Are facial expressions universal? You certainly might assume so. If you’re hit on the thumb with a hammer, you’ll make a pretty similar face to someone who was raised in a totally different culture on the other side of the planet. However, when it comes to orgasms, that’s not true at all.

A new piece of research has studied how two different cultures, Western and East Asian, interpret facial expressions associated with pain and orgasms. Previous reports have suggested that an o-face and a pained face are virtually indistinguishable, but this study says that simply isn’t the case.

Stranger still, they discovered some deep cross-cultural differences between orgasm faces. While Westerners expect to see their partner with a wide-eyed expression and gaping mouth, East Asian people anticipate a smiling face with tight lips (video below).

“This finding is counterintuitive, because facial expressions are widely considered to be a powerful tool for human social communication and interaction,” the study authors write.

As reported in the Proceedings of the National Academy of Sciences, psychologists led by the University of Glasgow in Scotland reached these findings by asking 80 people (half male and half female, half white European and half East Asian) to observe a number of computer-generated faces and label them as showing either “pain”, “orgasm”, or “other”. This was then used to create a series of better facial animations that over 100 people then scored and rated.

The findings indicate that pain faces and o-faces are vastly different and easily distinguishable. Meanwhile, people from both cultures associated the same expression – lowered eyebrows, gritted teeth, etc – with the sensation of pain. Why, then, do different cultures appear to associate different expressions with a universal sensation of sexual pleasure? 

“It is likely that Westerners and East Asians display different facial expressions in line with the expectations of their culture,” the study authors speculate.

^{Chen et al./PNAS}

“These cultural differences correspond to current theories of ideal effect that propose that Westerners value high arousal-positive states such as excitement and enthusiasm, which are often associated with wide-open eye and mouth movements, whereas East Asians tend to value low arousal-positive states, which are often associated with closed-mouth smiles.

"That is, Westerners are expected to display positive states as high arousal, e.g., excited, whereas East Asians are expected to display positive states as low arousal, e.g. calm."

The study authors hope that their work will pave the way for more research looking into the role of cultural and perceptual factors in facial expressions, something that is likely to become even easier with the increasing development of facial-recognition technologies.