Forcing a Smile Using Electrical Stimulation Can Boost Your Mood

Forcing a Smile Using Electrical Stimulation Can Boost Your Mood

By Rachel Nuwer

The expression “a smile a day keeps the blues away” may have some credence beyond the realm of greeting card messages. The lingering question of whether a smile or frown lifts or depresses emotion has persisted for decades and is still actively debated.

In a new study, researchers sought a more definitive answer by using electrical muscle stimulation to literally force people to curl up the corners of their mouth up or down into a smile or a frown. They found evidence that the physical act of making those expressions seems to directly impact human emotions, cause the person to feel more positive or negative.

The idea that the body plays a role in shaping how people feel and perceive the world is “old and fascinating,” says Sebastian Korb, a senior lecturer in psychology at the University of Essex in England and senior author of the research, which was published in Emotion. “But it’s not universally accepted.” Korb says that the new study suggests that facial activity does seem to influence emotions and adds evidence to this long-standing but contentious hypothesis. .

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The role that facial expressions play in influencing human emotion has roots in the 19th century, when Charles Darwin and philosopher and psychologist William James both postulated that physiological changes in the body could have an effect on emotion. In the 20th century researchers began to focus on the effect of facial expression, and in the 1970s this idea was formally described as the “facial feedback hypothesis.”

In the decades since then, the hypothesis has received mixed empirical support. In 1988 researchers in Germany published a study that has come to be known as the pen task. They divided participants into two groups and asked them to manipulate a pen with their mouth in different ways. Both groups held the pen straight out, perpendicular to their lips, but one group held the pen between their teeth, which facilitated a smilelike expression, while the other held the pen between their lips with their mouth closed, forming a kisslike expression. The participants then ranked how humorous they found a series of cartoons. Those whose mouth was stretched into a smile found the cartoons to be funnier than those with the expression that resembled a kiss, which the researchers interpreted as evidence supporting the facial feedback hypothesis.

The well-known study was challenged, however, in 2016, when a team of researchers—including Korb—tried to replicate the findings across 17 labs, each of which conducted a study with more than 100 participants. In contrast to the original study, the researchers’ results did not reveal any significant evidence that supported the facial feedback hypothesis.

“Some people said we should forget about the hypothesis entirely,” Korb says, “while others, like me, said, ‘Wait a second—maybe we shouldn’t throw the baby out with the bathwater.’ I started thinking about how we could find other methods to manipulate muscles in a more controlled way than sticking a pen into your mouth.”

For the new study, Korb and his colleagues turned to electrical stimulation—a method that allowed them to target specific muscles in the face for a specific amount of time. They placed electrodes on 58 participants’ skin and gradually increased the current until it induced a contraction that forced the face into a frown or a smile. Anatomical variability among the participants meant that each one received a slightly different level of current to activate the targeted muscle.

Each participant was exposed multiple times for five seconds to several experimental conditions: smiling or frowning while looking at a blank screen; smiling while looking at a happy image, such as a beautiful beach; and frowning while looking at a depressing image, such as a beach covered in garbage. They also performed the same set of experiments with weaker stimulations that did not produce any visible movement of participants’ facial muscles. After being exposed to each condition, the participants ranked how positive or negative they felt.

Across all measures, the researchers found correlations between the participants’ facial features and how they said they were feeling but no change in mood when they were exposed to the weaker stimulation. The strongest correlation occurred when smiles were paired with positive images. In the absence of the accompanying imagery, though, participants still ranked their mood lower when their facial muscles were forced to frown and higher when they were stimulated to smile. For the image-free findings, “the effect was not massive,” Korb says. “But remember, we’re only activating certain muscles to a very small degree for five seconds, so we’re already putting ourselves in a situation where it’s not obvious that we’d find an effect.”

Heather Lench, a professor of psychological and brain sciences at Texas A&M University, who was not involved in the research, says the new study was done well and “opens up a new way to induce facial expressions.”

Now that Korb and his colleagues have preliminary confirmation that the method works, they are planning additional studies, he says. Future research could investigate how activating different muscles in the face makes people feel or use electroencephalograms to determine how quickly the brain emotionally responds to those changes. Further work will also be needed, he adds, to untangle the more difficult question of whether it is truly the activity of facial muscles that influences emotion—or whether study participants are simply realizing that these muscles are being activated, which makes them think about the corresponding emotion.

Lench adds that there could also be practical applications for Korb and his colleagues’ findings. “If there is a decently strong relationship between muscle activation and emotion, it opens up an interesting application of the work—that people could self-stimulate their muscles using wearable devices, for example, to change their emotional state,” she says. “The health, ethical and societal implications of this kind of application are very interesting.”