面部表情的类别知觉及其个体差异

面部表情类别知觉效应是指连续变化的表情在人脑中按照类别表征, 且不同类别的表情之间存在明显的类别界线。介绍了面部表情类别知觉效应的行为和脑电研究范式及基础研究, 综述了攻击性、抑郁症、精神分裂症、社交焦虑等对面部表情类别知觉的影响, 以及面部表情类别知觉的发展研究。综述表明, 类别知觉研究能够揭示不同人群表情知觉类别界线及其偏移情况, 有助于解释相应的社会行为。未来研究应注重对面部表情类别知觉效应的个体差异和神经生理机制的探索。     

Children’s representations of facial expression and identity: Identity-contingent expression aftereffects

This investigation used adaptation aftereffects to examine developmental changes in the perception of facial expressions. Previous studies have shown that adults’ perceptions of ambiguous facial expressions are biased following adaptation to intense expressions. These expression aftereffects are strong when the adapting and probe expressions share the same facial identity but are mitigated when they are posed by different identities. We extended these findings by comparing expression aftereffects and categorical boundaries in adults versus 5- to 9-year-olds (n = 20/group). Children displayed adult-like aftereffects and categorical boundaries for happy/sad by 7 years of age and for fear/anger by 9 years of age. These findings suggest that both children and adults perceive expressions according to malleable dimensions in which representations of facial expression are partially integrated with facial identity.     

Categorical perception of facial expressions by 7-month-old infants.

Recent research indicates that adults show categorical perception of facial expressions of emotion. It is not known whether this is a basic characteristic of perception that is present from the earliest weeks of life, or whether it is one that emerges more gradually with experience in perceiving and interpreting expressions. We report two experiments designed to investigate whether young infants, like adults, show categorical perception of facial expressions. 7-month-old infants were shown photographic quality continua of interpolated (morphed) facial expressions derived from two prototypes of fear and happiness. In the first experiment, we used a visual-preference technique to identify the infants' category boundary between happiness and fear. In the second experiment, we used a combined familiarisation-visual-preference technique to compare infants' discrimination of pairs of expressions that were equally physically different but that did or did not cross the emotion-category boundary. The results suggest that 7-month-old infants (i) show evidence of categorical perception of facial expressions of emotion, and (ii) show persistent interest in looking at fearful expressions.     

Categorical and dimensional perceptions in decoding emotional facial expressions

We investigated whether categorical perception and dimensional perception can co-occur while decoding emotional facial expressions. In Experiment 1, facial continua with endpoints consisting of four basic emotions (i.e., happiness-fear and anger-disgust) were created by a morphing technique. Participants rated each facial stimulus using a categorical strategy and a dimensional strategy. The results show that the happiness-fear continuum was divided into two clusters based on valence, even when using the dimensional strategy. Moreover, the faces were arrayed in order of the physical changes within each cluster. In Experiment 2, we found a category boundary within other continua (i.e., surprise-sadness and excitement-disgust) with regard to the arousal and valence dimensions. These findings indicate that categorical perception and dimensional perception co-occurred when emotional facial expressions were rated using a dimensional strategy, suggesting a hybrid theory of categorical and dimensional accounts.     

Categorical and dimensional perceptions in decoding emotional facial expressions

We investigated whether categorical perception and dimensional perception can co-occur while decoding emotional facial expressions. In Experiment 1, facial continua with endpoints consisting of four basic emotions (i.e., happiness–fear and anger–disgust) were created by a morphing technique. Participants rated each facial stimulus using a categorical strategy and a dimensional strategy. The results show that the happiness–fear continuum was divided into two clusters based on valence, even when using the dimensional strategy. Moreover, the faces were arrayed in order of the physical changes within each cluster. In Experiment 2, we found a category boundary within other continua (i.e., surprise–sadness and excitement–disgust) with regard to the arousal and valence dimensions. These findings indicate that categorical perception and dimensional perception co-occurred when emotional facial expressions were rated using a dimensional strategy, suggesting a hybrid theory of categorical and dimensional accounts.     

The categorical perception of colors and facial expressions: The effect of verbal interference

A series of five experiments examined the categorical perception previously found for color and facial expressions. Using a two-alternative forced-choice recognition memory paradigm, it was found that verbal interference selectively removed the defining feature of categorical perception. Under verbal interference, there was no longer the greater accuracy normally observed for cross-category judgments relative to within-category judgments. The advantage for cross-category comparisons in memory appeared to derive from verbal coding both at encoding and at storage. It thus appears that while both visual and verbal codes may be employed in the recognition memory for colors and facial expressions, subjects only made use of verbal coding when demonstrating categorical perception.     

Categorical perception effects reflect differences in typicality on within-category trials

Many studies have shown better discrimination of two stimuli that cross a category boundary than of two stimuli belonging to the same category. This finding, known as categorical perception, is generally assumed to reflect consistently good performance on cross-category trials, relative to within-category trials. However, Roberson, D., Damjanovic, L., and Pilling, M. (Memory & Cognition, 35, 1814-1829, 2007) revealed that performance on within-category pairs of morphed facial expressions matched performance on cross-category trials when the target was a good exemplar of its category. Here, we investigate the generality of that finding by conducting new analyses of data from a series of studies of categorical perception in facial identity and color domains with speakers of different languages. Consistent with Roberson et al. (2007), the new analyses demonstrate that performance for central targets on within-category trials is as good as performance on cross-category trials. Participants perform badly on within-category items only when the target is closer to the category boundary than is the distractor. These results provide no support for the view that categorical perception is associated with increased perceptual sensitivity at category boundaries.     

Categorical Perception of Face Actions: Their Role in Sign Language and in Communicative Facial Displays

Can face actions that carry significance within language be perceived categorically? We used continua produced by computational morphing of face-action images to explore this question in a controlled fashion. In Experiment 1 we showed that question-type-a syntactic distinction in British Sign Language (BSL)-can be perceived categorically, but only when it is also identified as a question marker. A few hearing non-signers were sensitive to this distinction; among those who used sign, late sign learners were no less sensitive than early sign users. A very similar facial-display continuum between 'surprise' and 'puzzlement' was perceived categorically by deaf and hearing participants, irrespective of their sign experience (Experiment 2). The categorical processing of facial displays can be demonstrated for sign, but may be grounded in universally perceived distinctions between communicative face actions. Moreover, the categorical perception of facial actions is not confined to the six universal facial expressions.     

A face with a cue: exploring the inevitability of person categorization

Recent research has explored the dynamics of categorical thinking, with debate centering on the putative automaticity of this process. In a further investigation of this topic, the current inquiry assessed the influence of critical category‐cueing facial features on overt (i.e., category identification) and covert (i.e., category priming) measures of sex categorization. The results revealed that when a critical sex‐specifying facial cue (i.e., hairstyle) was present, priming effects emerged even under suboptimal processing conditions (i.e., facial blurring). When this cue was absent, however, priming no longer occurred. Interestingly, category identification was largely unimpeded by feature removal or facial blurring. Taken together, these results underscore the efficiency of categorical thinking and the importance of task objectives and feature‐based processing in person perception. Copyright © 2007 John Wiley & Sons, Ltd.     

Face encoding is not categorical: Consistent evidence across multiple types of contingent aftereffects

ABSTRACT

Race-contingent aftereffects indicate that faces of different races are encoded via dissociable visual channels. Race-contingent aftereffects reflect perceptions of typicality, indicating a gradual transition of activity across channels as faces change from looking more typical of one race to the other We examine whether faces forming more discrete categories (sex: male/female; species: human/monkey) are encoded in a similar fashion, or whether they are instead encoded via more dichotomous categorical judgements. Curves representing the rate of change of aftereffect magnitude as stimuli changed from male to female produced shallow slopes, closely resembling ratings of typicality, but differing significantly from slopes for categorical judgements. For species, aftereffect slopes were significantly shallower than both ratings of typicality and categorical judgements. Overall, these results suggest that the encoding of facial properties such as these is not categorical, but instead involves a graded response as stimulus typicality varies. Aftereffect slopes were similar across the two experiments, raising the possibility of a common system that is recruited during contingent adaptation, regardless of the specific dimension involved or the categories used by the experimenter.     

Categorical perception effects for facial identity in robustly represented familiar and self-faces: the role of configural and featural information

Categorical perception of robustly represented faces (self, friend) and unfamiliar faces is investigated, and the relative roles of configural and featural information are examined. Participants performed identification and discrimination tasks on morph series containing the self-face and a friend's face (self-Friend 1), two friends' faces (Friend 2-Friend 3), and two unfamiliar faces (Unfamiliar 1-Unfamiliar 2), presented in upright and inverted orientations. For upright faces, categorical perception effects were observed for both familiar morph series but not for the unfamiliar morph series, suggesting that robust representation is a requirement for categorical perception in facial identity. For inverted faces, categorical perception was observed for the self-Friend 1 morph series only. This suggests that categorical perception is tied to configural processing for familiar non-self-faces, but can be observed for self-faces during featural processing-consistent with evidence that self-face representations contain strong configural and featural components. Finally, categorical perception is not enhanced by the presence of the self-face relative to other familiar faces when upright, but shows a trend of being enhanced for self-faces when inverted, adding to the debate on the ways in which robustly represented faces can elicit categorical perception.     

A small-world network model of facial emotion recognition

Various models have been proposed to increase understanding of the cognitive basis of facial emotions. Despite those efforts, interactions between facial emotions have received minimal attention. If collective behaviours relating to each facial emotion in the comprehensive cognitive system could be assumed, specific facial emotion relationship patterns might emerge. In this study, we demonstrate that the frameworks of complex networks can effectively capture those patterns. We generate 81 facial emotion images (6 prototypes and 75 morphs) and then ask participants to rate degrees of similarity in 3240 facial emotion pairs in a paired comparison task. A facial emotion network constructed on the basis of similarity clearly forms a small-world network, which features an extremely short average network distance and close connectivity. Further, even if two facial emotions have opposing valences, they are connected within only two steps. In addition, we show that intermediary morphs are crucial for maintaining full network integration, whereas prototypes are not at all important. These results suggest the existence of collective behaviours in the cognitive systems of facial emotions and also describe why people can efficiently recognize facial emotions in terms of information transmission and propagation. For comparison, we construct three simulated networks—one based on the categorical model, one based on the dimensional model, and one random network. The results reveal that small-world connectivity in facial emotion networks is apparently different from those networks, suggesting that a small-world network is the most suitable model for capturing the cognitive basis of facial emotions.     

Pre-verbal infants perceive emotional facial expressions categorically

Adults perceive emotional expressions categorically, with discrimination being faster and more accurate between expressions from different emotion categories (i.e. blends with two different predominant emotions) than between two stimuli from the same category (i.e. blends with the same predominant emotion). The current study sought to test whether facial expressions of happiness and fear are perceived categorically by pre-verbal infants, using a new stimulus set that was shown to yield categorical perception in adult observers (Experiments 1 and 2). These stimuli were then used with 7-month-old infants (N = 34) using a habituation and visual preference paradigm (Experiment 3). Infants were first habituated to an expression of one emotion, then presented with the same expression paired with a novel expression either from the same emotion category or from a different emotion category. After habituation to fear, infants displayed a novelty preference for pairs of between-category expressions, but not within-category ones, showing categorical perception. However, infants showed no novelty preference when they were habituated to happiness. Our findings provide evidence for categorical perception of emotional expressions in pre-verbal infants, while the asymmetrical effect challenges the notion of a bias towards negative information in this age group.     

Who or what are you?: Facial orientation and person construal

An extensive literature has documented the cognitive benefits that accrue from a categorical conception of others. While informative, this work has overlooked the fact that, prior to the application of categorical thinking as an economizing cognitive tool, perceivers must first extract category-triggering information from available facial cues. What this suggests is that an impetus to construe others categorically may reside in the perceptual operations that guide the preliminary stages of person understanding. This possibility was explored in three experiments that investigated the effects of stimulus rotation on the efficiency of identity-based and category-based construal. In the first experiment, sex categorization was compared directly to identity-based construal. Subsequent experiments then investigated the efficiency of sex (Experiment 2) and race (Experiment 3) categorization when critical category-specifying facial cues were present and absent. The results demonstrated that categorical responding is driven by the extraction of featural information from faces, a finding that informs recent theoretical accounts of person perception. Copyright © 2007 John Wiley & Sons, Ltd.     

Face in profile view reduces perceived facial expression intensity: An eye-tracking study

Recent studies measuring the facial expressions of emotion have focused primarily on the perception of frontal face images. As we frequently encounter expressive faces from different viewing angles, having a mechanism which allows invariant expression perception would be advantageous to our social interactions. Although a couple of studies have indicated comparable expression categorization accuracy across viewpoints, it is unknown how perceived expression intensity and associated gaze behaviour change across viewing angles. Differences could arise because diagnostic cues from local facial features for decoding expressions could vary with viewpoints. Here we manipulated orientation of faces (frontal, mid-profile, and profile view) displaying six common facial expressions of emotion, and measured participants' expression categorization accuracy, perceived expression intensity and associated gaze patterns. In comparison with frontal faces, profile faces slightly reduced identification rates for disgust and sad expressions, but significantly decreased perceived intensity for all tested expressions. Although quantitatively viewpoint had expression-specific influence on the proportion of fixations directed at local facial features, the qualitative gaze distribution within facial features (e.g., the eyes tended to attract the highest proportion of fixations, followed by the nose and then the mouth region) was independent of viewpoint and expression type. Our results suggest that the viewpoint-invariant facial expression processing is categorical perception, which could be linked to a viewpoint-invariant holistic gaze strategy for extracting expressive facial cues.     

Un score individuel de reconnaissance d'une série de stimuli intermédiaires entre deux sources : la perception catégorielle des expressions faciales

Morphing is a computerized tool allowing the generation of pictures which are « hybrids » of two sources-pictures, in controlled proportions. Over the last decade, this tool did contribute greatly to the knowledge of mechanisms underlying facial expressions recognition. Especially, it appeared that categorical perception is involved. Indeed, while the physical variation from one source to the other is continuous and linear, the perceptual variation takes the form of a sigmoïdal or threshold function. The same applies to facial identity recognition and to recognition of face's gender. The present paper shows that data collected to evidence categorical perception can also be used to assess accuracy of expression recognition, whatever categorical or not, and to compare, say, the performance of an individual subject to that of a control group. In short, the proportion of subjects of the control group making the same choice as the individual subject is used as an estimator of the probability that this subject is issued from a normal population. This procedure furnishes criteria to decide if a given response is correct or not, which is not possible when free choices are recorded. This adaptation can be generalized to every tool designed to evaluate categorical perception.     

Individuals with Autism can Categorize Facial Expressions

The ability of high-functioning individuals with autism to perceive facial expressions categorically was studied using eight facial expression continua created via morphing software. Participants completed a delayed matching task and an identification task. Like undergraduate male participants (N = 12), performance on the identification task for participants with autism (N = 15) was predicted by performance on the delayed matching task for the angry-afraid, happy-sad, and happy-surprised continua. This result indicates a clear category boundary and suggests that individuals with autism do perceive at least some facial expressions categorically. As this result is inconsistent with findings from other studies of categorical perception in individuals with autism, possible explanations for these findings are discussed.     

The tipping point of animacy. How, when, and where we perceive life in a face

Faces capture humans' attention; yet, beyond aesthetic appreciation, it is presumably not the face itself that interests people but the mind behind it. Minds think, feel, and act in ways that have direct consequences for well-being, but despite their importance, how minds are perceived in faces is not well understood. We investigated this mechanism by presenting participants with morphed images created from animate (human) and inanimate (mannequin) faces. Life and mind were perceived to "appear" at a consistent location on the morph continuum, close to the human endpoint. This location constituted a categorical boundary, as evidenced by increased sensitivity to differences in image pairs that straddled this tipping point. Additionally, the impression of life was gleaned from the eyes more than from other facial features. These results suggest that human beings are highly attuned to specific facial cues, carried largely in the eyes, that gate the categorical perception of life.     

Sequential effects in facial expression categorization

Facial expressions are highly dynamic signals that are rarely categorized as static, isolated displays. However, the role of sequential context in facial expression categorization is poorly understood. This study examines the fine temporal structure of expression-based categorization on a trial-to-trial basis as participants categorized a sequence of facial expressions. The results showed that the local sequential context provided by preceding facial expressions could bias the categorical judgments of current facial expressions. Two types of categorization biases were found: (a) Assimilation effects-current expressions were categorized as close to the category of the preceding expressions, and (b) contrast effects-current expressions were categorized as away from the category of the preceding expressions. The effects of such categorization biases were modulated by the relative distance between the preceding and current expressions, as well as by the different experimental contexts, possibly including the factors of face identity and the range effect. Thus, the present study suggests that facial expression categorization is not a static process. Rather, the temporal relation between the preceding and current expressions could inform categorization, revealing a more dynamic and adaptive aspect of facial expression processing. (PsycINFO Database Record (c) 2013 APA, all rights reserved).