by Jillian Smith art by Leslie Yao
In A Cinderella Story, Jennifer Coolidge arguably plays her most iconic role as Fiona, the evil stepmother. In one comical scene, the evil stepdaughters get in the car with Fiona after failing to bring home the title of Homecoming Queen. “I am very, very, very upset about this,” she says through a half-grimace, half-smile. “You don’t look upset,” they reply. “Ugh—it’s the Botox. Can’t show emotion for another hour and a half” (A Cinderella Story, 2004).
Though overdramatized and goofy, the scene represents a real phenomenon. Since being approved by the Food and Drug Administration (FDA) for cosmetic use in 2002, Botox’s popularity has soared [1, 3]. Its accessibility, widespread advertisement, and relative safety are responsible for its popularity—recovery time is minimal with no long-term side effects, and complications are rare and minor [1, 2]. Botox is named for botulinum toxin type A, a toxin produced by the bacteria Clostridium botulinum [2, 4]. For a muscle to contract, the neurotransmitter acetylcholine must be released into the neuromuscular junction, the space where the end of a motor nerve meets muscle . However, Botox blocks this release, limiting the skin’s capacity for movement and therefore the patient’s range of facial expressions. After a few months, the effect wears off, so continued treatments are needed to maintain or reach the desired appearance .
Despite Botox’s popularity, one major question remains unanswered: does this limited ability to express emotions via facial expressions affect how Botox patients experience emotion? Scientists have long hypothesized that facial expressions influence the way that humans experience and interpret emotions. Psychological and neurological research is a starting point for understanding how this difference affects the brains of Botox users .
The Relevance of the Facial Feedback Hypothesis
If facial expressions intensify the experience of an emotion, then Botox injections that limit expressions might limit the experience of related emotions . Botox is of special interest to scientists researching the role of facial expressions in emotion because it can target specific facial features involved in conveying emotional expressions. A common injection site for cosmetic Botox is the area between the eyebrows—the glabella. It is injected into the corrugator supercilii muscle, which is part of a group of muscles that reaches far up into the forehead and works to pull the eyebrows together and down, often used to express anger or sadness . Botox can also reduce forehead lines, which express surprise, as well as crow’s feet and wrinkles around the mouth or nose, which are formed from smiling and expressing happiness . If these muscles are paralyzed, the patient will have a limited ability to produce facial expressions related to certain emotions: anger, sadness, surprise, and happiness, respectively.
Before diving into how producing facial expressions can affect emotions, it is helpful to define emotion. According to Merriam-Webster, an emotion is “a conscious mental reaction. . . subjectively experienced as strong feeling usually directed toward a specific object and typically accompanied by physiological and behavioral changes in the body”.
The issue with this definition is that it is somewhat vague—it is unclear to what degree “physiological and behavioral changes in the body” either preclude or result from emotion. The facial feedback hypothesis claims specifically that facial expressions have unique importance in the experience of emotion . Debates surrounding the role of facial expressions in emotion go as far back as Darwin, who hypothesized that facial expressions were inherited, not learned, and they had the ability to intensify emotion [6, 9].
William James, considered by many to be the “father of American psychology,” later theorized that subconscious physiological processes—“bodily changes”—precede emotion . He believed that once a stimulus is received, bodily changes occur, and the sensation of the bodily changes occurring is the emotion. For example, you see a bear, your heart rate and respiratory rate increase, and you recognize the sensation of your increased pulse and breathing, identifying them as the experience of fear. Because facial expressions are “bodily changes,” James believed that they could play a role in emotion . Possibly the most famous critique of James’ theory was conceived by former Harvard University physiologist Walter Cannon and his student, Philip Bard. The Cannon-Bard theory is based on the role of the thalamus, a brain structure that receives raw sensory information (e.g. color) and passes it on to its corresponding brain region for interpretation [6, 11, 12]. Cannon believed that because the thalamus had to receive information and integrate it before the brain could decide on a physical reaction, emotional and bodily changes had to occur simultaneously [6, 11, 13]. To use the same bear analogy: you see a bear, your brain processes what you’re seeing and recognizes it as dangerous. Simultaneously, you experience fear, and your brain increases your heart rate and respiratory rate.
James believed bodily changes could both modulate (regulate) and initiate emotional differentiation, which is the process of labeling emotions [6, 14]. For example, an increase in heart rate alone could make you feel fear, and if you began to run, you could be made to feel even more afraid. Alternatively, Cannon believed that the most important role of bodily changes in emotion was to regulate emotional differentiation [6, 14]. This would mean that bodily changes could only change how strongly you felt an emotion—a rapid heart rate would only be able to make you feel more afraid if you were already feeling afraid when it began to increase. These theories have been related back to facial expressions because the “bodily changes” addressed by James in particular include autonomous muscle movements like facial expressions. Consequently, the disagreement surrounding modulation versus initiation is still prevalent in the facial feedback hypothesis. Some theorists believe that facial expressions can initiate an emotional experience by activating brain pathways associated with a certain emotion, meaning making an “angry” facial expression would activate the same brain pathways as a more organic cause of anger [6, 15].
It is still unclear which of these views is more accurate, but both perspectives fail to consider that humans are constantly experiencing emotion . With this in mind, it may be
more important to consider whether facial expressions can affect emotion even without an external stimulus . Perhaps by forcing a “scared” facial expression, you can make yourself feel afraid even if no bear is endangering you. Has anyone ever told you something along the lines of, “smile, you’ll feel happier!”? If facial feedback can change an emotional experience without a stimulus, smiling alone should make you feel happier.
More extreme facial feedback theories implying that facial expressions are absolutely necessary for emotion have not been supported. Evidence suggests that facial expressions can “initiate” emotions or, rather, induce emotion regardless of whether an emotionally significant stimulus is present, but this effect is small .
Research, Botox, and the Brain
The use of Botox in facial feedback research theoretically minimizes biases that could affect other methodologies. For example, case studies on naturally occurring facial paralysis have smaller sample sizes, whereas there can be large sample sizes of people with Botox, making results more applicable to the general population. A common research technique is to have participants (without Botox or other impairments to facial expressions) simulate facial expressions [8, 16]. For example, some “pen-in-mouth” studies have participants hold a pen between their teeth or lips to produce a smile or frown, respectively, to evaluate how the simulated facial expressions affect the participants’ emotional experience [8, 16]. However, the results of pen-in-mouth studies have not been consistently replicated, and the effects can only be evaluated short term. Botox creates a consistent limit on the range of facial expressions a person can make, providing opportunities to research mood and more long-term effects of facial paralysis, presenting a possible solution to limitations in facial feedback research.
In the first study examining the effect of Botox on emotion, participants self-reported improved depression symptoms . The subjective nature of self-reporting made further investigation necessary. Another study compared mood improvements of patients without depression who received Botox in the glabella (recall this would have limited their ability to frown) to those who received other aesthetic cosmetic procedures and found a greater improvement in Botox patients . Since then, additional studies have demonstrated an improvement in mood following Botox treatment for patients with clinical depression [19, 20, 21]. For example, one study compared participants who received Botox injections into the corrugator supercilii muscle of the glabella to those who also received injections into the orbicularis oculi muscle, the muscle which creates crow’s feet . The study essentially compared people who had limited ability to frown with people who had limited ability to frown and smile. The first group demonstrated a greater improvement in mood, providing evidence to support the facial feedback hypothesis. It’s possible that in the second group, losing the ability to smile negated the positive effect seen in Botox patients who lose the ability to frown .
People with depression experience hyperactivity in the amygdala, an area of the brain involved in emotion and motivation, when viewing sad faces . They also experience reduced activity in the amygdala when viewing happy facial stimuli . In neuroscience, brain activity refers to the signaling that occurs in certain parts of the brain as they send and receive messages. People with depression have also been shown to experience higher resting-state amygdala connectivity with other brain areas, meaning the amygdala signals to other parts of the brain even when it is not actually processing stimuli, inducing emotion even when there is no stimulus that should cause that emotion .
One study particularly relevant to the role of the amygdala compared the brain activity of participants with and without glabellar Botox treatment . Participants viewed different facial expressions and brain activity was measured using functional magnetic resonance imaging (fMRI), allowing researchers to detect changes in brain activity associated with blood flow. Before receiving Botox, and after its effects had worn off, participants had increased activity in the amygdala when viewing angry media compared to happy media. However, after receiving Botox, this difference was not as pronounced. Therefore, it’s possible that muscles paralyzed by Botox decrease feedback to the amygdala, limiting emotional perception . This finding is supported by the repeated findings discussed earlier of improved depression symptoms after Botox treatment [17, 19, 20, 21]. The muscles involved in facial expressions send messages to the amygdala, so when they are paralyzed in Botox patients, these messages are decreased, potentially reducing the hyperawareness of the amygdala involved in depression .
This effect on the amygdala may also influence Botox patients’ ability to interpret emotions in others . Compared to people without Botox, Botox patients experience increased difficulty recognizing emotion in photos of facial expressions and detecting small changes in angry facial expressions [22, 27]. Botox patients have also been found to respond less strongly to emotional videos than patients with hyaluronic acid fillers—hyaluronic acid fillers give a similar appearance to Botox, but without the same paralyzing effect . Further, Botox patients have been shown to experience greater difficulty processing slightly emotional stimuli (for example, a picture of someone only slightly frowning) than highly emotional stimuli, like a picture of someone crying . These results suggest that feedback from facial muscles may be used to interpret more subtle emotional cues. In Botox patients, emotional stimuli—especially less “obvious” emotional stimuli, like very slight frowns, which are harder to encode—might have to be processed by other brain mechanisms that require more effort .
Pen-in-mouth studies, which involve simulating facial expressions, have shown that altering facial expressions changes the activity of mirror neurons. Mirror neurons respond to an action—like muscle movements of a facial expression—the same way, regardless of
whether it is performed or observed . For example, the anterior insula is activated both when experiencing and observing disgust [30, 31]. This makes mirror neurons important to the experience of empathy . Therefore, the sensorimotor areas of Botox patients might not receive the same information as someone without Botox when mimicking facial expressions because they experience a different pattern of facial expressions . Botox patients might not experience the same brain activation when observing someone convey an emotion using a facial expression that they cannot portray. Consequently, mirror neurons could possibly be less active due to Botox use over a long period of time. This idea suggests that Botox could play a role in empathy.
One possible limitation in Botox studies is the difficulty in determining whether improvements in mood are due to an increased feeling of attractiveness. One study observed an increase in self-esteem when Botox treatment was repeated until glabellar frown lines were completely eliminated, suggesting that improved mood may be related to the cosmetic effects of the procedure . A later study contradicted this, finding that even when participants reported no significant difference in how attractive they found themselves, they still experienced an improvement in mood . However, even if participants did not feel more attractive, they may have appeared happier or younger to others, and higher scores in measures of physical attractiveness have been associated with higher scores in measures of psychological well-being . Future studies might compare mood changes between patients with Botox and other cosmetic procedures, such as hyaluronic acid fillers, which could address the validity of these mood improvements.
Overall, the direct consequences of Botox on the brain remain unclear. Of the people who received cosmetic procedures in 2020, 66 percent were white, and an overwhelming 92
percent were women . However, are the white women who receive Botox—making up the majority of subjects in these studies—representative of the entire population of Americans? Further research should include more diverse samples, or use fMRI studies, which provide detailed images of brain activity, to better assess the differences in the brain before and after Botox . New sampling methods may be needed to fully understand the impact of Botox on more diverse groups of people, as previous methods tended to recruit people who already had (or planned to get) Botox—a group that we know to be fairly homogenous. Understanding the changes that occur in the brain following Botox injections will promote an understanding of the facial feedback hypothesis and reveal more specific pathways involved in the neural processing of facial expressions.
The experience of emotion is not easy to explain. It’s hard to even define what an emotion is, and although the facial feedback hypothesis explains an aspect of how we experience emotion, it is incomplete. The answers to important questions are still unclear, like facial expressions’ ability to modulate or initiate emotional experience and how important it is to the overall experience of emotion . It is important to view these hypotheses and their supporting evidence through a critical lens because even the assumptions they are based on are subjective. The facial feedback hypothesis is limited, but it guides research and investigation, and it will continue to spark more debates and questions.
Bringing Botox into the realm of facial feedback research increases the validity of such research, but Botox has its own limitations. In addition to its concentrated sample population, which mostly consists of white women, most research on Botox is dated. The majority of research on Botox immediately followed the approval of Botox for cosmetic use in 2002, but fewer studies have taken place since. Cosmetic Botox has lost the “newness” that drives research. Unless there is a significant discovery or change in the way the procedure is performed, it is unlikely we will see a peak in research around Botox and emotion anytime soon. Relying on old experiments to draw conclusions about Botox’s effect on emotion makes those conclusions less powerful.
In line with the facial feedback hypothesis, Botox apparently does have some effect on emotional experience, as seen in studies that evaluate mood and perception of emotional stimuli [6, 19, 20, 21, 22, 25, 26, 27]. Because it is also a low-risk, reversible procedure, it could possibly even be used to treat depression in the future. This treatment would mainly be beneficial to those who can afford Botox, as Botox requires continued treatment to maintain the effect . One treatment may not bankrupt the average American, but repeated treatments would be required to act as a long-term solution for depression. The cost could create a situation where wealthy people—namely, wealthy white people who are currently the majority of Botox patients—have access to an even higher standard of care and treatment options, while people of lower socioeconomic statuses do not . It has previously been established that the deciding factor in behavior toward cosmetic procedures is socioeconomic status .
Though the observed effects of Botox on emotion may support the facial feedback hypothesis, it is not clear to what extent Botox influences the experience of emotion as a whole (6). Although facial expressions limited by Botox have been shown to play some role in emotion, strong versions of the facial feedback hypothesis that claim facial expressions are necessary to processing emotion have not been empirically supported [6, 30]. The assertion that Botox treatment drastically changes patients’ overall experience and interpretation of emotion should be treated with skepticism. Rather, further research should investigate the extent to which Botox alters emotional experience and the brain pathways involved, an endeavor that will certainly bring even more questions to light.
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