Cross-cultural comparison of facial expression models of pain and orgasm. To identify any cross-cultural and culture-specific action units, we used MI to measure the relationship between AUs and culture (Methods, Cross-Cultural Comparison of the Facial Expression Models of Pain and Orgasm). Each color-coded face map shows the AUs that are common across cultures (red, low MI) or specific to one culture (blue, high MI, P < 0.05; see color bar to the left). As shown by the red coloring, pain shows several cross-cultural face movements (see AU labels below) and no culture-specific face movements. Orgasm also showed cross-cultural face movements (e.g., brow raiser, AUs 1 and 2) with culture-specific accents such as jaw drop (AU26) and mouth stretch (AU27) among Westerners, and lip corner puller (AU12) among East Asians. Credit: Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1807862115

A team of researchers from the UK and Spain has found evidence showing that contrary to popular belief, the orgasm face is not the same as the pain face. In their paper published in Proceedings of the National Academy of Sciences, the researchers describe their research and what they found.

It has become common for people to equate the faces of people experiencing orgasm with those experiencing serious pain—likely due to Hollywood interpretations of both. In this new effort, the researchers contradict such suggestions with evidence to the contrary.

To learn more about the faces people make while experiencing orgasm or intense pain, the researchers created a computer program to mimic a wide variety of gender-neutral facial expressions. They started with mathematical models that have been developed for animating faces—it included a core set of 42 movements representing different parts of a face. They then asked 80 adults (half male, half female) to determine if the expressions showed "orgasm," "pain" or something else. They used the results to build better models and then asked another 104 people to assess the simulated facial expressions.

The researchers found a clear distinction between perceptions of pain and pleasure—most of the volunteers agreed on which was which. But there was more to the study. The volunteers had also been divided into two cultural groups—half from Western cultures and half from Asian cultures. Both groups saw clear differences between orgasmic faces and pained faces, but they differed markedly in what they saw as the face of a person experiencing an orgasm. Those from western cultures tended to choose wide-eyed expressions with gaping mouths. Asian volunteers, on the other hand, chose smiling faces with tightened lips. The researchers suggest the differences could be explained by fundamental cultural beliefs such as the value that is placed on behavior related to high or low arousal states.

The movie illustrates the stimulus generation and task procedure using an example trial. On each trial, a dynamic face movement generator (1) randomly selected a combination of individual face movements called action units (AUs; 21) from a core set of 42 AUs (minimum = 1, maximum = 4, median = 3 AUs selected on each trial). A random movement is assigned to each AU individually using seven randomly selected temporal parameter values – onset latency, acceleration, peak amplitude, peak latency, sustainment, deceleration, and offset latency. In this example trial, four AUs are randomly selected – brow lower (AU4) color-coded in yellow, cheek raiser (AU6) color-coded in blue, nose wrinkler (AU9) color-coded in pink, and lip stretcher (AU20) color-coded in red. The randomly activated AUs are then combined to produce a random facial animation (here, ‘Stimulus trial’). Observers in each culture viewed the resulting facial animation played once for a duration of 2.25 seconds. If the random face movements matched their mental representation of a facial expression of ‘pain’ or ‘orgasm,’ they categorized it accordingly (here, ‘Pain’) and rated its intensity on a 5-point scale from ‘very weak’ to ‘very strong’ (here, ‘Strong’). Credit: Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1807862115

[The researchers contend that their study was more than just for curiosity's sake; they believe their findings could be useful in studies looking at how humans interact from a cultural perspective.

The movie shows example dynamic mental representations of the facial expressions of ‘pain’ or ‘orgasm’ from one observer in each culture. Credit: Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1807862115

Explore further Group finds facial expressions not as universal as thought

More information: Chaona Chen et al. Distinct facial expressions represent pain and pleasure across cultures, Proceedings of the National Academy of Sciences (2018). Journal information: Proceedings of the National Academy of Sciences Chaona Chen et al. Distinct facial expressions represent pain and pleasure across cultures,(2018). DOI: 10.1073/pnas.1807862115

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