From WebMD Medical News, October 12, 2004

Forget the stoic look. Pain can ruffle anyone’s feathers, twisting the face from eyebrows to chin.

In fact, facial expressions are a pretty good mirror of how much pain a person says they feel, according to German researchers.

Miriam Kunz of Philipps University Marburg in Marburg, Germany, worked with colleagues on the study, which recently appeared in The Journal of Pain.

According to the authors, several studies have concluded that self-reported pain and facial expression of pain are unrelated; however, many researchers argue the opposite.

In this study, the researchers put 40 young men and women through tests of mechanically and electrically induced pain.

First came the mechanically induced pain test.

The volunteers sat in armchairs, and the researchers placed increasingly heavy weights randomly on the volunteers’ left or right forearms. They got about 20-30 seconds of relief between weights.

After a 10-minute break, the electrically induced pain test began.

Participants were zapped by 5 electrical impulses at 5-20 second intervals on their lower limbs. “We chose stimuli of very mild intensities at the beginning,” say the researchers.

Participants’ faces were videotaped during the tests.

The scientists analyzed the subjects’ facial expressions, breaking down the grimaces into actions like raising or lowering the eyebrows, opening the mouth, raising the chin, and blinking the eyes.About 10 seconds after each application of pain, participants were asked how much pain they felt.

Their facial expressions of pain matched self-reported pain levels.

However, the effect was best seen when examining each person’s facial expressions over increasing pain intensities, not just in one instance.

“The absence of a facial expression of pain cannot necessarily be interpreted as a sign that no pain is being experienced,” say Kunz and colleagues.

Some people express pain more easily than others, both verbally and facially.

The findings could help in assessing pain in people with limited verbal communication skills, say the researchers.