We always knew it, but now science backs us up. 

When you order a coffee, you put at least some cream and sugar in it, right? You're not an animal — since you need that sweet, sweet caffeine to pull you out of your crippling hangover, you'll obviously add a little sugar and cream to make it not taste like ass. 

And recently, science has dug into what the hell is wrong with people who don't do that. Turns out, they're probably completely insane. 

Looking at the taste preferences of 500 people, it was found that those who enjoyed bitter flavors over sweet flavors were more likely to exhibit signs of “machiavellianism, psychopathy, narcissism, and everyday sadism.” The study, which is published in the journal "Appetite," was conducted at the University of Innsbruck, Austria, by psychologists Christina Sagioglou and Tobias Greitemeyer.

For this crazy study, participants had to rate on a six-point scale how much they enjoy food and drinks that are either sweet, sour, salty or bitter. These results were then compared to those obtained from four different types of personality tests that looked at specific traits.

One of the personality tests looked at their propensity for aggression, asking them to rate how much they agree with statements like “Given enough provocation, I may hit another person.” Another looked at how manipulative they are and a third test looked generally at the ‘Big 5’ personality traits. Finally, they looked at how much of a buzz the participants get out of other people’s pain by asking them to rate statements such as “I enjoy tormenting people” and “I sometimes replay my favorite scenes from gory slasher films.”

They found a significant correlation between those displaying more antisocial personality traits and those with a penchant for strong bitter tastes, particularly flavors like coffee, beer, tonic water and radishes. If your Tinder date orders black coffee, tonic water and radishes, you should run screaming right then and there. 

Now we've finally got proof how insane those black-coffee drinkers are. Thanks, science!