Botox Injections Put a Crease in Emotional Evaluations

By Bruce Bower, Science News

Botox treatment to erase unsightly frown lines may cause unforeseen emotional wrinkles. First-time Botox patients become slower at evaluating descriptions of negative emotions, possibly putting the patients at a social disadvantage, a new study indicates.

For more than a century, scientists have posited that facial expressions trigger and intensify relevant feelings, rather than simply advertise what an individual already feels. Botox patients provide a novel line of support for this idea, as well as for the notion that facial expressions activate links between brain regions responsible for emotions and language, says psychology graduate student David Havas of the University of Wisconsin–Madison.

Botox is short for botulinum toxin-A, a neurotoxic protein that causes temporary muscle paralysis beginning one to three days after an injection and lasting for three to four months.

Two weeks after their first Botox injections, 40 women took an average of about one-third of a second longer to read sentences describing angry and sad situations than they did immediately before the procedure, Havas and his colleagues found.

Critically, Botox patients show no decline in the speed with which they read sentences about happy situations, Havas’ team reports in an upcoming Psychological Science.

“These findings suggest that facial expressions are involved in assessing specific emotions or emotional situations,” Havas says.

Havas hypothesizes that Botox-induced paralysis of the frown muscle — which runs across the forehead just above the eyes, allowing it to pull the eyebrows inward and down — may gradually weaken brain circuits that coordinate negative emotions.

A 2009 fMRI study, led by German neurologist Andreas Hennenlotter, supports that idea. Women attempting to mimic images of angry and sad facial expressions displayed weaker activity in emotion-related brain areas two weeks after receiving Botox injections to the frown muscle, Hennenlotter’s group found.

Banishing frown lines with Botox can indeed have social repercussions, remarks psychologist Nicolas Vermeulen of Catholic University of Louvain in Belgium. Previous studies indicate that mimicry of facial expressions critically aids in understanding others’ emotions, intentions and behaviors, he points out.

“Botox patients who are interacting with others behind a locked face might be at risk to react in the wrong way to, say, an angry driver or an angry customer in a pub,” Vermeulen says.

In the Wisconsin experiments, volunteers displayed no losses of sentence comprehension. That may partly reflect the fact that they had an unlimited amount of time to peruse sentences. But real-life conversations involve exquisitely timed banter, and seemingly small disturbances in evaluating emotional statements may foster misunderstandings, Havas suggests.

In the study, volunteers read 20 happy, 20 sad and 20 angry sentences presented on a laptop computer just before undergoing the Botox procedure. They pressed a computer key to indicate having finished reading each sentence. Comprehension questions were administered at random after one-third of the sentences.

Two weeks later, participants performed the same task with a different set of emotionally evocative sentences.

Havas’ team recruited Botox patients through cosmetic-surgery clinics in the Madison area. Participants received a $50 credit toward the cost of treatment.

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