Does Dexter Like His Coffee Black?

ResearchBlogging.org
A skeptical friend sent me an interesting link this week. The headline makes the bold claim that a study suggests that people who like black coffee are more likely to be psychopaths. I’m sure you can guess my initial reaction: skepticism.

So let’s look at the research.

First, the choice of singling out black coffee is journalistic bullshit. The research is not so specific. Instead, the researchers categorized foods by taste and included coffee as a member of the “bitter” group.

Now, I think that’s a questionable categorization. Some coffee, especially strong coffee, can be bitter. However, when I hear or read the word “coffee”, I don’t think “bitter”. And that is directly related to the biggest problem with the study itself: the method was survey, not taste test. In other words, we don’t know if people truly preferred the tastes themselves. Self-reports of such things are problematic, especially when the food categorizations themselves are arguable.

What the researchers did: an online survey asked participants to rate their preferences for a list of food items, then to complete a number of scales such as personality inventories and measures of malevolent traits. What they found: a strong correlation of preference for sweet foods with agreeableness. Slightly weaker, but robust correlations of preference for bitter foods with psychopathy and “everyday sadism”.

So, in general, what they found is that agreeable people tend to prefer sweet foods more and bitter foods less than disagreeable people. And those who score higher on measures of psychopathy and sadism tend to prefer bitter foods more than those who score low on those measures.

The study itself isn’t bad and the findings are interesting, but it’s very, very limited due to the method.

There are a number of possible explanations for these findings. Taste preferences come from both genetics (our taste buds vary) and habits (what we eat shapes what we like to eat). Likewise, personality traits are like most human traits in that they are partly determined by genetics. It is possible that the small correlation seen here is at least partly a clustering of genetic traits.

It’s also possible that years of munching on radishes makes people cranky and disagreeable.

It’s also possible that rating foods primed people to associate those foods with personality traits (e.g., the authors note the stereotype of bitter foods being associated with bitter people), thereby affecting the outcomes of some personality measures–something the study authors fully acknowledge.

The authors also admit to another limitation of the self-report measure:

…in preferring bitter tasting foods more than less sadistic people, everyday sadists may perceive them as positive due to their potential to cause distaste [as opposed to their own preference], that is, to cause a negative experience in other people.

However, the findings are consistent with other research. For example, one study linked PROP sensitivity (Supertasters) with unpleasant emotional reactions to film clips depicting aggression. PROP Supertasters have a genetic predisposition to experience phenylthiocarbamide (PTC) as bitter, whereas most people find it tasteless. It is a bit of a stretch to conclude from this finding that aversion to bitterness is associated with stronger empathy, but it’s an interesting finding nonetheless.

Still, I have to wonder–and pardon my language here, but–who the fuck cares?

It’s not as if this research suggests that you should avoid sharing a table with someone at Starbucks simply because they order the Sumatra blend instead of a pumpkin spice latte or a mocha cappuccino. It just doesn’t.

 

Sagioglou C, & Greitemeyer T (2015). Individual differences in bitter taste preferences are associated with antisocial personality traits. Appetite, 96, 299-308 PMID: 26431683

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