Valence specific laterality effects in free viewing conditions: The role of expectancy and gender of image

Recent research has looked at whether the expectancy of an emotion can account for subsequent valence specific laterality effects of prosodic emotion, though no research has examined this effect for facial emotion. In the study here (n = 58), we investigated this issue using two tasks; an emotional face perception task and a novel word task that involved categorising positive and negative words. In the face perception task a valence specific laterality effect was found for surprise (positive) and anger (negative) faces in the control but not expectancy condition. Interestingly, lateralisation differed for face gender, revealing a left hemisphere advantage for male faces and a right hemisphere advantage for female faces. In the word task, an affective priming effect was found, with higher accuracy when valence of picture prime and word target were congruent. Target words were also responded to faster when presented to the LVF versus RVF in the expectancy but not control condition.These findings suggest that expecting an emotion influences laterality processing but that this differs in terms of the perceptual/experience dimension of the task. Further, that hemispheric processing of emotional expressions appear to differ in the gender of the image.     

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.     

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.     

Task relevant effects on the assessment of cerebral specialization for facial emotion

Hemispheric specialization for processing different types of rapidly exposed stimuli was examined in a forced choice reaction time task. Four conditions of recognition were included: tacial emotion, neutral faces, emotional words, and neutral words. Only the facial emotion condition produced a significant visual field advantage (in favor of the left visual field), but this condition did not differ significantly from the neutral face condition's left visual field superiority. The verbal conditions produced significantly decreased latencies with RVF presentation, while the LVF presentation was associated with decreased latencies on the facial conditions. These results suggested that facial recognition and affective processing cannot be separated as independent factors generating right hemisphere superiority for facial emotion perception, and that task parameters (verbal vs. nonverbal) are important influences upon effects in studies of cerebral specialization.     

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.     

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 effects of attention on ear advantages in dichotic listening to words and affects

This study examined the effects of attention on ear advantages using dichotic listening to words and affects, a focused-attention paradigm. We compared the mixed condition, in which attention is switched between the ears in each trial, to the blocked condition, in which attention is directed to one ear for an entire block of trials. Results showed a decreased right ear advantage for word processing only in the mixed condition and an increased left ear advantage for emotion processing in both attention conditions for hits index. The mixed condition showed smaller laterality effects than the blocked condition for words with respect to hits index, while increasing right ear predominance for intrusions. The greater percentage of intrusions in the right ear for the word task and in the mixed condition suggests that the right ear (left hemisphere) is most vulnerable to attention switching. We posit that the attention manipulation has a greater effect on word processing than on emotion processing and propose that ear advantages reflect a combination of the effects of attentional and structural constraints on lateralisation.     

On the automaticity of emotion processing in words and faces: event-related brain potentials evidence from a superficial task

The degree to which emotional aspects of stimuli are processed automatically is controversial. Here, we assessed the automatic elicitation of emotion-related brain potentials (ERPs) to positive, negative, and neutral words and facial expressions in an easy and superficial face-word discrimination task, for which the emotional valence was irrelevant. Both emotional words and facial expressions impacted ERPs already between 50 and 100 ms after stimulus onset, possibly reflecting rapid relevance detection. Following this initial processing stage only emotionality in faces but not in words was associated with an early posterior negativity (EPN). Therefore, when emotion is irrelevant in a task which requires superficial stimulus analysis, automatically enhanced sensory encoding of emotional content appears to occur only for evolutionary prepared emotional stimuli, as reflected in larger EPN amplitudes to faces, but not to symbolic word stimuli.     

内、外部情绪标注对情绪作用的ERPs研究

以往情绪标注的研究发现描述情绪面孔的情绪（外部情绪标注）可以降低被试的情绪。但是描述自己的情绪（内部情绪标注）结果如何尚存争议。研究采用了ERPs技术,以愉快和悲伤情绪面孔为实验材料,选择18名大学本科生为被试,比较了内部情绪标注、外部情绪标注及性别标注之间的差异。结果发现：外部情绪标注和性别标注相比,其LPP波幅均小于性别标注下LPP波幅,并且这种差异在Pz、CPz、Cz、FCz、Fz五个电极点均类似;而内部情绪标注和性别标注相比,其LPP波幅均小于性别标注下LPP波幅,但仅表现在Pz、CPz、Cz三个点上。这说明：无论内部情绪标注还是外部情绪标注,在命名后均能抑制情绪。研究结果支持阻断理论。     

词汇具体性对情绪名词效价加工影响的ERP研究

具体性和抽象性是词汇同一特性的两极, 是直接影响词汇加工过程的重要因素。本研究采用快速序列视觉呈现范式, 结合脑电技术探讨在有限注意资源内, 词汇具体性对情绪名词加工过程的影响。结果发现：名词加工早期和晚期阶段的ERP成分受到情绪效价的调节, 情绪词比中性词诱发了更大的N170和LPC波幅; 名词加工早期和晚期阶段的ERP成分也受到词汇具体性的调节, 具体词比抽象词诱发了更大的N170和LPC波幅; 词汇具体性影响情绪名词加工的晚期阶段, LPC波幅能够分辨出不同情绪效价的抽象词, 对于具体词仅能区分出情绪与非情绪, 这说明抽象词可能比具体词负载了更多的情绪信息, 反映出对情绪信息的精细加工过程。     

An emotional Stroop task with faces and words. A comparison of young and older adults

AntecedentsGiven the contradictions of previous studies on the changes in attentional responses produced in aging a Stroop emotional task was proposed to compare young and older adults to words or faces with an emotional valence.MethodThe words happy or sad were superimposed on faces that express the emotion of happiness or sadness. The emotion expressed by the word and the face could agree or not (cued and uncued trials, respectively). 85 young and 66 healthy older adults had to identify both faces and words separately, and the interference between the two types of stimuli was examined.ResultsAn interference effect was observed for both types of stimuli in both groups. There was more interference on positive faces and words than on negative stimuli.ConclusionsOlder adults had more difficulty than younger in focusing on positive uncued trials, whereas there was no difference across samples on negative uncued trials.     

Effects of prime task on affective priming by facial expressions of emotion

Priming of affective word evaluation by pictures of faces showing positive and negative emotional expressions was investigated in two experiments that used a double task procedure where participants were asked to respond to the prime or to the target on different trials. The experiments varied between-subjects the prime task assignment and the prime-target interval (SOA, stimulus onset asynchrony). Significant congruency effects (that is, faster word evaluation when prime and target had the same valence than when they were of opposite valence) were observed in both experiments. When the prime task oriented the subjects to an affectively irrelevant property of the faces (their gender), priming was observed at SOA 300 ms but not at SOA 1000 ms (Experiment 1). However, when the prime task assignment explicitly oriented the subjects to the valence of the face, priming was observed at both SOA durations (Experiment 2). These results show, first, that affective priming by pictures of facial emotion can be obtained even when the subject has an explicit goal to process a non-affective property of the prime. Second, sensitivity of the priming effect to SOA duration seems to depend on whether it is mediated by intentional or unintentional activation of the valence of the face prime.     

Judging Words at Face Value: Interference in a Word Processing Task Reveals Automatic Processing of Affective Facial Expressions

Earlier research has indicated that some characteristics of facial expressions may be automatically processed. This study investigated automaticity as evidenced by involuntary interference in a word evaluation task. Compound stimuli, consisting of words superimposed on pictures of affective faces, were presented to subjects who were given the task of evaluating the affective valence of the words while disregarding the faces. Results of three experiments showed that word evaluation was influenced by the concurrently shown affective faces. Overall, negative words were found to require longer latencies, indicating that more processing resources are invested in negative than in positive stimuli. This speed advantage for positive words was modified by the faces. Negative words were facilitated, relative to positive ones, when shown with a negative expression (e.g. a sad face). Correspondingly, negative words were inhibited, relative to positive ones, when shown with a positive expression (e.g. a happy face). The results are consistent with automatic, involuntary semantic processing of affective facial expressions.     

Vivid: How valence and arousal influence word processing under different task demands

In this study, we used event-related potentials to examine how different dimensions of emotion—valence and arousal—influence different stages of word processing under different task demands. In two experiments, two groups of participants viewed the same single emotional and neutral words while carrying out different tasks. In both experiments, valence (pleasant, unpleasant, and neutral) was fully crossed with arousal (high and low). We found that the task made a substantial contribution to how valence and arousal modulated the late positive complex (LPC), which is thought to reflect sustained evaluative processing (particularly of emotional stimuli). When participants performed a semantic categorization task in which emotion was not directly relevant to task performance, the LPC showed a larger amplitude for high-arousal than for low-arousal words, but no effect of valence. In contrast, when participants performed an overt valence categorization task, the LPC showed a large effect of valence (with unpleasant words eliciting the largest positivity), but no effect of arousal. These data show not only that valence and arousal act independently to influence word processing, but that their relative contributions to prolonged evaluative neural processes are strongly influenced by the situational demands (and by individual differences, as revealed in a subsequent analysis of subjective judgments).     

情绪概念加工与情绪面孔知觉的相互影响

通过3个实验探讨情绪概念加工与情绪面孔知觉是否存在相互影响, 以及加工深度对两者关系的影响。实验1采用情绪面孔启动范式, 探讨较深的情绪概念加工层面对情绪概念与情绪面孔的关系的影响。实验2更改概念任务, 探讨较浅的概念加工层面对两者关系的影响。实验3缩短启动面孔呈现时间, 探讨较浅的面孔知觉层面对两者关系的影响。通过研究主要得出以下结论：(1)情绪概念加工与情绪面孔知觉确实存在相互影响; (2)概念加工深度影响两者关系的方向性, 在较深的概念加工层面, 两者的关系是双向的, 在较浅的概念加工层面, 两者的关系是单向的; (3)知觉加工深度也影响两者关系的方向性, 在较深的知觉加工层面, 两者的关系是双向的, 在较浅的知觉加工层面, 没有发现两者的相互影响。本研究为抽象概念的具身表征提供了实证支持。     

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.     

Processing emotional category congruency between emotional facial expressions and emotional words

Facial expressions are critical for effective social communication, and as such may be processed by the visual system even when it might be advantageous to ignore them. Previous research has shown that categorising emotional words was impaired when faces of a conflicting valence were simultaneously presented. In the present study, we examined whether emotional word categorisation would also be impaired when faces of the same (negative) valence but different emotional category (either angry, sad or fearful) were simultaneously presented. Behavioural results provided evidence for involuntary processing of basic emotional facial expression category, with slower word categorisation when the face and word categories were incongruent (e.g., angry word and sad face) than congruent (e.g., angry word and angry face). Event-related potentials (ERPs) time-locked to the presentation of the word–face pairs also revealed that emotional category congruency effects were evident from approximately 170 ms after stimulus onset.     

情绪名词的具体性效应：来自ERP的证据

词汇的具体性和情绪性是影响词汇加工的不同因素, 高具体性和情绪性都能够促进词汇的加工。本研究同时操纵词汇的具体性和情绪性, 使用词汇判定任务和愉悦度判断任务, 探讨了情绪名词的具体性效应及其具体性效应是否受词汇情绪信息的影响。结果发现：情绪名词的具体性效应受内隐或外显情绪条件的影响, 具体的情绪词比抽象的情绪词反应时间更短、正确率更高, 诱发了更大的N400和减小的LPC, 但LPC的具体性效应只表现在内隐情绪任务中。词汇的具体性和情绪性的相互影响发生在内隐情绪任务中的语义加工阶段, 正性、负性的具体词和抽象词的加工在N400成分上差异不显著, 而中性具体词和抽象词在N400成分上差异显著, 说明词汇的情绪信息为抽象词的加工提供了充分的语境, 因此消除了具体词的加工优势。     

Emotions in word and face processing: Early and late cortical responses

Recent research suggests that emotion effects in word processing resemble those in other stimulus domains such as pictures or faces. The present study aims to provide more direct evidence for this notion by comparing emotion effects in word and face processing in a within-subject design. Event-related brain potentials (ERPs) were recorded as participants made decisions on the lexicality of emotionally positive, negative, and neutral German verbs or pseudowords, and on the integrity of intact happy, angry, and neutral faces or slightly distorted faces. Relative to neutral and negative stimuli both positive verbs and happy faces elicited posterior ERP negativities that were indistinguishable in scalp distribution and resembled the early posterior negativities reported by others. Importantly, these ERP modulations appeared at very different latencies. Therefore, it appears that similar brain systems reflect the decoding of both biological and symbolic emotional signals of positive valence, differing mainly in the speed of meaning access, which is more direct and faster for facial expressions than for words.