Botulinum toxin and the facial feedback hypothesis: Can looking better make you feel happier?

Botulinum toxin and the facial feedback hypothesis: Can looking better make you feel happier? Murad Alam, MD,a Karen C. Barrett, PhD,b Robert M. Hodapp, PhD,c and Kenneth A. Arndt, MDd,e,f,g Chicago, Illinois; Fort Collins, Colorado; Nashville, Tennessee; Boston and Chestnut Hill, Massachusetts; New Haven, Connecticut; and Hanover, New Hampshire The facial feedback hypothesis suggests that muscular manipulations which result in more positive facial expressions may lead to more positive emotional states in affected individuals. In this essay, we hypothesize that the injection of botulinum toxin for upper face dynamic creases might induce positive emotional states by reducing the ability to frown and create other negative facial expressions. The use of botulinum toxin to pharmacologically alter upper face muscular expressiveness may curtail the appearance of negative emotions, most notably anger, but also fear and sadness. This occurs via the relaxation of the corrugator supercilii and the procerus, which are responsible for brow furrowing, and to a lesser extent, because of the relaxation of the frontalis. Concurrently, botulinum toxin may dampen some positive expressions like the true smile, which requires activity of the orbicularis oculi, a muscle also relaxed after toxin injections. On balance, the evidence suggests that botulinum toxin injections for upper face dynamic creases may reduce negative facial expressions more than they reduce positive facial expressions. Based on the facial feedback hypothesis, this net change in facial expression may potentially have the secondary effect of reducing the internal experience of negative emotions, thus making patients feel less angry, sad, and fearful. ( J Am Acad Dermatol 2008;58:1061-72.)

CHANGING FACIAL EXPRESSIONS WITH BOTULINUM TOXIN The cosmetic use of botulinum toxin has changed the face of cosmetic surgery. A ubiquitous, minimally invasive procedure is now able to alter dynamic facial expressions in a manner that eludes detection by observers. As such, in users, toxin injections can modify the visible manifestations of emotions. It has been suggested that actors and actresses partaking of botulinum toxin injections are sacrificing emotional range for the imperative of seeming younger. Novice patients suspect that there is something to be feared by a drug so subtle yet powerful, and it is not uncommon to have a patient willing to undergo a From the Section of Cutaneous and Aesthetic Surgery,a Departments of Dermatology, Otolaryngology, and Surgery, Northwestern University, Chicago, Ill; the Department of Human Development and Family Studies,b College of Applied Human Science, Colorado State University, Fort Collins, Colo; the Department of Special Education,c Peabody College, Vanderbilt University, Nashville, Tenn; the Department of Dermatology,d Harvard Medical School, Boston, Mass; the Section of Cutaneous Oncology and Dermatologic Surgery,e Department of Dermatology, Yale University School of Medicine, New Haven, Conn; the Department of Medicine (Dermatology),f Dartmouth Medical School, Hanover, NH; and SkinCare Physicians of Chestnut Hill,g Chestnut Hill, Mass. Supported by the Northwestern University Department of Dermatology departmental funds. Disclosure: Botulinum toxin administration for cosmetic enhancement is included in the clinical practices of Drs Alam and Arndt.

facelift but evince concern about botulinum toxin injections. The cosmetic dermatologist’s answer to the patient fear of posttreatment expressionless has been deductive reasoning and encouragement. After all, babies, too, lack upper face wrinkles and yet are able to convey their emotional state without difficulty. It has been suggested that botulinum toxin injections may have other, indirect potential effects, including improving patients’ emotional states, culminating in less anger, fear, and sadness. To evaluate the accuracy of this assertion, the remainder of this paper will examine relevant concepts in current psychological theory. The confirmatory and Dr Alam has previously been an investigator on a clinical trial of botulinum toxin for hyperhidrosis; for this trial, funding was provided to Northwestern University Office of Clinical Trials by Allergan, the manufacturer of botulinum toxin. Dr Alam did not receive any honoraria, consulting fees, residual research funds, direct or indirect salary support, or any other renumeration from these research funds from Allergan or otherwise from Allergan. Drs Barrett and Hodapp have no conflicts of interest to declare. Reprint requests: Murad Alam, MD, Department of Dermatology, 676 N. St. Clair, Ste 1600, Chicago, IL 60611. E-mail: m-alam@ northwestern.edu. 0190-9622/$34.00 ª 2007 by the American Academy of Dermatology, Inc. doi:10.1016/j.jaad.2007.10.649

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physiological reactions; (3) the emotional experiences of others with whom the patient interacts; and (4) the emotional displays of others with whom the patient interacts. In short, botulinum toxin injections might have the potential to affect a large set of processes in the patient undergoing the procedure as well as in those with whom the patient interacts. To the extent that prolonged experience of fear, anger, and sadness is not associated with happiness, for the purposes of this paper, these emotions will be considered ‘‘negative.’’ Conversely, in this context, smiling, happiness, and joy will be considered ‘‘positive’’ emotions.

UPPER FACE MUSCLES AFFECTED BY BOTULINUM TOXIN INJECTIONS AND THE EMOTIONS TO WHICH THEY LIKELY PERTAIN

Fig 1. Forehead and brow superficial muscular anatomy, including frontalis, procerus, corrugator supercilii, orbicularis oculi, and zygomaticus major. In order from top to bottom, flat muscle of forehead is frontalis (note lateral and medial, or inner and outer, fibers); V-shaped muscle above nose is procerus; diagonal muscle extending medially from nose to periocular area is corrugator supercilii; muscle encircling eye is orbicularis oculi (note inner and outer fibers); and diagonal muscle on cheek from lateral face to perioral area is zygomaticus major.

contradictory evidence regarding these concepts will be used to draw conclusions. First, we describe the facial muscles that are typically affected by the injections and the emotions to which these most likely pertain. Second, a number of related but distinct emotion concepts will be discussed: (1) the ‘‘facial feedback’’ hypothesis, which suggests that facial display of emotions feeds back to influence (or for stronger versions of the hypothesis, determine) emotional experience; (2) physiological responses to facial displays; (3) ‘‘emotional contagion,’’ which involves emotional responses and experience in response to someone else’s emotional display; and (4) ‘‘facial mimicry,’’ which involves the imitation of others’ facial responses (which could lead to emotion contagion if the facial feedback hypothesis is correct). All of these areas of research are relevant to this discussion, because if these processes do systematically occur, then botulinum toxin injections might lead to changes respectively in: (1) the patient’s own emotional experiences; (2) the patient’s own

When botulinum toxin is injected into the upper face, the primary aesthetic targets are the glabellar rhytides (‘‘frown’’), horizontal forehead lines (‘‘look up’’), and crow’s feet (‘‘big smile’’). The muscles of expression most involved at each of these sites, are, respectively, corrugator supercilii and procerus (glabella), frontalis (forehead), and orbicularis oculi (crow’s feet; Fig 1). The corrugator and procerus seem to be most associated with negative emotions, given that they are intrinsic to brow furrowing. With regard to emotional significance, the corrugator is the best studied of the upper face muscles, and activation of this muscle, as indicated by electromyography (EMG), has been systematically associated with sadness, anger, and fear.1-6 The frontalis is also involved with negative emotions, including sadness and fear, but can also be crucial in non-negative emotional expressions, such as surprise, which can appear as the raising of the inner and outer fibers of this muscle.7-11 Because the frontalis is a large muscle, it abuts other muscle groups, and its actions can be confounded with the contractions of these and hence with a host of emotional expressions. In general, to the extent that botulinum toxin reduced the movements of corrugator and frontalis (especially the inner aspect), it should affect the display of negative emotion, and the various possible consequences of that, as described below. In contrast, the orbicularis oculi, which encircle the eyes, are involved with smiling, and hence expressions of happiness and joy. A few EMG studies have supported the activation of the smile muscle (zygomaticus major; see also Fig 1) in displays of happiness.1-2,6 However, the orbicularis oculi has proven difficult to assess accurately in EMG studies of emotion. Nevertheless, an abundance of research

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investigating the visible movement of orbicularis oculi has supported its role in expressions of happiness. Smiling was definitively studied in 1862 by the French neuroanatomist Duchenne de Boulogne.12,13 Duchenne’s central insight was that the smile of enjoyment could be distinguished from deliberately produced smiles by consideration of two muscles: the zygomaticus major, which pulls the lip corners up obliquely, and the orbicularis oculi, which encircles the eye and pulls skin from the cheek and forehead towards it. Some recent work has found that the true smile of enjoyment is contingent on the action of the pars lateralis part of the orbicularis, which raises the cheeks to produce crow’s feet rhytides.14,15 The entire orbicularis muscle is susceptible to actions of botulinum toxin. Other research suggests that although spontaneous positive emotion is more commonly associated with the smile that includes orbicularis oculi, it also is systematically associated with a smile that lacks orbicularis oculi but includes an open mouth, at least in children.16,17 Moreover, smiles that occur in negative contexts are more clearly associated with the presence of components of negative emotion than with the absence of orbicularis oculi.16,18,19 Thus, although botulinum toxin injections might reduce the movement of a muscle associated with positive emotion, there is evidence that there are other means of communicating positive emotion that are unaffected by the procedure. Thus, the display of the smile without orbicularis oculi involvement would not necessarily convey nonpositive states to others. The conclusions derived from EMG investigations of facial emotional expressions have limitations. Many investigations have reaffirmed the importance of the corrugator region as a fundamental discriminator of negative emotional states, including sadness, anger, and fear.20 Indeed, this primacy of corrugator supercilii was foreshadowed by Darwin, who dubbed it the muscle of ‘‘disturbance.’’ The impact of other muscle groups is less clear. Despite the similarity in emotional effect to the corrugator, the frontalis is difficult to isolate, even with precise placement of electrodes, because EMG signals are corrupted by interference from adjacent muscle groups. Similarly, the orbicularis oculi, shown to be activated in the genuine Duchenne smile, is less successfully analyzed with regard to its involvement with other positive emotions. The extant research on EMG and observable facial movement suggest that a reduction in the mobility of corrugator and frontalis should be associated with a diminished display of anger, fear, sadness, and surprise, and a

reduction in mobility of orbicularis oculi could reduce one important display of genuine positive emotion (but perhaps not the only such display). How might these changes in emotional display affect the patient and those with whom the patient interacts? To address this question, we will now summarize some of the literature on facial feedback, physiological responses to facial displays, and facial mimicry and contagion.

THE FACIAL FEEDBACK HYPOTHESIS In the simplest terms, the facial feedback hypothesis maintains that expressive behavior can activate or regulate emotions.10,21 As Izard notes, the seeds of this idea are lost in time, with examples occurring in ancient writings, including the Iliad. In Shakespeare’s Henry V, soldiers are charged on the eve of battle to construct fearsome expressions in preparation for their imminent exertions. In the scientific world, one of the first to mention the feedback idea was Charles Darwin,22 who noted that ‘‘even the simulation of an emotion tends to arouse it in our minds.’’ While he was not always consistent and also described emotions as proceeding from a ‘‘state of mind,’’ he clearly believed that even if not the sole determinant of emotions, expressive behavior had a major role in control of these emotions: The free expression by outward signs of an emotion intensifies it. On the other hand, the repression, as far as this is possible, of all outward signs softens our emotions. He who gives way to violent gestures will increase his rage; he who does not control the signs of fear will experience fear to a greater degree.

William James, about 2 decades later, concurred: ‘‘Refuse to express a passion and it dies. . .If we wish to conquer undesirable emotional tendencies in ourselves, we must assiduously, and in the first instance, go through the outward movements of those contrary dispositions which we prefer to cultivate.’’23 Other scholars further refined these theories, with Gellhorn24 providing some of the earliest laboratory evidence and Tomkins25 some of the first modern formulations of the theory. Using curare to relax laboratory animals’ striated muscles, Gellhorn found a decrease in sympathetic nervous system and hypothalamic responsiveness, which he ascribed to the therapeutic effects of reduced muscle tone on emotional tension. Tomkins hypothesized that there are specific patterns of neural firing that generate facial and vocal responses, and that feedback from these as well as from skin sensations create the experience of affect. Perhaps the clearest

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Fig 2. Subjects asked to hold a pen between their teeth so as to simulate a grin found a cartoon to be funnier than did subjects who were not asked to perform this maneuver.27

and most verifiable theoretical statement of the facial feedback hypothesis was offered by Laird,26 who postulated that a subject-blind, experimentercreated facial expression would induce a similar emotional experience in the subject. There have been a number of studies aimed at determining whether or not manipulation of the participants’ facial displays affect their emotional experiences. The best of these studies have carefully tried to manipulate facial displays in a fashion that minimizes the participants’ awareness that they are producing an emotional display. Even with this careful manipulation, results have generally favored the facial feedback hypothesis. Strack, Martin, and Stepper27 found that having subjects hold a pen between their teeth (a simulation of smiling) caused them to find cartoons funnier (Fig 2). Larsen, Kasimatis, and Frey28 attached two golf tees to either side of subjects’ foreheads and asked subjects to try to move the two tees together (a simulation of frowning); with the tees closer together, subjects rated unpleasant photographs more negatively (Fig 3). A research paradigm that further reduced the likelihood that participants recognized the ‘‘emotional expression’’ that they were being asked to display and reported emotions accordingly was Zajonc’s,29 in which individuals pronounced the phoneme u¨ (simulation of a scowl) or o (simulation of a relaxed face) for one minute. The u¨ caused a significant increase in forehead temperature, previously shown to be associated with negative feelings,30 and indeed, the participants rated the o sound as more pleasant than the u¨. Even when participants are not asked directly about their emotions, but are instead asked to make affective judgments that should be colored by

Fig 3. Subjects who had two golf tees attached to either side of their foreheads and were asked to try to move these together so as to simulate a frown concurrently rated unpleasant photographs more negatively than subjects who viewed the same photographs but did not simultaneously attempt the movement.28

emotion, evidence for facial feedback can be observed. When asked to evaluate the level of fame of several celebrities, subjects who were concurrently asked to furrow their brows reported the same celebrities to be less famous.31 Evidence for the facial feedback theory is not limited to contrived studies. A more naturalistic study approximating a real situation required research subjects to engage in positive or negative facial expressions while smelling pleasant and unpleasant odors. The subjects’ ratings of the quality of the odors depended mostly on the odors but were moderated by the type of face they were making at the time they smelled.32 There is some limited evidence that naturally occurring differences in expressiveness are associated with differences in emotionality, although the direction of effects can not be ascertained. Dysphoric persons, in keeping with their negative mood states, seem to show less responsiveness of zygomaticus major (the smile muscle) to positive stimuli, but sometimes react to happy stimuli with corrugator (frown) response. Corrugator activity in response to unhappy images was the same for the dysphoric and normal subsets.33 Some subjects appear to be inherently less expressive, and exhibit less intense and less differentiated facial emotional expressions,6 and there is evidence that such individuals also report less emotion. Evidence from contrived and naturalistic studies, as well as of naturally occurring individual differences, suggest that one’s facial behavior can affect one’s emotional experience.

PHYSIOLOGICAL RESPONSES TO EMOTION AND TO FACIAL DISPLAYS There is also evidence that facial displays are associated with physiologic change. Two major

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Fig 4. Fear. Contraction of Action Unit 1 (AU1), which raises the inner corner of the brow (via inner fibers of the frontalis). See also Fig 1. (Reprinted with the permission of Paul Ekman, from: Ekman P, Friesen WV, Hager JC. Facial action coding system: the manual network. Salt Lake City [UT ]: Information Research Corporation; 2002. p. 466.)

types of physiologic responses to facial displays have been investigated: autonomic nervous system responses, as measured by electrodermal and cardiovascular responses, and central nervous system responses, as measured by electroencephalographic (EEG), functional magnetic resonance imaging or positron emission tomography scans. In each case, physiologic responses associated with discrete facial expressions are quantified in terms of anatomically-based movement or electromuscular (EMG) responses. Observable muscular measurements that occur during facial emotional displays are typically recorded using one of two measurement tools: either the Facial Action Coding System (FACS) developed by Ekman and Friesen,7,8 or the Maximally Discriminative Facial Movement Coding System (Max) system developed by Izard.11 FACS is an anatomically based system that permits the reduction of any facial expression into visually distinguishable muscular actions through repeated slow-motion viewings of the video of the expression. Validated across age groups and cultures, FACS is designed to account for all observed facial movements, which are represented as either single numerical FACS codes or a combination of such codes. Manuals are available that present visual representations of each of hundreds of basic FACS expressions, as well as instructions on how to recreate these (Fig 4-8). Reliabilities for FACS scoring are typically greater than 0.80.34 The Izard scheme, Max, is similar but less exhaustive,

Fig 5. Intense fear. Simultaneous contraction of Action Unit 1 (AU1), which raises the inner corner of the brow (via inner fibers of the frontalis), and AU4i, which lowers and draws the eyebrows together (via the procerus and corrugator). The contraction of AU4 is mild (as designated by ‘‘i’’) rather than intense (‘‘ii’’). The combined effect of AU (114i) entails pulling of the medial portion of the eyebrows upwards and together, producing of an oblique, triangular shape to the eyebrows, causing of the skin in the center of the forehead to wrinkle horizontally, and possibly creating vertical lines, wrinkles, or bunching of the skin between the brows. See also Fig 1. (Reprinted with the permission of Paul Ekman, from: Ekman P, Friesen WV, Hager JC. Facial action coding system: the manual network. Salt Lake City [UT ]: Information Research Corporation; 2002. p. 470.)

in that it includes only those facial movements believed by the author to be relevant to emotion. Of the many experiments performed using the aforementioned techniques, some are particularly seminal and representative. Ekman and Levenson imbued the study of facial feedback with laboratory rigor in the 1970s and 1980s35-37; these efforts culminate in a widely discussed article in Science that examined physiologic responses to facial movements.9 In this study, six target emotions (surprise, disgust, sadness, anger, fear, and happiness) were evaluated via a ‘‘directed facial action task.’’38 In each case, a coach provided subjects not with a global command to make an expression representative of an emotion but rather a set of precise instructions regarding which muscles to contract so as to create a facial expression consistent with a particular emotion. For example, in lieu of posing anger, subjects were asked to: ‘‘pull your eyebrows down and together, raise your upper eyelid and tighten your lower eyelid, narrow your lips, and press them together.’’ It was found that similar autonomic

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Fig 6. Fear/surprise. Contraction of Action Unit 2 (AU2), which raises the outer corner of the brow (via the outer fibers of the frontalis). See also Fig 1. (Reprinted with the permission of Paul Ekman, from: Ekman P, Friesen WV, Hager JC. Facial action coding system: the manual network. Salt Lake City [UT ]: Information Research Corporation; 2002. p. 466.)

responses were elicited when subjects re-experienced actual emotions from the past and when they artificially created the facial experiences consistent with such emotions. Not only did negative expressions differ from positive expressions on autonomic parameters regardless of the method used to create these expressions, but expressions of particular emotions differed from each other on autonomic parameters. This study provides some of the initial evidence in support of the hypothesis that facial expressions, rather than being merely a manifestation of antecedent internal emotional states, can themselves create the internal and biologic experience of emotions. Studies that induce emotions via cognition have measured EMG and concomitant brain activity. Feeling bad or unhappy from recalling specific events or being cued by an external image has been shown to be associated with an increase in corrugator (brow furrowing; frowning) muscle1,2,39,40 and a decrease in right frontal alpha activity.3,41 Remembering pleasant events or seeing positive images is associated with a selective upregulation of zygomatic muscle firing42 (mouth corner raising; smiling) and a decline in left frontal alpha activity.4,43,44-60 Others have shown that even when incident stimuli are processed unconsciously, with the subject distracted by other sounds, the same EMG and EEG results are observed. There has been some criticism of studies of the facial feedback hypothesis

Fig 7. Genuine Duchenne smile. Simultaneous contraction of Action Unit 6 (AU6), which circles the eye, narrowing it by pulling more skin from around the eye (via the outer fibers of the orbicularis oculi); AU12, which pulls the corners of the lips back and upward (obliquely) creating a bow-shape to the mouth while deepening the nasolabial furrow thus pulling it laterally and up; and AU25ii, which permits parting of the lips, with resulting possible exposure of the inner mucosal area and teeth and gums. The combined effect of AU(6112125ii) entails the lip corners being pulled up obliquely, deepening of the nasolabial furrow, appearing of crow’s feet wrinkles, raising of the infraorbital triangle, and deepening of the infraorbital furrow. (Reprinted with the permission of Paul Ekman, from: Ekman P, Friesen WV, Hager JC. Facial action coding system: the manual network. Salt Lake City [UT ]: Information Research Corporation; 2002. p. 485.)

that utilize facial expression coding systems. One problematic claim is that such studies contain cues that lead participants to behave in certain ways.42 A similar worry is that instructions regarding facial expressions are silly or embarrassing, thus potentially changing emotional responses.61-63 Further, the evidence demonstrating the validity of the ‘‘categorical’’ model, the capacity of specific facial expressions to elicit specific emotions, is less than complete.64,65

FACIAL MIMICRY AND EMOTIONAL CONTAGION Facial mimicry and emotional contagion are two additional concepts that have been demonstrated empirically. Lanzetta66-68 was instrumental in exploring the extent of the latter, which can be loosely described as the process whereby one person’s emotions are transmitted to another, especially when the transmission occurs in the absence of significant conscious awareness. ‘‘Contagion’’69,70 of this type

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has applicability for group cohesion (eg, smiles can instigate acceptance, approval, and bonding) and group survival (eg, fearful facial displays and vocalizations can alert other group members to danger). Facial mimicry, on the other hand, entails the elicitation of spontaneous synchronous facial expressions in others in response to similar facial expressions in the index individual. Such mimicry has been documented in human infants as early as the first few days of life.71-73 In adults, more complex emotions are subject to transmission in this manner.74

FACIAL COSMETIC SURGERY AND THE FACIAL FEEDBACK HYPOTHESIS The literature just reviewed does suggest that facial expressions may affect the experience of emotion in self and other, although it is important to note that this influence is not absolute or exclusive. Factors other than facial emotional expression, including spontaneous autonomic nervous system states and active cognition, also affect subjective emotional experience. Still, it is surprising the extent to which facial expressions of emotions are viewed as central to or even isomorphic with these emotions. Regardless of the response, the fact that Ekman75 can pose the query, ‘‘Can there be emotion without facial expression?’’ confirms the power of the face. At issue are more than botulinum toxin injections for cosmetic improvement of the upper face. While such treatments are the most direct means for modifying the muscles of facial emotional expression (Fig 9), many other cosmetic interventions have a similar effect. Soft tissue augmentation materials infused into the nasolabial folds and perioral areas can alter the smile and grimace as well expressions of anger and sadness. Face lifts and periorificial laser resurfacing may have similar impacts, in particular blunting lines around the eyes and mouth and generally reducing the ability to dynamically crease facial skin. Curtailing negative emotions Based on the available evidence regarding the facial feedback hypothesis, alterations in facial expressiveness caused by the use of botulinum toxin and other cosmetic agents primarily may decrease the experience of negative emotions in treated individuals. The relaxation of the corrugator and adjacent muscles might induce a reduction in anger and other negative emotions (Fig 10). Unpleasant life episodes will still be felt, but these will not be reinforced by equally negative facial expressions. The theory of emotional contagion and facial mimicry posits that the treated person’s positive

Fig 8. Anger. Contraction of Action Unit w4 (AUw4), which lowers and draws the eyebrows together (using the procerus and corrugator) but, unlike AU4i, creates wrinkles between the brows that are more angular than vertical. See also Fig 1. (Reprinted with the permission of Paul Ekman, from: Ekman P, Friesen WV, Hager JC. Facial action coding system: the manual network. Salt Lake City [UT ]: Information Research Corporation; 2002. p. 465.)

facial expressions would affect the emotional states of others around them. If many people in the social orbit of a given target individual have reduced anger and sadness facial expressions, the cumulative effects of the less negative emotions in this person may be substantial. At times, negative emotions are adaptive. Will persons undergoing botulinum toxin injections remain so calm when their lives are in danger that they fail to protect themselves, or look unmoved when tragedy strikes, appearing callous? Again, this seems highly unlikely. Fortunately, even at therapeutic levels, the toxin-mediated diminution in negative facial expressions does not preclude successful communication of negative emotions. Botulinum toxin’s effect is not so complete that all of the muscle groups involved in any particular emotion are blocked from contracting. Moreover, most facial feedback suggests that facial displays primarily modulate emotional experience, rather than being solely responsible for it; whatever the facial expressions, these are only part of the complete emotional experience. Internal experience of emotion can modify, either by weakening or strengthening the emotional significance of external facial expressions. We have so far focused on the effects of dampening muscle movements associated with negative emotion. Another movement that would be

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Fig 9. Facial feedback as it may pertain to botulinum toxin therapy and other facial rejuvenation procedures. Chemical manipulation alters facial expression, reducing frown lines, leaving the face appearing more happy and less sad or angry. This more positive facial expression leads to internal emotional experience of happiness in the affected individual. Additionally, the happy expression elicits happier expressions from bystanders, thus further reinforcing the happy expression and happy emotional state of the index person.

dampened would be that of orbicularis oculi, a muscle associated with genuine positive emotion. Would individuals undergoing botulinum toxin injections have diminished ability to experience or express genuine positive emotion because of the reduced movement of orbicularis occuli? Research reviewed earlier suggests that there are other avenues for the expression of strong positive emotion, so this seems unlikely. We will discuss this issue further in the next section. Stimulating positive emotions As previously noted, so-called ‘‘Duchenne’’ smiling, which involves concurrent cheek-raising, is associated with more pleasure than lip smiling or lip pressing alone.76,77 Open-mouthed smiling is also indicative of enhanced positive affect.78,79 Subjects with cheek-raised, open-mouthed smiles find pleasant stimuli relatively more pleasant, and respond more positively to whatever they are seeing. If two Duchenne smilers regard each other, a positive feedback loop is generated that results in greater shared positive affect and visual engagement. Laughter provides further benefits. Physical health benefits of laughter include analgesic and stress hormoneereduction properties.80 It has been found that laughter may affect autonomic function by first stimulating and then depressing arousal, thus

promoting protective responses within the immune system.81,82 Interestingly, in a further validation of the facial feedback hypothesis, even forced laughter appears to improve mood. To the extent that openmouthed and cheek-raised smiles elicit similar smiling in the recipient and eventually trigger laughter, smiling may also appropriate the physiologic benefits of laughter. The reduction of negative emotional expression associated with cosmetic use of botulinum toxin may predispose to a more positive emotional expression. This, in turn, may lead to positive affect and smiling, with the attendant benefits of smiling and laughter. Significantly, the benefits of smiling are contingent on social interaction.83,84 Subjects experiencing positive affect will seldom smile if alone, but the feedback process initiated by social situations can elicit smiling, and hence the associated happiness. Hypotheses about the benefits of smiling and laughter may not be that far-fetched, because it has already been shown than habitually positive facial expressions can lead to better life outcomes decades in the future. Between childhood and old age, individuals’ capacities to maintain positive facial emotional expressions can result in markedly improved mood85 and quality of life. In one study, women’s college yearbook pictures were assessed by trained raters for degree of positive emotion displayed.86 When subjects were asked to rate the students in

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these pictures on several personality dimensions, the women with more positive facial expressions were ranked higher and interactions with these women were predicted to be more rewarding. More startlingly, positive emotional expressions were good indicators of favorable outcomes in marriage and personal well-being up to 30 years later. These results remained when the photographic representations were controlled for physical attractiveness and social desirability. Perhaps those who do not have an innate tendency to smile and look agreeable might achieve similar results by erasing a lifelong frown or grimace with botulinum toxin. Smiling stimulates the world to smile with you. Dampening positive emotions and enhancing negative emotions While it is reassuring to consider the ways in which botulinum toxin may improve emotional state and lead to a decrease in negative emotions, the alternative possibility must be considered as well. That is, even if the net effect of toxin injections is improvement of emotional state, it is highly likely that at least some emotional processes would be negatively affected. Because the facial muscles affected by toxin injections are not exclusively involved with negative emotions, emotions not specifically targeted for extinction or reduction would nonetheless be reduced. For instance, the ‘‘Duchenne smile’’ associated with orbicularis contraction should be less evident. Even though there is evidence that there is more than one way to express genuine positive emotion, reduction of the movement of orbicularis oculi might reduce the incidence of genuine positive emotion via lack of appropriate facial feedback.78,87 Finally, it is interesting to consider the small subset of botulinum toxin patients who ‘‘feel frozen’’ or ‘‘have a funny sensation’’ in the absence of objective evidence of posttreatment brow or lid ptosis. This group may note a worsening of their emotional state. It is certainly conceivable that the neuromuscular feedback associated with their uncomfortable sensations may be processed in the same manner as negative emotional expressions. Facial feedback may thus make the uncomfortable patient also sad or unhappy. Beyond facial feedback: Culture, language, and self-image Apart from the facial feedback hypothesis, there are other explanations for the apparent connectedness between facial expression and emotional state. Cultural and ethnic differences in modes of communication may be potential confounders. For instance,

Fig 10. A middle-aged woman with (A) brows knitted and (B) upward gaze before treatment. The same maneuvers, shown in (C) and (D), induce fewer dynamic creases and less angry and anxious expression 2 weeks after injection of the glabellar and forehead complex with botulinum toxin.

there are stereotypic differences in glabellar expressiveness between residents of Mediterranean countries, where gesticulation and exaggerated facial expressions are a vital component of speech, compared to some Far Eastern cultures, where facial muscle movement during oral communication may be more subtle. It is difficult to assert that Japanese

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are more serene than Italians; more likely, lifelong patterns of glabellar muscle use culminate in deep lines or the lack thereof. Parents may socialize their children to behave in culture-appropriate ways, with the nonverbal elements of language impacting the appearance in a manner unrelated to emotional state. Additionally, just as skin color and hair texture may differ across racial subtypes, so may the propensity for forehead wrinkling. A very angry person from a culture that disdains flagrant facial expressiveness may thus seem more placid than a calmer person from a background where even mildly annoying emotional states are transmitted loudly through facial contortion. So, while facial feedback may continue to operate within a given cultural context, across groups there may be group differences that outweigh, or are at least exogenous to, the impact of emotion on the appearance of the individual. Like cultural differences, individual self-image may also impact the manifestation of facial expressions that are emotionally significant. To put it simply, we may feel good because we look good. Botulinum toxin injections would potentially facilitate this process by making us feel better about ourselves. However, in this scenario, there would be no need for others to react well to us, thus improving our self image. Instead, the feedback effect could come from a mirror, with the individual looking at her own, less wrinkled self, and smiling in return. In other words, while the anatomic link between facial muscular activity and emotional state (and the potential role for botulinum toxin in between) is likely mediated by facial feedback, this hypothesis is not the exclusive and complete explanation.

CONCLUSIONS The growing patient acceptance of surgical makeovers88,89 and greater willingness of the medical profession to alter and improve the appearance of the aging face may reflect the belief that improved physical appearance can trigger enhanced wellbeing. The traditional logic behind this process has been that a beautiful exterior can lead patients to consciously reassess their own self-image; next, better-looking people are better received by others, which in turn further enhances self-esteem. The facial feedback literature suggests that, in addition to these deliberate changes, aesthetic procedures may induce endogenous, unconscious changes in muscle movement and hence mood. Botulinum toxin, facial fillers, resurfacing, and other cosmetic procedures may change facial emotional expressions. While the net effect on emotional state is difficult to quantify, it

seems possible that the emotional benefits of toxin injections may outweigh the costs. In modern society, the emphasis on cognition has left a peripheral role for emotions, but facial emotional expressions remain a major route for communication and transaction. As Lazarus90 has noted, more so even than conscious thought, ‘‘emotions contain the wisdom of the ages.’’ By better understanding and modifying the manifestations of our own emotions, we may potentially be able to improve our own life experience and felicitously influence that of others. Further research is necessary to quantify the extent to which this may be achievable. Until then, we are left with the tantalizing possibility that while cosmetic procedures may have beneficial effects that are more than skin deep. Writing more than a century ago, Edgar Allan Poe understood the ability of facial expressions to guide lives: When I wish to find out how wise or how stupid or how good or how wicked is anyone, or what are his thoughts at the moment, I fashion the expression of my face, as accurately as possible, in accordance with the expression of his, and then wait to see what thoughts or sentiments arise in my mind or heart, as if to match or correspond with the expression. We are extremely grateful to Paul Ekman, PhD, who gave generously of his time to guide us, provide us with reading material, and offer us the help of his staff. We the authors are entirely responsible for the errors, omissions, and oversimplifications that Professor Ekman urged us to avoid. REFERENCES 1. Schwartz GE, Fair PL, Slat P, Mandel MR, Klerman GL. Facial muscle patterning to affective imagery in depressed and nondepressed subjects. Science 1976;192:489-91. 2. Schwartz GE, Fair PL, Salt P, Mandel MR, Klerman GL. Facial expression and imagery in depression: an electromyographic study. Psychosom Med 1976;38:337-47. 3. Davidson RJ, Schwartz CG, Saron E, Bennett J, Goleman DJ. Frontal versus parietal EEG asymmetry during positive and negative affect. Psychophysiology 1979;16:202-3. 4. Ahern GL, Schwartz GE. Differential lateralization for positive and negative emotion in the human brain: EEG spectral analysis. Neuropsychologia 1985;23:745-55. 5. Wexler BE, Warrenburg S, Schwartz GE, Janer LD. EEG and EMG responses to emotion-evoking stimuli processed without conscious awareness. Neuropsychologia 1992;30:1065-79. 6. Smith CA, McHugo GJ, Lanzetta JT. The facial muscle patterning of posed and imagery-induced expressions of emotion by expressive and nonexpressive posers. Motivation and Emotion 1986;10:133-57. 7. Ekman P, Friesen WV. Measuring facial movements. Environ Psychol Nonverb Behav 1976;1:56-75. 8. Ekman P, Friesen WV. Facial action coding system: a technique for the measurement of facial movement. Palo Alto (CA): Consulting Psychologists Press; 1978.

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