The look of love - how our partner’s face can modulate pain

Why do we invite our partner to accompany with us when undergoing painful procedures? Is this the social support we need when in distress, or could their presence actually suppress pain?

Researchers from the Justus-Liebig-University Giessen in Germany investigated how faces of our partner or strangers, including their facial expression, would modulate pain.

Healthy female volunteers (n=36) involved in a romantic relationship were recruited for the study.

Pictures & Pains

Visual stimuli consisted of a face pictures. Pictures of a neutral stranger’s face, a stranger’s happy face or a stranger’s angry face taken from the Karolinska Directed Emotional Faces photo collection. The participants were also shown picture of their partner’s neutral face. Control pictures of an innate object were used, originating from the International Affective Picture System.

Heat pain stimulation was individually calibrated based on heat pain thresholds and the participants’ pain rating during a tonic heat stimulus. Participants underwent fifteen tonic pain stimulations at their individually calibrated heat pain temperature by Medoc’s Pathway System for 54 seconds, with intervals between 15-35 seconds. Of each picture type (partner, angry, neutral, happy and object) six pictures were randomly chosen. Each type of picture was presented in 3 trial during the 15 trials in a pseudo-randomized order, so that no more than two successive trials had the same picture category. In each trial there were 2 picture viewing times of each 15 seconds, 5 seconds per picture.

Pain was rated on Visual Analogue Scale (VAS) three times per trial during 8 seconds, on a VAS from 0-20 where 0 represented no pain and 20 represented worst pain imaginable. The first rating was after temperature stabilization (baseline), the second after the first picture viewing period, and the third after the second picture viewing period. Other measures taken were: Skin Conduction Level (SCL), Heart rate (HR), and surface electromyography (EMG) of the Corrugator brow muscles that are functionally responsible for frowning.

What modulates pain best?

There was no statistically significant difference in pain ratings before the visual stimuli were shown.

Interestingly, subjective pain ratings were rated significantly lower in the partner condition as compared to the neutral, angry and object conditions during the pain stimuli following the picture viewing. The happy stranger’s face was also significantly more effective in lowering pain ratings compared to the angry, neutral and object conditions. There was no significant difference however, between the happy and the partner pictures.

Other Interesting measures and pain

Skin conductance levels during heat pain stimulation were highest for the partner condition after being exposed to the visual stimuli, with no statistically significant differences at baseline.

EMG of the Corrugator muscle showed no differences at baseline, but a marked relaxation (i.e. lower EMG values) during heat stimulation for the partner condition as compared to the other face and object conditions. While for the happy face condition the EMG activity was also lower than the other photos except for the partner condition. The corrugator (frowning) measure showed a resemblance to the subjective pain ratings and point to a behavioral aspect of the participant’s perceived pain.

Do we need to bring our partner along to a painful medical procedure?

This specific study shows that it could certainly make a difference with regard to your level of perceived pain. But then again, a happy (friendly?) face of a stranger could also help!

Reference:

Hillmer, K., Kappesser, J., & Hermann, C. (2021). Pain modulation by your partner: An experimental investigation from a social-affective perspective. Plos one, 16(7), e0254069.