Identifying facial emotions: valence specific effects and an exploration of the effects of viewer gender

The valence hypothesis suggests that the right hemisphere is specialised for negative emotions and the left hemisphere is specialised for positive emotions (Silberman & Weingartner, 1986). It is unclear to what extent valence-specific effects in facial emotion perception depend upon the gender of the perceiver. To explore this question 46 participants completed a free view lateralised emotion perception task which involved judging which of two faces expressed a particular emotion. Eye fixations of 24 of the participants were recorded using an eye tracker. A significant valence-specific laterality effect was obtained, with positive emotions more accurately identified when presented to the right of centre, and negative emotions more accurately identified when presented to the left of centre. The valence-specific laterality effect did not depend on the gender of the perceiver. Analysis of the eye tracking data showed that males made more fixations while recognising the emotions and that the left-eye was fixated substantially more than the right-eye during emotion perception. Finally, in a control condition where both faces were identical, but expressed a faint emotion, the participants were significantly more likely to select the right side when the emotion label was positive. This finding adds to evidence suggesting that valence effects in facial emotion perception are not only caused by the perception of the emotion but by other processes.     

The valence-specific laterality effect in free viewing conditions: The influence of sex, handedness, and response bias

The right hemisphere has often been viewed as having a dominant role in the processing of emotional information. Other evidence indicates that both hemispheres process emotional information but their involvement is valence specific, with the right hemisphere dealing with negative emotions and the left hemisphere preferentially processing positive emotions. This has been found under both restricted (Reuter-Lorenz & Davidson, 1981) and free viewing conditions (Jansari, Tranel, & Adophs, 2000). It remains unclear whether the valence-specific laterality effect is also sex specific or is influenced by the handedness of participants. To explore this issue we repeated Jansari et al.'s free-viewing laterality task with 78 participants. We found a valence-specific laterality effect in women but not men, with women discriminating negative emotional expressions more accurately when the face was presented on the left-hand side and discriminating positive emotions more accurately when those faces were presented on the right-hand side. These results indicate that under free viewing conditions women are more lateralised for the processing of facial emotion than are men. Handedness did not affect the lateralised processing of facial emotion. Finally, participants demonstrated a response bias on control trials, where facial emotion did not differ between the faces. Participants selected the left-hand side more frequently when they believed the expression was negative and the right-hand side more frequently when they believed the expression was positive. This response bias can cause a spurious valence-specific laterality effect which might have contributed to the conflicting findings within the literature.     

The perception of positive and negative facial expressions by unilateral stroke patients

There remains conflict in the literature about the lateralisation of affective face perception. Some studies have reported a right hemisphere advantage irrespective of valence, whereas others have found a left hemisphere advantage for positive, and a right hemisphere advantage for negative, emotion. Differences in injury aetiology and chronicity, proportion of male participants, participant age, and the number of emotions used within a perception task may contribute to these contradictory findings. The present study therefore controlled and/or directly examined the influence of these possible moderators. Right brain-damaged (RBD; n = 17), left brain-damaged (LBD; n = 17), and healthy control (HC; n = 34) participants completed two face perception tasks (identification and discrimination). No group differences in facial expression perception according to valence were found. Across emotions, the RBD group was less accurate than the HC group, however RBD and LBD group performance did not differ. The lack of difference between RBD and LBD groups indicates that both hemispheres are involved in positive and negative expression perception. The inclusion of older adults and the well-defined chronicity range of the brain-damaged participants may have moderated these findings. Participant sex and general face perception ability did not influence performance. Furthermore, while the RBD group was less accurate than the LBD group when the identification task tested two emotions, performance of the two groups was indistinguishable when the number of emotions increased (four or six). This suggests that task demand moderates a study’s ability to find hemispheric differences in the perception of facial emotion.     

THE LATERALISATION OF EMOTION: A CRITICAL REVIEW

Recent experimental investigations on patients with unilateral brain lesions and on neurologically intact people are reviewed with a view to appreciating the role of lateralised processes in emotion. Distinctions are drawn between the perception of emotion, the expression of emotion and the interaction of these two factors in studies of latéralisation. In spite of a mass of contradictory findings, and despite the interaction of structural and cognitive factors in some studies of emotion, there are some fairly robust findings. The right hemisphere seems to be specially involved in tasks requiring emotional analysis, particularly when the tone of the displayed emotion is negative. The right hemisphere, too, appears to be particularly involved in displaying some negative emotions. Among the important problems which await resolution, we do not know whether emotional events are apprehended independently of cognitive ones, nor how mood affects the “Cerebral balance of power”.     

Examining the hemispheric distribution of semantic information using lateralised priming of familiar faces

The way in which the semantic information associated with people is organised in the brain is still unclear. Most evidence suggests either bilateral or left hemisphere lateralisation. In this paper we use a lateralised semantic priming paradigm to further examine this neuropsychological organisation. A clear semantic priming effect was found with greater priming occurring when semantically related prime faces were presented to the left visual field than when presented to the right visual field. Possible explanations for this finding are discussed in terms of the bilateral distribution of different classes of semantic information, a possible role of associative processes within semantic priming and interhemispheric transfer.     

Facial expressions are more easily produced on the upper-lower compared to the right-left hemiface

Clinical research has concentrated on differences in intensity of expression between the right and left hemiface as a means to assess hemispheric differences in motor control. However, observations by social psychologists suggest that control of facial expression may be organized predominantly across the upper-lower hemiface because during social interactions individuals may produce brief facial blends of emotions, in which the upper and lower face display a different emotion. Full facial versus upper/lower and right/left facial blends of emotion were posed by 20 subjects, 10 men and 10 women ranging in age from 20 to 37 years. The subjects rated the difficulty of each pose on a 5-point Likert scale. Digital photographs of the poses were taken and the full and half-facial poses were shown in random order to four judges who indicated what pose was being performed. The results were very robust and confirmed that facial blends of emotion are more easily and accurately posed on the upper-lower than on the right-left hemiface. Our results are consistent with recent anatomical studies showing separate cortical areas for motor control of the upper versus lower face in primates. Based on recent research exploring hemispheric differences in perceiving facial blends of emotion, the left hemisphere may be more involved with modulating lower facial expressions and the right hemisphere more involved with modulating upper facial expressions.     

Happiness takes you right: The effect of emotional stimuli on line bisection

Emotion recognition is mediated by a complex network of cortical and subcortical areas, with the two hemispheres likely being differently involved in processing positive and negative emotions. As results on valence-dependent hemispheric specialisation are quite inconsistent, we carried out three experiments with emotional stimuli with a task being sensitive to measure specific hemispheric processing. Participants were required to bisect visual lines that were delimited by emotional face flankers, or to haptically bisect rods while concurrently listening to emotional vocal expressions. We found that prolonged (but not transient) exposition to concurrent happy stimuli significantly shifted the bisection bias to the right compared to both sad and neutral stimuli, indexing a greater involvement of the left hemisphere in processing of positively connoted stimuli. No differences between sad and neutral stimuli were observed across the experiments. In sum, our data provide consistent evidence in favour of a greater involvement of the left hemisphere in processing positive emotions and suggest that (prolonged) exposure to stimuli expressing happiness significantly affects allocation of (spatial) attentional resources, regardless of the sensory (visual/auditory) modality in which the emotion is perceived and space is explored (visual/haptic).     

Decoding facial blends of emotion: Visual field,attentional and hemispheric biases

Most clinical research assumes that modulation of facial expressions is lateralized predominantly across the right-left hemiface. However, social psychological research suggests that facial expressions are organized predominantly across the upper-lower face. Because humans learn to cognitively control facial expression for social purposes, the lower face may display a false emotion, typically a smile, to enable approach behavior. In contrast, the upper face may leak a person’s true feeling state by producing a brief facial blend of emotion, i.e. a different emotion on the upper versus lower face. Previous studies from our laboratory have shown that upper facial emotions are processed preferentially by the right hemisphere under conditions of directed attention if facial blends of emotion are presented tachistoscopically to the mid left and right visual fields. This paper explores how facial blends are processed within the four visual quadrants. The results, combined with our previous research, demonstrate that lower more so than upper facial emotions are perceived best when presented to the viewer’s left and right visual fields just above the horizontal axis. Upper facial emotions are perceived best when presented to the viewer’s left visual field just above the horizontal axis under conditions of directed attention. Thus, by gazing at a person’s left ear, which also avoids the social stigma of eye-to-eye contact, one’s ability to decode facial expressions should be enhanced.     

Decoding facial blends of emotion: Visual field,attentional and hemispheric biases

Most clinical research assumes that modulation of facial expressions is lateralized predominantly across the right-left hemiface. However, social psychological research suggests that facial expressions are organized predominantly across the upper-lower face. Because humans learn to cognitively control facial expression for social purposes, the lower face may display a false emotion, typically a smile, to enable approach behavior. In contrast, the upper face may leak a person’s true feeling state by producing a brief facial blend of emotion, i.e. a different emotion on the upper versus lower face. Previous studies from our laboratory have shown that upper facial emotions are processed preferentially by the right hemisphere under conditions of directed attention if facial blends of emotion are presented tachistoscopically to the mid left and right visual fields. This paper explores how facial blends are processed within the four visual quadrants. The results, combined with our previous research, demonstrate that lower more so than upper facial emotions are perceived best when presented to the viewer’s left and right visual fields just above the horizontal axis. Upper facial emotions are perceived best when presented to the viewer’s left visual field just above the horizontal axis under conditions of directed attention. Thus, by gazing at a person’s left ear, which also avoids the social stigma of eye-to-eye contact, one’s ability to decode facial expressions should be enhanced.     

Intensity profiles of emotional experience over time

A full understanding of emotions and emotion characteristics can only be reached when their dynamic nature is taken into account. As such, a primary objective of the present study is to describe and account for variability in temporal profiles of experienced emotional intensity. Participants were asked to make detailed drawings of intensity profiles of recently experienced episodes of anger, sadness, joy and affection. Functional data analysis revealed three features that together accounted for 84% of the total variability: (i) steepness at onset; (ii) skewness; and (iii) the number of peaks. Emotions differed with regard to the first two features, with the rise at onset being steeper for sadness and joy and affection being the most negatively skewed emotion under study. Individual differences regarding each of the three features were found, however, they did not strongly generalise across emotions.     

A valence-specific lateral bias for discriminating emotional facial expressions in free field

Findings from subjects with unilateral brain damage, as well as from normal subjects studied with tachistoscopic paradigms, argue that emotion is processed differently by each brain hemisphere. An open question concerns the extent to which such lateralised processing might occur under natural, freeviewing conditions. To explore this issue, we asked 28 normal subjects to discriminate emotions expressed by pairs of faces shown side-by-side, with no time or viewing constraints. Images of neutral expressions were shown paired with morphed images of very faint emotional expressions (happiness, surprise, disgust, fear, anger, or sadness). We found a surprising and robust laterality effect: When discriminating negative emotional expressions, subjects performed significantly better when the emotional face was to the left of the neutral face; conversely, when discriminating positive expressions, subjects performed better when the emotional face was to the right. We interpret this valence-specific laterality effect as consistent with the idea that the right hemisphere is specialised to process negative emotions, whereas the left is specialised to process positive emotions. The findings have important implications for how humans perceive facial emotion under natural conditions.     

Rumination,emotional intensity and emotional clarity

It has been suggested that a high tendency to ruminate presents a deficient emotion regulation. Past research found that people with high tendency to ruminate show sustained attention for negative stimuli and increased negative thinking, which may result in intensified experiences of negative emotions. Moreover, high level of rumination was associated with low emotional understanding. Accordingly, we hypothesized (1) high ruminators (HR) experience more intense emotional reactions than low ruminators (LR) for negative but not positive emotions, (2) LR have higher emotional clarity than HR, and (3) there would be the same pattern of results for brooding but not for reflective pondering. Participants completed a demographic questionnaire, a rumination response style questionnaire, and the Beck Depression Inventory-II. They also rated emotional intensity and identified emotion type for scene pictures from the CAP-D (Categorized Affective Pictures Database). The highest (HR) and lowest (LR) quarters of ruminators were compared on levels of emotional intensity and emotional clarity. We found HR experienced negative emotions more intensely than LR, with no difference for positive emotions. In contrast to our hypothesis, the two groups did not differ in their emotion understanding. This pattern of results was found for brooding but not for reflective pondering. Our research sheds light on the mechanism underlying rumination and emotion regulation.     

Selection,Optimization, and Compensation in the Domain of Emotion Regulation: Applications to Adolescence,Older Age,and Major Depressive Disorder

Emotions often are well calibrated to the challenges and opportunities we face. When they are not, we may try to regulate our emotions. Interestingly, there seems to be considerable variation both in the strategies people use to regulate emotions and in the success of these emotion regulation efforts. The Selection, Optimization, and Compensation with Emotion Regulation framework suggests that variation in the resources required for particular emotion regulation strategies may be a crucial determinant of emotion regulation use and success within individuals across situations, between individuals, and between groups of individuals. In this review, we consider the ways in which two resources for emotion regulation (working memory and social support) might differ among three groups, namely adolescents, older adults, and adults with major depressive disorder. We link these between‐group differences in resources to differences in emotion regulation and make suggestions for future research.     

Valence specific laterality effects in prosody: expectancy account and the effects of morphed prosody and stimulus lead

The majority of studies have demonstrated a right hemisphere (RH) advantage for the perception of emotions. Other studies have found that the involvement of each hemisphere is valence specific, with the RH better at perceiving negative emotions and the LH better at perceiving positive emotions [Reuter-Lorenz, P., & Davidson, R.J. (1981) Differential contributions of the 2 cerebral hemispheres to the perception of happy and sad faces. Neuropsychologia, 19, 609-613]. To account for valence laterality effects in emotion perception we propose an 'expectancy' hypothesis which suggests that valence effects are obtained when the top-down expectancy to perceive an emotion outweighs the strength of bottom-up perceptual information enabling the discrimination of an emotion. A dichotic listening task was used to examine alternative explanations of valence effects in emotion perception. Emotional sentences (spoken in a happy or sad tone of voice), and morphed-happy and morphed-sad sentences (which blended a neutral version of the sentence with the pitch of the emotion sentence) were paired with neutral versions of each sentence and presented dichotically. A control condition was also used, consisting of two identical neutral sentences presented dichotically, with one channel arriving before the other by 7 ms. In support of the RH hypothesis there was a left ear advantage for the perception of sad and happy emotional sentences. However, morphed sentences showed no ear advantage, suggesting that the RH is specialised for the perception of genuine emotions and that a laterality effect may be a useful tool for the detection of fake emotion. Finally, for the control condition we obtained an interaction between the expected emotion and the effect of ear lead. Participants tended to select the ear that received the sentence first, when they expected a 'sad' sentence, but not when they expected a 'happy' sentence. The results are discussed in relation to the different theoretical explanations of valence laterality effects in emotion perception.     

Visual-Field Bias in the Judgment of Facial Expression of Emotion

The left and right hemispheres of the brain are differentially related to the processing of emotions. Although there is little doubt that the right hemisphere is relatively superior for processing negative emotions, controversy exists over the hemispheric role in the processing of positive emotions. Eighty right-handed normal male participants were examined for visual-field (left-right) differences in the perception of facial expressions of emotion. Facial composite (RR, LL) and hemifacial (R, L) sets depicting emotion expressions of happiness and sadness were prepared. Pairs of such photographs were presented bilaterally for 150 ms, and participants were asked to select the photographs that looked more expressive. A left visual-field superiority (a right-hemisphere function) was found for sad facial emotion. A hemispheric advantage in the perception of happy expression was not found.     

Visual-field bias in the judgment of facial expression of emotion

The left and right hemispheres of the brain are differentially related to the processing of emotions. Although there is little doubt that the right hemisphere is relatively superior for processing negative emotions, controversy exists over the hemispheric role in the processing of positive emotions. Eighty right-handed normal male participants were examined for visual-field (left-right) differences in the perception of facial expressions of emotion. Facial composite (RR, LL) and hemifacial (R, L) sets depicting emotion expressions of happiness and sadness were prepared. Pairs of such photographs were presented bilaterally for 150 ms, and participants were asked to select the photographs that looked more expressive. A left visual-field superiority (a right-hemisphere function) was found for sad facial emotion. A hemispheric advantage in the perception of happy expression was not found.     

End of the line: Line bisection,an unreliable measure of approach and avoidance motivation

Approach motivation leads to greater left hemisphere activation, whereas an avoidant motivational state activates the right hemisphere. Recent research, which served as the basis for the current experiment, suggests line bisection provides a simple measure of approach/avoidance lateralisation. Findings from Experiment 1 indicated that the landmark task was sensitive enough to identify lateral asymmetries evoked by happy and angry faces; however, follow-up experiments failed to replicate this finding. When task instructions were slightly modified or when a mixed design was used, motivation did not influence landmark task performance. The use of images in lieu of faces also failed to produce a significant effect. Importantly, a straight replication of Experiment 1 produced a null result. Line bisection does not appear to be a suitable measure of lateralised approach/avoidance biases, possibly due to the high individual variability inherent in visuospatial biases. Implications for null hypothesis significance testing are also discussed.     

No strong evidence for lateralisation of word reading and face recognition deficits following posterior brain injury

Face recognition and word reading are thought to be mediated by relatively independent cognitive systems lateralised to the right and left hemispheres, respectively. In this case, we should expect a higher incidence of face recognition problems in patients with right hemisphere injury and a higher incidence of reading problems in patients with left hemisphere injury. We tested this hypothesis in a group of 31 patients with unilateral right or left hemisphere infarcts in the territory of the posterior cerebral arteries. In most domains tested (e.g., visual attention, object recognition, visuo-construction, motion perception), we found that both patient groups performed significantly worse than a matched control group. In particular, we found a significant number of face recognition deficits in patients with left hemisphere injury and a significant number of patients with word reading deficits following right hemisphere injury. This suggests that face recognition and word reading may be mediated by more bilaterally distributed neural systems than is commonly assumed.     

Hemispheric asymmetry in the processing of negative and positive words: A divided field study

Research on the lateralisation of brain functions for emotion has yielded different results as a function of whether it is the experience, expression, or perceptual processing of emotion that is examined. Further, for the perception of emotion there appear to be differences between the processing of verbal and nonverbal stimuli. The present research examined the hemispheric asymmetry in the processing of verbal stimuli varying in emotional valence. Participants performed a lexical decision task for words varying in affective valence (but equated in terms of arousal) that were presented briefly to the right or left visual field. Participants were significantly faster at recognising positive words presented to the right visual field/left hemisphere. This pattern did not occur for negative words (and was reversed for high arousal negative words). These results suggest that the processing of verbal stimuli varying in emotional valence tends to parallel hemispheric asymmetry in the experience of emotion.     

The relation between social sharing and the duration of emotional experience

People often socially share their emotions to regulate them. Two-mode theory of social sharing states that cognitive sharing will contribute to emotional recovery, whereas socio-affective sharing will only temporarily alleviate emotional distress. Previous studies supporting this theory, measured emotional recovery in terms of residual emotional intensity. Until now, another important time-dynamic aspect of emotions, emotion duration, has been largely ignored. In two experience sampling studies we addressed this gap. In Study 1, participants reported on the duration of anger, fear, and sadness episodes; additionally time-varying information on the occurrence and mode of sharing was collected. This study revealed that sharing led to a shortening in emotion duration, in particular when it was socio-affective in nature. In Study 2 we investigated whether this result could be interpreted in terms of our measure of duration primarily reflecting emotional relief rather than recovery. In this study, the same method as in Study 1 was used; additionally, residual emotional intensity was measured three days after emotion onset. Study 2 largely replicated the findings from Study 1. Furthermore, duration appeared to be empirically distinct from residual intensity. Finally, no relation between sharing and residual intensity was found, even when considering the sharing mode.