Ž . Psychiatry Research 102 2001 109124 Are emotions contagious? Evoked emotions while viewing emotionally expressive faces: quality, quantity, time course and gender differences Barbara Wild a, , Michael Erb b , Mathias Bartels a a Department of Psychiatry, Uni ersity of Tubingen, Osianderstr.24, 72076 Tubingen, Germany ¨ ¨ b Sektion fur experimentelle Kernspintomographie, Department of Neuroradiology, Uni ersity of Tubingen, 72076 Tubingen, ¨ ¨ ¨ Germany Received 28 February 2000; received in revised form 18 December 2000; accepted 21 January 2001 Abstract In human interactions, frequently one individual becomes ‘infected’ with emotions displayed by his or her partner. Ž .Ž We tested the predictions by Hatfield et al. 1992 Primitive emotional contagion. Re iew of Personal and Social . Psychology 14, 151 177 that the automatic, mostly unconscious component of this process, called ‘primitive emotional contagion’, is repeatable and fast, that stronger facial expressions of the sender evoke stronger emotions in the viewer and that women are more susceptible to emotional contagion than men. We presented photos from the Ž .Ž Pictures of Facial Affect Ekman and Friesen, 1976 . Pictures of Facial Affect. Consulting Psychologists Press, Palo . Ž . Alto on a PC varying the affective content happy and sad , the expressive strength and the duration of presentation. After each photo, subjects rated the strength of experienced happiness, sadness, anger, disgust, surprise, fear and pleasure. Feelings of happiness or sadness were significantly, specifically and repeatedly evoked in the viewer even with presentations lasting only 500 ms. Stronger expressions evoked more emotion. The gender of the viewer had weak effects. We hypothesize that this fast and repeatable reaction is likely to have a ‘prewired’ neural basis. We propose that the induction of emotional processes within a subject by the perception of emotionally expressive faces is a powerful instrument in the detection of emotional states in others and as the basis for one’s own reactions. Detailed knowledge of emotional reactions to faces is also valuable as a basis for psychiatric studies of disorders in Ž . affect andor communication and in studies using functional imaging fMRI or PET where faces are increasingly used as stimuli. 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Perception; Emotional contagion; Emotion; Recognition Corresponding author. Tel.: 49-7071-2982311; fax: 49-7071-292141. Ž . E-mail address: [email protected]B. Wild . 0165-178101$ - see front matter 2001 Elsevier Science Ireland Ltd. All rights reserved. Ž . PII: S 0 1 6 5 - 1 7 8 1 01 00225-6
aDepartment of Psychiatry, Uni�ersity of Tubingen, Osianderstr.24, 72076 Tubingen, Germany¨ ¨bSektion fur experimentelle Kernspintomographie, Department of Neuroradiology, Uni�ersity of Tubingen, 72076 Tubingen,¨ ¨ ¨
Germany
Received 28 February 2000; received in revised form 18 December 2000; accepted 21 January 2001
Abstract
In human interactions, frequently one individual becomes ‘infected’ with emotions displayed by his or her partner.Ž . ŽWe tested the predictions by Hatfield et al. 1992 Primitive emotional contagion. Re�iew of Personal and Social
.Psychology 14, 151�177 that the automatic, mostly unconscious component of this process, called ‘primitiveemotional contagion’, is repeatable and fast, that stronger facial expressions of the sender evoke stronger emotions inthe viewer and that women are more susceptible to emotional contagion than men. We presented photos from the
Ž . ŽPictures of Facial Affect Ekman and Friesen, 1976 . Pictures of Facial Affect. Consulting Psychologists Press, Palo. Ž .Alto on a PC varying the affective content happy and sad , the expressive strength and the duration of presentation.
After each photo, subjects rated the strength of experienced happiness, sadness, anger, disgust, surprise, fear andpleasure. Feelings of happiness or sadness were significantly, specifically and repeatedly evoked in the viewer � evenwith presentations lasting only 500 ms. Stronger expressions evoked more emotion. The gender of the viewer hadweak effects. We hypothesize that this fast and repeatable reaction is likely to have a ‘prewired’ neural basis. Wepropose that the induction of emotional processes within a subject by the perception of emotionally expressive facesis a powerful instrument in the detection of emotional states in others and as the basis for one’s own reactions.Detailed knowledge of emotional reactions to faces is also valuable as a basis for psychiatric studies of disorders in
Ž .affect and�or communication and in studies using functional imaging fMRI or PET where faces are increasinglyused as stimuli. � 2001 Elsevier Science Ireland Ltd. All rights reserved.
0165-1781�01�$ - see front matter � 2001 Elsevier Science Ireland Ltd. All rights reserved.Ž .PII: S 0 1 6 5 - 1 7 8 1 0 1 0 0 2 2 5 - 6
( )B. Wild et al. � Psychiatry Research 102 2001 109�124110
1. Introduction
In human interactions, frequently one individ-ual becomes ‘infected’ with emotions displayed byhis or her partner. In psychiatric settings, thisphenomenon can help therapists understand theirclients’ feelings if they are unable to express themverbally. It may, however, also complicate contactand communication with depressed subjects orpatients with reduced facial activity due to neu-roleptic medication.
The term ‘emotional contagion’ describes acomplex process involving conscious perceptionsand social evaluations as well as a more auto-matic, unintentional mechanism largely inaccessi-
Ž .ble to awareness Hatfield et al., 1994 . This lattercomponent is called ‘primitive contagion’. It canbe defined as ‘the tendency to automatically mimicand synchronize movements, expressions, pos-tures, and vocalizations with those of anotherperson and, consequently, to converge emotio-
Ž .nally’ Hatfield et al., 1992; Hsee et al., 1990 .Thus, emotional contagion has been conceptual-ized as a three-stage process in which the percep-tion of facial expressions triggers facial mimicry,which in turn causes afferent feedback from fa-cial receptors or neural structures involved infacial movements and, thus, evokes emotionsŽ .Hatfield et al., 1992; Doherty, 1998 .
Hatfield and coworkers, in their book on emo-Ž .tional contagion Hatfield et al., 1994 , made a
number of predictions about the details of theemotional contagion process. In particular, theyhypothesized that subjects with stronger expres-sion of emotions should evoke more emotional
Ž .contagion p. 130 and that subjects with strongerfacial mimicry, e.g. women, should be more sus-
Žceptible to emotional contagion Hatfield et al.,.1992 . They also hypothesized that emotional
contagion is an automatic, ‘moment to moment’Ž .process p. 10 .
The occurrence of facial mimicry in direct con-tact with, as well as during observation of films orphotos of emotionally expressive faces, has been
Žwell documented see extensive review by Hat-. Ž .field et al., 1994 . Walbott 1991 filmed subjects
while they judged emotions displayed in photos
Žfrom the Pictures of Facial Affect fear, anger,disgust, happiness, sadness, surprise and con-
.tempt . Afterwards, the subjects were presentedwith their own facial reactions. They were able tojudge the emotions conveyed to them by theoriginal stimuli at an accuracy level above chance.However, Walbott did not document the subjects’own emotions while watching the photos. Dim-
changes within several hundred millisecondsŽ .Dimberg, 1997 after the repeated presentationof photos of emotionally expressive faces. Thiseffect was specific for the emotions involved, i.e.happy faces evoked increased activity in the zygo-matic muscles � as in smiling; angry faces in thecorrugator muscles � as in frowning. The reac-
Žtion was also accompanied by emotions Lundq-.vist and Dimberg, 1995; Dimberg, 1988b , al-
though not in exact correspondence: happy facesincreased happiness, angry faces generated fear.Similar results were obtained by Vaughan and
Ž .Lanzetta 1980 .Ž .Dimberg and Lundqvist 1990 , as well as a
Žnumber of other groups for an extensive review,.see Kring and Gordon, 1998 , have found that
women are more facially expressive than menwhen reacting to emotional stimuli. The findingsregarding sex differences of emotional experi-ences, however, were mixed. Kring and GordonŽ .1998 used film clips and subsequently inquiredabout feelings of happiness, sadness, anger, fear,surprise and disgust. They found no differences inthe subjects’ reports of experienced emotions withregard to sex, although females were more fa-cially expressive than men. Similar results were
Ž .reported by Zuckerman et al. 1981 , GreenwaldŽ . Ž .et al. 1989 , Lang et al. 1993 and Wagner et al.
Ž .1993 . Stronger facial expressivity concomitantwith stronger emotional experiences in women
Ž .was found by Schwartz et al. 1980 , Choti et al.Ž . Ž .1987 and Gross and Levenson 1993 . Most ofthese studies, however, used stimuli other thanfacial expressions to evoke emotions. Doherty et
Ž . Ž .al. 1993 cf. Hatfield et al., 1994 , using a ques-tionnaire, found that women reported being moresusceptible to emotional contagion than men did.To our knowledge, no study, aside from the one
( )B. Wild et al. � Psychiatry Research 102 2001 109�124 111
Ž .by Dimberg and Lundqvist 1990 , has directlyaddressed the subject of gender differences inemotional contagion.
It has been shown that the experimental ma-nipulation of facial activity can produce specific
Žchanges in corresponding emotional feelings see.reviews by Laird, 1984; Laird and Bresler, 1990 .
Laird and his co-workers demonstrated this forŽanger, sadness, fear, happiness and disgust Laird,
.1984; Duclos et al., 1989 . Using other methods ofŽ .manipulation, Strack et al. 1988 and Levenson
Ž .et al. 1990 also showed that facial movementswere capable of inducing emotions.
Emotional contagion has been demonstrated inŽnon-experimental social situations ranging from
neonate�parent interactions to clinical settingsand contacts between non-human primates; see
.review by Hatfield et al., 1994 as well as in anumber of experiments. Mood transmission wasdemonstrated from ‘senders’ to viewers or listen-
Žers by: direct interactions Sullins, 1991; Gump. Žand Kulik, 1997 ; images presented on video Hsee
. Žet al., 1990; Doherty, 1998 ; photos Dimberg,1988b; Sokolowski, 1992; Lang et al., 1993;Lundqvist and Dimberg, 1995; Kemps et al., 1996;
.Surakka and Hietanen, 1998 or audio recordingsŽ .Hietanen et al., 1998 . Aside from altering con-scious emotional states, photos of emotionallyexpressive faces have been shown to have aninfluence on a number of unconscious processes.Depending on the emotion, they elicit differentialeffects on sympathetic dermal and cardiovascular
Žreactions in the viewer Dimberg, 1988a; Lang et. Ž .al., 1993 , facial EMG Dimberg, 1997 , skin reac-
Žtion to conditioned stimuli Lanzetta and Orr,.1986; Dimberg, 1988a; Esteves et al., 1994 ,
Ževent-related potentials P450, Orozco and Ehlers,.1998 , amygdalar activation in functional imaging
Ž Žstudies even with subliminal presentation Mor-.ris et al., 1998; Whalen et al., 1998 and altered
Ž .speed in a writing task Sokolowski, 1992 as wellŽas attitudes towards everyday life scenes Kemps
.et al., 1996 .These studies, however, differ in regard to
which emotions were successfully transmitted. Forhappiness, positive evidence was reported by Hsee
Ž . Ž .and Doherty 1998 . In contrast, Sullins 1991 , inan experiment observing non-verbal communica-tion between facially high and low expressive sub-jects, only reported mood convergence for anxi-ety, aggression, sadness and fatigue, and not for
Ž .elation they did not ask about happiness . Facesexpressing fear or anger seemed to be stronglyevocative of emotions and autonomous reactionsŽLanzetta and Orr, 1986; Dimberg, 1982, 1988a,b;Lundqvist and Dimberg, 1995; Gump and Kulik,
.1997 in observers. The induced emotions, how-ever, also included disgust and fear as a reactionto angry faces and disgust as a reaction to fearfulfaces. Expressions of sadness mainly induced sad-
A major drawback of most studies demonstrat-ing the effects of emotional contagion is the useof behavioral sequences with durations of more
Žthan 1 min Hsee et al., 1990; Sullins, 1991;.Gump and Kulik, 1997; Doherty, 1998 . Where
shorter stimuli were used, they were ‘blocked’and emotional reactions were only recorded for
Žthese ‘blocks’ Lundqvist and Dimberg, 1995;.Dimberg, 1988b; Surakka and Hietanen, 1998 .
However, if primitive emotional contagion is a‘moment-by-moment’ process which is evoked by
Žfacial expressions in normal social contacts most.of which are shorter than 10 s; Frank et al., 1993 ,
it should also be evoked by stimuli with a shortpresentation duration.
The goal of the present study was, thus, toinvestigate in detail the timing, quality and quan-tity of experiential reactions to single short pre-sentations of faces displaying happy or sad ex-pressions in women and men. To do this, weestablished a highly standardized procedure. Pho-
Žtos of happy and sad faces digitized version ofphotos from the Pictures of Facial Affect, Ekman
.and Friesen, 1976 , varying systematically in thedegree of expressed emotion, were presented on acomputer screen. Each presentation was immedi-ately followed by the presentation of a computer-ized questionnaire. The strength of experiencedhappiness, sadness, anger, disgust, surprise andfear had to be marked on continuous scales rang-ing from ‘not at all’ to ‘very strong’. We alsoasked how ‘pleasant�unpleasant’ the picture pre-
( )B. Wild et al. � Psychiatry Research 102 2001 109�124112
sentation was perceived to be using a similarscale. We tested for an effect of presentation
Ž .duration 0.5�10 s and for gender effects. We areaware that the subjects’ answers were completelysubjective, but saw no other way to investigatethese conscious feelings other than to ask about
Ž .them. We agree with Laird and Bresler 1990that ‘verbal reports of emotional experiences havethe same status as reports of any other experi-ence � those of perceptions, for example’ andare ‘ordinarily truthful reflections of an individ-ual’s experience’.
We developed the following hypotheses: ifemotional contagion is an automatic and ‘mo-
Ž .ment-to-moment’ process, it 1 should also bepresent with stimulus presentations in the dura-
Ž .tion range of normal facial expressions �10 s .Ž .Furthermore, 2 the emotion-evoking effect of a
stimulus should be stable and repeatable. We alsowanted to test the propositions by Hatfield et al.Ž . Ž .1994 that 3 stronger expressions evoke stronger
Ž .emotions and 4 that women are more suscepti-ble to emotional contagion than men.
2. Methods
The study had three parts. We presented 40different pictures: in part one for 6 s each; in parttwo for durations varying randomly from 2 to 10 s.Because we had not seen any effect of the pre-sentation duration, we used the four picturesfrom each category which evoked the highestdegrees of happiness and sadness, respectively,and presented them in random order five timeseach for 0.5�2 s in part three.
2.1. Subjects
In part one, we tested 15 volunteers: sevenmale, eight female, average age 32.5 years, aver-age schooling 12.1 years; in part two, 10 volun-teers: one male, nine female, average age 36.9years, average schooling 12.6 years; in part three,11 volunteers: two male, nine female, average age29.1 years, average schooling 12.5 years. Thesevolunteers were recruited from the faculty, staffand students of the Departments of Psychology
and Psychiatry. All were Caucasian, native Ger-man language speakers and all were right-handedŽaccording to the Edinburgh Handedness Inven-
.tory, Oldfield, 1971 . The subjects had no previ-ous knowledge of the study and had no informa-tion about its goals. Using a semistructured inter-view, we excluded subjects with relevant previousand�or present psychiatric or neurological dis-
Žorders i.e. all subjects who had previously re-ceived counseling by a psychiatrist or psy-chologist, or reported symptoms of depression,psychosis, dementia or addiction, or who had hada brain injury, stroke, epilepsy or inflammatory
.CNS disease and subjects with first-degree-rela-tives with depressive or psychotic disorders. Allsubjects scored within the normal range on the
ŽBeck Depression Inventory BDI; Beck et al.,.1961; Hautzinger et al., 1994, score �12 .
2.2. Procedure
Subjects were comfortably seated in front of aŽ .PC screen Trident 800�600, 256 colors and
informed as to the task they were to perform.
2.2.1. InstructionsSubjects were shown an example of a picture of
a face and told that they would repeatedly seesimilar pictures on the screen. In order to focusattention on the visual stimulus and to inducesimilar cognitive processes in all subjects, we in-structed them to imagine meeting the picturedperson in a neutral social situation � such as ina cafe or on a bus � but without having direct´communication with the person. We explainedthat we were interested in their feelings whilethey were looking at the picture and that theywould be asked about them immediately aftereach picture by means of a questionnaire on thePC screen. The subjects were familiarized with
Ž .the questionnaire see below and trained in theuse of the PC mouse as an answering device.They were requested to fill in all fields in thequestionnaire. They could correct inaccurate an-swers as long as the questionnaire was still visible.They were told that they had unlimited time fortheir answers, but that they should try to bespontaneous. We stressed that there were no
( )B. Wild et al. � Psychiatry Research 102 2001 109�124 113
right or wrong answers and that we were onlyinterested in their actual feelings, derived exclu-sively from looking at the picture.
2.2.2. Stimulus materialWe used the digitized and morphed version of
Žthe Pictures of Facial Affect Ekman and Friesen,.1976 produced and described by Benson and
Ž . Ž .Perrett 1993 , Perrett et al. 1994 and Calder etŽ .al. 1997, 2000 . They consist of black-and-white
pictures of faces, each displaying only one emo-Ž .tion, e.g. happiness Fig. 1 shows examples . The
pictures have been digitally changed so that onlythe face, and no other body parts, such as hair,
Ž .are visible. By ‘morphing’ digitally mixing pic-tures of the same face displaying a neutral and anemotional expression and through a caricaturizingprocess, the strength of the emotional expressionwas varied, in this case between 75% and 150%of the target emotion. The original neutral andhappy faces of the same subject in the Pictures of
Ž .Facial Affect Ekman and Friesen, 1976 weredefined as 0% and 100%, respectively. In bothexpressions, 195 anatomical points were manuallydefined and difference vectors between corre-
sponding points defined. Moving the landmarkpoints along the difference vectors in the sameproportion generated levels between 0% and100%. The caricaturization exaggerates the facialexpression by extending the vector by, e.g., afactor of 1.5 to reach the 150% level. Calder et al.Ž .1997 demonstrated a reaction time advantagefor the recognition of the emotional expressionproportional to the level of the strength of theexpression.
In parts one and two, we used 40 pictures, 20each of happy and sad faces, five at each emotio-
Ž .nal strength 75%, 100%, 125%, 150% and from10 different subjects, i.e. two per emotion and persubject. For part three, we selected the four pic-
Ž .tures of each emotion happiness�sadness thathad received the highest ratings for the target
Žemotion happiness for happy pictures and sad-.ness for sad pictures among all subjects in part
one.
2.2.3. Stimulus and questionnaire presentationIn part one, the 40 pictures were presented in
random order, each for 6 s. Immediately aftereach picture, the questionnaire followed on the
Ž . Ž .Fig. 1. Stimuli. Examples of photos of happy upper row and sad stimuli lower row at four different expression-strength levelsŽ . Ž .75%, 100%, 125% and 150% and the neutral 0% picture for comparison on the very left. The 0% and 100% levels correspond to
Ž .the original items from the Pictures of Facial Affect subject PE .
( )B. Wild et al. � Psychiatry Research 102 2001 109�124114
Žscreen. It consisted of the following items see. Ž .Appendix A for the original German version : 1
‘I perceived the picture as pleasant�unpleasant.Ž .2 The picture evoked in me the following feel-ings: happiness, surprise, fear, sadness, disgust,anger’. Under each of the words for the emotionsand under the first question were placed rectilin-ear fields as continuous scales with a ‘�’ at theright end and a ‘�’ at the left. Using the PCmouse, the subjects could place one mark in eachfield. Subjects were instructed to place the marksaccording to the degree of their emotions betweenthe two end points, which symbolized that this
Ž . Ž .emotion was absent ‘�’ or extreme ‘�’ .We chose the response dimensions of happi-
ness, sadness, disgust, anger, fear and surprise,inasmuch as there is strong evidence that they aredisplayed by all humans independently of e.g.,cultural differences and can thus be best decodedŽ .Ekman et al., 1987; Ekman, 1992; Plutchik, 1994 .We also asked about ‘pleasure’. This category hasbeen found to be a basic dimension of emotional
Ž .experiences Lang et al., 1993 , and the GermanŽ .term ‘angenehm�unangenehm’ gave the best se-
lectivity in a verbal differential of emotionsŽ .Hamm and Vaitl, 1993 .
After answering all the questions, subjects couldterminate the questionnaire by clicking on a com-puter screen field ‘End’. This automatically startedthe next picture. The time between presentationof the questionnaire and its termination wasrecorded, and it is termed ‘answering duration’.After 20 pictures, the subjects had a break duringwhich they were encouraged to get up and walkaround. In preliminary experiments, this hadproved to be useful since 40 pictures in a rowwere judged to be too tiring or boring.
Part two was similar to part one, except thatthe duration of presentation was randomly variedbetween 2, 4, 6, 8 or 10 s so that each subject saweight pictures for each of the presentation dura-tions.
For part three, we selected the four pictures ofŽ .each emotion happiness�sadness that had re-
ceived the highest ratings for the target emotionŽ .happiness for happy face and vice versa amongall subjects in part one. Subjects viewed each ofthese eight photos � in random order � five
times, each with the duration of presentationvarying randomly between 0.5 and 2 s. Aside fromthis, part three was similar to part one.
2.2.4. Statistical e�aluationThe subjects’ answers were recoded into values
between 0 and 100, 0 reflecting the cursor posi-tion closest to ‘�’ and 100 closest to ‘�’ on thescales. Statistical testing was performed using theSPSS� software package. Differences between thehappy and sad picture types were evaluated usingtwo-tailed paired t-tests. We used ANOVAs with
Ž .the picture type happy�sad , gender of the viewerand gender of the depicted subject as factors and
ing duration as dependent variables to test forsignificant effects and interactions. This was doneseparately for the three experimental parts. Asecond group of ANOVAs with the same depen-dent variables was performed to test for effects ofpresentation duration in parts two and three. Theeffect of repeated presentation in part three wasevaluated using a repeated measures ANOVA.
3. Results
3.1. Significant effects of picture type
Ž .The picture type happy�sad had a highly sig-nificant effect on the evoked feelings of pleasureŽ . Žt��18.1, P�0.001 , happiness t�26.0, P�
a Ž .Averages and S.D. in parentheses in part one and part two for all subjects comparing response to happy and sad faces with2 Ž . Ž .significance and R of the difference reached in ANOVAs with the evoked emotion as dependent variable and a happy type, b
sad type and subject as factor.
fear. The answering duration for these was shorterŽ .see Figs. 2 and 3 and Table 1 .
The level of R2 in an ANOVA is a measure ofthe percentage of the detected variance that canbe explained by the examined factors. R2 was inthe range between 28% and 52% for the evokedfeelings of happiness, sadness and pleasure inparts one and two, and below 10% for the other
Ž .feelings see also Table 1 . For the feelings ofanger, disgust, surprise and fear, inter-individualdifferences were much larger and explained moreof the detected variance, so that using subject asa random factor in the ANOVA increased the R2
Ž .values remarkably Table 1 .
3.2. Effects of picture strength and effect of pre�iouslypresented picture
We used pictures with four different levels ofŽstrength of the depicted emotion see Section 2
.and Fig. 1 . We found no significant systematiceffect of picture strength in parts one and two inan ANOVA with picture strength and type asfactors. However, when individual levels werecompared with two-sided t-tests for repeatedmeasurements with a Bonferroni correction formultiple testing, the following significant differ-
ness, pleasure and surprise and less sadness at the125% level than at the 75% level. The results forthe 100% level showed mainly the same trend,but were not significant. The pictures on the150% level, compared to the 75% level, evokedless happiness and pleasure, whereas surprise wassignificantly higher and sadness was significantlylower.
For sad faces, the 75% level significantly evokedless sadness than the 125% level and less surprisethan the 100% and the 150% levels.
( )B. Wild et al. � Psychiatry Research 102 2001 109�124116
Ž . Ž .Fig. 2. Evoked happiness a and sadness b . The figuresŽ .show the answers averaged over all subjects �1 S.D. for
each individual stimulus in part one when subjects were askedŽ . Ž .about feelings of happiness a and sadness b after viewing
�� ��� �Ž . Ž .happy � and sad � faces. Answers could range betweenŽ . Ž .0 emotion not present and 100 emotion very strong . The
difference between the two stimulus types was significantŽ .P�0.001 for both emotions.
There were no other significant differences forthe other levels and the other emotions.
We found no longer-lasting effect of the pic-ture type, i.e. the type of picture prior to the teststimulus had no significant effect in parts one andtwo.
3.3. Effects of picture presentation duration andrepetition
In part two, we varied the presentation dura-tion between 2 and 10 s. We found no significanteffects when performing an ANOVA with presen-tation duration percentile ranks as a factor andwhen comparing the quartiles for the shortest andlongest presentation durations. In part three, wetherefore used presentation durations as brief as
Ž .our equipment permitted between 0.5 and 2 s .In order to get the strongest possible effects, weused only the four photos of each categoryŽ .happy�sad that had evoked the strongest feel-ings of happiness�sadness in part one and re-peated their presentation five times each. Againwe could not detect any significant effect. Thepictures evoked the same emotional reactions asin parts one and two, independent of presentationduration.
Ž .Fig. 3. Evoked emotions. Mean values �S.D. of all subjects’answers in part one for each emotional quality separately for
Ž . Ž .happy filled circles and sad open squares picture type. Starsindicate a significant effect of picture type in paired two-sided
Ž�� .t-tests comparing the two picture types : P�0.01 . An-Ž .swers could range between 0 emotion not present and 100
Ž .emotion very strong .
( )B. Wild et al. � Psychiatry Research 102 2001 109�124 117
aAverages and S.D. of all answers of all subjects in part one separately from happy and sad pictures.
Repeated presentation had a significant effect� Ž .on the evoked feelings of surprise F 4 �9.1,
� � Ž . �P�0.0001 and fear F 4 �3.1, P�0.017 withdiminishing evoked emotions of surprise and fearafter repeated presentation. Scheffe post-hoc tests´showed this to be due to significant differencesbetween the first presentation and the third,
Fig. 4. Repetition effects. The figure shows the reduction ofŽsurprise after repeated presentation mean values�95% con-
.fidence interval for the mean of all subjects in part oneseparated out for the five repetitions of presentation and the
Ž .fourth and fifth for surprise Fig. 4 , whereas forfear there was only a significant differencebetween the second and fourth presentations.
3.4. Gender effects
The main effect of the gender of the viewerwas an interaction between gender and picture
� Ž . �type for pleasure F 1 �16.7, P�0.001 . Fe-males experienced happy faces as more pleasantand sad faces as more unpleasant than malesŽ .Fig. 5a . The gender of the viewer had only weak
� Ž . �effects on evoked disgust F 1 �4.8, P�0.03� Ž . �and fear F 1 �4.6, P�0.03 , with females ex-
periencing more disgust and fear than men. Therewere no interactions with gender of the depictedperson.
In contrast, the gender of the depicted person� Ž .had significant effects on pleasure F 1 �22.4,
� � Ž . �P�0.001 , happiness F 1 �9.8, P�0.002 , dis-� Ž . � � Ž .gust F 1 �17.5, P�0.001 , sadness F 1 �13.7,
� � Ž . �P�0.001 , and fear F 1 �8.4, P�0.004 , butnot on anger and surprise. Pictures of femaleswere judged as more pleasant and evoked morehappiness and sadness and less disgust and fear
Ž .than pictures of males Fig. 5b .There were significant interactions of depicted
� Ž .gender with picture type for happiness F 1 �9.8,� � Ž . �P�0.002 and sadness F 1 �12.9, P�0.001 .
( )B. Wild et al. � Psychiatry Research 102 2001 109�124118
Ž . Ž .Fig. 5. Gender effects: VIEWER a and FOTO b . Compar-Žison between male and female subjects women�circles, men
. Ž . Ž .�squares as viewer in a and depicted in b . Mean valuesŽ .�S.D. of all subjects’ answers in part one for each emotional
Ž . Žquality separately for happy filled markers and sad open.markers picture type. Stars indicate significant effect of gen-
Ž�der in an ANOVA with gender and picture type as factors :�� . ŽP�0.05, : P�0.01 . Answers could range between 0 emo-
. Ž .tion not present and 100 emotion very strong .
Two-sided t-tests revealed that this was due tothe fact that the photos of happy women evokedmore happiness than those of happy men and thephotos of sad women evoked more sadness.
4. Discussion
Ž .The main results of this study were: 1 viewingfaces with sad or happy expressions specifically
Ž .evoked the expressed feelings in the viewer; 2this was a fast process taking place within 500 ms;Ž .3 we found weak effects of the strength of
Ž .displayed facial emotion; and 4 the gender ofthe viewer had no marked effect on the ‘targetemotions’ of happiness and sadness. In contrast,photos of happy women evoked more happinessand photos of sad women evoked more sadness
Ž .than photos of men. 5 Answering duration wasshorter after the viewing of happy faces.
4.1. Emotional contagion � time course, quantityand specificity
Most of our findings fit well within the theoreti-cal framework of the ‘emotional contagion’ hy-
Ž .pothesis Hsee et al., 1990; Hatfield et al., 1992 .Only the missing gender effect is at variance withit. Our results are a replication and extension of
Ž .findings by Dimberg 1988b and Lundqvist andŽ .Dimberg 1995 . They showed that faces express-
ing sadness, anger, disgust and happiness evokednot only specific matching facial EMG responses,but also corresponding conscious feelings in theviewer. In contrast to our study, however, Dim-
Ž . Ž .berg 1988b and Lundqvist and Dimberg 1995measured the experiential component of the emo-
Žtions only after repeated 6�8 s with 25�45-s.inter-stimulus intervals stimulus presentation.
Our results demonstrate that an emotional expe-rience in the observer of facial emotional expres-sions can be elicited with single presentations.This is not entirely surprising, as single presenta-tions of emotionally expressive faces evoke au-tonomic reactions and corresponding facial move-
Žments e.g. Dimberg, 1982, 1988a,b; Walbott,.1991 . After single presentations of mixed visual
Ž .stimuli, Cacioppo et al. 1986 and Lang andco-workers were also able to demonstrate affec-tive experiential reactions in a number of studiesŽe.g. Lang et al., 1993; Hamm and Vaitl, 1993;Greenwald et al., 1989; with the IAPS �
( )B. Wild et al. � Psychiatry Research 102 2001 109�124 119
Internations Affective Picture Set with photos of.objects, scenes and subjects .
We used answering duration as an indicator ofworking speed. Inter-individual differencesconcerning the ability to manipulate the com-puter mouse and learning effects on motor speedwere likely to be present, but should influence therating of happy and sad faces similarly. Answeringduration was longer after viewing sad faces. Wecannot decide whether this was due to a directinfluence of negative mood on working speed. Itcould also be that a more mixed picture of emo-tions was evoked by sad faces, which may havemade the questionnaire more difficult to answerafter these presentations. Also, the higher ratingsof sadness, anger and fear may have seemed lesssocially desirable or acceptable to the subjectsand they may have thus hesitated to express them.In any case, however, the longer answering dura-tion is an indirect result of emotions evoked bythese faces. This finding replicates data by
Ž .Sokolowski 1992 of a retarding influence of neg-ative mood induction on working speed in a dif-ferent paradigm. Furthermore, it may be relatedto the clinical experience of a psychomotorslowing in depression.
The finding that presentation durationsbetween 500 and 1000 ms were long enough toelicit an emotional reaction are in line with re-cent findings that object recognition is remark-ably fast and conscious awareness of visual sti-
Žmuli takes place within 200�300 ms Treisman.and Kanwisher, 1998 . Identification of facially
expressed emotions is possible after short presen-Žtation durations e.g. 180 ms, Hugdahl et al.,
. Ž .1993; 500 ms, Calder et al., 1997 . Dimberg 1997demonstrated that facial EMG reactions to pic-tures with emotional content commence within
¨500 ms. Ohman and his co-workers reported thatŽeven subliminal 30 ms followed by a masking
.neutral face presentation of photos of emotionalfacial expressions can elicit skin conductivity con-
Ž .ditioned reactions e.g. Esteves et al., 1994 andchanges in regional blood flow in the amygdala as
15 Žmeasured with H O-PET scanning Morris et al.,2.1998; using the same pictures as our study and
Ž .with fMRI Whalen et al., 1998 . Unfortunately,our equipment did not permit the presentation of
durations shorter than 500 ms. However, our re-sults demonstrate that for a single presentation ofa face displaying happiness or sadness, 500 ms issufficient to elicit conscious affective reactions.This also seems plausible, inasmuch as in normalsocial contacts, it is necessary and possible todecode and potentially react to usually short-termed and ever-changing emotional facial dis-plays.
We used pictures that varied in the strength ofthe expressed emotion to test the hypotheses thatstronger expressions evoke more emotional con-tagion. We could indeed identify a weak increas-ing effect on the perceived emotions of happi-ness, sadness, surprise and pleasure when com-paring the 75% and the 125% level. This was notthe case with the 150% level. This may be due tothe fact that some subjects perceived the faces atthis level of distortion as ‘funny’ or ‘strange’ andtoo strongly caricaturized. Our results are in linewith three studies using the same picture set.
Ž .Calder et al. 1997 found that the time taken toidentify the expressed emotion shortens with in-creased strength of expression. Using PET, Mor-
Ž .ris et al. 1996 reported an increasing neuronalresponse of the left amygdala to faces with in-creasing degrees of expressed fear. Phillips et al.Ž .1997 in an fMRI study could not replicate this,but found increasing activation of the anteriorinsular cortex with increasing depictions of dis-gust.
The question arises as to what extent theseexperiential emotional reactions are specific forthe depicted emotion. As reported above, subjectsnot only indicated experiencing happiness orpleasure but also, to a certain extent, other feel-ings. With regard first to the six ‘basic’ emotionsŽ .Ekman, 1992 , happiness, sadness, anger, disgust,fear and surprise, a comparison of the absolute
Ž .values Fig. 3 showed that the two ‘target’ emo-tions and surprise were present at higher levelsthan the other emotions. We calculated the R2
values in the ANOVA with and without subject asŽ .random factor Table 1 as a measure of the
importance of this factor on the observed variabil-ity. This also pointed to a main effect of thedepicted emotions on the target emotions sadnessand happiness, whereas the other emotions were
( )B. Wild et al. � Psychiatry Research 102 2001 109�124120
influenced more by inter-personal variations. Thatsurprise was prominent among the ‘non-target’emotions � but not significantly differentbetween happy and sad pictures � may be ex-plained by a statement that several subjects madespontaneously after the experiments. They re-ported surprise at experiencing changing emo-tions in this artificial situation. This fits with theobservation of a significant decrease of surpriseafter repeated presentation. This is also an indi-cation that subjects indeed reported their ownemotions.
C onsidering the valence dim ensionŽ .pleasant�unpleasant , sad faces evoked unpleas-ant feelings and happy faces pleasant emotions.These findings are in line with those of Lang et
Ž .al. 1993 , who studied emotions evoked by theIAPS picture set and compared ratings of thepleasant�unpleasant valence with forced-choiceselections of angry, disgusted, fearful, happy, sad,surprised and neutral as descriptions of emotionalexperience. They found that evoked sadness anddisgust corresponded with unpleasant feelings,whereas happiness corresponded with pleasure.Our findings fit in with their conclusion of ahierarchical relationship between the dimensionalŽ .pleasant�unpleasant valence and the state-specific emotions. It seems likely that these termsdescribe emotional experiences on different ver-bal levels and probably on different neurophysio-logical levels.
4.2. Gender effects
Ž .Hatfield et al. 1992 proposed that womenshould experience more emotional contagionsince, on average, they react with stronger facialexpressions. Our results do not unequivocallysupport this. The women in our study reportedgreater differences in pleasure between happyand sad pictures than men, but not more happi-ness or sadness.
To our knowledge, the only other study tocompare experiences of the pleasant�unpleasantdimension and specific emotions with respect to
Žgender differences but using partly different. Ž .emotion categories is by Wagner et al. 1993
Ž .the presentation of slides with mixed contents .
The only gender effect on experienced emotionsthey found was that men had a tendency to ratethemselves as more guilty.
Ž .Greenwald et al. 1989 , looking at valenceratings of emotional experiences after viewingpictures from the IAPS set, found that womentended to rate danger-related material as moreunpleasant and appetitive material as more pleas-ant than men. Our finding of a missing effect ofthe sex of the viewer on the ‘target emotions’,happiness and sadness, replicates results from
Ž .Lundqvist and Dimberg 1995 , who used theŽoriginal Pictures of Facial Affect Ekman and
. Ž .Friesen, 1976 , and Kring and Gordon 1998 ,who used film-clips and inquired about feelings ofhappiness, sadness, anger, fear, surprise and dis-gust. They found no sex differences in the sub-jects’ reports of experienced emotions, althoughthe female groups were facially more expressivethan men. Their interpretation was that men andwomen are likely to have the same emotionalexperiences, but behave according to different
Žsocially learned ‘display rules’ Ekman and.Friesen, 1969 for facial expressions.
It is possible that the studies referred to heremissed a gender difference because they did notinquire about the pleasure dimension. It may alsobe that the ratings or the underlying experiencesof the pleasant�unpleasant dimension are dif-
Žferent from those of more specific emotions e.g..happiness and sadness . One could speculate that
this dimension may be more closely related to thefacial expression of emotions than those of speci-fic emotions and that, for this reason, they showthe described gender effect.
Our subjects did generally experience moreemotions when looking at female than when look-ing at male faces, although the pictures wereselected so that there would be no differencebetween male and female pictures in regard tothe displayed emotions, as rated by Calder et al.Ž .1997 . This fits with the findings of Dimberg and
Ž .Lundqvist 1990 that pictures of female facesdisplaying happiness or anger tended to be ratedas showing more emotion in the respective di-mensions than male photos.
In conclusion, for a given stimulus, female and
( )B. Wild et al. � Psychiatry Research 102 2001 109�124 121
male viewers did not seem to differ markedly intheir perceived emotions, but tended to rate emo-tions expressed by women higher than those ex-pressed by men and to react more strongly to
Ž .them Dimberg and Lundqvist, 1990 . This is per-haps surprising, as one might expect that the
Žhigher female facial expressiveness Dimberg and.Lundqvist, 1990; Kring and Gordon, 1998 is taken
into account when rating and reacting to femalefaces. However, this result is in accordance with
Ž .the theory favored already by Darwin 1998 thatthe perception of and reactions to emotional ex-pressions in faces are biologically ‘prewired’Ž .Dimberg, 1988a; Young, 1997 and are indepen-dent of cultural ‘display rules’ at least in theirearly stages of cerebral processing.
Another finding supporting this ‘biological’ hy-pothesis is that repeated presentation of the samepictures did not change any of the experiencedemotions, except for surprise. It seemed as if thesubjects almost automatically reacted with emo-tional experiences mirroring the emotions thatthey were seeing displayed. This fits with the
Ž . Ž .results of Morris et al. 1996 , Breiter et al. 1996Ž .and Phillips et al. 1997 that fearful, happy or
Ždisgusted faces activate specific brain areas e.g..amygdala and insular cortex in comparison to
neutral faces, although the subjects, performing agender discrimination task were not aware thatthe emotional content was crucial to the experi-ment.
4.3. Emotional contagion as a ‘prewired’ decodinginstrument for emotions in social contacts
Taken together, these findings support the hy-potheses that emotional contagion is a fast processthat is active in the duration range of normalfacial expressions and that the emotion-evokingeffect is stable and repeatable. Furthermore, wefound evidence that stronger expressions evokestronger emotions.
We conclude that the momentary feelingsevoked by looking at emotional faces are most
Ž .likely a mixture of emotions: 1 specifically corre-sponding to the depicted emotion and induced via
Ž .a process of ‘primitive emotional contagion’; 2Ževoked by the general situation e.g. experimental
. Ž .setup ; and 3 influenced by the subject’s individ-ual inner ‘emotional status’. We propose that theemotional contagion effect of looking at emotio-nally expressive faces in this particular paradigmis strong enough and specific enough to be usedas an induction procedure for the emotions ofhappiness and sadness.
In our view, ‘primitive emotional contagion’ isvery likely to have a biologically ‘prewired’ neuralbasis because it acts rapidly, repeatedly and al-most automatically. Our data, however, do notpermit a decision as to whether this is based on:Ž .1 a ‘facial afference loop’ using afferent infor-mation from facial muscle receptors after mimicry
Ž .of perceived expressions; 2 an ‘efference copy’Ž .from the motor areas to limbic regions; or 3
direct input from regions of higher visual process-Ž .ing e.g. fusiform gyrus to the medial temporal,
orbitobasal and dorsofrontal and insular cortexand the basal ganglia. This functional networkhas been demonstrated in a number of functionalimaging and clinical studies to be involved in the
Žprocessing of faces Borod et al., 1986; Ojemannet al., 1992; Allison et al., 1994; Morris et al.,1996; Sprengelmeyer et al., 1996; Kanwisher etal., 1997; Lane et al., 1997; Phillips et al., 1997;
.Young, 1997 .The fast and automatic induction of emotional
experiences by the perception of emotionally ex-pressive faces should be a powerful instrument tosimultaneously decode emotional states in otherpeople and to form the basis for potential reac-tions. Further research must explore whether sub-jects who are good ‘decoders’ of facially expressedemotions also experience stronger emotions whendoing this.
In several psychiatric patient groups, deficits inthe decoding of facially expressed emotions have
Žbeen demonstrated e.g. in schizophrenia, Mandalet al., 1998; in depression, Hale, 1998; inalexythymia, Parker et al., 1993; in alcohol depen-
.dence, Philippot et al., 1999 , although it is un-clear whether this is emotion-specific or part of ageneral perceptual deficit. It has not yet beentested whether this deficit leads to reduced emo-tional contagion. There is evidence for a changedrelationship between emotional experience andfacial emotional expression in schizophrenic
( )B. Wild et al. � Psychiatry Research 102 2001 109�124122
Ž .patients. Kring et al. 1993 found that althoughschizophrenic patients with flat affect while view-ing a film expressed emotions facially to a lesserdegree than normal subjects, they reported emo-tional experiences similar to the normal subjects.Facial expression recognition deficits were notcorrelated with the amount of affect expression
Ž .affect Shaw et al., 1999 . The induction of emo-tions by manipulating expressive behavior wasimpaired in schizophrenic and, to a lesser degree,
Ž .in depressed patients Flack et al., 1999 . How-ever, the systematic exploration of emotional con-tagion paradigms, e.g. to improve mood in psychi-atric patients or train communication skills, stillremains to be done.
Acknowledgements
This work was supported by a grant fromfortune to B. Wild. We are very grateful to Paul¨Ekman and David Perrett for their permission touse the stimuli and to Appletree Rodden for hishelp and contagious humor.
Appendix A
The original German text of the questionnaireis: ‘Ich empfand das Bild als angenehm�un-angenehm. Das Bild lste in mir die folgendenGefhle aus: Freude, berraschung, Furcht, Trauer,Ekel, rger’.
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