Facial Reactions to Facial Expressions

Previous research has demonstrated that different patterns of facial muscle activity are correlated with different emotional states. In the present study subjects were exposed to pictures of happy and angry facial expressions, in response to which their facial electromyographic (EMG) activities, heart rate (HR), and palmar skin conductance responses (SCRs) were recorded. It was found that happy and angry faces evoked different facial EMG response patterns, with increased zygomatic region activity to happy stimuli and increased corrugator region activity to angry stimuli. Furthermore, both happy and angry faces evoked HR decelerations and similar SCR magnitudes. The results are interpreted as suggesting that facial EMG recordings provide a method for distinguishing between response patterns to “positive” and “negative” emotional visual stimuli.     

Electromyographic responses to static and dynamic avatar emotional facial expressions

Facial muscular reactions to avatars' static (neutral, happy, angry) and dynamic (morphs developing from neutral to happy or angry) facial expressions, presented for 1 s each, were investigated in 48 participants. Dynamic expressions led to better recognition rates and higher intensity and realism ratings. Angry expressions were rated as more intense than happy expressions. EMG recordings indicated emotion-specific reactions to happy avatars as reflected in increased M. zygomaticus major and decreased M. corrugator supercilii tension, with stronger reactions to dynamic as compared to static expressions. Although rated as more intense, angry expressions elicited no significant M. corrugator supercilii activation. We conclude that facial reactions to angry and to happy facial expressions hold different functions in social interactions. Further research should vary dynamics in different ways and also include additional emotional expressions.     

Are facial expressions contagious in the Japanese?

Previous studies, mainly with Caucasian samples, have shown that facial expressions of emotion are contagious, a phenomenon known as facial mimicry. This study examined facial mimicry using a Japanese sample. Participants were shown a series of Japanese faces (from Matsumoto and Ekman, 1988) on a computer screen expressing "happiness", "sadness", "anger", or "disgust". While viewing the facial expressions, electoromyograms (EMG) of the participants' faces were recorded to see whether their own facial muscles corresponding to the stimulus faces were activated. Consistent with the previous studies using Caucasian samples, all four facial expressions were mimicked. The peak time of mimicry of angry or happy faces was later, while that of disgusted faces was relatively sooner. The potential relation of facial mimicry to "emotional contagion", a social phenomenon whereby subjective feelings transfer between people, is discussed.     

Gender differences in facial reactions to facial expressions

This study explored whether males and females differ in facial muscle reactivity when exposed to facial expressions. The study also examined whether the sex of the stimulus faces differentially influences the response patterns to facial stimuli. Thus, the sex was manipulated in a 2 x 2 factorial design by exposing males and females to slides of angry and happy faces displayed by both sexes. Facial electromyographic (EMG) activity was measured from the corrugator and zygomatic muscle regions. The subjects were also required to rate the stimuli on different dimensions. The results showed that angry faces evoked increased corrugator activity whereas happy faces evoked increased zygomatic activity. As predicted, these effects were more pronounced for females, particularly for the response to happy faces. Interestingly, there were no facial EMG effects for gender of stimulus. It was further found that males and females perceived the stimuli similarly. The results are consistent with previous findings indicating that females are more facially reactive than are males.     

Electromyographic study of facial expressions during pathological laughing and crying.

We studied facial expressions during pathological laughing and crying in 6 patients using EMG investigation. Increased EMG discharges of M. frontalis and M. corrugator supercilii are characteristic of pathological laughing and crying in addition to an increase of EMG discharges of M. orbicularis oculi, M. levator labii superiors, M. zygomaticus major, M. risorius and M. mentalis which we observed during natural laughing. Its patterns of facial expressions are similar to that of crying in normals. From the fact that normals show the same expression of laughing and crying in an extreme emotional outburst, we speculate that pathological laughing and crying is maximal manifestations of facial expressions caused by a release phenomenon of the upper center.     

Automatic facial responses to briefly presented emotional stimuli in autism spectrum disorder

Emotion processing, including automatic facial mimicry, plays an important role in social reciprocity. Disruptions in these processes have implications for individuals with impaired social functioning, such as autism spectrum disorders (ASDs). Past research has demonstrated that ASDs are impaired in the recognition of briefly presented emotions and display atypical mimicry of emotions presented for protracted duration. Mimicry (electromyography; EMG) of briefly presented emotions was investigated in adults with ASDs. Concurrent measures of skin conductance and cardiac responses were used as markers of orientation and stimulus detection, respectively. A backward masking task was employed whereby the emotional face (happy, angry) was presented for 30 ms followed by a neutral face “mask”. An implicit comparison task required rapid gender identification. The ASD group failed to differentiate by valence in their EMG (zygomaticus, corrugator) and demonstrated atypical pre- and post-stimulus arousal. These findings may provide a potential mechanism for marked deficits in social reciprocity.     

Relationships between facial electromyography and subjective experience during affective imagery

Sixty subjects were exposed for 40 s each to 48 imagery situations designed to reflect happy, sad, angry and fearful conditions. Facial electromyographic (EMG) activity from zygomatic, corrugator, masseter and lateral frontalis muscle regions was recorded, and experienced emotion was measured on a scale tapping these four emotions. Results showed that: (1) zygomatic activity reliably differentiated happy imagery, corrugator activity reliably differentiated sad imagery, but masseter activity did not differentiate angry imagery and lateral frontalis activity did not differentiate fearful imagery; (2) different intensities of specific emotional imagery situations evoked the expected differential patterns of self-report and EMG; (3) higher correlations between self-report and EMG for ‘present’, rather than ‘future’ ratings of experienced emotion emerged for positive affect only; and (4) the use of a standardized imagery scale, rather than the self-generated, personally-relevant affective situations used in previous studies, allowed for more sensitive measurement of the relationship between facial muscle activity and subjective experience of emotion during affective imagery.     

Emotion in motion: Facial dynamics affect infants' neural processing of emotions

Research investigating the early development of emotional processing has focused mainly on infants' perception of static facial emotional expressions, likely restricting the amount and type of information available to infants. In particular, the question of whether dynamic information in emotional facial expressions modulates infants' neural responses has been rarely investigated. The present study aimed to fill this gap by recording 7-month-olds' event-related potentials to static (Study 1) and dynamic (Study 2) happy, angry, and neutral faces. In Study 1, happy faces evoked a faster right-lateralized negative central (Nc) component compared to angry faces. In Study 2, both happy and angry faces elicited a larger right-lateralized Nc compared to neutral faces. Irrespective of stimulus dynamicity, a larger P400 to angry faces was associated with higher scores on the Negative Affect temperamental dimension. Overall, results suggest that 7-month-olds are sensitive to facial dynamics, which might play a role in shaping the neural processing of facial emotional expressions. Results also suggest that the amount of attentional resources infants allocate to angry expressions is associated to their temperamental traits. These findings represent a promising avenue for future studies exploring the neurobiological processes involved in perceiving emotional expressions using dynamic stimuli.     

Facial reactions to happy and angry facial expressions: evidence for right hemisphere dominance

Previous research on asymmetric effects of emotional expression and brain-hemispheric asymmetry has supported opposing theories of hemispheric dominance in the control of emotional reactions. In the present study, 32 subjects were exposed to pictures of happy and angry facial stimuli while facial electromyographic (EMG) activity from the zygomatic major and the corrugator supercilii muscle regions was detected from the left and right sides of the face. The subjects reacted spontaneously and rapidly with larger zygomatic EMG activity to happy facial stimuli and larger corrugator EMG activity to angry stimuli. These distinct reactions were significantly larger on the left side of the face. It is concluded that the present results support the hypothesis that the right brain hemisphere is predominantly involved in the control of spontaneously evoked emotional reactions.     

A Psychometric Study of Surface Electrode Placements for Facial Electromyographic Recording: I. The Brow and Cheek Muscle Regions

Despite the burgeoning literature using facial electromyography (EMG) to study cognitive and emotional processes, the psychometric properties of facial EMG measurement have received little attention. Two experiments were conducted to assess the reliability and validity of facial EMG as a measure of specific facial actions. In Experiment 1, two recording sites in the brow region were compared for their ability to differentiate facial actions hypothesized to be due to the activation of the corrugator supercilii from facial actions presumed to be due to the activation of proximate muscles (e.g. depressor supercilii, procerus, frontalis, levator labii superioris alaeque nasi, orbicularis oculi), and four sites in the infraorbital triangle were compared for their ability to differentiate facial actions hypothesized to be due to the activation of the zygomaticus major from facial actions presumed to be due the activation of proximate muscles (e.g. zygomaticus minor, risorius, buccinator, orbicularis oculi, orbicularis oris). Fifteen subjects were instructed to pose a series of facial actions while EMG activity was sampled simultaneously at all sites. In Experiment 2, 5 subjects returned to the laboratory for a more extensive investigation of surface EMG activity over the zygomaticus major muscle region. The results of this experiment confirmed the findings of Experiment 1. Overall, the results demonstrate that certain recording sites located over specific facial muscle regions are more sensitive and valid indices of particular facial actions than other nearby sites.     

Facial reactions, autonomic activity and experienced emotion: a three component model of emotional conditioning

The present study was designed to evaluate whether aversively conditioned responses to facial stimuli are detectable in all three components of the emotional response system, i.e. the expressive/behavioral, the physiological/autonomic and the cognitive/experienced component of emotion. Two groups of subjects were conditioned to angry or happy facial expression stimuli using a 100 dB noise as UCS in a differential aversive conditioning paradigm. The three components of the emotional response system were measured as: Facial-EMG reactions (corrugator and zygomatic muscle regions); autonomic activity (skin conductance, SCR; SCR half recovery time, T/2; heart rate, HR); and ratings of experienced emotion. It was found that responses in all components of the emotional response system were detectable in the angry group as greater EMG and autonomic resistance to extinction and greater self-reported fear. More specifically the angry group showed a resistant conditioning effect for the facial-EMG corrugator muscle that was accompanied by resistant conditioning for SCR frequency, slower SCR recovery, resistant conditioning in HR and a higher self-reported fear than the happy group. Thus, aversive conditioning to angry facial stimuli induce a uniform negative emotional response pattern as indicated by all three components of the emotional response system. These data suggest that a negative 'affect program' triggers responses in the different emotional components. The results suggest that human subjects are biologically prepared to react with a negative emotion to angry facial stimuli.     

Amplitude and bilateral coherency of facial and jaw-elevator EMG activity as an index of effort during a two-choice serial reaction task

In earlier studies, positive but inconsistent relationships have been reported between mental effort and electro-myogram (EMG) amplitude in task-irrelevant limb muscles. In this study, we explored whether facial EMG activity would provide more consistent results. Tonic EMG activity of six different facial and jaw-elevator muscles was bilaterally recorded during a two-choice serial reaction task with paced presentation of auditory or visual signals. In Experiment 1, task load (signal presentation rate) was kept constant for 20 min at the level of the subject's maximal capacity. In Experiment 2, task load was increased in a stepwise fashion over six successive 2-min periods from sub- to supramaximal capacity levels. EMG amplitude and coherency between momentary bilateral amplitude fluctuations were measured. In Experiment 1, EMG amplitude of frontalis, corrugator supercilii, and orbicularis oris inferior showed a strong gradual increase throughout the task period, whereas task performance remained fairly stable. Orbicularis oculi, zygomaticus major, and temporalis EMG showed a much smaller increase or no increase. In Experiment 2, the first three muscles showed a fairly consistent increase in EMG amplitude with increasing task load. Orbicularis oculi and zygomaticus major were not active until task load became supramaximal. Effects of stimulus modality or laterality were not found in any experiment. These results are consistent with the notion that EMG amplitude of frontalis, corrugator, and orbicularis oris provides a sensitive index of the degree of exerted mental effort.     

Reactions to facial expressions: effects of social context and speech anxiety on responses to neutral, anger, and joy expressions

Male and female participants (n=19) high or low in speech fear viewed pictures of faces posed in anger, neutral, and joyful expressions for 8s each. Zygomaticus major and corrugator supercilii EMG, skin conductance, and heart rate were measured during picture viewing, and subjective ratings were made after each picture. Compared to anger expressions, joy expressions were responded to with greater zygomatic EMG, less corrugator EMG, and greater heart rate and skin conductance. Physiological response to neutral expressions was similar to response to anger expressions. Expressions posed by women were responded to physiologically more negatively than expressions posed by men. More fearful participants exhibited more negative and less positive facial expressions, and skin conductance responses suggesting greater attention when viewing negative expressions. Results suggest that reactions to facial expressions are influenced by social context, and are not simple mimicry.     

Timing and voluntary suppression of facial mimicry to smiling faces in a Go/NoGo task—An EMG study

Results obtained with a novel emotional Go/NoGo task allowing the investigation of facial mimicry (FM) during the production and inhibition of voluntary smiles are discussed. Healthy participants were asked to smile rapidly to happy faces and maintain a neutral expression to neutral faces, or the reverse. Replicating and extending previous results, happy faces induced FM, as shown by stronger and faster zygomatic activation to happy than neutral faces in Go trials, and a greater number of false alarms to happy faces in NoGo trials. Facial mimicry effects remained present during participants’ active inhibition of facial movement. Latencies of FM were short with 126-250 ms in Go trials, and 251-375 ms in NoGo trials. The utility of the Go/NoGo task, which allows the assessment of response inhibition in the domain of facial expression by installing strong prepotent motor responses via short stimulus presentation times and a great number of Go trials, is discussed.     

Virtual friend or threat? The effects of facial expression and gaze interaction on psychophysiological responses and emotional experience

The present study aimed to investigate the impact of facial expression, gaze interaction, and gender on attention allocation, physiological arousal, facial muscle responses, and emotional experience in simulated social interactions. Participants viewed animated virtual characters varying in terms of gender, gaze interaction, and facial expression. We recorded facial EMG, fixation duration, pupil size, and subjective experience. Subject's rapid facial reactions (RFRs) differentiated more clearly between the character's happy and angry expression in the condition of mutual eye-to-eye contact. This finding provides evidence for the idea that RFRs are not simply motor responses, but part of an emotional reaction. Eye movement data showed that fixations were longer in response to both angry and neutral faces than to happy faces, thereby suggesting that attention is preferentially allocated to cues indicating potential threat during social interaction.     

Emotional face expressions are differentiated with brain oscillations.

The differentiation of "facial expressions" is a process of higher mental activity, which has considerable applications in "psychology of moods and emotions". We applied the approach of event-related oscillations (EROs) to investigate the modulation of electrical manifestations related to emotional expression in EEG recordings of 20 healthy subjects. EROs of "neutral, angry and happy" faces in 13 electrical recordings sites (F(3), F(4), C(z), C(3), C(4), T(3), T(4), T(5), T(6), P(3), P(4), O(1), O(2)) were analyzed. Following the recording session, the subjects were asked to express the degree of their emotional involvement (valence and arousal) using the Self-Assessment Manikin ratings. Amplitude frequency characteristics (AFCs) were used to determine the frequencies of interest and the ranges for digital pass-band filtering applied accordingly. Consecutively, peak to peak amplitude measures of oscillatory responses were computed for the selected frequency bands and for the differentiation of the different stimuli. A differentiation between angry and happy facial expressions was observed especially in the alpha (9-13 Hz) and beta (15-24 Hz) frequencies, however, only when selecting stimuli with high mood involvement. Therefore, these frequency bands are the main focus of this report. The amplitudes of the alpha responses upon angry face stimulation were significantly higher than upon presentation of the happy faces at posterior locations. At F(3), C(z) and C(3), beta responses upon angry face stimulation were significantly higher in amplitude compared with the happy face stimulation. It is discussed that the frontal theta response is highly increased in comparison to all theta responses also encountered in studies of face recognition: During observation of facial expression, the occipital theta is much higher. We conclude and emphasize that the analysis of brain oscillatory responses distributed over the scalp in combination with subjective ratings of emotional impact of stimuli provide a good basis for analysing the influence of emotional information processing in the brain. In congruence with others, the results support the phylogenetical viewpoint suggesting that angry face stimulations are faster and more ample in responding. Furthermore, frontal, temporal, parietal and occipital lobes seem to be involved in processing of facial expressions, as reflected in an ensemble of different frequency brain oscillatory responses distributed over the scalp.     

Facial Muscle Patterning and Subjective Experience During Affective Imagery: Sex Differences

Facial electromyographic (EMG) activity was recorded from the zygomatic, corrugator, masse-ter and frontalis muscle regions in 30 male and 30 female subjects. Forty-eight items were selected to reflect happy, sad, angry and fearful situations. Subjects imagined each of the items for 40 sec and rated how they felt on a scale tapping the four emotions. The results indicated that for certain emotions, muscle regions and ratings, females (as compared to males): 1) generated facial EMG patterns of greater magnitude (relative to rest) during affective imagery, 2) reported a stronger experience of emotion to the imagery, 3) showed greater within-subject correlations between the experience of emotions and facial EMG, 4) evidenced somewhat higher corrugator and significantly lower masseter EMG activity during rest, and 5) generated greater facial EMG changes during a post-imagery, voluntary facial expression condition. Cultural and biological interpretations of the data are considered. The importance of evaluating gender in psychophysiological studies of emotion is stressed.     

Looking at facial expressions: dysphoria and facial EMG

Previous research on interpersonal deficits among dysphoric individuals has been equivocal, with some studies finding that dysphoric persons show an increase in negative behavior and other studies finding no group differences. Most studies in this area have employed self-report instruments and behavioral coding systems to examine interpersonal displays. Using a different approach, we examined facial electromyography (EMG) reactivity to pictures of happy and unhappy expressions among dysphoric persons. Dysphoric and non-dysphoric persons viewed happy and unhappy facial expressions while zygomatic EMG and corrugator EMG activity was recorded. Results indicated that both groups showed the appropriate increase in corrugator EMG to unhappy expressions; however, dysphoric persons did not show the expected increase in zygomatic EMG activity to happy expressions while the control participants did show this response. Unexpectedly, the dysphoric group displayed an increase in corrugator EMG activity (e.g. frown response) to the happy facial expressions. These findings indicate that dysphoric persons have impaired interpersonal reactivity that is specific to happy facial displays.     

Threat sensitivity as assessed by automatic amygdala response to fearful faces predicts speed of visual search for facial expression

It has been argued that the amygdala represents an integral component of a vigilance system that is primarily involved in the perception of ambiguous stimuli of biological relevance. The present investigation was conducted to examine the relationship between automatic amygdala responsivity to fearful faces which may be interpreted as an index of trait-like threat sensitivity and spatial processing characteristics of facial emotions. During 3T fMRI scanning, pictures of human faces bearing fearful, angry, and happy expressions were presented to 20 healthy volunteers using a backward masking procedure based on neutral facial expressions. Subsequently, a computer-based face-in-the-crowd task using schematic face stimuli was administered. The neural response of the (right) amygdala to masked fearful faces correlated consistently with response speed to negative and neutral faces. Neither amygdala activation during the masked presentation of angry faces nor amygdala activation during the presentation of happy faces was correlated with any of the response latencies in the face-in-the-crowd task. Our results suggest that amygdala responsivity to masked facial expression is differentially related to the general visual search speed for facial expression. Neurobiologically defined threat sensitivity seems to represent an important determinant of visual scanning behaviour.     

Reduced spontaneous facial mimicry in women with autistic traits

Deficits in empathizing and perspective taking are defining characteristics of autism-spectrum disorders. Converging evidence suggests that these socio-emotional abilities are rooted in basic mechanisms that subserve imitative behavior, and may vary with autistic traits across the population as a whole. We investigated this notion by assessing spontaneous and instructed mimicry of facial expressions in healthy male and female volunteers scoring extremely high or low on the autism-spectrum quotient questionnaire. Mimicry was recorded using electromyography of the corrugator supercilii and zygomaticus major. Results show that spontaneous mimicry in the corrugator supercilii was strongest in female participants with low AQ-scores. Mimicry in the zygomaticus major, and in the instructed facial mimicry condition, did not differ between groups. These findings indicate that the degree to which individuals exhibit spontaneous mimicry may vary as a function of both gender and autistic traits.