Exploring the Positive and Negative Implications of Facial Feedback

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Exploring the Positive and Negative Implications of Facial Feedback

Michael B. Lewis

Cardiff University

The facial feedback effect (e.g.,Strack et al., 1988) is explored in three experiments. It was found that when someone lowers their eyebrows, following instructions, their mood becomes more negative. If, however, they are instructed to raise their eyebrows they become more surprised by facts. Finally, if people are instructed to wrinkle their noses, then odors are evaluated as more unpleasant. While providing further diverse evidence for facial feedback, the experiments are also considered in the context of facial muscular paralysis induced as part of cosmetic treatments using botulinum toxin. The research presented here supports the previously suggested idea that such treatments could reduce depression, but other possible psychological impacts of such treatments are considered.

Keywords: facial feedback, emotional expression, depression, surprise, disgust

Charles Darwin (1872) observed that constructing the facial expression associated with an emotion leads to that emotion being aroused in the mind. This reflects the idea that a facial expression not only communicates emotion to observers but also feeds back to the poser such that the emotion is intensified. An important experimental demonstration of this facial feedback effect was conducted byStrack, Martin, and Stepper (1988), who had participants hold a pen in their mouths. To produce facial action consistent with smiling, some participants held the pen with their teeth and with their lips pulled away from the pen. To produce facial expressions inconsistent with smiling, some participants held the pen with their lips and with their teeth away from the pen. Cartoons were rated as more amusing by the former group of participants, whose facial expressions were smiles, than the latter. It was argued that the action of smiling, even when not explicitly told to, makes one more positive in one’s evaluations. Strack et al.’s demonstration of the facial feedback effect was replicated bySoussignan (2002). In this replication, however, electromygraphic (EMG) activity was recorded to assess whether the muscular action was being main- tained. A positive facial expression led to a more positive evaluation of a stimulus in this experiment as well.

This facial feedback effect can be seen as part of the idea of embodied emotion.Niedenthal (2007) provides a description of how emotion itself can be seen as a matter of reexperiencing something through ‘perceptional, somatovisceral and motoric’

means (p1002). In facial feedback, the motoric action of forming a facial expression is sufficient to reexperience that expression.

Facial feedback effects are not restricted to just smiling.Flack (2005, see alsoFlack, Laird & Cavalaro, 1999) explored the effects of posing facial expressions similar to anger, fear, sadness, as well as happiness. Participants rated themselves on six emotions while

holding the four expressions. When the sad-like expression was formed (eyebrows relaxed so that they drop down and lower lip pushed up) participants rated themselves as more sad. Similar results were found for anger, fear, and happiness, with changes in the relevant emotional rating.

While the numerous demonstrations of facial feedback effects (only some of which are described here) are striking and tell us something of the embodiment of emotion, there are practical implications regarding this research. The first is that facial feedback has been proposed to have a role to play in the observation that people with facial paralysis often have symptoms of depression (Twerski & Twerski, 1986).

Van Swearingen, Cohn, and Bajaj-Luthra (1999) investigated the role that specific impairment in the ability to smile had on depression. They tested a group of people with varying degrees of facial paralysis. The extent of these people’s depression was related to the size of the impairment in their ability to smile: Those with higher depression scores had a greater impairment in their ability to smile. It is suggested, therefore, that the failure to be able to smile means that those individuals do not get the positive feedback associated with that facial expression.

The second practical implication (and possible application) of facial feedback research stems from the toxins produced by the botulism bacteria. Specifically, botulinum toxin A (BTA) is a drug that can be injected into specific muscles to reduce activity and even establish a temporary paralysis of those particular muscles.

While this treatment is useful for a range of conditions, it is most commonly used in the cosmetic industry as a treatment for facial lines—a treatment that is often referred to by a brand name for the BTA drug: Botox (Carruthers & Carruthers, 1997). Injections of BTA into the corrugator muscles (which lower and bring the eyebrows together) cause the patient to have reduced mobility in their frown response and vertical (glabelar) frown lines become reduced (Carruthers, Lowe Menter et al., 2002). The frontalis muscles (which raise the eyebrows) are targeted to reduce horizontal frown lines in a similar way. From what we know about the facial feedback effects, these cosmetic treatments are not going to be without their psychological consequences. What some of these consequences might be is the focus of this study. Several previous Michael B. Lewis, School of Psychology, Cardiff University, Cardiff,

UK.

Correspondence concerning this article should be addressed to Michael B. Lewis, School of Psychology, Cardiff University, Park Place, Cardiff, CF10 3AT, United Kingdom. E-mail:[email protected]

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studies, however, have already revealed some evidence for the psychological impact of BTA treatments. As described below, these demonstrate effects on mood, neurological activity, and cognitive processing.

Finzi and Wasserman (2006)have proposed that BTA injections and the facial feedback effect can be exploited in a treatment for depression in a manner similar to the reverse of the effects observed byVan Swearingen and colleagues (1999). The corrugator facial muscles can be temporarily paralyzed by injections of BTA leading to reduced movement so that the person is unable to frown.

These people would then not receive the facial feedback from frowning and so negative affect would be harder to maintain. Finzi and Wasserman treated 10 people who had symptoms of depression with BTA injections into the corrugator muscles. Subse- quently, nine of them showed a complete reduction of their depressive symptoms whereas the tenth showed a marked reduction in symptoms.

One limitation ofFinzi and Wasserman’s (2006)study was the lack of a control group; however, further evidence for an effect of BTA on mood comes from a study byLewis and Bowler (2009).

In this study, patients who had received cosmetic treatment were tested for their mood. Patients who had received BTA injections for frown lines were significantly less depressed and less anxious than patients who had received other forms of cosmetic treatment.

This was consistent with the hypothesis that frowning increases negative affect. Again, there are limitations in this study as prior mood was not assessed and hence this was an observational study.

Research into the neuropsychological effects of BTA treatments was carried out byHennenlotter et al. (2009). Brain activity was assessed for participants who had been treated with BTA to the corrugator muscles and controls as they mimicked facial expressions. They found reduced localized brain activity when imitating an angry face for BTA-treated patients compared with controls.

This implies that facial feedback changes the activity within the emotion-processing parts of the brain during emotion imitation.

This too provides evidence that BTA treatments have an effect on the experience of emotions and possibly even the social transfer of emotions.

One further study that has explored the potential psychological impact of cosmetic BTA treatment was conducted by Havas, Glenberg, Gutowski, andLucaelli (in press). By testing patients before and after BTA treatments they found that the treatment led to angry and sad sentences being read more slowly after treatment.

This experiment did not have a nontreated control group but did compare angry and sad sentences to happy sentences (which showed no change), so it adds more evidence to the psychological impact of BTA treatments.

The impact of BTA on the experience of emotion was also assessed in a study by Davis, Senghas, Brandt, and Ochsner (2010). Their study found that people who had BTA treatment to their forehead and eye regions reported a decrease in the strength of their emotional experience. This result, it is reported, is consistent with the facial feedback hypothesis in that those participants would not have been able to express the emotions so well following treatment and so the loss of emotional experience would be attributable to the loss of feedback from those facial expressions.

The research into the emotions that has been conducted recently using BTA treated participants has allowed for a further insight into facial feedback. In all of the behavioral studies with typical

participants such as those byStrack and colleagues (1988)there is a question mark over whether the feedback is a result of motor efferent processes following the signal to contract the facial muscles or facial afference as a result of the contraction itself. Partic- ipants who have been BTA treated still display the efferent signals, but the toxin’s effect is to prevent the contraction of the muscle.

The lack of feedback implied by the studies into the effects of BTA suggests that it is the muscle afference rather than the efferent signal that is responsible for the facial feedback.

Much of the research into the effects of BTA and facial feedback has focused upon a few expressions: happiness, sadness, and anger. These are important emotional expressions, but there are others that have been found to be universal (Ekman, 1992;Ekman

& Friesen, 1971). These include fear, surprise, and disgust. Any of these facial expressions could potentially have a feedback effect and may be affected by BTA injections used in cosmetic treatments. These treatments may have a variety of positive or negative effects. The experiments presented here evaluate some of the potential effects that common cosmetic treatments might have by exploring the impact of contracting specific facial muscles rather than forming a specific facial expression as in many facial feedback experiments (e.g.,Duclos, Laird, Schneider, Sexter, Stern and Van Lighten, 1989, had participants use a range of facial muscles to produce specific emotional expressions).

Experiment 1, below, investigates the facial feedback related to sad expressions, whereas Experiments 2 and 3 explore surprise and disgust, respectively. Together, these widen our understanding of the range and impact of the effect that facial action has on the actor him/herself. Unlike experiments such as those byFlack (2005), the current experiments focused on the effect of a single muscle group.

While this may produce weaker effects thanFlack’s (2005)mul- tiple muscle manipulation, the results will identify specific effects of muscle groups and so map onto possible localized treatments of BTA.

Experiment 1: The Corrugator Muscles and Sadness The first experiment presented here aims to add to the evidence for a facial feedback effect on mood produced by the corrugator muscles. A previous experiment has already explored the effect of frowning on picture evaluation. Larsen, Kasimatis, and Frey (1992)found that when participants lowered their eyebrows (using a manipulation involving golf tees attached to the forehead) they reported that pictures with a negative valence made them feel more sad than if they did not lower their eyebrows. Their experiment, however, confounded expression with effort in that there was not a condition in which a facial expression was made that was not frowning, and so the observed effect could have been caused by any kind of facial action.

The experiment presented here explored mood independently of any additional stimuli to investigate whether contracting the corrugator muscle is sufficient on its own to impact upon a person mood. A clinically relevant measure of mood was used here, which was the same as that used in the research byLewis and Bowler (2009), allowing a comparison between the current data and the patient data. The experiment also compares the effect of frowning against another expression that is incompatible with frowning to ensure that any observed effects are not a This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

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result of effort alone. That is the raising of the eyebrows using the frontalis muscles.

Method Participants

The participants were 54 undergraduates who received course credit. All but six were female, and they were aged between 19 and 25 years.

Stimuli

The Irritability-Depression-Anxiety (IDA) Scale as published bySnaith and Zigmond (1994)was provided as a paper questionnaire. This contains 14 questions with four response options each.

The subscales vary between a minimum of 0 and a maximum of 12 for irritability or 15 for depression and anxiety. Higher scores mean the participant in more irritable, depressed, or anxious de- pending on the subscale.

Procedure

It was suggested to the participants that the experiment con- cerned concentration methods. Participants were either instructed to raise their eyebrows as high as possible (eyebrows-up condition—the experimenter demonstrated this by contacting his frontalis muscles), lower their eyebrow as low as possible (eyebrows- down condition—this was demonstrated by contracting the corrugators muscles), or avoid moving their eyebrows either up or down (eyebrows-middle condition). This manipulation was between participants so that each participant was randomly assigned to one of the conditions.

Once the participant had practiced the facial manipulation as instructed, they were given the IDA questionnaire to complete while holding that expression. At the end of the questionnaire, they relaxed that facial expression and reported how well they held the instructed facial manipulation during the questionnaire on a scale from 0 to 10. The researcher monitored each participant’s facial actions from a distance with a viewing angle of approximately 45 degrees from the participant’s midline.

Design

The independent variable was the instructions given to participants as whether to raise their eyebrows, lower them, or avoid moving them. The dependent variable was the score on the IDS questionnaire. The experiment was between participants as repeat- ing the IDS questionnaire was not possible.

Results

All participants rated themselves as performing well in the facial manipulation (all scores greater than 4), and so none were excluded from the analysis. An ANOVA on these scores revealed a significant effect, F(2, 51)⫽ 13.50; p ⬍ .01. Pairwise comparisons showed that participants in the eyebrow-middle condition (M⫽ 8.6) found the task easier (ps⬍ 0.01) than in either the eyebrow- raised (M⫽ 7.0) or eyebrow-lowered conditions (M ⫽ 6.5), which did not significantly differ between each other (p⬎ .05).

Figure 1shows the mean score on the IDA questionnaire for each of the three facial manipulations. An ANOVA was conducted on the participants’ IDA scores with between-participants factor of facial manipulation. This analysis revealed a significant effect of facial manipulation, F(2, 51)⫽ 9.728; p ⬍ .001. Pairwise com- parison confirmed that scores in the eyebrows-down condition were significantly higher than in either the eyebrows-up or the eyebrows-middle condition (ps ⬍ 0.01) even after Bonferroni corrections. The IDA scale can be partitioned into three components of irritability, depression and anxiety. An analysis was conducted on each of these and found a significant effect of facial manipulation on depression, F(2, 51)⫽ 5.443; p ⬍ .01, and anxiety, F(2, 51) ⫽ 18.731; p⬍ .01, but not irritability, F(2, 51) ⫽ 2.759; p ⫽ .073.

Discussion

The results demonstrate that the action of lowering one’s eyebrows, as in a frown, is sufficient to make one’s mood significantly more negative. As this operation appears no more effortful than raising one’s eyebrows (based on the participants’ ratings) then it is unlikely that this is a consequence of effort. The normal range for the depression score on the IDS is 0 to 3.5 whereas the borderline morbid score is between 3.5 and 8.5.Figure 1shows that the participants were on average borderline depressed. The severity of their depression, however, was moderated by their facial muscular action such that those who were frowning were more depressed.

This result is consistent with the findings ofFinzi and Wasser- man (2006) with clinically depressed patients and Lewis and Bowler (2009)with nondepressed patients in that paralysis of the frown muscles correlated a more positive mood. The current experiment, however, demonstrated that the effect of facial muscular action on mood can be almost instantaneous with the action itself. The mere forming of the frown expression is sufficient to produce a negative mood detectable via a clinically relevant measure. Obviously, the current experiment used nonclinical partici-

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Irritability Depression Anxiety

Eyebrows-up Eyebrows-middle Eyebrows-down

IDA Scale rating

Figure 1. The mean ratings on the IDA scale for the three facial manipulations in Experiment 1. The whole scale value is the sum of three individual components. Error bars show standard errors.

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pants but it demonstrates the role that expression can play in maintaining mood. The effect of frowning itself is sufficient to move someone from the normal range of the scale into a range that would be considered to be borderline morbid.

The study of the effect of BTA byFinzi and Wasserman (2006) failed to have control patients and the study byLewis and Bowler (2009)was an observational study. These failings in the studies meant that questions remained over whether paralyzing the frown muscles really affected mood. The current study, by using a controlled experiment, provides additional support for the fact that the use of BTA to paralyze facial muscles will have a measurable effect on mood, albeit the size of this effect would be equivalent to someone just learning not to frown.

Experiment 2: The Frontalis Muscles and Surprise In Experiment 1, the raising of the eyebrows was used as a control condition to ensure that any effect was not a result of facial effort. Participants who exerted effort in raising their eyebrows were less depressed than those who lowered them but there was no significant difference between raising and not moving the eyebrows. Raising the eyebrows was chosen because it was incompatible with the action under study; however, this action is closely related to a particular emotional expression: surprise.

Like happiness and sadness, surprise is one of Ekman and Friesen’s (1971) universal emotions and so is communicated in similar ways cross culturally. It is an emotion that communicates disbelief or the awareness that something is unusual or unexpected to others. If facial feedback occurs for this emotional expression then raising one’s eyebrows will increase one’s feelings of disbelief or unexpectedness. Something that might be considered as believable or normal will be evaluated as less believable and unusual when a person’s eyebrows are raised in a surprise-like manner.

Surprise has been previously explored within the context of facial feedback by Reisenzein and Studtmann (2007). Using instructions to raise or lower eyebrows (together with widening or narrowing of eyes), no facial feedback effect was found on how surprising an oddball stimulus was. So the startle associated with an oddball stimulus is not increased by the facial feedback of a surprise-like expression. In fact, this is not surprising given what is known about startle responses and facial expressions:Reisenzein, Bördgen, Haltbernd, and Matz (2006), for example, found little facial-muscular activity in response to oddball trials even when participants did report a feeling of surprise. Although a startling stimulus may surprise us, it appears to be poorly associated with facial expressions of surprise.

Facial expressions of surprise are universally recognizable but are not associated with startle, so it may be that something else is being communicated by those raised eyebrows. It is possible that disbelief is the primary emotion being communicated in the surprised face. Communicating disbelief or incredulity would be useful in a complex society—possibly even more so than communicating startle. While raising eyebrows might not increase startle it may increase disbelief through facial feedback. Here, surprise is used to mean the feeling of disbelief of something.

The facial feedback of disbelief was explored in the current experiment by testing whether raising one’s eyebrows affected how surprising a particular fact is perceived to be. The facial-

feedback effect would suggest that this facial action will lead to facts being considered more surprising and less believable than either lowering the eyebrows or not making any facial action.

The participants were 24 undergraduates who received course credit. All were female, and they were aged between 19 and 25 years.

Stimuli

Thirty surprising “facts” were selected. While these were col- lected from websites that purported that these were true, no additional information was acquired to confirm their veracity and so it is possible that some disputed or even incorrect facts were presented as well as true facts. Examples of the facts used are “There is a rare medical condition called Exploding Head Syndrome” or

“Every drop of seawater contains 1 billion gold atoms.” These 30 statements were split into three groups of 10 for the experiment.

Procedure

A similar procedure was used here as in Experiment 1 with participants being instructed to raise their eyebrows as high as possible (eyebrows-up condition), lower their eyebrow as low as possible (eyebrows-down condition), or avoid moving their eyebrow either up or down (eyebrows-middle condition). The same cover story was used as in Experiment 1. This time, however, the manipulation was within participants so that each participant per- formed in each condition and the order of the conditions was counterbalanced across participants.

For each condition, the participant established the facial manipulation and was then presented with 10 facts to rate on how surprising or unbelievable they were. The scale used a range from 1 (Not surprising at all) to 10 (Very surprising). It was explained that something that you know to be true would not be surprising whereas something that you would have thought was false would be surprising. After rating the facts, participants relaxed their facial expression and reported how well they held the instructed facial manipulation during the questionnaire on a scale from 0 to 10.

There was a short interval before they began the next condition with a different facial manipulation while rating a new set of 10 facts until all three sets had been rated.

Design

The independent variable was the instructions given to participants as whether to raise their eyebrows, lower them, or to avoid moving them. The dependent variable was the average surprising score given to the 10 facts in each condition. The experiment was within participants with the sets of 10 facts being counterbalanced over the three facial manipulation conditions.

Results

All participants rated themselves as being able to hold the three facial manipulations well (above 4 on the scale). The average for This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

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the no eyebrow movement condition was higher (8.29) than for the either up (7.50) or down (7.63), but there was no significant difference between the three conditions, F(2, 46)⫽ 2.543; p ⬎ .05.

Figure 2shows the mean surprising ratings in each of the three conditions. An ANOVA revealed that there was a significant effect of facial manipulation on the ratings, F(2, 46)⫽ 5.831; p ⬍ .01.

Pairwise comparisons using a Bonferroni correction revealed significant differences between the eyebrows-up and eyebrows- middle condition (p⫽ .012) and the eyebrows-up and eyebrows- down condition (p⫽ .002).

Discussion

Experiment 2 demonstrates that raising one’s eyebrows makes a fact appear more surprising. This is a new demonstration of the facial-feedback effect. The surprise-like expression produced by this facial manipulation provides feedback that becomes incorpo- rated into the evaluation of the fact being read.

The current finding is at odds with those of Reisenzein and Studtmann (2007), who failed to find a surprise facial feedback effect. One explanation for this is that the two studies are looking at different aspects of surprise. Reisenzein and Studtmann explored the startle component of surprise. The current experiment, however, evaluated the disbelief component of surprise. It may be the case that startled surprise is not unambiguously linked to raised eyebrows whereas disbelief is. If this were the case then the facial expression referred to as surprise may be better described as disbelief. Alternatively, startle and disbelief may be represented by the same expression but only disbelief shows the facial feedback effect—possibly because startle is too fast a response to incorpo- rate facial motoric information.

Comparing Experiments 1 and 2 provides a useful insight as the same facial manipulations were made. In Experiment 1, lowering the eyebrows increased depression more than raising them or having them relaxed. In Experiment 2, raising the eyebrows increased surprise ratings more than lowering them or having them relaxed. This combination of results demonstrates that the effects

of the facial muscular action are specific to the emotion to which it is related. An unrelated facial action appears to have little effect on either a person’s mood or their evaluation of facts. The facial feedback process is producing a specific effect directly related to the emotion that would be interpreted by from that facial muscular action.

Just as Experiment 1 had practical implications owing to current cosmetic practices, so does Experiment 2. Injection of BTA into the frontalis muscles is a recognized and popular treatment for horizontal frown lines. Patients treated in this way will temporarily (for a period of months) lose the ability to raise their eyebrows.

The current experiment, therefore, would lead to the hypothesis that those patients would not find facts as surprising or hard to believe as untreated people because they would not be able to construct the facial expression associated with surprise. This cosmetic treatment, therefore, may lead to people being more accept- ing of the information they are given and hence be more gullible.

While this is only a hypothesis at the moment, given the size of the effects observed in BTA effects on mood, it is a hypothesis that warrants testing.

Experiment 3: The Levator Labii Superioris Muscles and Disgust

Sadness and surprise are two facial expressions that have been shown to exert a facial feedback affecting mood or evaluations respectively as shown above. There are various other facial expressions that can be formed that communicate a variety of emotions. It is wholly possible that these expression also feedback the emotion to the poser. In this third experiment, the facial expression associated with the disgust emotion is investigated. In the discussion below is it explained why disgust may be important in the management of some forms of obsessive– compulsive disorder.

An important part of the disgust facial expression is formed by the wrinkling of the nose using the nasal part of the levator labii superioris muscles. Like happiness, sadness, and surprise, disgust is one of Ekman and Friesen’s (1971) universal emotions. It is argued therefore that the disgust expression is a semiautomatic response to a stimulus (or recollection of a stimulus) that is disgusting.

The facial feedback of disgust-like expressions was investigated byDuclos et al. (1989). Their participants were instructed to raise their lower lip and narrow their eyes as they rated themselves on a range of emotions. The disgust rating with this pattern of facial action was stronger than facial actions related to fear or sadness but not anger. This provides some evidence of facial feedback of disgust although it is not clear what it was that they felt more disgust about.

Kraut (1982)reported a facial feedback effect on the pleasantness of odors. In that experiment participants rated odors after smelling them, either making a pleasant smell emotion or an unpleasant smell emotion regardless of the actual valence of the emotion they were sniffing. Odors rated when making a pleasant- odor facial expression were rated as more pleasant than those rated when making an unpleasant-odor facial expression. Although this is an important demonstration, the current experiment builds upon it in two ways. First, the facial expression instructions do not invoke emotions so that the participants were not aware that they were making a disgust facial expression. This is important in order

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Eyebrows-up Eyebrows-middle Eyebrows-down

Mean surprising rating

Figure 2. The mean surprising ratings for the sets of 10 facts for the three facial manipulations in Experiment 2. Error bars show by-participant standard errors.

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that any effect is a result of feedback and not association with the instructions given. Second, the current experiment uses comparison conditions that are not associated with pleasantness. It is possible that the Kraut result was observed because the pleasant- odor facial expression improved the ratings rather than the unpleasant-odor facial expression making the odor seem more unpleasant. The current experiment compares disgust with facial postures that are incompatible with disgust but are not positive facial expressions.

The current experiment aimed to evaluate whether the facial expression of disgust would feed back to affect the evaluation of stimuli. If this does happen then stimuli would be evaluated as more disgusting when a disgust-like facial expression is posed.

The participants were 33 undergraduates who received course credit. All but one were female, and they were aged between 19 and 25 years.

Stimuli

Twelve plastic pots containing 12 different odors were used.

These were presented in tubs with air tight seals. The odors were manufactured by Dale Air and were selected from the more unpleasant end of their catalogue including ‘farmyard,’ ‘urine,’ and

‘vomit.’

Procedure

It was explained to participants that the experiment aimed to explore how different odors were detected within different parts of the nasal cavity. They were told that facial muscular action was used to send the odor to different parts of the nasal cavity. Three forms of facial muscular action were introduced. The first was the nose-up condition where the tip of the nose was pulled up as far as possible by wrinkling the nose. It did not matter whether the tip did not move much but the participant needed to feel like the nose tip was raised. This was demonstrated by contracting the levator labii superioris muscles. The second was nose-down in which the tip of the nose was pulled down as far as possible by using the facial muscles to pull the top lip down. Again, participants should feel as if the tip of the nose is lower even if it does not move much. This was demonstrated by contracting the depressor anguli oris with lips together but teeth apart. Finally, there was a nose-middle condition which involved keeping the facial muscles relaxed.

The nose-up, -down, and -middle conditions were rotated as participants sniffed the contents of each of 12 boxes such that every participant rated four boxes in each of the three conditions.

Which odors were rated in which condition was rotated between participants. The contents of their box were rated on their intensity (0 –10) and their pleasantness (0 –10). The facial manipulation was held until the rating had been completed. After the 12 odors had been rated, the participant rated him/herself on how well they had been able to follow the instructions regarding the facial manipulation (0 –10). As the facial manipulation was novel, they were also

asked what they thought the experiment was about. All of the participants believed the cover story until they were debriefed.

Results

All participants rated themselves as performing well in the facial manipulation (all scores greater than 4) and so none were excluded from the analysis.Figure 3shows the mean pleasantness scores for each of the three facial manipulations.

An ANOVA conducted on the odor intensity scores revealed no significant effect of facial manipulation, F(2, 64) ⫽ .509; p ⫽ .603. An ANOVA conducted on pleasantness scores, however, did reveal a significant effect, F(2, 64)⫽ 5.343; p ⫽ .007. Pairwise comparisons using a Bonferroni correction revealed significant differences between the nose-up and nose-middle condition (p⫽ .004) and the nose-up and nose-down condition (p⫽ .0123).

Discussion

The results of the study demonstrate that wrinkling of the nose by contraction of the nasal part of the levator labii superioris has an effect on the way that an odor is interpreted. Although intensity of the odor is not significantly affected, the pleasantness is. A facial expression of disgust (even without any other disgust related cues) leads to an evaluation of a stimulus as being more unpleasant.

While the finding of the current experiment generalizes the facial feedback effect to a new expression, it may have practical implications. Obsessive– compulsive disorder (OCD) is a condition associated with disgust.Power and Dalgleish (1997)describe how people with this disorder can be compulsive washers or compulsive checkers. The former experience more disgust when exposed to potential contaminants than the latter. Compulsive washers have also been shown to have different patterns of brain activity to potentially disgusting stimuli than compulsive checkers (Phillips et al., 2000).Sprengelmeyer, Young, Pundt et al. (1997) found that patients with OCD showed poorer recognition of the disgust facial expressions than control patients—possibly as a

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Nose-up Nose-middle Nose-down

Mean pleasantness rating

Figure 3. The mean pleasantness ratings for the sets of four odors for the three facial manipulations in Experiment 3. Error bars show by-participant standard errors.

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result of a coping method that aims to reduced the activation of disgust-induced behaviors. Within a normal population, Tolin, Woods, and Abramowitz (2006) showed that washing-related OCD-like behaviors were associated with higher disgust sensitiv- ity. It is possible that disgust is to OCD as sadness is to depression.

This is an idea championed byStein, Liu, Shapira, and Goodman (2001). A consequence of this idea is that a method that reduces the feeling of disgust may have implications for the treatment of OCD. A speculative proposal offered here, therefore, is that by localized treatment of the nasal part of the levator labii superioris muscles with BTA a person may be less likely to evaluate a stimulus as disgusting (because they would not be able to initiate the disgust facial expression). While intermediary implication need to be worked through (possibly using EMG as a tool), such a treatment might lead to a reduction of the symptoms of OCD where there is a fear of contamination. So, just like BTA treatment to reduce frowning has been proposed as a treatment for depression, BTA treatment to reduce the nose wrinkling action is proposed here as a treatment for OCD.

General Discussion

The experiments presented here demonstrate that the effect of facial feedback can be operationalized through the contraction of specific localized facial muscles. Experiment 1 demonstrated that frowning (through contraction of the corrugator muscles) has an almost instantaneous effect on a person’s mood such that they are more depressed. Experiment 2 found that raising ones eyebrows (using the frontalis muscles) had the effect of making one report facts as being more surprising. Experiment 3 investigated the effect of wrinkling one’s nose (using the levator labii superioris muscles) versus an incompatible action on evaluation of a set of odors. Wrinkling the nose to form a disgust-like expression led to the odors being rated as more unpleasant.

The real importance in these findings comes from the fact that there are people who are choosing to restrict the motion of their facial muscles using pharmacological methods (i.e., BTA injections). The increasingly common use of BTA injections in cosmetic treatments for facial lines means that there are people who cannot frown, whereas there are others who cannot raise their eyebrows. The findings presented here indicate that paralysis of individual muscle groups can have marked effects on our emotions and our perceptions. From what we know of facial feedback, there may be a wide range of consequences beyond just one’s facial appearance.

The unintended and long-term consequences of cosmetic BTA injections remain to be fully explored but could include making people happier (as has already been suggested byFinzi & Was- serman, 2006, andLewis & Bowler, 2009). The results of Exper- iment 1 support this as an outcome of treatments that paralyze the corrugator muscles. Another common cosmetic treatment is injections of BTA into the frontalis muscles to horizontal frown lines (Carruthers & Carruthers, 1997). Such patients would not be able to raise their eyebrows and so, based on the findings of Experiment 2, would receive information and be less surprised and questioning of it.

BTA injection into the levator labii superioris muscles is not a common cosmetic treatment. However, based on Experiment 3 it would be predicted that following such a procedure the patient

would feel less disgust. While more research needs to be carried out, this finding offers the possibility of a new treatment for the management of disgust-related disorders such as OCD.

It is worth noting that in Experiments 1 and 2 there were no checks that the concentration cover story was wholly believed by the participants. It is possible that some of the participants were aware of the facial expression they were forming. This, however, was not a problem for Experiment 3 as all participants reported believing the cover story.

To conclude, the research presented here demonstrates that feedback from individual muscles do affect mood and perceptions in specific ways relating to the expression being formed. It is proposed that BTA injections during cosmetic treatment may interfere with this feedback in both positive and negative ways, and clinicians and patients alike should be aware of these.

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Received March 12, 2010 Revision received January 30, 2012

Accepted April 17, 2012 䡲