inhibiting facial expressions: limitations to the voluntary control of facial expressions of emotion

P1: GCR/GFU/GEE/GGT P2: GDP/GCP/GFU/LMD/GCQ/FJQ/GGT/GCX QC: GCZ

Motivation and Emotion [me] PP106-299689 March 28, 2001 11:35 Style file version Nov. 19th, 1999

Motivation and Emotion, Vol. 24, No. 4, 2000

Inhibiting Facial Expressions: Limitations to theVoluntary Control of Facial Expressions of Emotion1

Arvid Kappas,2,3 Francois Bherer,2 and Melanie Theriault2

Recently, A. J. Fridlund (e.g., 1994) and others suggested that facial expressions ofemotion are not linked to emotion and can be completely accounted for by socialmotivation. To clarify the influence of social motivation on the production of facialdisplays, we created an explicit motivation by using facial inhibition instructions.While facial electromyographic activity was recorded at three sites, participantssaw humorous video stimuli in two conditions (inhibition, spontaneous) and neutralstimuli in a spontaneous condition. Participants showed significantly more EMGactivity in the cheek region and less EMG activity in the brow region when they triedto completely inhibit amused expressions as compared with the neutral control task.Our results suggest that explicit motivation in the sense of voluntary control is notsufficient to mask the effects of spontaneous facial activation linked to humorousstimuli.

Most contemporary perspectives postulate that facial activity is largely determinedby the emotional state of the expresser (e.g., Ekman, 1984; Izard, 1997) or a conse-quence of emotion eliciting appraisals (e.g., Scherer, 1992; Smith & Scott, 1997;see also Kappas, in press). These expressions are usually thought to be modulatedby implicit or explicit social rules, the so-called display rules (Ekman & Friesen,1969). Because of the hypothesized dual determinants of facial activity, these mod-els are sometimes referred to as two-factor models (Fridlund, 1991). However, sev-eral researchers (e.g., Chovil, 1991, 1997; Fern´andez-Dols & Ruiz-Belda, 1995;

1This work was supported by a grant of the Canadian Social Sciences and Humanities Research Council(SSHRC) to Arvid Kappas. Parts of these data have been presented at the Thirty-Seventh AnnualMeeting of the Society for Psychophysiological Research in Cape Cod, Massachusetts, 1997. Theauthors thank Robert Kleck, Craig Smith, and the anonymous reviewers for their helpful comments.

2Universite Laval, School of Psychology.3Address all correspondence to Arvid Kappas, Department of Psychology, The University of Hull,Hull HU6 7RX, United Kingdom; e-mail: [email protected].

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260 Kappas, Bherer, and Theriault

Fernandez-Dols, S´anchez, Carrera, & Ruiz-Belda, 1997; Fridlund, 1994, 1997)have recently challenged this view, suggesting that according to a behavioralecology view or a social communications view facial expressions can be com-pletely accounted for by social motivation or social intent.

According to Fridlund (1994) facial displays do not imply the presence ofan internal affective state in an expresser. Specifically, he interprets changes inintensity of facial activity due to implicit sociality as demonstrating that it is socialmotivation that exclusively determines facial activity (Fridlund, 1991; but see Hess,Banse, & Kappas, 1995). Each facial display, according to Fridlund (1994, 1997;Fridlund et al., 1990; Chovil & Fridlund, 1991; see also Chovil, 1997), signalsan intent or social motivation rather than being the expression of an underlyingemotional state. For instance, a smile would indicate readiness to play or to affiliateand not the presence of happiness. This point of view is not unrelated to Frijda’s(e.g., Frijda, 1986; Frijda & Tcherkassof, 1997) argument that facial activity canreflect action tendencies (see also Salzen, 1981). However, Frijda clearly does notreject the notion that emotional processes are highly relevant to facial displays.

Recently, Kappas (1996, 1999) pointed out that both behavioral ecology andtwo-factor perspectives are problematic in that they fail to predict specific facialactivity in a given situation. Unfortunately, there is currently no comprehensivetheory of display rules (see also Boucher, 1974). Furthermore, the concept of dis-play rules is often invoked as a post hocexplanansin cases in which facial displaysobserved in experiments or real-world situations do not follow the predictions ofa given emotion theory (Fridlund, 1994). In contrast, the behavioral ecology viewuses social motivation as a unitary explanatory concept but also fails to provide anytheory that could predict which pattern of facial activity will be shown in whichcontext at which intensity (Kappas, 1996). Although the notion of social motiva-tion being the sole determinant of facial expression seems to be more simple andelegant than a two-factor approach, an important unresolved issue is how socialmotivation and voluntary control interact.

Fridlund is quite clear that, depending on the definition of emotion, emotionis not a cause for involuntary facial movements and he attempts to explain allfacial displays without recourse to emotions or emotion terms (see also Fridlund,1997). However, Chovil states more strongly that “verbal and nonverbal acts can beviewed as symbolic messagges that are directed to others” (1991, p. 142). For her,“verbal and nonverbal communicative acts are not regarded as distinct from eachother but rather as parts of the same process” (1997, p. 323). Here facial displaysseem to be compared to speech, which usually is regarded as a volitional act.

In this study, we try to clarify the influence of volitional intent on the pro-duction of facial displays, using an instructed inhibition procedure. If there isfacial activity linked to affective stimuli that can not be controlled by intent, whilethere is an explicit motivation for inhibition, it would discount any extreme behav-ioral ecology or social communications view that would reduce or equate social



Inhibiting Facial Expressions 261

motivation to volitional control. However, such a demonstration would not chal-lenge less extreme versions of this view that emphasize social-communicativefunctions served by facial actions. The goal of this study is therefore not to refuteeither the behavioral ecology or the two-factor perspectives, but rather is to clarifythe boundary conditions of the voluntary control of facial displays.

In exploring such boundary conditions it is necessary to find a reasonabletest of the limits of volitional control. For example it is unreasonable to ask anindividual to produce a facial display that is physically impossible. Also the in-dividual needs to understand clearly which pattern of facial activity she is askedto produce intentionally. Otherwise, a failure to produce a specific pattern mightbe because of a failure to communicate what exactly the experimenter wanted theparticipant to do. Lastly, there are movements that are for neurological reasonsdifficult or impossible to perform, such as a unilateral eyebrow raise on both sidesof the face (see Rinn, 1991). In the context of the present study we have choseninstead to use an expression that everyone can easily produce and that can be com-municated without any ambiguity—the absence of expression. In our opinion, ifparticipants are asked not to show any expression but they are not able to fullycontrol their facial activity in the presence of a humorous stimulus (which in adual factor theory provides apushto facial activity), limits of volitional controlhave been demonstrated.

Facial inhibition tasks have been used previously, particularly in the con-text of facial feedback studies (e.g., Bush, Barr, McHugo, & Lanzetta, 1989;Kappas, McHugo, & Lanzetta, 1989; Lanzetta, Cartwright-Smith, & Kleck, 1976;Vaughan & Lanzetta, 1980; see also Smith, McHugo, & Kappas, 1996). In thesestudies it was shown that participants were able to reduce facial activity comparedwith spontaneous control conditions. However, it has to be noted that completeinhibition was never required, as these authors were interested only in the effectof a relative decrease of facial activity on self-report of emotion or physiologicalactivity. We argue that as we create a motivation or intent to inhibit completely anysigns of amusement when watching funny stimuli we can test whether this intentcan fully account for facial activity.

Obviously, there are implications of the results for the competing theoriesexplaining facial activity. Specifically, if participants are indeed able to inhibit anysign of amusement toward a funny stimulus, both views, a dual factor view and thebehavioral ecology (or social communications) view could account for the results.If however, participants are not able to completely inhibit their smiles, the resultscan only be accounted for by a dual factor view—besides the voluntary controlthere exists apushthat is related to the funniness of a stimulus. These results wouldshow that whether the causal construct is labeled emotion or social motivation, itis in competition with an explicit motivation to inhibit. As Kappas (1996) pointedout, if the intensity of an emotional stimulus influences social motivation, theneither facial expressions must be accounted for by social motivation and emotion




(see also Hess, Banse, & Kappas, 1995), or the information processing required forsocial motivation to express must be very similar to emotional appraisal, just thatit takes in addition to an evaluation of implications of the stimulus for the well-being of the individual, an evaluation of the relational implications of specificexpressions into account.

An important issue in this approach is how to evaluate the success of theinhibition instruction, specifically, what to measure and what to use as a criterion.Given that we want to compare potentially very low levels of facial activity, it isnecessary to use a highly sensitive measure. Facial electromyography (EMG) hasbeen shown to be extremely sensitive to small differences in facial activation evenwhen they are not visible with the naked eye (see Fridlund & Cacioppo, 1986).Previous studies have shown smiling to be associated with activation at the site ofthe zygomaticus major muscle (cheek) and the site of the orbicularis oculi muscle(producing the crow’s feet wrinkles around the eyes), and frowning to be associatedwith activation at the site of the corrugator supercilii muscle (see Cacioppo, Petty,Losch, & Kim, 1986). Thus, we chose to measure facial activity at these threesites. Although ideally facial muscle activity should approach zero under inhibi-tion instructions, there is always some level of activity, particularly in the contextof a task that does not require relaxation but rather alert watching of a stimuluson a television monitor. Hence, we decided to include a condition where partici-pants watched a neutral stimulus without inhibiting their facial activity. Thus, thecritical comparison for our hypothesis is between the inhibited-amusement con-dition (IA) and the spontaneous-neutral condition (SN), whereas the comparisonbetween IA and spontaneous amusement (SA) is considered a manipulation check.If there were no reduction of cheek muscle activity, when participants were askedto inhibit their responses to the humorous stimuli, we would have to conclude thatparticipants did not follow instructions. Furthermore, self-report of amusement isrelevant because it is necessary to ensure that participants are really amused by thestimuli. Ideally, there should be no difference in experienced amusement betweenthe spontaneous and the inhibited amusement condition. However, there has beenprevious research in the context of the facial feedback hypothesis (shown earlier)that has found a reduction of subjective or physiological emotional reactions linkedto the inhibition of facial responses. Some of these findings have been criticizedas tests of the facial feedback hypothesis because participants might choose dis-traction strategies to accomplish a reduction in the intensity of facial displays. Ifunder these circumstances self-report or physiological responses would decrease,compared with spontaneous conditions, one could not evaluate the impact of facialfeedback (Kappas, 1989). The reduction in any aspect of an emotional reactioncould then be due to differences in the attention allocated to the humorous stimulior the interpretation of the stimulus in the sense of an emotion-antecedent ap-praisal. This criticism would also apply to the current study. If there were a clearreduction in the subjective response to the humorous stimuli from the spontaneous




amusement to the inhibited-amusement condition, one could argue that the testcomparing the facial responses in the inhibited-amusement condition with thespontaneous neutral condition is compromised. Lastly, asking the participants toevaluate the intensity of their own expression will allow us to evaluate the de-gree to which participants are aware of their success or failure to control facialactivity.

METHOD

Participants

A total of 38 participants (18 men, 20 women), ranging in age between 18 and33 years, participated in an experiment lasting approximately 1 h.4 All participantshad normal or corrected vision and spoke French as their primary language. Theywere recruited on the campus of Universit´e Laval and were not paid for theirparticipation.

Material

Facial activity was measured using 11 mm-diameter Sensor Medics Ag/AgClelectrode pairs, placed at the sites of the corrugator supercilii, zygomaticus major,and orbicularis oculi respectively. All electrodes were placed according to Fridlundand Cacioppo (1986) and were compared with a reference electrode (19 mm)placed on the forehead. Med Associates electrolyte solution (TD40) was used asthe conducting medium and the skin was cleaned using disposable pads contain-ing alcohol (70%) and pumice stone. The electromyographic (EMG) signals wereamplified using a Contact Precision Instruments (CPI) system and smoothed us-ing a contour-following integrator (CPI) with a 200-ms time constant. Electrodeimpedance was verified using a UFI checktrode device (model 1089 mkII). Ifelectrode impedance was greater than 10 kÄ the procedure was repeated until theimpedance fell below this criterion.5 A notch filter was used to reduce backgroundnoise at 60 Hz and all data were recorded at a sampling rate of 10 Hz to the harddisk of the computer.

During the experiment, the participants were presented with 11 film seg-ments of approximately 1-min duration each. The eight funny segments wereselected from the television shows “America’s funniest home videos” and “Drˆoles

4Two participants were excluded from the analysis of all physiological data because of equipmentmalfunctioning.

5Because this experiment was conducted in the context of a class on research methods, additionalphysiological measures were taken (electrodermal activity, respiration, heart rate, finger temperature).However, these measures do not relate specifically to the hypothesis investigated here and the analysesand results will therefore not be presented in this paper.




de videos.” All segments contained selections of short episodes showing eitherhumans or animals engaging in “funny” behaviors or situations. Three animatedshort features by Frederic Bach were used as neutral segments. They showedpeaceful scenes of people engaging in various behaviors. The stimuli were sele-cted based on informal pretests according to their accessibility to the participantsand their humorous or neutral features.

All participants completed questionnaires after each stimulus concerning feltemotional intensity, their expressed amusement, and problems regarding the com-prehension of the content of the stimuli (relevant for the English language segmentsin “America’s funniest home videos.”) All three questions required circling a num-ber between 1 (not at all) and 6 (extremely).

Procedure

Participants were informed before the beginning of the experiment that theywould be participating in a study on the inhibition of facial expressions. Theythen signed a consent form and completed a second form requesting demographicdata. Thereafter, participants were guided to the experimental room, the electrodeswere placed, and participants were given an instruction sheet with informationon the procedure of the experiment. Moreover, the experimenter indicated thatparticipants had to press a pedal following the completion of the questionnairesafter every trial and that they could contact him/her through the intercom systemat any time.

The experimental session started with two practice trials each showing a funnysegment. Instructions of spontaneity and inhibition were assigned to the first andsecond trials respectively. The instruction of spontaneity read as follows: “Now,feel free to act normally and without constraints, do not make any efforts to inhibitthe activity of your facial muscles.” The instruction of inhibition read as follows:“Now, as best as you can, make sure that none of your facial muscles move untilthe end of the presentation.” After the practice trials, the experimenter returned tothe experimental room and encouraged the participant to ask questions about anyaspect of the procedure and the task he/she felt unclear about.

All participants saw stimuli in all three conditions defined by two factors,namely, the spontaneity versus inhibition instruction and the humorous versusneutral feature of the stimuli. Conditions were presented three times in three dif-ferent trial blocks. Each trial block contained a spontaneous-neutral (SN) condi-tion, which represented the comparison level, a spontaneous-amusement condition(SA), and an inhibited-amusement (IA) condition. The position of each conditionin a specific trial block was randomly assigned. Stimuli for the spontaneous con-dition were randomly selected from a group of six and randomly assigned to theinstruction condition. The neutral stimulus was randomly selected from a groupof three stimuli and was always associated with the spontaneity instruction. The




instruction of spontaneity or inhibition was given to the participants prior to thepresentation of each stimulus, using an audio recording presented via the intercomsystem to standardize delivery of the instructions. After the presentation of allstimuli, electrodes were removed and the participants were debriefed concerningthe objectives of the experiment and the expected results. The participants werethen also told that they were filmed to allow the analysis of EMG data by elim-inating movement artifacts and they were asked to sign a second consent formregarding use of the video recordings.

RESULTS

Self-Report

Subjects generally comprehended all stimuli well, regardless of the condi-tion in which they were presented (M = 1.76 on a scale from 1,no problemsto 6, extreme problems). A two-factor repeated measures ANOVA (condition×repetition) for comprehension yielded no significant effects. All repeated mea-sures analyses of variance used the MANOVA approach to repeated measures. Forself-report of amusement, a two-factor repeated measures ANOVA (condition×repetition) showed a significant effect for condition,F (2, 70)= 116.75,p < .001,and for repetition,F (2, 70)= 6.25,p < .003, but not for the interaction of the twofactors. Amusement reported for the neutral segment was significantly lower thanfor the spontaneous amusement condition,F (1, 70)= 156.66,p < .001, or theinhibited amusement condition,F (1, 70)= 191.80,p < .001 (see Table I). Therewas no significant difference between the two amusement conditions. The signifi-cant effect for repetition seems to be because of an increase in amusement ratingsafter the first repetition. For self-rated level of facial activity, only a main effectfor condition emerged,F (2, 70)= 63.86, p < .001, in the two-factor repeated

Table I. Facial Electromyographic Activity and Self-Report of Amusement andIntensity of Expression for the Three Conditions Averaged Over Repetition

Amusement

Spontaneous Inhibited Spontaneous-neutral

Muscle sitesZygomaticus major .48 (.27) −.20 (.18) −.28 (.15)Orbicularis oculi .26 (.18) −.13 (.13) −.13 (.16)Corrugator supercilii −.02 (.17) −.08 (.09) .10 (.15)

Self-reportAmusement 3.62 (.56) 3.83 (.62) 1.62 (.58)Expression 3.57 (.66) 2.13 (.64) 1.61 (.62)

Note. Numbers in parentheses indicate the standard deviations of the means. FacialEMG is indicated asz scores standardized within participants. Self-reports were mea-sured on a scale from 1 to 6.




measures ANOVA. Here, all conditions differed from each other (see Table I)with subjects judging their level of expression lowest in the neutral condition fol-lowed by the inhibited amusement condition,F (1, 70)= 8.30,p < .005, and thespontaneous amusement condition,F (1, 70)= 64.38,p < .001. Obviously, thetwo spontaneous conditions also differed from each other regarding self-report ofexpressive intensity,F (1, 70)= 118.90,p < .001).

Muscular Activity

To compensate for interindividual differences in electrode placement andphysiognomy, all integrated EMG data werez-transformed for each participantover all trials. A doubly multivariate analysis of variance with the two factorscondition (3) and repetition (3) was performed for thez-transformed integratedEMG activity at the three muscle sites of zygomaticus major, orbicularis oculi, andcorrugator supercilii. A multivariate effect was found for condition,F (6, 30)=35.89,p < .001, but not for repetition and not for the interaction between the twofactors (see Table I). UnivariateF-tests showed the condition effect for EMG ac-tivity at the sites of zygomaticus major,F (2, 70)= 102.57,p < .001; orbicularisoculi, F (2, 70)= 52.16,p < .001; and corrugator supercilii,F (2, 70)= 10.92,p < .001. A priori planned contrasts were performed to check whether or not thespontaneous expression of amusement differed from the inhibited expression ofamusement (manipulation check) and whether or not the inhibited expression ofamusement differed from the spontaneous expression to the neutral stimuli. Asfar as the manipulation check is concerned, there were the expected differences inactivity at the zygomaticus major site,F(1, 35)=93.56,p < .001, and at the orbic-ularis oculi site,F (1, 35)= 76.09,p < .001. Both muscles, involved in smiling,showed higher activity during the spontaneous than during the inhibition condi-tions (see Table I). Activity at the corrugator supercilii site did not differ for thetwo amusement conditions. The comparison for the main hypothesis showed thatthe activity at the site of zygomaticus major was higher when participants inhibitedamusement than when watching a neutral stimulus without an instruction to inhibitfacial activity,F (1, 35)= 5.84, p < .021. This pattern was reversed for activityat the corrugator supercilii site, participants showed more brow activity during theneutral stimulus than when inhibiting their expression of amusement,F (1, 35)=38.24,p < .001. There was no significant difference in activation at the orbicularisoculi site when watching the neutral stimulus and inhibiting amusement.

DISCUSSION

The data suggested that participants showed higher activation at the site ofzygomaticus major when inhibiting their amusement than when watching a neutralstimulus. This difference manifested itself not only in the EMG data, but the




self-report also indicated that subjects were aware of their failure to control fullytheir reaction to the humorous stimulus. The finding that the neutral stimuluswas accompanied by more activity in the brow region (corrugator supercilii site)further reinforces the interpretation that the facial activity in the cheek regionwas associated with expressions consistent with a positive affective state. Couldthis pattern of results be explained as indicating that the neutral stimulus wasrather negative and not neutral? Based on the self-reports it is clear that the neutralstimulus, if anything, has to be considered as being slightly positive, which rendersthe pattern of results even more meaningful. It is unlikely that participants’ facialactivity at the muscle sites studied is fully under volitional control in the presenceof the affective stimuli used in this study. Furthermore, there were no differences insubjectively experienced amusement between the two amusement conditions. Thispattern of results indicates that participants tried to control their expressions and nottheir subjective experience of the stimuli. Our findings are certainly consistent witha dual-factor point of view, assuming the higher activity at the cheek region and thelower activity at the brow region as indicators of nonverbal leakage. Concerning thebehavioral ecology view the pattern is less clear. Our results do not support a viewin which social motivation as a single factor drives all facial actions. In fact, if thereis a push for a particular reaction that cannot be countered by the explicit motivationnot to react, there seem to be at least two factors at work. In other words, it should notbe difficult to inhibit any reaction to a stimulus in a behavioral ecology framework.If there are signs of conflict between volitional and nonvolitional components thereseems to be a challenge to the one-factor explanation.

At this point, it is difficult to distinguish motivational and affective origins/causes of facial activity as one might link specific affective states to specific in-tentions or action tendencies. For example, one could argue that the facial activityassociated with smiling even when being alone and explicitly instructed not tosmile, as in the current study, is to serve a habitual communicative function(Fridlund, 1996, personal communication). However, and we consider this thestrong point of the present study, one can not argue that this activity expresses anyvolitional socialintent, as theintentionshould have been clearly not to expressany amusement.6

6Note that Fridlund also uses the word intent in the context of describing causes of facial action—not inthe sense of volition but in the sense of having a direction. More than 100 years ago Brentano arguedthat all mental phenomena are intentional in the sense that they have a direction toward an object(Grossmann, 1995; see also Reisenzein & Sch¨onpflug, 1992). This usage of the word intentional doesnot imply volition. Thus, technically it is possible to state that all facial expressions are intentional,representing the belief that there is an object to all facial expressions. Yet, we argue that there is causefor confusion in such statements as in many cases intention will be interpreted by some readers asimplying volition. The latter term in turn will often be interpreted as implying conscious processing,or an act that reflects a decision about following a specific plan to achieve a specific goal. When facedwith definitional problems such as “. . . in this way, ‘intentionality’ does not necessarily involve theidea of intention—in the sense that actions are intentional (though somewhat confusingly, intentionsare intentional states in the sense under discussion)” (Crane, 1995, p. 412), we should avoid thisterminology altogether.




Specifically, we wonder then what the role of volition and conscious control isin the use of the term social motivation in the context of behavioral ecology. It wouldgo beyond the scope of the present study to attempt such an explicit formulationof social motivation for facial activity. Instead, we consider our data as a challengefor a clear formulation of this concept as it relates to facial activity to allow thedevelopment of critical tests concerning these competing theoretical points ofview. One relevant test might be to study facial activity of patients with impairedspontaneous or voluntary facial activity (see Rinn, 1991; but see Fridlund, 1997)in different social contexts. Traditionally, voluntary control has been associatedwith social regulation of facial activity in two-factor theories and to some degreein behavioral ecology as well. However, though voluntary control certainly playsan important role in facial activity it is clearly not the only contributor as our studyshows.

Lastly, there is the issue of whether or not a failure to inhibit the reactionsto the funny stimuli is relevant, if it can only be shown using electromyographictechniques. Perhaps judges would not be able to distinguish whether a given facewas recorded in the inhibition condition or while participants were watching theneutral stimulus? However, we believe that the encoding of facial expressionsshould be studied independent of the decoding by observers in this context. Ourstudy relates to the mechanisms involved in regulating facial muscular activity.If complete control of facial actions is not necessary to “fool” one’s interactionpartner, then there are potential implications for the acquisition of facial inhibition,be it at a phylogenetic or at an ontogenetic time scale. However, these considera-tions are more appropriate for a discussion of the functions of facial behavior thatwould go beyond the scope of the current study (see also Kappas, 1997; Kappas& Descoteaux, in press).

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inhibiting facial expressions: limitations to the voluntary control of facial expressions of emotion

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