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You surely know the pop-psychology take on the introversion and extroversion dichotomy by now. If you find hours of socializing at, say, a big party or networking event, to be draining — well! You, my friend, just might be an introvert. There are other differences between these personality types, too, of course, but this one — about whether you find socializing to be energizing or draining — is the one that seems to pop up most often.

All of which makes this point, made this week by University of Pennsylvania psychologist Scott Barry Kaufman, especially interesting: No one has ever actually published a study investigating the question of socializing and its effect on these two diverging personality types. And as it turns out, the sheer exhaustion that comes of hanging out for too long with your fellow humans may not be an introverts-only thing.

For this new study, published in the Journal of Personality, Finnish researchers tracked 48 people for 12 days; five times a day, the study volunteers were to stop what they were doing to fill out a survey about what they’d been doing, and how they’d felt, in the past hour. Here’s what they found, according to Kaufman:

They found that the more people were acting extraverted … the more they reported being in a positive mood and feeling lower levels of fatigue in the moment, but after 3 hours they reported higher levels of fatigue. The level of fatigue depended on the number of people met during the last hour, the intensity of the social interactions, and how much they had a specific goal in mind when they were studying or working. Interestingly, these effects were found for both introverts and extraverts.

It’s true, by the way, that this study was on the small side, and one wonders whether the tiresome setup of the study itself is perhaps at least partially what drove these poor, brave study volunteers to exhaustion, as someone on Twitter pointed out. (Also of note: The researchers tracked both extroversion and conscientiousness, but as Kaufman rightly points out, it’s not so surprising that conscientiousness — that is, carefulness and attention to detail — might be tiring after a while.) But the idea that too much socializing is tiring no matter on which side of the extrovert-introvert divide you fall is a new one, and an intriguing one, too.

It may suggest, for instance, that the typical way that people think and write about this particular dimension of personality might be a little too black-and-white, anyway. “Everybody sometimes gets tired from too many social interactions … ,” Kaufman writes. “Just some of us are consistently more so on a regular basis than others.” Other people: exhausting to be around for too long, no matter who you are.