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Facial expressions of emotion reveal neuroendocrine and cardiovascular stress responses.

BACKGROUND: The classic conception of stress involves undifferentiated negative affect and corresponding biological reactivity. The present study hypothesized a new conception that disaggregates stress into emotion-specific, contrasting patterns of biological response. METHODS: Ninety-two healthy adults engaged in stress-challenge tasks, during which cardiovascular responses, hypothalamic-pituitary-adrenocortical (HPA) axis responses (i.e., cortisol), emotional expressions (i.e., facial muscle movements), and subjective emotional experience (self-reported) were assessed. RESULTS: Pronounced individual differences emerged in specific emotional responses to the stressors. Analyses of facial expressions revealed that the more fear individuals displayed in response to the stressors, the higher their cardiovascular and cortisol responses to stress. By contrast, the more anger and disgust (indignation) individuals displayed in response to the same stressors, the lower their cortisol levels and cardiovascular responses. Individual differences in optimistic appraisals appeared to mediate these correlated patterns. CONCLUSIONS: Facial expressions of emotion signal biological responses to stress. Fear expressions signal elevated cortisol and cardiovascular reactivity; anger and disgust signal attenuated cortisol and cardiovascular reactivity, patterns that implicate individual differences in stress appraisals. Rather than conceptualizing stress as generalized negative affect, studies can be informed by this emotion-specific approach to stress responses.

Adult↗

Enhanced amygdala responses to emotional versus neutral schematic facial expressions.

Human facial emotional expressions are complex. This may confound studies examining brain responses to these stimuli in control and clinical populations. However, several lines of evidence suggest that a few elementary facial features convey the gist of emotional expressions. Using fMRI, we assessed brain responses to line drawings of emotionally valenced (i.e. angry and happy) and neutral faces in healthy human subjects. Significantly increased fMRI signal was found in the amygdala, hippocampus and prefrontal cortex in response to emotional vs neutral schematic faces. Although direct comparisons of schematic and human faces will be needed, these initial results suggest that schematic faces may be useful for studying brain responses to emotional stimuli because of their simplicity relative to human faces.

Adult↗

Expressive facial animation synthesis by learning speech coarticulation and expression spaces.

Synthesizing expressive facial animation is a very challenging topic within the graphics community. In this paper, we present an expressive facial animation synthesis system enabled by automated learning from facial motion capture data. Accurate 3D motions of the markers on the face of a human subject are captured while he/she recites a predesigned corpus, with specific spoken and visual expressions. We present a novel motion capture mining technique that "learns" speech coarticulation models for diphones and triphones from the recorded data. A Phoneme-Independent Expression Eigenspace (PIEES) that encloses the dynamic expression signals is constructed by motion signal processing (phoneme-based time-warping and subtraction) and Principal Component Analysis (PCA) reduction. New expressive facial animations are synthesized as follows: First, the learned coarticulation models are concatenated to synthesize neutral visual speech according to novel speech input, then a texture-synthesis-based approach is used to generate a novel dynamic expression signal from the PIEES model, and finally the synthesized expression signal is blended with the synthesized neutral visual speech to create the final expressive facial animation. Our experiments demonstrate that the system can effectively synthesize realistic expressive facial animation.

Artificial Intelligence↗

A specific neural substrate for perceiving facial expressions of disgust.

Recognition of facial expressions is critical to our appreciation of the social and physical environment, with separate emotions having distinct facial expressions. Perception of fearful facial expressions has been extensively studied, appearing to depend upon the amygdala. Disgust-literally 'bad taste'-is another important emotion, with a distinct evolutionary history, and is conveyed by a characteristic facial expression. We have used functional magnetic resonance imaging (fMRI) to examine the neural substrate for perceiving disgust expressions. Normal volunteers were presented with faces showing mild or strong disgust or fear. Cerebral activation in response to these stimuli was contrasted with that for neutral faces. Results for fear generally confirmed previous positron emission tomography findings of amygdala involvement. Both strong and mild expressions of disgust activated anterior insular cortex but not the amygdala; strong disgust also activated structures linked to a limbic cortico-striatal-thalamic circuit. The anterior insula is known to be involved in responses to offensive tastes. The neural response to facial expressions of disgust in others is thus closely related to appraisal of distasteful stimuli.

Adult↗

Caricaturing facial expressions.

The physical differences between facial expressions (e.g. fear) and a reference norm (e.g. a neutral expression) were altered to produce photographic-quality caricatures. In Experiment 1, participants rated caricatures of fear, happiness and sadness for their intensity of these three emotions; a second group of participants rated how 'face-like' the caricatures appeared. With increasing levels of exaggeration the caricatures were rated as more emotionally intense, but less 'face-like'. Experiment 2 demonstrated a similar relationship between emotional intensity and level of caricature for six different facial expressions. Experiments 3 and 4 compared intensity ratings of facial expression caricatures prepared relative to a selection of reference norms - a neutral expression, an average expression, or a different facial expression (e.g. anger caricatured relative to fear). Each norm produced a linear relationship between caricature and rated intensity of emotion; this finding is inconsistent with two-dimensional models of the perceptual representation of facial expression. An exemplar-based multidimensional model is proposed as an alternative account.

Adult↗

Facial expression accompanying pain.

The study of facial expression accompanying pain is of both practical and theoretical importance. It has been suggested that nonverbal behavior may provide accurate information on pain states to supplement self-report and that perhaps facial expressions could even serve as accurate measures of pain in the absence of verbal report. Recent studies of specific facial expressions accompanying pain have benefited greatly from the techniques and findings of earlier research on facial expressions of emotion. These research findings also raise a number of questions concerning relationships between pain and emotion expressions, and provide some tools (e.g. direct facial measurement systems) for answering them. A review of empirical research indicates that there are distinct facial expressions which accompany acute painful experiences with some regularity, and that these expressions occur in both infants and adults, at least in Western cultures. Important areas for future research include cross-cultural studies, investigations of the circumstances under which these facial expressions occur and the possibilities for masking or falsifying them and research into facial behaviors related to chronic pain.

Facial Expression↗

Investigation of facial recognition memory and happy and sad facial expression perception: an fMRI study.

We investigated facial recognition memory (for previously unfamiliar faces) and facial expression perception with functional magnetic resonance imaging (fMRI). Eight healthy, right-handed volunteers participated. For the facial recognition task, subjects made a decision as to the familiarity of each of 50 faces (25 previously viewed; 25 novel). We detected signal increase in the right middle temporal gyrus and left prefrontal cortex during presentation of familiar faces, and in several brain regions, including bilateral posterior cingulate gyri, bilateral insulae and right middle occipital cortex during presentation of unfamiliar faces. Standard facial expressions of emotion were used as stimuli in two further tasks of facial expression perception. In the first task, subjects were presented with alternating happy and neutral faces; in the second task, subjects were presented with alternating sad and neutral faces. During presentation of happy facial expressions, we detected a signal increase predominantly in the left anterior cingulate gyrus, bilateral posterior cingulate gyri, medial frontal cortex and right supramarginal gyrus, brain regions previously implicated in visuospatial and emotion processing tasks. No brain regions showed increased signal intensity during presentation of sad facial expressions. These results provide evidence for a distinction between the neural correlates of facial recognition memory and perception of facial expression but, whilst highlighting the role of limbic structures in perception of happy facial expressions, do not allow the mapping of a distinct neural substrate for perception of sad facial expressions.

Adult↗

Differential amygdala responses to happy and fearful facial expressions depend on selective attention.

Facial expressions of emotion elicit increased activity in the human amygdala. Such increases are particularly evident for expressions that convey potential threat to the observer, and arise even when the face is masked from awareness. We used functional magnetic resonance imaging (fMRI) to examine whether the amygdala responds differentially to threatening (fearful) versus nonthreatening (happy) facial expressions depending on whether the face is attended or actively ignored. In separate runs, participants were cued to attend to a face or a house within semitransparent, spatially overlaid composite pairs, presented either side of fixation, and were required to perform a demanding same/different judgment. We found significant attentional modulation of activity in category-specific 'face' (fusiform gyrus) and 'place' (parahippocampal gyrus) regions, with activity in each area increasing selectively when its preferred stimulus was attended versus ignored. In contrast, activity in the amygdala differed according to the valence of the facial expression and the category of the attended stimulus. For happy faces, activity in the amygdala was greater in the attend-face than in the attend-house condition, whereas for fearful faces, activity was greater in the attend-house than in the attend-face condition. We conclude that differential amygdala responses to fearful versus happy facial expressions are tuned by mechanisms of attention and that the amygdala gives preference to potentially threatening stimuli under conditions of inattention.

Adult↗

Configural information in facial expression perception.

Composite facial expressions were prepared by aligning the top half of one expression (e.g., anger) with the bottom half of another (e.g., happiness). Experiment 1 shows that participants are slower to identify the expression in either half of these composite images relative to a "noncomposite" control condition in which the 2 halves are misaligned. This parallels the composite effect for facial identity (A. W. Young, D. Hellawell, & D. C. Hay, 1987), and like its identity counterpart, the effect is disrupted by inverting the stimuli (Experiment 2). Experiment 3 shows that no composite effect is found when the top and bottom sections contain different models' faces posing the same expression; this serves to exclude many nonconfigural interpretations of the composite effect (e.g., that composites are more "attention-grabbing" than noncomposites). Finally, Experiment 4 demonstrates that the composite effects for identity and expression operate independently of one another.

Adult↗

Enhanced neural activity in response to dynamic facial expressions of emotion: an fMRI study.

Dynamic facial expressions of emotion constitute natural and powerful media of communication between individuals. However, little is known about the neural substrate underlying the processing of dynamic facial expressions of emotion. We depicted the brain areas by using fMRI with 22 right-handed healthy subjects. The facial expressions are dynamically morphed from neutral to fearful or happy expressions. Two types of control stimuli were presented: (i) static facial expressions, which provided sustained fearful or happy expressions, and (ii) dynamic mosaic images, which provided dynamic information with no facial features. Subjects passively viewed these stimuli. The left amygdala was highly activated in response to dynamic facial expressions relative to both control stimuli in the case of fearful expressions, but not in the case of happy expressions. The broad region of the occipital and temporal cortices, especially in the right hemisphere, which included the activation foci of the inferior occipital gyri, middle temporal gyri, and fusiform gyri, showed higher activation during viewing of the dynamic facial expressions than it did during the viewing of either control stimulus, common to both expressions. In the same manner, the right ventral premotor cortex was also activated. These results identify the neural substrate for enhanced emotional, perceptual/cognitive, and motor processing of dynamic facial expressions of emotion.

Adult↗

Depressive and elative mood inductions as a function of exaggerated versus contradictory facial expressions.

Two studies concerned the relation between facial expression cognitive induction of mood and perception of mood in women undergraduates. In Exp. 1, 20 subjects were randomly assigned to a group who were instructed in exaggerated facial expressions (Demand Group) and 20 subjects were randomly assigned to a group who were not instructed (Nondemand Group). All subjects completed a modified Velten (1968) elation- and depression-induction sequence. Ratings of depression on the Multiple Affect Adjective Checklist increased during the depression condition and decreased during the elation condition. Subjects made more facial expressions in the Demand Group than the Nondemand Group from electromyogram measures of the zygomatic and corrugator muscles and from corresponding action unit measures from visual scoring using the Facial Action Scoring System. Subjects who were instructed in the Demand Group rated their depression as more severe during the depression slides than the other group. No such effect was noted during the elation condition. In Exp. 2, 16 women were randomly assigned to a group who were instructed in facial expressions contradictory to those expected on the depression and elation tasks (Contradictory Expression Group). Another 16 women were randomly assigned to a group who were given no instructions about facial expressions (Nondemand Group). All subjects completed the depression- and elation-induction sequence mentioned in Exp. 1. No differences were reported between groups on the ratings of depression (MAACL) for the depression-induction or for the elation-induction but both groups rated depression higher after the depression condition and lower after the elation condition. Electromyographic and facial action scores verified that subjects in the Contradictory Expression Group were making the requested contradictory facial expressions during the mood-induction sequences. It was concluded that the primary influence on emotion came from the cognitive mood-induction sequences. Facial expressions only seem to modify the emotion in the case of depression being exacerbated by frowning. A contradictory facial expression did not affect the rating of an emotion.

Cognition↗

Facial expression and emotion.

Cross-cultural research on facial expression and the developments of methods to measure facial expression are briefly summarized. What has been learned about emotion from this work on the face is then elucidated. Four questions about facial expression and emotion are discussed: What information does an expression typically convey? Can there be emotion without facial expression? Can there be a facial expression of emotion without emotion? How do individuals differ in their facial expressions of emotion?

Arousal↗

Facial expression during induced pain.

Facial expressions contribute substantially to judgments of sufferer's pain but have not been rigorously described. We obtained a detailed description of 72 female volunteers' facial reactions to the cold pressor experience, using Ekman and Friesen's (1978a) objective, anatomically based Facial Action Coding System. In addition, we examined the impact of exposure to social models tolerant or intolerant to pain. The facial actions systematically provoked by cold pressor exposure comprised a narrowing of the eye aperture from below, raising the upper lip, pulling the lip corners, parting of the lips, or dropping the jaw, and eyes closing or frequently blinking; however, there was rich individual variation in the facial displays. The reactions were most salient at onset, indicating blends of startle, adaptive reaction, emotional expression, and pain, but they declined in vigor over time, although self-report of pain continued to mount. The relation between subjective distress and facial expression was greatest at the beginning of noxious stimulation. The social models had a potent impact on verbal report and pain tolerance but not on facial expression, indicating relative independence of components within the rich range of expressive reactions of painful experience.

Adolescent↗

EMPATH: a neural network that categorizes facial expressions.

There are two competing theories of facial expression recognition. Some researchers have suggested that it is an example of "categorical perception." In this view, expression categories are considered to be discrete entities with sharp boundaries, and discrimination of nearby pairs of expressive faces is enhanced near those boundaries. Other researchers, however, suggest that facial expression perception is more graded and that facial expressions are best thought of as points in a continuous, low-dimensional space, where, for instance, "surprise" expressions lie between "happiness" and "fear" expressions due to their perceptual similarity. In this article, we show that a simple yet biologically plausible neural network model, trained to classify facial expressions into six basic emotions, predicts data used to support both of these theories. Without any parameter tuning, the model matches a variety of psychological data on categorization, similarity, reaction times, discrimination, and recognition difficulty, both qualitatively and quantitatively. We thus explain many of the seemingly complex psychological phenomena related to facial expression perception as natural consequences of the tasks' implementations in the brain.

Discrimination, Psychological↗

College students' perception of facial expressions.

95 college students were administered the Facial Expressions subtest of the Diagnostic Analysis of Nonverbal Accuracy to measure perception of nonverbal cues. Participants also completed the Nowicki-Strickland Locus of Control Scale and responded to a short questionnaire regarding their beliefs about their own ability to perceive nonverbal cues as well as how effective they felt others were in perceiving nonverbal cues. A significant correlation between locus of control and perception of adult facial expressions indicated those students with a more internal locus of control had higher scores on correct perception of adult facial expression. There was no significant correlation between locus of control and facial expressions of children. Sex differences were also found in perception of nonverbal cues. Female students scored higher in correctly perceiving facial expressions than the men. Participants also scored higher in correctly perceiving facial expressions of children than of adults.

Adult↗

Quantifying facial expression recognition across viewing conditions.

Facial expressions are key to social interactions and to assessment of potential danger in various situations. Therefore, our brains must be able to recognize facial expressions when they are transformed in biologically plausible ways. We used synthetic happy, sad, angry and fearful faces to determine the amount of geometric change required to recognize these emotions during brief presentations. Five-alternative forced choice conditions involving central viewing, peripheral viewing and inversion were used to study recognition among the four emotions. Two-alternative forced choice was used to study affect discrimination when spatial frequency information in the stimulus was modified. The results show an emotion and task-dependent pattern of detection. Facial expressions presented with low peak frequencies are much harder to discriminate from neutral than faces defined by either mid or high peak frequencies. Peripheral presentation of faces also makes recognition much more difficult, except for happy faces. Differences between fearful detection and recognition tasks are probably due to common confusions with sadness when recognizing fear from among other emotions. These findings further support the idea that these emotions are processed separately from each other.

Adult↗

[Facial expression of the vertical dimension before and after orthognathic surgery].

The dynamic analysis of faces of the patients asking for a restoration for an aesthetic injury with a combined orthodontical-surgical treatment requires, besides a static morphological study: with photographs an cephalometric tracings; the study of their facial expression. In order to find out a method of classification of the units of expressive facial behavior, the mobility of the face is studied through the coding of the facial activity by P. EKMAN and W. FRIESEN i.e. the F.A.C.S.: Facial Action Coding System: From the video-recordings of faces and their photographic versions obtained after a pause on the video recorder, these authors have improvised a technic based on the visual observation of the anatomical basis of the movement in connection with facial expression and their description through minimal anatomical action units or A.U. These minimal units of behaviour combine to form mimics. Thanks to the F.A.C.S., the facial mimic of 18 patients before and after orthognatic surgery, and of six samples without dentofacial deformations has been studied. 18,844 AU have been observed, among 6,278 mimics made all together, with 604 different types. A classification of the mimics made by everyone and repeated in time has enabled us to establish a king of "norm" related to expression, allowing us some comparisons with expression of deformed patients. On one hand, for all of the patients examined, we have observed the mimics of the patients after surgery were more identical to the mimics of the samples. On the other hand, some differences have been distinguished concerning the changes of expressivity after surgery depending on the type of morphology before surgery: thus, rather a normal activity of the shrinking of the orbicularis oris has been observed, as well as the buccinator, among the open bites that had been operated on; and the activity of the uppe lip deriving from the "levator Labu Superious Caput infra orbitalis" has become more normal, and rather a normal activity of the lower lip deriving from mentalis, among the operated deep-bites. These results are akin to the clinical observations and suggest that the F.A.C.S. will be able to provide a coding for the study of facial expression.

Emotions↗

Right hemisphere facial expressivity during natural conversation.

Most studies of facial expressivity in patients with focal brain lesions have examined the ability to produce emotional expression in laboratory settings using various experimental paradigms. In this study, we compared facial expressivity in right hemisphere damaged patients (RHD), left hemisphere damaged patients (LHD), and normal controls (NHD) during videotaped semistructured interviews with the patient and spouse in their home. Three research assistants rated 120 10-sec segments of videotape per patient on a 7-point expressivity scale. We found that RHD patients showed reduced facial expressivity in comparison to both LHD and NHD subjects during spontaneous conversation. In particular, RHD patients demonstrated significantly less smiling and laughter than LHD patients and normal controls. These findings were not a general feature of communicative competence in RHD patients as discourse production equaled that of normal controls. These results support the hypothesis that the right hemisphere mediates facial expressivity during spontaneous social interaction.

Aged↗