December 30, 2017

Bitter and twisted

From the New York Daily News: Study finds gin and tonic drinkers are more likely to be psychopaths, sadists

That’s not quite what the study finds. A slightly revised version is a couple of paragraphs into the story (credit for linking, but with a penalty for not mentioning it’s from 2015)

Researchers at Innsbruck University found that people who enjoy bitter flavors like the tonic water in a gin and tonic, black coffee, and dark chocolate are more prone to “Machiavellianism, psychoticism, and narcissism,” among other traits.

Here’s the list of ‘bitter’ flavoured foods they used (from)

bitter melon, cabbage, coffee, cottage cheese, grapefruit, radishes, rye bread, tea, and tonic water.

You might well think that preferences for these foods had a lot of other cultural associations on top of bitterness, and that added sugar or salt would make a big difference. And the researchers agreed, writing

Thus, due to the bitter items’ poor face validity, we refrained from formulating precise predictions regarding them. Moreover, previous research has shown that assessing taste preference is not a simple endeavor. For example, many preference measures often yield low reproducibility or are influenced by social desirability. Thus, we included this list for exploratory reasons.

They did find correlations between preferences for this list of ‘bitter’ foods and the negative personality traits (to the extent that they’re measurable on Mechanical Turk workers) — but the correlation predicted about 2% of the variability in psychopathy and sadism, and about 1% of the variability in Machiavellianism. And those are probably over-estimates given the selection bias of the news process.

There’s a more important problem, though, with the idea that ordering a gin and tonic at the bar reveals your friend’s hidden psychopathic nature. As always, the question in statistics is “compared to what”, and a G&T is not the only notably bitter beverage often consumed at the pub.


Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

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