened and unsweetened version of an identical drink; a latte typically contains one or two shots of espresso along with steamed milk, giving it a different caffeine load than a standard brewed black coffee, depending on portion size and number of shots. A single shot of espresso contains roughly 63 milligrams of caffeine, while an 8-ounce cup of standard brewed coffee contains closer to 96 milligrams, so a small latte with one shot can actually deliver less caffeine than a plain black coffee, not more, depending on how each is prepared. Any change in mood or focus someone notices after switching drinks is at least as plausibly explained by a change in caffeine or sugar intake as by anything resembling a personality shift, and caffeine’s short-term effects on alertness and mood are a well-established, separate area of research from taste-personality correlations, governed by a person’s dose and tolerance rather than by whether milk was involved.
What this does not prove
The original study is correlational, drawn from adult samples in the United States, and cannot establish which came first, a bitter-leaning personality trait or a bitter-leaning taste preference, let alone whether one causes the other. The replication attempt was small and used a different measurement approach, which limits how much weight it can carry either for or against the original finding. What the research supports, read honestly, is a modest and specific claim: people who already prefer bitter tastes tend, on average and across some but not all follow-up studies, to score somewhat higher on certain antisocial personality traits. It does not support the claim that changing a drink order changes a personality, and no study has tested that question directly. A viral claim that swapping a latte for black coffee will reshape who someone is has taken a real, if modest and contested, correlational finding and rewritten it into a causal story the underlying research was never designed to test.
