Brain and Behavior

Smiling Makes Us See Happiness in Expressionless Faces

Do you smile at people in the grocery store in an attempt to seem kind or polite? Well, according to a new study from the University of Essex, you may be more likely to see happiness in expressionless faces, simply because you smiled. Even a brief weak grin may be enough to make the face of stranger appear more joyful to you.

The Research

Using a painless current to manipulate muscles into a short, uncontrollable smile, a team of researchers set out to determine if even a weak smile (500 milliseconds) was enough to induce the perception of happiness in others.

The research team began by checking to ensure that the painless currents didn’t alter the participants’ mood. Once they ruled out that the electrical stimulation itself made people feel happier, the team showed 47 people (ages 18 to 38) digital avatars with expressionless faces and asked the participants to assess whether each looked happy or sad. In half the trials, electrical stimulation was used to activate the smile muscles just as the digital avatar’s face was being showed. (Nine participants were later excluded from the EEG analysis due to low-quality data, bringing the final sample size to 38).

The findings indicated that producing even that very short, weak smile was enough for the participants to perceive happiness in the faces of the expressionless digital avatars. This suggests that neuromuscular electrical stimulation-induced facial feedback can bias facial emotion recognition and modulate the neural correlates of face processing.

“We are currently conducting more AI research to further explore the phenomenon in healthy participants,” explains University of Essex ‘s Dr. Sebastian Korb from the Department of Psychology. “In the future, however, we hope to apply this technique to explore facial emotion recognition, for people with conditions like Parkinson’s, who are known to have reduced spontaneous facial mimicry and impaired facial emotion recognition. Moreover, we have published guidelines to allow other researchers to safely start using electrical facial muscle stimulation.”

Limitations of the Study

The scientists admit that there are several limitations to the study. These include:

  1. Only the Zygomaticus muscle was targeted to induce a weak smile. Future studies should explore the impact of more robust smiles by targeting more than one muscle.
  2. The study was limited to investigating the effects on smiling (positive), not frowning (negative).
  3. The study only administered the painless current at face onset, not at different times relative to showing the expressionless faces.

The findings were published in the February 8 journal Social Cognitive and Affective Neuroscience.


Wendy Burt-Thomas writes about the brain, mental health and parenting.

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