Pleasure or Pain? The Difference Can Be Hard to Tell

That's according to new research out of Albright College in Reading, Pa.

"Although very distinct emotions, facial expressions of those who are experiencing pain appear surprisingly similar to those who are experiencing heightened sexual pleasure," says Dr. Susan Hughes, assistant of psychology at Albright, and lead author of the study, "Sex Differences in the Assessment of Pain Versus Sexual Pleasure Facial Expressions."

The study, which was published in the December 2008 issue of the Journal of Social, Evolutionary and Cultural Psychology, investigated the sex differences between distinguishing facial photos of males and females expressing either pain or sexual pleasure. Ninety-one participants were shown photos from the Internet and were asked to identify the emotion expressed in the image.

"Overall, participants were more able to correctly identify an expression of pain," says Hughes. "Perhaps it's because it's more important that we recognize threatening events we should avoid. Or just the fact that we have more exposure to different individuals expressing pain on a more frequent, daily basis."

Women were most accurate in identifying other women expressing pain. "This was the only condition were female raters performed better than men," says Hughes. "It has been shown that females demonstrate a higher level of empathy and realizing other females' pain may be a result of that."

"Men, however, were much better at identifying female sexual pleasure than were other women," she says. "Since there are not as many obvious cues of sexual pleasure and orgasm for women as there are for men, men made need to rely more on facial expression to determine if she's having a good time " and so that he may be invited back again."

The study is among the first to empirically examine the similarities between the appearance of facial expressions of sexual pleasure and extreme pain by looking at sex differences in the rater's perception and the sex of the image.

"It appears that we're better at identifying pain than pleasure," says Hughes, "especially when it's a woman in pain."