Does smiling make us happy, or do we smile because we are happy? How much can our facial expressions influence our psychological health? These are questions scientists have asked for hundreds of years.
As increasing research supports, the seemingly simple act of smiling holds profound implications for our mental well-being. Whether genuine or forced, smiling can influence our emotional state, a concept explored through the facial feedback hypothesis and supported by both historical and contemporary research.¹
The facial feedback hypothesis posits that our facial expressions can influence our emotions. Essentially, the act of forming a facial expression sends signals to the brain that can create or intensify the corresponding emotional experience. For example, smiling leads to feelings of happiness, while frowning might evoke sadness or anger. This hypothesis suggests a bidirectional relationship between emotions and expressions, where not only do our feelings influence our expressions, but our expressions can also shape our feelings!²
In the 19th century, French neurologist Guillaume Duchenne conducted pioneering work on facial expressions through the study of facial musculature. Through his work, he found smiles that engage the muscles around the eyes constitute a genuine smile, or “Duchenne smile.” This stood in contrast to smiles that only involved muscles around the mouth, such as the more polite or forced smiles. Duchenne found that each smile, the genuine Duchenne smile and the less sincere smile, involved two very distinct neural pathways.3
Classic example of a Duchenne smile, which engages the muscles around the eyes.
Later, Charles Darwin expanded on Duchenne’s research in his book The Expression of the Emotions in Man and Animals, proposing that expressions were evolutionarily adaptive and universal. He also suggested that expressing an emotion could amplify the feeling itself, aligning with the later development of the facial feedback hypothesis, where “empirical research has found that facial feedback has the ability to both modulate present emotions and to initiate emotions.”4
Interestingly, the answer is often no. Smiling, whether genuine or not, can trigger positive neurological and hormonal responses. When we smile, the brain releases neurotransmitters such as dopamine, serotonin, and endorphins. These chemicals reduce stress and elevate mood.5
A research study conducted in Wales even found that Botox (botulinum toxin) injections that inhibited the ability to frown decreased depression in participants, while Botox injections that prevented the use of muscles around the eyes that typically produce “smile lines” increased rates of depression among those treated. This study shows how a smile, or the inability to frown, can produce positive emotions and the inability to genuinely smile can inhibit or lessen feelings of happiness.6
One study examined whether “covertly manipulating positive facial expressions would influence cardiovascular and affective responses to stress.” While performing stressful tasks, participants held chopsticks horizontally in their mouths in a way that produced a Duchenne smile, a standard smile, or a neutral expression. One half was also told to explicitly smile, and the other half was told to continue holding the chopsticks vertically, which produced an unintentional smile.
Image demonstrating the chopsticks experiment, with the first image showing a neutral expression, the second image showing an insincere or non-Duchenne smile, and the third image demonstrating a Duchenne smile.5
The group with genuine smiles saw the highest levels of stress reduction, while the group with forced smiles exhibited less dramatic stress reduction. Overall, smiling participants exhibited lower heart rates during stress recovery than the neutral group, leading the researchers to conclude that “there are both physiological and psychological benefits from maintaining positive facial expressions during stress,” whether they were genuine or not.7
Smiling has a powerful cumulative effect. Research from studies observing natural smiles as well as forced smiles says smiling can positively influence health. Specifically, smiling appears to help regulate the body's response during periods of acute stress, aid in quicker recovery from stressful events, and contribute to long term decreased risk of illness.¹
The power of a smile lies not just in what it communicates to others but in what it signals internally. Smiling, even if it feels forced, can elevate our mood, reduce stress, and foster social bonds. Historical insights from Duchenne and Darwin, combined with decades of psychological and neurological research, reveal that the simple acts of curving our lips and crinkling our eyes can set powerful biochemical and emotional processes into motion. In a fast-paced world brimming with stressors, the smile remains one of our most accessible tools and safeguards for physical, mental, and social well-being.
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