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Standardized mood induction with happy and sad facial expressions
8tychiarr.v Reseawh, 5 I : 19-3 I Elsevier
19
Standardized Mood Facial Expressions Frank Schneider, Received
Induction
With
Happy
and Sad
Ruben C. Gur, Raquel E. Gur, and Larry R. Muenz
October II, 1992; revised version received April I2, 1993; accepted June I, 1993.
Abstract. The feasibility of applying ecologically valid and socially relevant emotional stimuli in a standardized fashion to obtain reliable mood changes in healthy subjects was examined. The stimuli consisted of happy and sad facial expressions varying in intensity. Two mood-induction procedures (happy and sad, each consisting of 40 slides) were administered to 24 young healthy subjects, who were instructed to look at each slide (self-paced) and try to feel the happy or sad mood expressed by the person in the picture. On an emotional self-rating scale, subjects rated themselves as relatively happier during the happy mood-
induction condition and as relatively sadder during the sad mood-induction condition. Conversely, they reported that they were less happy during the sad mood-induction condition and less sad during the happy mood-induction condition. The effects were generalized to positive and negative affect as measured by the Positive and Negative Affect Scale. The intraindividual variability in the effect was very small. In a retest study after 1 month, the mood-induction effects showed good stability over time. The results encourage the use of this mood-induction procedure as a neurobehavioral probe physiologic neuroimaging studies for investigating the neural substrates emotional experience. Key Words. Emotion, facial expression.
mood induction,
neurobehavioral
probes,
in of
neuroimaging,
Mood-induction procedures are being used extensively in experimental psychology (cf. Gerrards-Hesse et al., in press), particularly with the resurgence of interest in the interaction of emotion and cognition (Lazarus, 1991). Several mood-induction procedures have been described in the literature, also with respect to psychopathology (Goodwin and Williams, 1982). They differ in the method and duration of stimulation, their effectiveness, and the standardization of procedures. The main methods include imagination (e.g., Velten, 1968; Clark, 1983; Kenealy, 1986; Taylor and Cooper, 1992), hypnosis (e.g., Weiss et al., 1987), music (e.g., Albersnagel, 1988; McFarland, 1984) film clips (e.g., Ekman et al., 1990; Schneider et al., 1990), social interaction (e.g., McIntyre et al., 1991; Schneider et al., 1992a, 1992c), imitation of a facial expression (e.g., Schiff and Lamon, 1989; Levenson et
Frank Schneider, M.D., Ph.D., was Visiting Associate Professor (at the time this article was submitted); Ruben C. Gur, Ph.D., and Raquel E. Gur, M.D., Ph.D., are Professors, and Larry R. Muenz, Ph.D., is Adjunct Associate Professor of Biostatistics in Psychiatry, all in the Department of Psychiatry, University of Pennsylvania, Philadelphia, PA. (Reprint requests to Dr. F. Schneider, Psychiatrische Klinik, Universitat Tiibingen, Osianderstrasse 22, D-72076 Tubingen, Germany.) 0165-1781/94/$07.00
@ 1994 Elsevier Science Ireland
Ltd
20 al., 1990; Wallbott, 1991), pictures/startle response (e.g., Lang et al., 1993), and memories for positive and negative life events (e.g., Abele, 1990; de Jong-Meyer et al., 1990). To increase the effectiveness of such procedures, some authors combined different types of methods. Many of these procedures are not clearly described, and standardization data are rare. Their ecological validity and social relevance are frequently equivocal, and effectiveness is assumed without obtaining confirmation with standard rating scales. When such measures are provided, often the mood changes are slight or absent in some subjects. The choice of an appropriate measure to describe a mood-induction effect is not obvious. For example, there are numerous psychophysiological measures that can be recorded during or after a task. These include autonomic responses (e.g., Levenson et al., 1990), such as heart rate or skin conductance, as well as central measures, in particular electroencephalography (e.g., Davidson et al., 1990). Behavioral measures of specific mood changes in relation to the induced emotion (happy, sad, and others) include rating-scales (e.g., Rosenthal, 1982; Schneider et al., 1992~). coding (e.g., Ekman, 1982), or the automated analysis of the subjects’ facial expressions (e.g., Himer et al., 1991). Recent advances in physiologic neuroimaging procedures have enabled experimentally controlled studies of the neural substrates for cognition. Through the use of neurobehavioral probes (Cur et al.. 1992~) in healthy subjects and psychiatric patients, regionally specific effects have been demonstrated for a range of cognitive tasks (e.g., Risberg et al., 1977; Gur et al., 1982, 1987: Leli et al., 1982: Reivich et al., 1984; Posner et al.. 1988). and abnormalities in activation have been related to psychopathology (e.g., Gur et al., 1983, 1985, 1989: Weinberger et al., 1986. 1988). While some studies have examined the effects of anxiety on cerebral metabolism [e.g.. Reivich et al., 1983; Gur et al.. 1987) and blood flow (e.g., Cur et al.. 1988; Mathew and Wilson, 1990). this methodology has not been applied systematicaily to the study of emotion. The aim of this study was to develop and standardiz.e an effective and socially relevant mood-induction procedure. applicable for physiologic neuroimaging studies (Cur et al.. 1992~). In this initial step, we focused on the consistency of induction effects across healthy subjects and the reproducibility of these effects as reflected in the experience of happy and sad emotion, dimensions examined extensively in behavioral studies.
Methods Subjects. The subjects were 2-1college undergraduates (12 men, I2 women) at the University of Pennsylvania with a mean age of 19.7 years (SD = 1.9) and a mean of 13.8 years of education (SD = 1.2). They were right-handed as assessed by a laterality questionnaire (Oldfield, 1971). Participants underwent screening for medical. neurological. and psychiatric disorders and were all healthy, were not taking any regular medication, and had no history of any LXM-/I/- R (American Psychiatric Association. 1987) disorder in Eirst-degree relatives. Task. The stimuli consisted of straight-angle monochromatic photographs of happy and sad facial expressions varying in intensity. The procedure for constructing the stimuli has been detailed elsewhere (Erwin et al.. 1992). In brief, II7 Caucasian professlonal actors were instructed to display the emotions while their pictures were taken. The models Mood-induction
21 were draped in black fabric and photographed against a black backdrop to eliminate all clothing and ambient distracters. This set of photographs was reviewed by six raters for asymmetry and for ambiguity of emotion expressed (not classifiable as happy, sad, or neutral). Acceptable photographs were then rated by 160 students. Raters classified the emotion portrayed, and a stimulus was accepted if at least 70% of raters agreed upon the emotion represented and less than 5% of the raters judged the face to portray a nontarget emotion. These photographs were used in a happy-neutral and sad-neutral discrimination task in healthy subjects (Erwin et al., 1992) and patients with schizophrenia (Heimberg et al., 1992) and depression (Gur et al., 19926). To construct the stimulus set, we used the 169 slides for which more than 90% of the subjects in Erwin et al. (1992) agreed about the intended emotion of happy or sad: 52 female happy, 24 female sad, 59 male happy, and 34 male sad. These were presented to six raters who rated the genuineness of expression (yes-no) and whether only one emotion as opposed to emotional blends was displayed (yes-no). They also rated the intensity of the expressed target emotion on a 5-point Likert-type scale (0 = not at all; 4 = most intense). Only unitary and genuine facial expressions were retained. We chose 40 happy and 40 sad stimuli, so that the final two sets had an equal gender representation and were of comparable intensity (happy: mean = 2.27, SD = 0.72; sad: mean = 2.09, SD = 0.58; t = -1.19, df = 78, NS). No more than three different pictures of one single actor in each of the two tasks were allowed. There were 10 male and 11 female actors in the sad condition; and 11 male and 1 I female actors in the happy one. The slides in each of the two tasks (happy mood-induction task, sad mood-induction task) were ordered in a random fashion with the constraints that no more than three slides of the same sex and only one slide of a single actor could occur in a set of seven slides. The instructions were as follows: During this task, I would like you to try to become happy [sad]. To help you do that. I will be showing vou slides with faces exuressing hanniness Isadnessl. Look at each face and use it toh’elp you feel happy [sadj. For egan$le, yoican imagine what would make the person on the slide express that emotion, or you can think of a personal event or memory that made you feel emotions like those expressed by the person in the picture. When you feel happy [sad] and are no longer interested in the slide, push the button and the next slide will appear. Don’t rush, look at each slide, and try to feel the same emotion [happy/sad] expressed by the person in the picture. Scales. The dependent measure for the mood-induction effect was the Positive and Negative Affect Scale (PANAS; Watson et al., 1988), used frequently in psychological studies (e.g., McIntyre et al., 1991). The PANAS is a 5-point unipolar intensity scale, which includes ratings for factor-referenced emotional descriptors for orthogonal positive and negative dimensions, respectively. In addition, we measured valence specificity with an Emotional SelfRating (ESR) scale, which provides ratings for six different emotions (anger, disgust, fear, happiness, sadness, and surprise), using the same Likert-type unipolar intensity scale (1 = not at all, 2 = a little, 3 = moderately, 4 = quite a bit, 5 = extremely). This measure was similar to the subjective ratings of emotions used in other studies (e.g., in Ekman et al., 1990). Both of these scales required a rating of “How did you actually feel while you watched the slides?” While scales such as the ESR are frequently used in such research, reliability and validity data are lacking. Therefore, we chose the PANAS as the main dependent measure. It has published normative and clinical data, provides an interval scale level, and has a broader range (20 items), resulting in higher variability appropriate for statistically evaluating retest coefficients. The ESR was used only as a manipulation check to ascertain the specificity of the experienced emotion (i.e., whether subjects felt happy, sad, surprised, angry, fearful, or disgusted during the happy and sad mood-induction procedures). Facial Emotion Discrimination. To control for interindividual differences in the ability to discriminate happy and sad emotions, the PENN Facial Discrimination Test (PFDT) was
22 administered. This task is a booklet adaptation of the longer slide version described in Erwin et al. (1992) and contains similar facial stimuli as described above. The booklet includes 20 neutral, IO happy, and 10 sad faces, with equal numbers of male and female faces in each group. The task requires the individual to view each photograph and indicate his or her perception of the emotion depicted. The subject responds using a 7-point bipolar intensity scale. The answer key polarity was reversed in half of the subjects. Procedures. Subjects were administered state anxiety scales immediately before and after the study and trait anxiety scales immediately before the study (STAI; Spielberger et al., 1970). Analyses of these data did not reveal any significant sex differences or time-of-administration effects on anxiety. Because we wanted the subjects to became familiar with the range of emotional expressions and type of stimuli, we administered the PFDT first. After a short break, the two moodinduction procedures were administered in a counterbalanced order (within sex). Both induction procedures lasted approximately IO minutes and were separated by a S-minute break. Retest Study. Sixteen of the 24 subjects were tested a second time after an average of I month (mean = 31.5 days, SD = 13.7, range = 13-53). The same procedure was repeated. Data Analysis. Mood induction. The PANAS was scored in the standard fashion, which yields a positive and a negative summary score (Watson et al., 1988). The dependent measure for quantifying the individual mood-induction effect was derived from these scores and defined as follows: PANAS-MIn,,,,.s,d = PANAS-MIn,,,, - PANAS-MIs,d (where PANAS-MIn,,,,.s,d is the mood-induction effect, PANAS-MIn,,,, is the difference between the positive and negative affect score for the happy induction condition, and PANAS-MIs,d is the same difference for the sad condition). A similar form of data analysis was used with the ESR. The mood-induction scores from the ESR ratings were defined as follows: ESR-MIn,,,,.s,d = ESR-MIn,,,, - ESR-MIs,d (where ESR-Mln,,,,.s,d is the mood-induction effect, ESR-MIn,,,? is the difference between the happy and sad score for the happy induction condition, and ESR-Mls,d is the same difference for the sad condition). We considered the individual effect of mood induction as strong when ESR-MIn,,,,.s,d was > 3, moderate when it was I or 2, none when it was 0, and reverse when it was negative. For the analysis of variance (ANOVA), used to examine the scores were not necessary, and the original rating self-ratings, the subtracted ESR-MI Happy_Sad scores for each scale in each mood-induction task were used. PFDT. The number of true positives (i.e., responses in the “happy” range for a happy expression and in the “sad” range for a sad expression), false positives (scores in the emotional range for neutral stimuli), true negatives (“neutral” responses to neutral faces), and false negatives (“neutral” responses to emotional faces) were computed, as described in Erwin et al. (1992). For the present analysis, percent correct was used by dividing the total number of correct responses by the total number of items (*loo). Statistical Analysis. The hypothesis that mood-induction procedures alter mood (Mln,,r,_ sad > 0) was tested using betweenand within-group factors ANOVA (SAS GLM PROCedure; SAS Institute Inc., 1988) with sex as a grouping factor and mood induction (happy, sad) and PANAS scale (positive, negative) as repeated measures. The scale X mood induction interaction served as a test for the hypothesis. To ascertain the specificity of the experienced emotion against other emotion ratings on the ESR, the correlation of happy and sad scales with all other scales, as well as the correlation between happy and sad scales, was obtained. Each pair of scales with significant intercorrelations was then examined with a repeated measures ANOVA (mood induction, ESR scale). To determine stability over time (session 1: first testing; session 2: retest session after 4 weeks), we computed the difference score for PANAS-Ml n,,ppY_sadin session I and in session
23 2. Stability would be reflected in a nonsignificant paired I test, against the hypothesis Ho: MIH~,,~>_~~~ session 2 different from MIHappy_sadsession 1. Retest reliability was examined by the correlation of our main dependent measure, PANAS-MIHappy_sad scores from session 1 and session 2. The K coefficient was used for raw ESR scores.
Results Mood Induction. PANAS. Table 1 presents the PANAS results. The 2 (sex) X 2 (scale: positive, negative affect) X 2 (mood induction: happy, sad) ANOVA yielded a significant scale X mood-induction interaction (F= 18.83; df’= 1,22;p = 0.0003, with more positive affect during the happy mood-induction condition compared with the sad moodinduction condition. Likewise, more negative affect was present during the sad mood-induction condition and less negative affect during the happy mood-induction condition. The intercorrelation between the positive and the negative score of the PANAS was not significant (r = -0.06, df= 23). The intensity of induced affect during happy mood-induction is comparable to the intensity of induced affect during sad mood induction. No significant difference was found in a test of the positive affect scale during happy induction and the negative affect during sad induction with the difference of positive affect during happy induction and negative affect during happy induction (t = 1.06, df’= 22, p > 0.10). Retest study. The same ANOVA was used to assess the PANAS data for the 16 subjects participating in the retest study. The significant effects were similar: scale X mood induction (F= 11.47; df = I, 14; p = 0.004. None of the paired t tests for differences Table 1. Means for the Emotional Negative Affect Scale (PANAS)
Self-Ratings Happy
Scale PANAS-Positive PANAS-Negative
ESR-Happy
(ESR) and the Positive Sad
mood induction
mood induction
26.06 (8.12)
21 .oo (7.1 1)
26.50
(6.26)
22.69
(7.58)
11.25
(1.42)
15.38
(4.28)
10.93
(1.24)
14.88
(4.27)
3.58 (0.65)
1.42 (0.72)
3.63 (0.81)
1.56 (0.73)
ESR-Sad
1.08(0.28)
2.88 (1.08)
1.19 (0.40)
2.63 (1.09)
ESR-Anger
1.04 (0.20)
1.46 (0.59)
1 .oo (0.00)
1.69 (0.79)
ESR-Disgust ESR-Fear ES&Surprise Note. Study 1: upper line (n = ‘24) Retest/Study
and
1.04(0.20)
1.54 (0.98)
1 .oo (0.00)
1.75 (1.06)
1.04 (0.20)
1.46 (0.88)
1.06(0.25)
1.31 (0.48)
1.83 (0.76)
1.25 (0.53)
1.88 (0.72)
1.31 (0.70)
2: lower line (n = 16). Standard deviations are shown m parentheses.
24 between session I and session 2 on the positive or negative scales of the PANAS in either mood-induction condition reached significance. ESR. Table 1 also presents the results for ESR. There was a significant scale X mood induction interaction (F = 110.43; df = 1, 22; p = O.OOOl), with higher happy ratings during the happy mood-induction condition and lower happy ratings during sad mood-induction condition. Similarly, higher sad ratings were obtained during the sad mood-induction condition and lower sad ratings during the happy moodinduction condition. Examination of the intercorrelations among scales revealed no significant correlation with the happy scale except for a negative correlation with the sad scale (r = -0.49, df = 23, p = 0.014). The sad scale correlated positively with disgust (r = 0.73, df’= 23, p = O.OOOl), anger (r = 0.51, df= 23, p = 0.012), and fear (r = 0.49, df = 23, p = 0.016). Thus, we performed four 2 (scale) X 2 (mood induction) ANOVAs as described above, where “scale” was happy vs. surprise, sad vs. fear, sad vs. anger, and sad vs. disgust, respectively. For all of these ANOVAs, the scale X mood induction interaction was highly significant: happy vs. surprise (F= 31.57; df= 1, 23;~ = 0.0001); sad vs. fear (F= 44.17; df= I, 23;~ = 0.0001); sadvs.anger(F=53.18;df=1,23;p=0.0001;sadvs.disgust(F=61.57;df=1,23; p = 0.0001). Retest study. We performed the same ANOVA with the ESR data for the 16 subjects who participated in the retest study. The significant effects were similar: scale X mood induction (F= 76.22; df = 1, 14; p = 0.0001). None of the paired f tests for the difference between session I and session 2 yielded significant differences from 0 in any of the six ESR scales for either task. Retest Reliability. The correlation of PANAS-M IH,.+pp+ad at session 1 with the same score at session 2 was r = 0.75, df= 23, p = 0.0008. For the ESR, for happy mood-induction ratings, K was 0.02 for happiness, -0. IO for sadness, 0.0 for anger (table was in one cell), 0.0 for disgust, -0.07 for fear, and 0.28 for surprise. The corresponding coefficients for sad mood induction were 0.23 for happiness, 0.04 for sadness, 0.24 for anger, 0.29 for disgust, 0.05 for fear, and 0.06 for surprise. Differences. Fig. 1 illustrates the results for individual subjects on ESR-MIu,,,,_s,d. As can be seen, none of the subjects in session 1 had a reversed response. A moderate effect for ESR-MIH, JlppY.sadwas obtained for 25% (n = 6). and 7574 (n = 1X) showed a strong induction effect. Similar results were observed for session 2: None showed a reversed reaction, Sci; (n = I) no reaction, 19% (n = 3) a moderate effect, and 750x (n = 12) a strong effect. Individual
Corollary Display
Analyses. time. There
were no differences between the happy and sad moodinduction condition on how long subjects were interested in a single slide (f < 1, Q’= 22). The mean display time for each slide in the happy task was 5.5 seconds (SD = 2.3) and for the sad task 5.5 (SD = 3.0). PFDT. The median of the percent correct score was 95.0% (individual range: 77.5-100.0). On the average, there were 9.9 (out of 10) correct responses for the happy discrimination compared with 9. I for the sad discrimination.
i : .._ : I:I
Fig. 1. Effect of the happy and sad mood-induction individual subject 4-
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-1
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LIIIIII1IIII1II1IIIII1I1III1IIII1111II111111111111 HSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHSHS
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MOOD SESSION SESSION
INDUCTION
TASK
1 2
The abscissa shows the happy (H) and sad (S) induction condition, and the ordinate shows the difference of “happy” minus “sad” emotional self-rating (ESR-MI sappy-sad) for each subject. The 24 subjects who participated in session 1 (solid line) and 16 of those who also participated in session 2 (dashed line) are displayed.
Discussion Standardized happy and sad mood induction with facial stimuli seems effective and shows good stability over time. This was reflected in an emotional self-rating of happiness and sadness, and the effects were apparently generalized to positive and negative affect as measured by the PANAS. Subjects rated themselves as happier during the happy, relative to the sad mood-induction condition, and as sadder during the sad compared with the happy mood-induction condition. Conversely, they reported that they were less happy during the sad, relative to the happy moodinduction condition, and less sad during the happy compared with the sad moodinduction condition. The intraindividual variability in the effect of this mood-induction procedure seems small. As seen in Fig. 1, all subjects in session 1 and all except one in session 2 showed the intended effect. A strong effect was observed in 75% of the subjects. Thus, in our population of well-screened healthy young undergraduates, the moodinduction procedure appears consistently effective. The strength and consistency of these findings differ from other mood-induction procedures described in the literature. For example, the Velten procedure is effective only in approximately 60% of all subjects (according to the meta-analysis in Gerrards-Hesse et al., in press). The small variability of the effect in the present sample could be problematic for studies focusing on individual differences. However, this small amount of variability may
1
26 reflect the homogeneous sample. This homogeneity, while optimal for testing initial efficacy, is not suitable for addressing individual differences (e.g., extraversionintroversion or repression-sensitization). It would be important in future studies to examine a broader range of healthy subjects as well as specific clinical populations. Retest reliability of the mood-induction procedure, as measured by the PANAS, was good. However, because of truncated range and small variability, K coefficients for ESR scales were insufficient. We believe that our retest reliability for ESR scales is good and that the low values of the K statistic are examples of the paradoxical phenomenon discussed by Feinstein and Cicchetti (1989; Cicchetti and Feinstein, 1989). They note: . . if two suitably “blinded” observers happen to achieve high agreement . when their variability is evaluated, they might justifiably complain about the penalty imposed by K because the investigator happened to choose a challenge population that was highly unbalanced . . . for its proportion of normal (or abnormal) entities. [Feinstein and Cicchetti, 1989, p. 54811 The penalty to which they refer is a limit on the maximum concordance, in the presence of highly imbalanced outcomes, to possibly much less than IOOyo. The limit can greatly lower the value of K. Imbalanced outcomes are the case with the ESR scales which, at both time points, are concentrated at the same end of their range. Incidentally, a solution to this paradox is to accompany K by two other measures, the observed proportions of positive agreement and of negative agreement (Cicchetti and Feinstein, 1989, p. 554). The results of the PFDT show that all subjects could easily discriminate facial expressions of happy and sad emotions. With a median percent correct score of 95y& they were nearly perfect in categorizing the displayed emotion as happy, sad, or neutral, respectively, We believe that this task should be administered conjointly with the mood-induction procedure, particularly in clinical populations, to assure that differences in the effectiveness of induction are not attributable to difficulties in emotional discrimination. There were no sex differences in the observed effects. While several studies have reported sex differences in emotional discrimination (e.g., Burton and Levy, 1989; Erwin et al., 1992), most studies dealing with mood induction did not look for differential gender effects. These studies have not typically used a well-balanced mixture of male and female stimuli. In an earlier divided visual field study with discriminations of positive and negative facial expressions, we used an equal number of male and female actors and were not able to find any sex differences (Schneider et al., 19926). Further studies should examine baseline effects of mood changes, a major issue with which we struggled when we designed the present study. To obtain a measure of baseline mood variability, however, requires multiple assessments over some period of time. Such an effort is certainly needed but would have been premature before the effectiveness of the new induction procedure had been established, which was the purpose, admittedly limited, of the present study. Furthermore, future studies have to address the influence of different emotional qualities besides happiness and sadness and the intensity of the experienced emotion. We observed a moderate
27 amount of emotional intensity for both happy and sad induction procedures, which seems, in the context of emotion and arousal, appropriate for neuroimaging. An observer-based rating of mood seems to be helpful in validating the induction. However, we are not aware of the availability of such procedures. Common clinical expert rating scales, while appropriate for measuring temporal variation in clinical studies over longer time spans, are not useful for quantifying momentary changes in mood. Other methods we have used in the past for objectifying mood changes, such as psychophysiological measures and observer ratings, require extensive equipment and did not unequivocally reflect emotional experiences. For example, we described emotional ratings of the facial expression (Schneider et al., 1992~) used a selfdeveloped computer-based method to analyze facial movements (Schneider et al., 1990, 1992a), and employed the Facial Action Coding System (Schneider et al., 1992~). While these data provided useful information, correlations with self-ratings of experienced emotions were often weak and hence none can be considered a marker. Having confirmed the induction effects in the present experiment, we have taken up this issue in subsequent studies with neuroimaging and used heart rate in a r33xenon study (Schneider et al., in press). In the present study, we made detailed observations of all subjects during the induction procedure and found behavioral evidence for its effectiveness. Many of the subjects smiled or laughed during the happy mood-induction, and most of them looked dysphoric during sad moodinduction, with several becoming tearful. Our focus was on the self-report of emotions actually perceived during the moodinduction procedure. As with other self-report measures (Gur, 1987), they are susceptible to demand characteristics and other response biases (Berkowitz and Troccoli, 1986). However, mood experience is inherently a subjective event that depends on self-reports for its verification. Future studies can examine more closely the influence of demand characteristics on results of this mood-induction procedure. The present investigation demonstrates the feasibility of applying ecologically valid emotional stimuli in a standardized fashion to obtain reliable mood changes in healthy individuals. This suggests that reliable effects of mood-induction can be obtained when this procedure is used in physiologic neuroimaging studies (Gur et al., 1992~). The present approach has an advantage over imitation procedures, which have also been effective in mood induction, since imitation requires facial muscle activity. There is one published article suggesting that facial muscle movements can contaminate results of neuroimaging studies (Drevets et al., 1992). However, using appropriate methods, such as cross-registering magnetic resonance scan to the actual positron emission tomographic image or using a proportional stereotactic method, would prevent such false conclusions. The presented mood-induction procedure also has an advantage over procedures such as Velten’s (1968) in that it does not rely on linguistic processes which activate specific neural networks. Due to the autosuggestive nature of this task, it would be of benefit to determine whether the ability to respond to this procedure is associated with other personality dimensions such as hypnotic susceptibility (Hilgard, 1970) or suggestibility (Barber and Wilson, 1979). Applying this procedure in populations with psychopathology could help determine whether difficulties in appropriate emotional responses to socially relevant stimuli, such as faces, may be associated with specific disturbances.
28
The social relevance of the tasks, tapping a dimension which relates to the ability to respond to interpersonal cues, suggests that it would be pertinent to social interactions. In a recently completed study (Schneider et al., submitted), mood induction was diminished in schizophrenic patients, especially for happiness, relative to normal control subjects. Hallucinations, as measured by clinical rating, were associated with more pronounced mood-induction effects. Clarifying the role of emotion in schizophrenia may help in understanding the etiology of the illness by using standardized procedures in physiological neuroimaging. Additionally, this can help elucidate the nature of impairments in social interaction behavior, which have implications for expressed emotion research as well as psychosocial intervention strategies. This could lead to the application of standardized mood induction with facial expressions as part of the diagnostic battery in psychiatry. Given the nature of this procedure, it could also be worth contemplating as an adjunct for an emotional and/ or social therapy in psychiatric and psychological disturbances. This research was supported by a Research Award of the DGPNder Deutschen Gesellschaft fur Psychiatric und Nervenheilkunde (German
Acknowledgments.
Duphar-Stiftung
Psychiatric Association; FS), the NATO Science Committee (FS), the MacArthur Foundation Mental Health Research Network I, and the National Institute of Mental Health (Mental Health Clinical Research Center on Regional Brain Function in Schizophrenia, MH-43880).
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19
Standardized Mood Facial Expressions Frank Schneider, Received
Induction
With
Happy
and Sad
Ruben C. Gur, Raquel E. Gur, and Larry R. Muenz
October II, 1992; revised version received April I2, 1993; accepted June I, 1993.
Abstract. The feasibility of applying ecologically valid and socially relevant emotional stimuli in a standardized fashion to obtain reliable mood changes in healthy subjects was examined. The stimuli consisted of happy and sad facial expressions varying in intensity. Two mood-induction procedures (happy and sad, each consisting of 40 slides) were administered to 24 young healthy subjects, who were instructed to look at each slide (self-paced) and try to feel the happy or sad mood expressed by the person in the picture. On an emotional self-rating scale, subjects rated themselves as relatively happier during the happy mood-
induction condition and as relatively sadder during the sad mood-induction condition. Conversely, they reported that they were less happy during the sad mood-induction condition and less sad during the happy mood-induction condition. The effects were generalized to positive and negative affect as measured by the Positive and Negative Affect Scale. The intraindividual variability in the effect was very small. In a retest study after 1 month, the mood-induction effects showed good stability over time. The results encourage the use of this mood-induction procedure as a neurobehavioral probe physiologic neuroimaging studies for investigating the neural substrates emotional experience. Key Words. Emotion, facial expression.
mood induction,
neurobehavioral
probes,
in of
neuroimaging,
Mood-induction procedures are being used extensively in experimental psychology (cf. Gerrards-Hesse et al., in press), particularly with the resurgence of interest in the interaction of emotion and cognition (Lazarus, 1991). Several mood-induction procedures have been described in the literature, also with respect to psychopathology (Goodwin and Williams, 1982). They differ in the method and duration of stimulation, their effectiveness, and the standardization of procedures. The main methods include imagination (e.g., Velten, 1968; Clark, 1983; Kenealy, 1986; Taylor and Cooper, 1992), hypnosis (e.g., Weiss et al., 1987), music (e.g., Albersnagel, 1988; McFarland, 1984) film clips (e.g., Ekman et al., 1990; Schneider et al., 1990), social interaction (e.g., McIntyre et al., 1991; Schneider et al., 1992a, 1992c), imitation of a facial expression (e.g., Schiff and Lamon, 1989; Levenson et
Frank Schneider, M.D., Ph.D., was Visiting Associate Professor (at the time this article was submitted); Ruben C. Gur, Ph.D., and Raquel E. Gur, M.D., Ph.D., are Professors, and Larry R. Muenz, Ph.D., is Adjunct Associate Professor of Biostatistics in Psychiatry, all in the Department of Psychiatry, University of Pennsylvania, Philadelphia, PA. (Reprint requests to Dr. F. Schneider, Psychiatrische Klinik, Universitat Tiibingen, Osianderstrasse 22, D-72076 Tubingen, Germany.) 0165-1781/94/$07.00
@ 1994 Elsevier Science Ireland
Ltd
20 al., 1990; Wallbott, 1991), pictures/startle response (e.g., Lang et al., 1993), and memories for positive and negative life events (e.g., Abele, 1990; de Jong-Meyer et al., 1990). To increase the effectiveness of such procedures, some authors combined different types of methods. Many of these procedures are not clearly described, and standardization data are rare. Their ecological validity and social relevance are frequently equivocal, and effectiveness is assumed without obtaining confirmation with standard rating scales. When such measures are provided, often the mood changes are slight or absent in some subjects. The choice of an appropriate measure to describe a mood-induction effect is not obvious. For example, there are numerous psychophysiological measures that can be recorded during or after a task. These include autonomic responses (e.g., Levenson et al., 1990), such as heart rate or skin conductance, as well as central measures, in particular electroencephalography (e.g., Davidson et al., 1990). Behavioral measures of specific mood changes in relation to the induced emotion (happy, sad, and others) include rating-scales (e.g., Rosenthal, 1982; Schneider et al., 1992~). coding (e.g., Ekman, 1982), or the automated analysis of the subjects’ facial expressions (e.g., Himer et al., 1991). Recent advances in physiologic neuroimaging procedures have enabled experimentally controlled studies of the neural substrates for cognition. Through the use of neurobehavioral probes (Cur et al.. 1992~) in healthy subjects and psychiatric patients, regionally specific effects have been demonstrated for a range of cognitive tasks (e.g., Risberg et al., 1977; Gur et al., 1982, 1987: Leli et al., 1982: Reivich et al., 1984; Posner et al.. 1988). and abnormalities in activation have been related to psychopathology (e.g., Gur et al., 1983, 1985, 1989: Weinberger et al., 1986. 1988). While some studies have examined the effects of anxiety on cerebral metabolism [e.g.. Reivich et al., 1983; Gur et al.. 1987) and blood flow (e.g., Cur et al.. 1988; Mathew and Wilson, 1990). this methodology has not been applied systematicaily to the study of emotion. The aim of this study was to develop and standardiz.e an effective and socially relevant mood-induction procedure. applicable for physiologic neuroimaging studies (Cur et al.. 1992~). In this initial step, we focused on the consistency of induction effects across healthy subjects and the reproducibility of these effects as reflected in the experience of happy and sad emotion, dimensions examined extensively in behavioral studies.
Methods Subjects. The subjects were 2-1college undergraduates (12 men, I2 women) at the University of Pennsylvania with a mean age of 19.7 years (SD = 1.9) and a mean of 13.8 years of education (SD = 1.2). They were right-handed as assessed by a laterality questionnaire (Oldfield, 1971). Participants underwent screening for medical. neurological. and psychiatric disorders and were all healthy, were not taking any regular medication, and had no history of any LXM-/I/- R (American Psychiatric Association. 1987) disorder in Eirst-degree relatives. Task. The stimuli consisted of straight-angle monochromatic photographs of happy and sad facial expressions varying in intensity. The procedure for constructing the stimuli has been detailed elsewhere (Erwin et al.. 1992). In brief, II7 Caucasian professlonal actors were instructed to display the emotions while their pictures were taken. The models Mood-induction
21 were draped in black fabric and photographed against a black backdrop to eliminate all clothing and ambient distracters. This set of photographs was reviewed by six raters for asymmetry and for ambiguity of emotion expressed (not classifiable as happy, sad, or neutral). Acceptable photographs were then rated by 160 students. Raters classified the emotion portrayed, and a stimulus was accepted if at least 70% of raters agreed upon the emotion represented and less than 5% of the raters judged the face to portray a nontarget emotion. These photographs were used in a happy-neutral and sad-neutral discrimination task in healthy subjects (Erwin et al., 1992) and patients with schizophrenia (Heimberg et al., 1992) and depression (Gur et al., 19926). To construct the stimulus set, we used the 169 slides for which more than 90% of the subjects in Erwin et al. (1992) agreed about the intended emotion of happy or sad: 52 female happy, 24 female sad, 59 male happy, and 34 male sad. These were presented to six raters who rated the genuineness of expression (yes-no) and whether only one emotion as opposed to emotional blends was displayed (yes-no). They also rated the intensity of the expressed target emotion on a 5-point Likert-type scale (0 = not at all; 4 = most intense). Only unitary and genuine facial expressions were retained. We chose 40 happy and 40 sad stimuli, so that the final two sets had an equal gender representation and were of comparable intensity (happy: mean = 2.27, SD = 0.72; sad: mean = 2.09, SD = 0.58; t = -1.19, df = 78, NS). No more than three different pictures of one single actor in each of the two tasks were allowed. There were 10 male and 11 female actors in the sad condition; and 11 male and 1 I female actors in the happy one. The slides in each of the two tasks (happy mood-induction task, sad mood-induction task) were ordered in a random fashion with the constraints that no more than three slides of the same sex and only one slide of a single actor could occur in a set of seven slides. The instructions were as follows: During this task, I would like you to try to become happy [sad]. To help you do that. I will be showing vou slides with faces exuressing hanniness Isadnessl. Look at each face and use it toh’elp you feel happy [sadj. For egan$le, yoican imagine what would make the person on the slide express that emotion, or you can think of a personal event or memory that made you feel emotions like those expressed by the person in the picture. When you feel happy [sad] and are no longer interested in the slide, push the button and the next slide will appear. Don’t rush, look at each slide, and try to feel the same emotion [happy/sad] expressed by the person in the picture. Scales. The dependent measure for the mood-induction effect was the Positive and Negative Affect Scale (PANAS; Watson et al., 1988), used frequently in psychological studies (e.g., McIntyre et al., 1991). The PANAS is a 5-point unipolar intensity scale, which includes ratings for factor-referenced emotional descriptors for orthogonal positive and negative dimensions, respectively. In addition, we measured valence specificity with an Emotional SelfRating (ESR) scale, which provides ratings for six different emotions (anger, disgust, fear, happiness, sadness, and surprise), using the same Likert-type unipolar intensity scale (1 = not at all, 2 = a little, 3 = moderately, 4 = quite a bit, 5 = extremely). This measure was similar to the subjective ratings of emotions used in other studies (e.g., in Ekman et al., 1990). Both of these scales required a rating of “How did you actually feel while you watched the slides?” While scales such as the ESR are frequently used in such research, reliability and validity data are lacking. Therefore, we chose the PANAS as the main dependent measure. It has published normative and clinical data, provides an interval scale level, and has a broader range (20 items), resulting in higher variability appropriate for statistically evaluating retest coefficients. The ESR was used only as a manipulation check to ascertain the specificity of the experienced emotion (i.e., whether subjects felt happy, sad, surprised, angry, fearful, or disgusted during the happy and sad mood-induction procedures). Facial Emotion Discrimination. To control for interindividual differences in the ability to discriminate happy and sad emotions, the PENN Facial Discrimination Test (PFDT) was
22 administered. This task is a booklet adaptation of the longer slide version described in Erwin et al. (1992) and contains similar facial stimuli as described above. The booklet includes 20 neutral, IO happy, and 10 sad faces, with equal numbers of male and female faces in each group. The task requires the individual to view each photograph and indicate his or her perception of the emotion depicted. The subject responds using a 7-point bipolar intensity scale. The answer key polarity was reversed in half of the subjects. Procedures. Subjects were administered state anxiety scales immediately before and after the study and trait anxiety scales immediately before the study (STAI; Spielberger et al., 1970). Analyses of these data did not reveal any significant sex differences or time-of-administration effects on anxiety. Because we wanted the subjects to became familiar with the range of emotional expressions and type of stimuli, we administered the PFDT first. After a short break, the two moodinduction procedures were administered in a counterbalanced order (within sex). Both induction procedures lasted approximately IO minutes and were separated by a S-minute break. Retest Study. Sixteen of the 24 subjects were tested a second time after an average of I month (mean = 31.5 days, SD = 13.7, range = 13-53). The same procedure was repeated. Data Analysis. Mood induction. The PANAS was scored in the standard fashion, which yields a positive and a negative summary score (Watson et al., 1988). The dependent measure for quantifying the individual mood-induction effect was derived from these scores and defined as follows: PANAS-MIn,,,,.s,d = PANAS-MIn,,,, - PANAS-MIs,d (where PANAS-MIn,,,,.s,d is the mood-induction effect, PANAS-MIn,,,, is the difference between the positive and negative affect score for the happy induction condition, and PANAS-MIs,d is the same difference for the sad condition). A similar form of data analysis was used with the ESR. The mood-induction scores from the ESR ratings were defined as follows: ESR-MIn,,,,.s,d = ESR-MIn,,,, - ESR-MIs,d (where ESR-Mln,,,,.s,d is the mood-induction effect, ESR-MIn,,,? is the difference between the happy and sad score for the happy induction condition, and ESR-Mls,d is the same difference for the sad condition). We considered the individual effect of mood induction as strong when ESR-MIn,,,,.s,d was > 3, moderate when it was I or 2, none when it was 0, and reverse when it was negative. For the analysis of variance (ANOVA), used to examine the scores were not necessary, and the original rating self-ratings, the subtracted ESR-MI Happy_Sad scores for each scale in each mood-induction task were used. PFDT. The number of true positives (i.e., responses in the “happy” range for a happy expression and in the “sad” range for a sad expression), false positives (scores in the emotional range for neutral stimuli), true negatives (“neutral” responses to neutral faces), and false negatives (“neutral” responses to emotional faces) were computed, as described in Erwin et al. (1992). For the present analysis, percent correct was used by dividing the total number of correct responses by the total number of items (*loo). Statistical Analysis. The hypothesis that mood-induction procedures alter mood (Mln,,r,_ sad > 0) was tested using betweenand within-group factors ANOVA (SAS GLM PROCedure; SAS Institute Inc., 1988) with sex as a grouping factor and mood induction (happy, sad) and PANAS scale (positive, negative) as repeated measures. The scale X mood induction interaction served as a test for the hypothesis. To ascertain the specificity of the experienced emotion against other emotion ratings on the ESR, the correlation of happy and sad scales with all other scales, as well as the correlation between happy and sad scales, was obtained. Each pair of scales with significant intercorrelations was then examined with a repeated measures ANOVA (mood induction, ESR scale). To determine stability over time (session 1: first testing; session 2: retest session after 4 weeks), we computed the difference score for PANAS-Ml n,,ppY_sadin session I and in session
23 2. Stability would be reflected in a nonsignificant paired I test, against the hypothesis Ho: MIH~,,~>_~~~ session 2 different from MIHappy_sadsession 1. Retest reliability was examined by the correlation of our main dependent measure, PANAS-MIHappy_sad scores from session 1 and session 2. The K coefficient was used for raw ESR scores.
Results Mood Induction. PANAS. Table 1 presents the PANAS results. The 2 (sex) X 2 (scale: positive, negative affect) X 2 (mood induction: happy, sad) ANOVA yielded a significant scale X mood-induction interaction (F= 18.83; df’= 1,22;p = 0.0003, with more positive affect during the happy mood-induction condition compared with the sad moodinduction condition. Likewise, more negative affect was present during the sad mood-induction condition and less negative affect during the happy mood-induction condition. The intercorrelation between the positive and the negative score of the PANAS was not significant (r = -0.06, df= 23). The intensity of induced affect during happy mood-induction is comparable to the intensity of induced affect during sad mood induction. No significant difference was found in a test of the positive affect scale during happy induction and the negative affect during sad induction with the difference of positive affect during happy induction and negative affect during happy induction (t = 1.06, df’= 22, p > 0.10). Retest study. The same ANOVA was used to assess the PANAS data for the 16 subjects participating in the retest study. The significant effects were similar: scale X mood induction (F= 11.47; df = I, 14; p = 0.004. None of the paired t tests for differences Table 1. Means for the Emotional Negative Affect Scale (PANAS)
Self-Ratings Happy
Scale PANAS-Positive PANAS-Negative
ESR-Happy
(ESR) and the Positive Sad
mood induction
mood induction
26.06 (8.12)
21 .oo (7.1 1)
26.50
(6.26)
22.69
(7.58)
11.25
(1.42)
15.38
(4.28)
10.93
(1.24)
14.88
(4.27)
3.58 (0.65)
1.42 (0.72)
3.63 (0.81)
1.56 (0.73)
ESR-Sad
1.08(0.28)
2.88 (1.08)
1.19 (0.40)
2.63 (1.09)
ESR-Anger
1.04 (0.20)
1.46 (0.59)
1 .oo (0.00)
1.69 (0.79)
ESR-Disgust ESR-Fear ES&Surprise Note. Study 1: upper line (n = ‘24) Retest/Study
and
1.04(0.20)
1.54 (0.98)
1 .oo (0.00)
1.75 (1.06)
1.04 (0.20)
1.46 (0.88)
1.06(0.25)
1.31 (0.48)
1.83 (0.76)
1.25 (0.53)
1.88 (0.72)
1.31 (0.70)
2: lower line (n = 16). Standard deviations are shown m parentheses.
24 between session I and session 2 on the positive or negative scales of the PANAS in either mood-induction condition reached significance. ESR. Table 1 also presents the results for ESR. There was a significant scale X mood induction interaction (F = 110.43; df = 1, 22; p = O.OOOl), with higher happy ratings during the happy mood-induction condition and lower happy ratings during sad mood-induction condition. Similarly, higher sad ratings were obtained during the sad mood-induction condition and lower sad ratings during the happy moodinduction condition. Examination of the intercorrelations among scales revealed no significant correlation with the happy scale except for a negative correlation with the sad scale (r = -0.49, df = 23, p = 0.014). The sad scale correlated positively with disgust (r = 0.73, df’= 23, p = O.OOOl), anger (r = 0.51, df= 23, p = 0.012), and fear (r = 0.49, df = 23, p = 0.016). Thus, we performed four 2 (scale) X 2 (mood induction) ANOVAs as described above, where “scale” was happy vs. surprise, sad vs. fear, sad vs. anger, and sad vs. disgust, respectively. For all of these ANOVAs, the scale X mood induction interaction was highly significant: happy vs. surprise (F= 31.57; df= 1, 23;~ = 0.0001); sad vs. fear (F= 44.17; df= I, 23;~ = 0.0001); sadvs.anger(F=53.18;df=1,23;p=0.0001;sadvs.disgust(F=61.57;df=1,23; p = 0.0001). Retest study. We performed the same ANOVA with the ESR data for the 16 subjects who participated in the retest study. The significant effects were similar: scale X mood induction (F= 76.22; df = 1, 14; p = 0.0001). None of the paired f tests for the difference between session I and session 2 yielded significant differences from 0 in any of the six ESR scales for either task. Retest Reliability. The correlation of PANAS-M IH,.+pp+ad at session 1 with the same score at session 2 was r = 0.75, df= 23, p = 0.0008. For the ESR, for happy mood-induction ratings, K was 0.02 for happiness, -0. IO for sadness, 0.0 for anger (table was in one cell), 0.0 for disgust, -0.07 for fear, and 0.28 for surprise. The corresponding coefficients for sad mood induction were 0.23 for happiness, 0.04 for sadness, 0.24 for anger, 0.29 for disgust, 0.05 for fear, and 0.06 for surprise. Differences. Fig. 1 illustrates the results for individual subjects on ESR-MIu,,,,_s,d. As can be seen, none of the subjects in session 1 had a reversed response. A moderate effect for ESR-MIH, JlppY.sadwas obtained for 25% (n = 6). and 7574 (n = 1X) showed a strong induction effect. Similar results were observed for session 2: None showed a reversed reaction, Sci; (n = I) no reaction, 19% (n = 3) a moderate effect, and 750x (n = 12) a strong effect. Individual
Corollary Display
Analyses. time. There
were no differences between the happy and sad moodinduction condition on how long subjects were interested in a single slide (f < 1, Q’= 22). The mean display time for each slide in the happy task was 5.5 seconds (SD = 2.3) and for the sad task 5.5 (SD = 3.0). PFDT. The median of the percent correct score was 95.0% (individual range: 77.5-100.0). On the average, there were 9.9 (out of 10) correct responses for the happy discrimination compared with 9. I for the sad discrimination.
i : .._ : I:I
Fig. 1. Effect of the happy and sad mood-induction individual subject 4-
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MOOD SESSION SESSION
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TASK
1 2
The abscissa shows the happy (H) and sad (S) induction condition, and the ordinate shows the difference of “happy” minus “sad” emotional self-rating (ESR-MI sappy-sad) for each subject. The 24 subjects who participated in session 1 (solid line) and 16 of those who also participated in session 2 (dashed line) are displayed.
Discussion Standardized happy and sad mood induction with facial stimuli seems effective and shows good stability over time. This was reflected in an emotional self-rating of happiness and sadness, and the effects were apparently generalized to positive and negative affect as measured by the PANAS. Subjects rated themselves as happier during the happy, relative to the sad mood-induction condition, and as sadder during the sad compared with the happy mood-induction condition. Conversely, they reported that they were less happy during the sad, relative to the happy moodinduction condition, and less sad during the happy compared with the sad moodinduction condition. The intraindividual variability in the effect of this mood-induction procedure seems small. As seen in Fig. 1, all subjects in session 1 and all except one in session 2 showed the intended effect. A strong effect was observed in 75% of the subjects. Thus, in our population of well-screened healthy young undergraduates, the moodinduction procedure appears consistently effective. The strength and consistency of these findings differ from other mood-induction procedures described in the literature. For example, the Velten procedure is effective only in approximately 60% of all subjects (according to the meta-analysis in Gerrards-Hesse et al., in press). The small variability of the effect in the present sample could be problematic for studies focusing on individual differences. However, this small amount of variability may
1
26 reflect the homogeneous sample. This homogeneity, while optimal for testing initial efficacy, is not suitable for addressing individual differences (e.g., extraversionintroversion or repression-sensitization). It would be important in future studies to examine a broader range of healthy subjects as well as specific clinical populations. Retest reliability of the mood-induction procedure, as measured by the PANAS, was good. However, because of truncated range and small variability, K coefficients for ESR scales were insufficient. We believe that our retest reliability for ESR scales is good and that the low values of the K statistic are examples of the paradoxical phenomenon discussed by Feinstein and Cicchetti (1989; Cicchetti and Feinstein, 1989). They note: . . if two suitably “blinded” observers happen to achieve high agreement . when their variability is evaluated, they might justifiably complain about the penalty imposed by K because the investigator happened to choose a challenge population that was highly unbalanced . . . for its proportion of normal (or abnormal) entities. [Feinstein and Cicchetti, 1989, p. 54811 The penalty to which they refer is a limit on the maximum concordance, in the presence of highly imbalanced outcomes, to possibly much less than IOOyo. The limit can greatly lower the value of K. Imbalanced outcomes are the case with the ESR scales which, at both time points, are concentrated at the same end of their range. Incidentally, a solution to this paradox is to accompany K by two other measures, the observed proportions of positive agreement and of negative agreement (Cicchetti and Feinstein, 1989, p. 554). The results of the PFDT show that all subjects could easily discriminate facial expressions of happy and sad emotions. With a median percent correct score of 95y& they were nearly perfect in categorizing the displayed emotion as happy, sad, or neutral, respectively, We believe that this task should be administered conjointly with the mood-induction procedure, particularly in clinical populations, to assure that differences in the effectiveness of induction are not attributable to difficulties in emotional discrimination. There were no sex differences in the observed effects. While several studies have reported sex differences in emotional discrimination (e.g., Burton and Levy, 1989; Erwin et al., 1992), most studies dealing with mood induction did not look for differential gender effects. These studies have not typically used a well-balanced mixture of male and female stimuli. In an earlier divided visual field study with discriminations of positive and negative facial expressions, we used an equal number of male and female actors and were not able to find any sex differences (Schneider et al., 19926). Further studies should examine baseline effects of mood changes, a major issue with which we struggled when we designed the present study. To obtain a measure of baseline mood variability, however, requires multiple assessments over some period of time. Such an effort is certainly needed but would have been premature before the effectiveness of the new induction procedure had been established, which was the purpose, admittedly limited, of the present study. Furthermore, future studies have to address the influence of different emotional qualities besides happiness and sadness and the intensity of the experienced emotion. We observed a moderate
27 amount of emotional intensity for both happy and sad induction procedures, which seems, in the context of emotion and arousal, appropriate for neuroimaging. An observer-based rating of mood seems to be helpful in validating the induction. However, we are not aware of the availability of such procedures. Common clinical expert rating scales, while appropriate for measuring temporal variation in clinical studies over longer time spans, are not useful for quantifying momentary changes in mood. Other methods we have used in the past for objectifying mood changes, such as psychophysiological measures and observer ratings, require extensive equipment and did not unequivocally reflect emotional experiences. For example, we described emotional ratings of the facial expression (Schneider et al., 1992~) used a selfdeveloped computer-based method to analyze facial movements (Schneider et al., 1990, 1992a), and employed the Facial Action Coding System (Schneider et al., 1992~). While these data provided useful information, correlations with self-ratings of experienced emotions were often weak and hence none can be considered a marker. Having confirmed the induction effects in the present experiment, we have taken up this issue in subsequent studies with neuroimaging and used heart rate in a r33xenon study (Schneider et al., in press). In the present study, we made detailed observations of all subjects during the induction procedure and found behavioral evidence for its effectiveness. Many of the subjects smiled or laughed during the happy mood-induction, and most of them looked dysphoric during sad moodinduction, with several becoming tearful. Our focus was on the self-report of emotions actually perceived during the moodinduction procedure. As with other self-report measures (Gur, 1987), they are susceptible to demand characteristics and other response biases (Berkowitz and Troccoli, 1986). However, mood experience is inherently a subjective event that depends on self-reports for its verification. Future studies can examine more closely the influence of demand characteristics on results of this mood-induction procedure. The present investigation demonstrates the feasibility of applying ecologically valid emotional stimuli in a standardized fashion to obtain reliable mood changes in healthy individuals. This suggests that reliable effects of mood-induction can be obtained when this procedure is used in physiologic neuroimaging studies (Gur et al., 1992~). The present approach has an advantage over imitation procedures, which have also been effective in mood induction, since imitation requires facial muscle activity. There is one published article suggesting that facial muscle movements can contaminate results of neuroimaging studies (Drevets et al., 1992). However, using appropriate methods, such as cross-registering magnetic resonance scan to the actual positron emission tomographic image or using a proportional stereotactic method, would prevent such false conclusions. The presented mood-induction procedure also has an advantage over procedures such as Velten’s (1968) in that it does not rely on linguistic processes which activate specific neural networks. Due to the autosuggestive nature of this task, it would be of benefit to determine whether the ability to respond to this procedure is associated with other personality dimensions such as hypnotic susceptibility (Hilgard, 1970) or suggestibility (Barber and Wilson, 1979). Applying this procedure in populations with psychopathology could help determine whether difficulties in appropriate emotional responses to socially relevant stimuli, such as faces, may be associated with specific disturbances.
28
The social relevance of the tasks, tapping a dimension which relates to the ability to respond to interpersonal cues, suggests that it would be pertinent to social interactions. In a recently completed study (Schneider et al., submitted), mood induction was diminished in schizophrenic patients, especially for happiness, relative to normal control subjects. Hallucinations, as measured by clinical rating, were associated with more pronounced mood-induction effects. Clarifying the role of emotion in schizophrenia may help in understanding the etiology of the illness by using standardized procedures in physiological neuroimaging. Additionally, this can help elucidate the nature of impairments in social interaction behavior, which have implications for expressed emotion research as well as psychosocial intervention strategies. This could lead to the application of standardized mood induction with facial expressions as part of the diagnostic battery in psychiatry. Given the nature of this procedure, it could also be worth contemplating as an adjunct for an emotional and/ or social therapy in psychiatric and psychological disturbances. This research was supported by a Research Award of the DGPNder Deutschen Gesellschaft fur Psychiatric und Nervenheilkunde (German
Acknowledgments.
Duphar-Stiftung
Psychiatric Association; FS), the NATO Science Committee (FS), the MacArthur Foundation Mental Health Research Network I, and the National Institute of Mental Health (Mental Health Clinical Research Center on Regional Brain Function in Schizophrenia, MH-43880).
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