Neuropsychologin, Vol. 27, No. 7. pp. 923-935, 1989 Prmted in Great Britain.

002%3932/89 %3.oO+O.Kl 0 1989 Maxwell Pergamon Macmillan plc

INDUCING EMOTION BY UNILATERAL CONTRACTION OF FACIAL MUSCLES: A NEW LOOK AT HEMISPHERIC

SPECIALIZATION AND THE EXPERIENCE OF EMOTION

BERNARD B. SCHIFF and MARY LAMON

Department of Psychology, University of Toronto, Toronto, Ontario, M5S lA1, Canada

(Received 11 July 1988; accepted 7 February 1989)

Abstraet-Subjects who maintained voluntary contractions of the left facial muscles experienced sadness. Right facial contractions resulted in a more positive but difficult to characterize experience. These contractions had similar effects on the affective tone of stories told about an ambiguous picture. These findings indicate that emotions can be aroused by unilateral muscle contractions without intervening cognitions. They provide a new methodology for studying the roles of the cerebral hemispheres in emotional experience. Finally, they support the conclusion that the right hemisphere is involved with negative emotional experiences and indicate that the left hemisphere is involved with experiences that are more positive but not readily characterized.

IN THIS paper we are concerned with hemispheric specialization for the experience of emotion. There is a substantial body of clinical and experimental research which has investigated whether the cerebral hemispheres are differentially involved in emotion. This research has addressed emotional cognitive processes and behaviors, as well as experience [27]. Since there is no reason to believe that all psychological processes associated with emotion are lateralized in the same way, it is important in discussing functional brain asymmetries to discriminate between the data of different aspects of emotion.

There is agreement that some kind of lateralization of function for the experience of emotion does occur; however, there is no consensus as to the respective roles of each hemisphere. One view is that the right hemisphere is involved in the experiencing of emotion and that the left hemisphere is not [2, 14, 271. Another view is that both hemispheres are involved in emotional experience, each being specialized for particular classes of emotion. The usual formulation of this position is that the right hemisphere is involved in negative emotions and that the left hemisphere is involved in positive emotions [27]. A variant of this is that the right hemisphere is involved with the emotions of avoidance, and the left hemisphere with those of approach [3, 193.

These different models of hemispheric specialization for subjective feeling states are derived from data of methodologically diverse studies of unilaterally brain damaged, mood disordered and unimpaired subjects. There are problems in interpretation which are unique to the study of the clinical populations that may have contributed to the inconsistent conclusions about brain organization 12, 14,271. In this paper, however, we consider only issues in the experimental research with unimpaired subjects, and in particular ones that arise from the problematic nature of research into subjective phenomena. We describe a new

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924 BERNARD B. SCHIFF and MARY LAMON

method for studying hemispheric specialization for the experience of emotion and report the discovery of a phenomenon regarding the induction of emotional states.

In most of the research on hemispheric specialization and emotional experience, experimenters have attempted to manipulate the emotional state of the subjects and have inferred asymmetries in brain function from asymmetries in a variety of behavioral or physiological measures. The methods for inducing emotion have included presenting stimuli such as photographs, film material, and words with emotional content, or asking the subjects to engage in emotional imagery or to respond to emotional questions [2, 14, 271.

The authors assumed that the subjective states of the subjects in these experiments reflected the emotional tone of the manipulations. In most cases no attempts were made to assess the effectiveness of these stimuli in producing emotional states. Furthermore, any reports of subjective states would have been highly suspect because of the explicit response demands cued by the experimental stimuli. Finally, each of these methods of mood induction engaged the subjects in cognitive activities, and any measure of differential hemispheric activity might have equally well reflected lateralization of function for the processing of affective information as for the regulation of emotional experience. An assumption that the cerebral organization underlying the processing of affective information is the same as that underlying the experience of emotion is unwarranted.

There are, in addition, logical problems in inferring functional brain asymmetries for a psychological function from behavioral asymmetries. It is possible, for instance, that each hemisphere is specialized for the experience of different emotions but that the behavioral manifestations of emotional activation are controlled by only one. There are also the special problems of inferring emotional states from facial expressions or other behavioral expressions of emotion which are subject to deliberate control. Not only can we not necessarily infer emotional states from these behaviors [ll], but at least in the case of facial expressions, we know that the neural organization and hemispheric lateralization is different for deliberate and spontaneous responses [lo, 25).

It is not surprising, with this absence of control over the relevant variables, that there are inconsistent conclusions about hemispheric specialization for emotional experience.

A second approach has been to measure emotional reactions to stimuli presented selectively to each hemisphere. This approach avoids the problems in making inferences about the subject’s emotional state, and about the lateralization of hemispheric activity. The data of emotional experience are reported directly and the relationship between these reports and the activated hemisphere is also direct and does not rely on assessing asymmetries in behavioral measures. Of course, there can be problems with the validity of verbal report. However, in properly controlled experiments, where there are no extraneous cues influencing the subjects behavior, different emotional reports consequent to presenting the identical stimulus to each hemisphere would be free of such considerations.

There are, to our knowledge, only five studies which have used this method to study lateralization offunction for emotional experience. In three studies [4,5,23], photographs of emotional or neutral faces were presented separately to the left and right hemispheres. In the other two studies [6,7], films with emotional content were, likewise, presented unilaterally to each hemisphere. Subjects rated the emotional tone of these stimuli on a variety of affective dimensions, and in two studies [4,5] subjects also rated their emotional responses directly. An overall view of these experiments reveals a complex relationship between the emotional valence of the presented stimuli, the hemisphere to which they were projected, and the affective dimensions on which the stimuli were rated. So, for instance, DAVIDSON et al. [4,5]

INDUCING EMOTION BY UNILATERAL CONTRACTION OF FACIAL MUSCLES 925

found that sad pictures were rated as more happy when projected to the left hemisphere as compared to the right hemisphere, but there were no effects with the happy or neutral pictures. DIMOND et al. [6], on the other hand, found that all stimuli were rated more horrific and unpleasant when projected to the right hemisphere, but no differences between the hemispheres were found for the ratings of humour or pleasantness. The pattern of results across experiments supports the view that the left hemisphere is biased towards positive and the right hemisphere is biased towards negative emotional experiences, however, interpreta- tions are difficult because of these complicated relations.

A third approach to studying hemispheric specialization of emotion is presented here. It is conceptually similar to that described above in that it is based on the selective activation of each hemisphere, but avoids the complexities which result from measuring emotional reactions to affective stimuli. In this case the cerebral hemispheres are activated differentially by having subjects contract muscles unilaterally.

A similar approach has been applied to the study of cognitive functions of the cerebral hemispheres with some success. The direction of eye and head movements have been attributed to arousal of the hemisphere contralateral to the direction of movement [lS]. When the direction of movement has been manipulated experimentally, cognitive performance [15, 16, 18, 223 and affective judgment [S, 91 have been shown to reflect the properties of the hemisphere contralateral to the directed movement. These results are consistent with the functional cerebral distance hypothesis [20].

In the research reported here, subjects contracted muscles unilaterally in the lower part of the face. The relevant sensory and motor pathways are primarily crossed [25] and these contractions necessarily result in increased activity in the respective parts of the contralateral hemisphere. We investigated reports of emotional experience consequent to these contractions.

Our hypothesis was that under appropriate testing conditions, subjects performing such unilateral muscle contractions would tend to experience emotional changes that are associated with the activated hemisphere. Accordingly, we expected that subjects would report different experiences depending on the side of the facial contraction. The nature of these experiences should inform us regarding the nature of hemispheric specialization for the experience of emotion.

EXPERIMENT 1

The purpose of this study was to explore whether subjects would experience emotions while maintaining unilateral contractions of facial muscles. To accomplish this, we used test procedures that were designed to maximize the likelihood that subjects would experience and would be willing to report emotions. These procedures were intuitive and semiclinical, and did not conform to standard experimental practice.

The subjects were instructed to pull back and lift each corner of their mouths (see Fig. 1). This facial movement was chosen because it utilizes muscles in the lower half of the face which is contralaterally innervated [25], and because it is relatively easy to perform.

Subjects

METHOD

The subjects were 12 acquaintances of the experimenter. They were selected because the experimenter considered that they would be sufficiently comfortable feeling unexplained emotions, that they would not interfere with such experiences and would also be willing to report them. There were four men and eight women.

926 BERNARD B. SCHIFF and MARY LAMON

Design

This experiment employed a within subjects design. The independent variable was the side of the facial contraction, left or right, and the dependent variable was the subject’s report of his or her experience following each contraction. The side of the first contraction was balanced across subjects, however the sequence of subsequent left and right contractions was different for each subject, and was determined by the experimenter’s judgment about the subject’s emotional state. So, for instance, if the experimenter thought that a subject was beginning to show signs of emotion the same side was repeated once or more depending on the outcome.

Procedure

Subjects were tested individually and privately in several locations. They were told that they were to perform the facial contractions described above, and to maintain them until the experimenter told them to relax. Each contraction lasted for about 1 min. The subjects were asked to pay attention to whatever emotional experiences they might have while maintaining these contractions, to let them occur without judgment, and to report on them when they were asked to relax. They were asked to breathe normally during these contractions and to maintain eye contract with the experimenter. The experimenter attempted to create a relaxed and personal atmosphere which would support the experiencing and the expression of feelings.

RESULTS

Ten of the twelve subjects reported emotional experiences subsequent to the facial contractions. Following left face contractions they all reported feeling sad or depressed and had sad facial expressions. Three subjects began to weep. None had any explanations for their mood changes. They described the feeling as coming upon them without warning and without reason. None could attribute these feelings to any events, external or internal, and all expressed surprise that they were feeiing so sad.

Following right face contractions these subjects reported feeling “sarcastic”, “cocky”, “up”, “good” and “smug”. There were no reports or signs of sadness. When the right contraction was performed during a dysphoric state produced by the left contraction, all subjects reported that the sad feeling “lifted” or “disappeared”, again without any apparent reason.

These ten subjects all started reporting emotional experiences after the first two or three contractions. The other two subjects did not report such experiences after a series of over ten contractions. They reported feeling self conscious or silly because of the grimaces on their faces, or feeling nothing. There were no apparent explanations for the difference between these two subjects and the others. It is possible that personal or interpersonal variables may have inhibited their experience and/or report of emotions. This is a familiar problem for students of emotions [l 11, and would be especially pertinent here where, in some cases, strong emotions appeared without explanation and under unusual circumstances.

DISCUSSION

These results strongly suggest that emotions can be activated by unilateral facial muscle contractions, and that different emotions are induced depending on the side of the contraction. Left face contractions were followed by reports of sadness and depression. Right face contractions produced reports of positive affect (“up”, “good”) and what can be characterized best as a mixture of positive affect and aggression (“cocky”, “smug”).

Although it seems unlikely that the consistent and dramatic reports were determined by cues provided by the experimenter, this cannot be ruled out because of the semiclinical procedures used. Also, we cannot exclude the possibility that the aroused emotions were related to the effort of the responses. The next two experiments were designed to eliminate these possibilities.

INDUCING EMOTION BY UNILATERAL CONTRACTION OF FACIAL MUSCLES 927

FIG. 1. Appearance of the face when subject performs the experimental manipulation of pulling back and lifting one corner of the mouth on the left and the right side respectively.

INDUCING EMOTION BY UNILATERAL CONTRACTION OF FACIAL MUSCLES 929

EXPERIMENT 2

In this experiment we replicated the first study in the laboratory to see if the emotional changes would be detected under standardized experimental test conditions and measure- ments.

Subjects

METHOD

Subjects were 30 right-handed male and female undergraduate volunteers who participated in order to receive a course credit in an introductory psychology course.

The experiment employed a within subjects design. The independent variable was side offace contraction, left or right. Each subject performed two left and two right face contractions. Order of contractions was counterbalanced across subjects. The dependent measure was the participant’s report of his or her emotional experience following each contraction.

Apparatus

The experimenter, a hired technician, sat opposite each subject at a table in the middle of an empty room. A tape recorder was placed on the table so as to record subjects’ reports.

Procedure

Subjects were asked to sign consent forms in which they agreed to perform facial muscle contractions, report on their experiences, and allow these reports to be audiotaped. They were then tested for handedness using a 6 item hand usage questionnaire [24]. A criterion of five out of six right-handed responses was used to establish handedness. Data from left-handed participants were not analyzed.

Standard instructions were read aloud. The instructions informed the subjects that they would be asked to contract one side of the face and hold that contraction for 45 set after which they would be told to relax. The experimenter demonstrated the facial contraction, and instructed the subjects to perform it by pulling back and raising one corner of the mouth as much as they could. They were instructed to breathe normally throughout the contraction and to attend to feelings rather than to thoughts or facial sensory experiences. The subjects performed one such contraction on each side of the face. Half the subjects did the left side first and the others, the right side. All subjects reported which side was easier to do.

Each subject performed four contractions (LRLR or RLRL) and reported their experiences after each one. Reports were recorded on audiotape. Each consecutive contraction was performed after the subjects completed their reports, which allowed at least 30 set between contractions. The experimenter did not make deliberate eye contact or interact in any way that might influence the subjects to have emotional experiences.

RESULTS

Audiotapes of each report following each contraction were transcribed. Each report was typed onto a separate page. Order of reports was randomized across subjects and conditions. Two judges were chosen who had experienced and observed the emotional effects of unilateral contractions. They independently judged each report as having followed a left or a right facial contraction, or as “unknown” for those which they could not classify.

There were 120 mood reports from 30 subjects. The judges made the same decision for 106 of these reports. The 14 reports for which they did not agree were ones that only one of the judges classified, and were reports of feeling embarrassed, weird, or tense. There were no reports for which the judges made opposite classifications. They agreed that 50 could not be classified. These were generally reports of facial sensory experiences, of feeling nothing, or of feeling “the same as before”. They also agreed on classifications for 56 reports generated by

930 BERNARD B. SCHIFF and MARY LAMON

22 of the 30 subjects. Twenty-eight of these reports were predicted to have followed a left contraction and 28, a right contraction.

The accuracy of the judges’ classifications were assessed for the 56 reports on which they agreed. Of the left face, 75%, and of the right face, 71% classifications were correct. A test for the efficacy of prediction [12] yielded a Phi coefficient of 0.47 which was significant, x*(l)= 12.38, PtO.OO1. The results replicate findings from Experiment 1.

Of the subjects who produced classifiable responses 66% reported that the left contraction was easier to do.

DISCUSSION

The results of this experiment replicate those of Experiment 1. The judges were able to distinguish between responses that followed a left face contraction from those that followed a right face contraction with a high degree of reliability. The judges had each experienced and read descriptions of the phenomenon described in Experiment 1, and made the discriminations subjectively on the basis of those experiences. This method was used, rather than a more objective one, because we have not yet sufficiently characterized these states to confidently establish objective criteria, especially of emotions following right face

contractions. This method also allowed us to ascertain that the emotional phenomena following left and right face contractions in this experiment were indeed similar to those described in Experiment 1.

It is clear from the data on the relative ease of the right and left face contractions reported by the subjects in this experiment that the dysphoria following the left contraction was not due to the difficulty of the muscular response. More than half the subjects found the left sided contraction easier to do. Similarly, the reports followed right face contraction were not confounded by effort.

It was necessary for the experimenter in this study to be familiar with the findings in Experiment 1, so that she could respond appropriately if any of the subjects showed undue distress subsequent to the left face contraction and so that she could debrief the subjects on completion of testing. (All subjects whose last contraction had been on the left side of the face were asked to contract the right side of their faces before leaving the experimental room so as to alleviate any residual negative affect. One subject became very upset following a left face contraction and refused to proceed with the experiment. That subject was debriefed and then performed a right face contraction which successfully removed his dysphoria.)

Even though the experimenter had expectations of the experimental outcomes, we believe that we can conclude that the findings of this experiment were not confounded by experimenter produced cues. While the reports following right face contractions were sufficiently consistent to be classified correctly, we did not have a simple characterization of them that could be the basis of a communicated expectation. Also, the dysphoria following left face contractions, which was in some cases profound, could hardly be produced in response to subtle or even explicit demands.

Accordingly, we conclude that unilateral muscle contractions can induce emotions. Left face contractions resulted in dysphoria and right face contractions alleviated the dysphoria produced by the left face contractions and resulted in a state that is more difficult to characterize but appears to be a mixture of positive affect and aggression.

In the next experiment, we investigated the effects of these contractions on emotion using a measure other than self report.

INDUCING EMOTION BY UNILATERAL CONTRACTION OF FACIAL MUSCLES 931

EXPERIMENT 3

The purpose of this experiment was to test the emotional effects of unilateral contractions on a measure other than self report. We studied the effects of these contractions on the emotional tone of stories told in response to selected pictures from the Thematic Apperception Test (T.A.T.) [l].

One picture (No. 11) was chosen as the target picture because stories told about it have been described as offering good clues regarding the mood of the subject. Two other pictures (Nos. 13B and 14) were chosen as practice pictures because they were described as not being sensitive to emotional states [l]. Picture 11 (the target) is an ambiguous stimulus in that it is not easy to discern its objective content. Pictures 13B and 14 (the practice pictures) are, on the other hand, very clearly defined and easily recognized images. The claims made about the relative utility of these pictures in reflecting the emotional states of the story tellers are supported by experimental evidence that emotional states affect the perception of unstructured but not structured stimuli [ 133. They are also consistent with DAVIDSON’S [S] speculation that the visual field differences in emotional ratings of affective stimuli emerge only in response to stimuli which do not overpoweringly elicit strong emotional responses

themselves. We, therefore predicted that unilateral facial contractions would affect the emotional tone

of stories told about the target (ambiguous) picture, and not those told about the practice (unambiguous) pictures. More specifically, we predicted that the emotional tone of the stories about the target picture would reflect the emotions that these contractions were shown to induce in the first two experiments.

METHOD Subjects

Subjects were 36 right-handed male and female undergraduate volunteers who participated in order to receive a course credit in an introductory psychology course. Subjects were assigned on an alternating basis to either right or left face contraction conditions.

Design

The experiment employed a between-within subjects design. Side of face contraction, right or left, was a between subjects manipulation and picture type was a within subjects variable. The dependent measure was the proportion of negative, positive, and neutral propositions generated for each of the three pictures.

Materials

Testing was done under the same circumstances as in Experiment 2. The three pictures were standard T.A.T. materials.

Procedure

Consent forms, the test for handedness, and face contraction instructions were the same as those used in Experiment 2. As in Experiment 2, the instructions were standard for all subjects and the experimenter did not interact with the subject beyond this. For this experiment, each subject was instructed to perform the face contraction, maintain it for 45 set, and then relax for 10 to 15 sec. Each subject performed this sequence four times.

Following the four facial contractions, subjects were presented with instructions for describing the three TAT pictures. Subjects were told that they would be presented with three pictures, and that their task was to make up as dramatic a story as they could describing what they saw in the picture, what had led up to the events depicted in the picture, and what outcome was likely to ensue. The experimenter was familiar with the effects of unilateral face contractions on emotion but was nai’ve as to the predictions regarding their effects on the responses to the three pictures. The pictures were then presented, one at a time, in a fixed order. Pictures 13B and 14, the practice pictures, were shown first, followed by Picture 11, the target. Subjects viewed each picture for 45 set, returned it to the experimenter, and made up as dramatic a story as they could. The experimenter interacted with subjects only to

932 BERNARD B. SCH~FF and MARY LAMON

encourage the more reticent story tellers to say more. This took the form of“is that all?“, or “can you say more?“, or when the subject omitted any of the three parts of the story (past, present or future) to remind them to include it.

All stories were recorded on audio tape and then transcribed. Each story was divided into propositions, a proposition being defined as an idea unit loosely consisting of a topic and a comment on that topic.

RESULTS

There were a total of 924 propositions with approx. equal numbers for each face contraction and picture condition. The order of the propositions was randomized across conditions, pictures, and subjects. Two independent raters scored each proposition as positive, negative, or neutral in emotional tone. The raters agreed on more than 90% of the propositions. The disagreements were resolved by discussion, except for 10 which were classified as neutral. The proportions of positive, negative and neutral propositions for each picture for each face contraction condition are shown in Fig. 2. As expected, there were no differences between contraction conditions for any class of propositions for the practice pictures 1 and 2. However, for Picture 3, the target picture, there was a greater proportion of negative propositions in the left contraction condition than in the right contraction condition, t(34)=3.22, PcO.005, and there was a greater proportion of both positive and neutral propositions in the right contraction condition than in the left contraction condition, t(34)=2.12, P~0.04, and t(34)= 1.86, P-co.05 respectively.

Picture 1

Positive Negatwe Neutral

CondIllon

I El Le” Face Contractim

m Riillt Face Contranbn

Positive Negative Neutral Positive Negative Neutral

Picture 2 Picture 3

Emotional Tone of Propositions

FIG. 2. The proportions of emotionally positive, negative, and neutral propositions in stories told about the practice pictures (1 and 2) and the target picture (3) following contractions of the left and

right side of the face respectively.

An analysis of variance comparing the three classes of propositions within the left contraction condition for Picture 3 was significant, F (2, 5 1) = 25.82, PC 0.0001. A Student- Neumann-Keul’s multiple range test showed that there were more negative than neutral propositions, and more neutral propositions than positive, P < 0.01. For propositions within the right contraction condition for Picture 3, the analysis of variance was not significant, F (2, 51)= 2.91, P>O.O6. There were no differences between the proportion of negative, neutral and positive propositions.

INDUCING EMOTION BY UNILATERAL CONTRACTION OF FACIAL MUSCLES 933

Therefore, the left face contraction produced more negative propositions than the right face contraction and also produced stories that were distinctly negative in tone. The right face contraction produced more positive and neutral propositions than the left face contraction, however, the stories were not readily characterized as to emotional tone.

DISCUSSION

The results of this experiment support our predictions. The emotional tone of the stories told about the target picture following unilateral facial muscle contractions reflected the emotions induced by these contractions as described in Experiments 1 and 2. In those experiments, the left face contractions had produced distinctly negative emotions while the right face contractions had induced a positive emotional state that was difficult to characterize. Parallel to this, the left face contractions produced stories that were predominantly negative in tone (they had significantly more negative propositions than either neutral or positive propositions). The right face contractions resulted in stories which were more positive than those which followed the left contractions (they had significantly more positive and neutral propositions) but were difficult to characterize as to emotional tone (they had equivalent numbers of positive, negative and neutral propositions).

The stories told about the two practice pictures, on the other hand, were not differentially affected by the side of the facial contraction.

These data provide independent support for the conclusions of Experiments 1 and 2. Furthermore, if there were any remaining questions regarding the validity of the emotional reports in the first two experiments, this third experiment demonstrates conclusively that this is not a problem. The experimenter was naive of as to the predictions regarding the target and the practice pictures. If the emotional reports were merely compliance with the experimenter’s expectation, there would be no way for the subjects to make the further inference that only the target picture should reflect these reports.

GENERAL DISCUSSION

We have demonstrated that unilateral contractions of facial muscles can induce emotional states that are reflected in self report as well as in stories that are told about an ambiguous picture. The emotions experienced were not related to the difficulty in performing the contractions. The effects of these contractions, furthermore, appeared to be fairly robust. In Experiment 3 their influence was manifested in stories about the target pictures which were told at least 4 or 5 min following the facial contraction during which time the subjects were telling stories about Pictures 1 and 2.

The findings reviewed above are consistent with the hypothesis that these emotions result from arousal of the cerebral hemisphere contralateral to the contracted muscles. The left contractions resulted in sadness and feelings of being “down” or “blue” which have been implicated in right hemisphere functions [2,27]. The emotions reported following right face contractions were a mixture of positive affect and agression (smug, cocky, up, good). This is consistent with the position that the left hemisphere has a role in the experience of emotion [27] and in particular with DAVIDSON’S [3] view that positive affect and anger, both expressions of approach, are associated with left hemisphere functioning. The congruence of these findings with current perspectives on hemisphere functioning indicates the utility of this method for investigating the neurology of experience.

934 BERNARD B. SCHIFF and MARY LAMON

Our data support the view that both hemispheres are involved in emotional experience; however, further investigations are needed to describe their respective roles. In particular, we must address why sadness was the only negative emotion reported after left face contractions, and find techniques which will allow for more complete and precise descriptions of the experiences induced by unilateral facial contractions.

There are many other questions to be answered regarding the nature of the phenomenon we have reported. Are the effects on emotions restricted to unilateral contraction of facial muscles? (We have preliminary data to indicate that similar effects can be produced by contracting skeletal muscles). Does the arousal of emotion depend on feedback, either from the muscles or skin involved by the facial contraction, or is it related to central events associated with the initiation and maintenance of the motor response? Are cerebral blood flow and brain temperature, which ZAJONC [29] has recently revived as subjects of interest in the study of facial movement, differentially affected by unilateral contractions, and what other measures of brain activity will reveal the C.N.S. consequences of these contractions? The answers to these questions may provide interesting insights into the basis of emotional experience.

These findings also are relevant to the controversy regarding the role of cognition in emotional experience. Some have argued that emotion is always secondary to cognitive appraisal of events, either current, remembered or imagined [21,26], whereas others have maintained that emotions can precede cognitions [17,28]. The subjects in these experiments all reported that the emotions subsequent to the facial contractions occurred spontaneously and without explanation. There were no reports of intervening cognitions, and no environmental stimuli to cue a particular emotional response. Unilateral facial contractions appear to induce emotional experiences without cognitive mediation. One implication of this is that asymmetries in facial expression, whether spontaneous or deliberate, may actually influence the emotional experience.

In conclusion, we have reported here the discovery that it is possible to turn on emotions with unilateral contractions of facial muscles. This provides a methodology which may allow for further insights into the psychology, neurology and physiology of emotion. It is a demonstration that emotions can occur without cognitive mediation, which may, when more fully understood have implications for mood management.

Acknowledgements-We thank Alison Fleming, Jonathan Freedman, Robert Lockhart and Morris Moscovitch for their careful reading of and comments on the manuscript.

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