A fascinating follow-on to Paula Niedenthal’s work on mirroring emotions: Duke University researchers have found that people who undergo Botox have a harder time reading other people’s emotions.

A few well-placed Botox injections can erase your hard-won character lines. But that may also make you less likely to pick up on other people’s emotions.

That’s because the botulinum toxin, which reduces wrinkles by temporarily paralyzing small muscles in the face, can make it hard to furrow the brow or make other expressions that convey emotion. And our own facial expressions, researchers now show, may be essential to recognizing the feelings of others.

This unexpected Botox effect is a fascinating window on how we understand what other people are feeling. A good part of that process requires unconscious mimicry of the other person’s facial expression….

“The tendency to mimic facial expressions is rapid, automatic and highly emotion-specific,” write David Neal and Tanya Chartrand in an intriguing paper just published online by Social Psychological and Personality Science.

Neal and Chartrand say the subtle contraction of our facial muscles when we mirror a friend’s happiness or woe generates a feedback signal to our brains. Those incoming signals from facial nerves help the brain interpret how the other person is feeling….

In one experiment, the researchers recruited 31 women who were already having either Botox treatments or injections of a dermal filler, which plumps up wrinkles but doesn’t paralyze muscles. After the treatment, the women were shown a series of images that showed people’s eyes embodying different emotional states. Study subjects were asked to judge, as quickly as possible, what emotion the eyes conveyed.

The Botox patients scored significantly worse than those who got a dermal filler. That meant the Botox patients’ ability to make fast judgments about another person’s emotions was blunted. (The Botox didn’t eliminate their ability to judge emotion. They still were about 70 percent accurate.)…

The cognitive implications go well beyond Botox users. But the findings do make Neal and Chartrand wonder if prolonged use of Botox would hobble people’s ability to perceive others’ emotions and give others empathetic facial feedback.

“Mimicry promotes liking and emotional sharing,” the researchers say, “and may contribute to long-term relationship satisfaction.”