It's a question that's been repeated in high schools and colleges throughout time, published throughout the media, and even has studies to back it up - do you look the same when you orgasm as you do when you, say, stub your toe?
According to urban myth, the answer would be yes. But new research shows that answer might be completely wrong.
Okay… okay, so maybe this isn't the hardest hitting piece of science we've ever covered here at ScienceAlert.
But sometimes myths need to be busted – and as the researchers explain, your O and pain face being the same doesn't even make that much sense.
"Humans often use facial expressions to communicate social messages," explain the researchers from the University of Glasgow and De Montfort University in a new paper.
"However, observational studies report that people experiencing pain or orgasm produce facial expressions that are indistinguishable, which questions their role as an effective tool for communication."
So where does this myth come from? Well, as the researchers explain, there have been studies that show that we humans can't tell the different between the facial expressions of pain and orgasm.
"Real-world studies show that the facial expressions produced during pain and orgasm - two different and intense affective experiences - are virtually indistinguishable," they explain.
"However, this finding is counterintuitive, because facial expressions are widely considered to be a powerful tool for social interaction."
But if it's not helping us to communicate something (like if we're enjoying ourselves or in pain) then what's the point?
The researchers set out to answer this question with a set of animated faces that could make up to 42 movements in different parts of the face.
They then asked nearly 200 people (half from Western cultures, and half from Asian cultures) to assess the expressions on the animated face. Were they orgasming, in pain, or something else entirely?
What the researchers found is that there was a clear distinction between our perceptions of pleasure and pain. We didn't get them mixed up, which you would expect if they did look the same.
But not only that, they also found that what we expected an orgasm to look like differed.
"In each culture, the facial expression models of pain and orgasm are both physically and perceptually distinct," they explain in the paper.
"Cross-cultural comparisons also show differences in the facial expression models of orgasm, including wide-open eyes among Westerners and smiling in East Asians. In contrast, facial expression models of pain are similar across cultures."
You can see what this looks like in this slightly creepy video below:
Now, although this study is all a bit of a laugh, the researchers contend that their study was more than just a light debunking – testing cultural differences like this could help studies looking at how different cultures of humans interact.
"Our results therefore question the nondiagnosticity of these facial expressions and suggest that they could serve as effective tools for social communication and interaction," explain the researchers.
"Our results also address existing questions of whether culture influences how facial expressions are represented and used to communicate basic social messages."
And next time you stub your toe and someone yells about orgasm faces, you can smugly show them this article.
The research was published in PNAS (yes, haha, we laughed too).