تفاوت در حالات چهره از چهار احساس جهانی

Abstract The facial action coding system (FACS) was used to examine recognition rates in 105 healthy young men and women who viewed 128 facial expressions of posed and evoked happy, sad, angry and fearful emotions in color photographs balanced for gender and ethnicity of poser. Categorical analyses determined the specificity of individual action units for each emotion. Relationships between recognition rates for different emotions and action units were evaluated using a logistic regression model. Each emotion could be identified by a group of action units, characteristic to the emotion and distinct from other emotions. Characteristic happy expressions comprised raised inner eyebrows, tightened lower eyelid, raised cheeks, upper lip raised and lip corners turned upward. Recognition of happy faces was associated with cheek raise, lid tightening and outer brow raise. Characteristic sad expressions comprised furrowed eyebrow, opened mouth with upper lip being raised, lip corners stretched and turned down, and chin pulled up. Only brow lower and chin raise were associated with sad recognition. Characteristic anger expressions comprised lowered eyebrows, eyes wide open with tightened lower lid, lips exposing teeth and stretched lip corners. Recognition of angry faces was associated with lowered eyebrows, upper lid raise and lower lip depression. Characteristic fear expressions comprised eyes wide open, furrowed and raised eyebrows and stretched mouth. Recognition of fearful faces was most highly associated with upper lip raise and nostril dilation, although both occurred infrequently, and with inner brow raise and widened eyes. Comparisons are made with previous studies that used different facial stimuli.

Introduction Facial expressions are used in humans and animals for communication, in particular to convey one's emotional state (Darwin, 1965). This communication can be reflexive, as situations may evoke emotions that are spontaneously expressed on the face. In other instances, particularly in humans, facial expressions may be volitional signals intended for communication and not reflect the true emotional state of the person (Ekman and Friesen, 1975). Impairment in emotional processing, specifically emotion recognition, has been described in psychiatric disorders including schizophrenia, depression and bipolar disorder, and neurological disorders (review: Kohler et al., 2004). Since the earliest descriptions of schizophrenia, decreased and muted facial expressions of emotions has been reported as a hallmark of the illness, however, there have been few attempts to investigate this impairment further in schizophrenia and other psychiatric disorders. Six basic emotions—happiness, sadness, anger, fear, disgust and surprise—and their corresponding facial expressions are recognized across different cultures (Huber, 1931, Eibl-Eibesfeldt, 1970, Izard, 1971 and Ekman and Friesen, 1975). Descriptions have been made about which facial muscles are involved in the formation of each of the basic emotions (Huber, 1931, Plutchik, 1962, Ekman and Friesen, 1975 and Gosselin et al., 1997). For happy expressions, Ekman and Friesen (1975) described facial expressions of tense lower eyelids, raised cheeks and lip corners pulled up; for sad expressions, inner eyebrows raised and drawn together, and lip corners pulled down; for anger expressions, lowered eyebrows drawn together, tense lower eyelids, pressed lips or lips parted in a square shape; for fear expressions, eyebrows raised and drawn together, wide open eyes with tense lower eyelids and stretched lips. Based on facial muscle movement, Ekman and Friesen (1978) developed the Facial Action Coding System (FACS) by identifying the presence of specific actions of facial muscles called Action Units (AUs). Gosselin et al. (1997) tested Ekman and Friesen's predictions about facial expressions of six emotions in two conditions—posed or unfelt and evoked or felt. In that study, actors used two different methods of displaying facial expressions of six emotions—trying to experience the target emotion according to the Stanislawski technique, while expressing the emotion (evoked emotion) or merely displaying the emotion without the emotional experience (posed emotion). FACS analyses of facial expressions by a single rater revealed that AUs for each emotion were concordant with Ekman and Friesen's descriptions. Occurrence rates of AUs for evoked and posed facial expressions showed considerable overlap, in particular for happy and surprise expressions. Other studies that investigated facial landmark changes associated with emotional expression focused on measurement of muscle activity with electromyography (EMG). Limitations of this methodology include that only select muscle groups, such as corrugator supercilii orbicularis oculi and zygomaticus major have been measured, showing the corrugator to be associated with sad and the zygomaticus with happy emotions (Schwartz et al., 1976). Tassinary and Cacioppo (1989) elucidated that expressions of action units involving brow and cheek regions are associated with discrete facial muscle activity as measured by surface EMG. More recently, considerable overlap has been shown between surface and intramuscular recordings of facial EMG during happy, sad and angry expressions (Aniss and Sachdev, 1996). In our study, three FACS certified raters examined 128 images of extremely happy, sad, angry and fearful faces that were selected for use in a functional imaging study and piloted for recognition in a group of healthy subjects. Disgust was not included because of our assumption that it may not present a pure emotion, but rather a mixture of other universal emotions (Kohler et al., 2003). Surprise was not included because its valence depends entirely on the triggering event and it can be therefore any of the other emotions, with a rapid onset. The purpose of our study was to investigate which facial changes are most frequent in happy, sad, angry and fearful expressions, and which facial changes are essential for accurate recognition of the particular emotion. The study included the following specific aims: (1) Which action units characterize the different emotions? We hypothesized that each emotion can be defined by the presence of action units common to faces with the particular emotion. (2) Which action units distinguish different emotions from each other? We hypothesized that facial expressions of each emotion consist of unique action units that are distinct from other emotions. (3) How do posed and evoked emotions differ with respect to action units? We hypothesized that different action units are used for the expression of posed and evoked emotions. (4) Do men and women utilize different action units for the expression of emotions? We hypothesized that certain emotions, in particular anger, are expressed differently by men and women. (5) Which action units are associated with recognition of each emotion? We hypothesized that the presence of characteristic action units are associated with proper detection of the particular emotion. We propose that findings based on accurate descriptions of facial muscle groups in people without psychiatric disorders will facilitate investigations into the effects of psychiatric illness on facial emotion expression in persons with psychiatric disorders. This knowledge will lead to better understanding of how interpersonal nonverbal communication is affected in psychiatric disorders. In particular, this will give us information whether disorders, such as schizophrenia or affective disorders, are associated with muted, but appropriate facial muscle movement or recruitment of different muscle groups.

Results 3.1. Characterization of emotional expressions FACS ratings revealed separate profiles for Happy, Sad, Anger and Fear expressions (Fig. 1, Table 1). Characteristic, uniquely absent and present AUs were found for each emotion. Expressions of Anger and Sad shared the most characteristic AUs (5), while Fear and Happy shared the fewest (2). Characteristic AUs for Happy included in descending order of frequency 12, 7, 26, 6, 10, 1 and 25. AUs 6 and 12 were uniquely present, while AUs 4 and 20 were uniquely absent in Happy expressions. Characteristic AUs for Sad included 4, 7, 20, 10, 17, 25, 1 and 15. AU 17 was unique for Sad expressions while AU 26 was specifically absent. Characteristic AUs for Anger included AUs 4, 7, 10, 16, 25, 5, 20, 9 and 26. AUs 9 and 16 were uniquely present in Anger, while AU 1 was uniquely absent. Characteristic AUs for Fear included AUs 5, 26, 1, 4, 2 and 20. AUs 5 and 2 were uniquely present, while AUs 7 and 10 were uniquely absent in Fear. Facial expressions of emotion. Fig. 1. Facial expressions of emotion. Figure options Table 1. FACS of emotions (number present of 32 faces per category) AU Name Fisher's Exacta Happy Sad Anger Fear 1 Inner Brow Raiser p<0.001 9 10 1** 18 2 Outer Brow Raiser p<0.001 7 0 1 13* 4 Brow Lower p<0.001 2** 24 26 14 5 Upper Lid Raiser p<0.001 2 1 12 28 6 Cheek Raiser p<0.001 20* 3 2 0 7 Lid Tightener p<0.001 23 21 20 6** 9 Nose Wrinkler p=0.001 2 0 9* 0 10 Upper Lip Raiser p=0.038 17 14 17 4** 12 Lip Corner Puller p<0.001 32* 3 1 2 15 Lip Corner Depressor p=0.050 0 8 6 1 16 Lower Lip Depressor p<0.001 1 0 16* 0 17 Chin Raiser p<0.001 0 12* 4 1 20 Lip Stretcher n.s. 4** 15 11 9 23 Lip Tightener n.s. 0 1 5 0 24 Lip Pressor n.s. 0 3 3 0 25 Lips Part n.s. 8 12 13 3 26 Jaw Drop p<0.001 23 4** 9 23 27 Mouth Stretch n.s. 0 0 1 5 38 Nostril Dilator p=0.006 0 0 0 6* n.s.=not significant. a df=3; all p values after Bonferroni correction. * Unique qualifying AU. ** Unique disqualifying AU. Table options 3.2. Co-occurrence of action units AUs occurring together more than 75% of the time were considered to be clustered. In Happy, we found clustering of AU 1 with 2 (88%), and AU 12 with 6 (77%), AU 7 (84%) and 26 (84%); in Sad, AU 4 with 7 (76%) and 20 (77%); in Anger, AU 4 with 7 (78%); in Fear, AU 1 with 2 (77%), and AU 26 with 5 (78%). 3.3. Condition of expression Effects of condition—evoked or posed—were only significant in expressions of Anger. AU 16 (Fisher's Exact=8.00, df=1, P=0.012) and AU 20 (Fisher's Exact=11.22, df=1, P=0.002) were more frequent in evoked than posed expressions. After correction for multiple comparisons, the finding for AU 20 remained significant. 3.4. Gender of face No significant differences between male and female posers were found for expressions of Happy, Sad, Anger and Fear. 3.5. Recognition of emotions Recognition rates for Happy faces was 91.2%, for Sad faces 84.0%±10.6 (S.D.), for Anger faces 68.9%±24.3 (S.D.) and for Fear faces 67.9%±22.6 (S.D.). These rates are similar to recognition rates in our previous publications, which employed different faces from the same archival set of pictures and different testing paradigms (Kohler et al., 2003 and Kohler et al., 2004). 3.6. Effect of condition on recognition of emotions Recognition rates were similar for posed and evoked expressions of Happy faces. Recognition rates for Sad faces were 82.4% in the posed condition and 85.6% in the evoked condition (OR=0.79, P=0.01). For example, this means that posed sad faces were less likely—specifically 0.79 times as likely to be correctly identified, when compared to evoked sad faces. Recognition rates for Angry faces were 65.6% in the posed and 72.2% in the evoked condition (OR=0.74, P<0.001). Recognition rates for Fearful faces were 61.7% in the posed and 74.2% in the evoked condition (OR=0.56, P<0.001). 3.7. Relationship between recognition of emotion and presence of AUs The relationship between emotion recognition and presence of AUs was assessed using multivariable GEE logistic regression models, adjusting for the multiple faces assessed by each rater. Happy: Since AU 12 was always present, no correlation could be calculated. Of the remaining characteristic AUs, the presence of 6, 7, and 26 were positively associated with happy recognition. The odds of 4.27 for AU 6 being present means that correct identification of happy faces is more than four times greater when AU 6 is present compared to when AU 6 is absent. Of the non-characteristic AUs, the presence of AU 2 was positively and AU 20 was negatively associated with happy recognition. Sad: Of the characteristic AUs, the presence of 4, 17 and 25 were positively associated, AUs 1, 7, 10 and 20 were not correlated and AU 15 was negatively associated with sad recognition. Anger: Of the characteristic AUs, the presence of 4, 5 and 16 were positively associated, AUs 7, 9, 10, 20, 25, and 26 were not associated with anger recognition. Of the non-characteristic AUs, the presence of AUs 15 and 24 were positively, while the presence of AU 23 was negatively associated with anger recognition. Anger was better recognized in the posed, rather than evoked condition. Fear: Of the characteristic AUs, the presence of 5, 1 and 26 were positively associated, AUs 2 and 20 were not associated and AU 4, was negatively associated with fear recognition. Of the non-characteristic AUs, the presence of AU 10 and 38 were positively associated with fear recognition. Fear was less often recognized in the posed (OR=0.56, P<0.001), rather than evoked condition. The presence of AUs and significant odds ratios are described in Table 2. Table 2. Presence of action units and correct emotion recognition AU 1 2 4 5 6 7 9 10 12 15 Happy CAU • • • • • OR, 95% CI n.s. 2.37, 1.65–3.40 4.27, 2.92–6.24 2.34, 1.81–3.04 n.s. n.a. Sad CAU • • • • • OR, 95% CI n.s. 1.88, 1.50–2.36 n.s. n.s. 0.60, 0.48–0.75 Anger CAU • • • • • OR, 95% CI 7.27, 5.10–10.38 1.81, 1.48–2.22 n.s. n.s. n.s. 2.18, 1.64–2.89 Fear CAU • • • • OR, 95% CI 3.01, 2.54–3.58 n.s. 0.65, 0.55–0.77 3.48, 2.45–4.95 4.43, 3.01–6.52 AU 16 17 20 23 24 25 26 27 38 Happy CAU • • OR, 95% CI 0.57, 0.43–0.78 n.s. 1.93, 1.41–2.65 Sad cAU • • • OR, 95% CI 1.41, 1.11–1.80 n.s. 1.38, 1.09–1.75 Anger cAU • • • • OR, 95% CI 3.81, 2.93–4.95 n.s. 0.67, 0.55–0.82 3.03, 2.26–4.06 n.s. n.s. Fear cAU • • OR, 95% CI n.s. 1.51, 1.31–1.74 1.61, 1.38–1.89 cAU=characteristic action unit. OR=odds ratios for recognition, when AU present (all p-values <0.001, except for AU25 in Sad: p=0.007). n.a.=not applicable, could not be calculated. n.s.=not significant odds ratio for recognition when characteristic AU present. Table options 3.8. Relationship between recognition of emotion and absence of characteristic AUs In an effort to examine the recognizability of emotional faces lacking key components—or characteristic AUs—for the specific emotion, we present odds ratios for recognition of Sad, Angry and Fear faces with none, one, two or three of the characteristic AU present that are associated with recognition (Section 3.6) (Table 3). In Happy faces, AU 12 was always present and the effect of its absence on recognition of Happy could not be examined. Table 3. Recognition rates and odds ratios for emotional faces without characteristic action units (cAU)* CAU No cAUs present (%/OR) 1 cAU present (%/OR) 2 cAUs present (%/OR) 3 cAUs present (%/OR) Happy 12,6,7 n.a./– 71.3/– 90.5/3.76 95.2/7.79 Sad 4,17,25 68.7/– 84.0/2.38 86.6/2.89 90.2/4.16 Anger 4,5,16 24.8/– 60.7/4.72 77.5/10.47 85.9/18.42 Fear 1,5,26 32.0/– 54.3/2.45 65.0/3.83 80.4/8.37 n.a. since AU 12 is always present. OR=odds ratio for recognition of faces with one, two or three characteristic AU present for the specific emotion when compared to faces without these characteristic AU (Sad, Anger and Fear) and one characteristic AU present (Happy). * Limited to cAU with positive correlations with recognition.