Chimeric Faces Research Articles

Fear is more right lateralized than happiness and anger: Evidence for the motivational hypothesis of emotional face perception?

ABSTRACT Facial emotion processing (FEP) tends to be right hemisphere lateralized. This right-hemispheric bias (RHB) for FEP varies within and between individuals. The aim of the present research was to examine evidence pertaining to the prominent theories of FEP hemispheric bias as measured by a half-emotional half-neutral (no emotion) chimeric faces task. FEP hemispheric bias was indexed using laterality quotients (LQs) calculated from a Chimeric Faces Task completed by 427 adults recruited from the general population aged 18–67 years. Participants indicated which of two identical (but mirrored) emotional-neutral chimeric faces were more emotive. While all investigated emotions (fear, anger, and happiness) were right lateralized, fear was significantly more right lateralized than anger and happiness. These results provide evidence for both the right hemisphere hypothesis and the motivational hypothesis of emotion perception.

Analysing the brain networks corresponding to the facial contrast-chimeras.

How humans recognise faces and objects effortlessly, has become a great point of interest. To understand the underlying process, one of the approaches is to study the facial features, in particular ordinal contrast relations around the eye region, which plays a crucial role in face recognition and perception. Recently the graph-theoretic approaches to electroencephalogram (EEG) analysis are found to be effective in understating the underlying process of human brain while performing various tasks. We have explored this approach in face recognition and perception to know the importance of contrast features around the eye region. We studied functional brain networks, formed using EEG responses, corresponding to four types of visual stimuli with varying contrast relationships: Positive faces, chimeric faces (photo-negated faces, preserving the polarity of contrast relationships around eyes), photo-negated faces and only eyes. We observed the variations in brain networks of each type of stimuli by finding the distribution of graph distances across brain networks of all subjects. Moreover, our statistical analysis shows that positive and chimeric faces are equally easy to recognise in contrast to difficult recognition of negative faces and only eyes.

Deepfake as the basis for digitally collaging “impossible faces”

Subject of study. In this study, we present a novel method for the synthesis of video images using deepfake face swap, a technology that enables the creation of authentic video clips with false or swapped faces without evident traces of manipulation. The creation process of video images of “impossible faces,” such as a chimeric face, whose left and right sides belong to different people, or Thatcherized faces, wherein the eyes and mouth regions are rotated by 180°, is described stepwise using the DeepFaceLab software as an example. Aim of study. This study aimed to present and validate deepfake technology as a method of digitally collaging “impossible face” images. Method. Examples of method implementation were demonstrated using experimental results related to the perception patterns of moving “impossible faces” and their differences. Main results. The phenomena of perception previously recorded under static conditions were reproduced for dynamic models; accordingly, new interpretations can be inferred. Original faces were evaluated positively under static and dynamic conditions, independent of image inversion. Images of “impossible faces” under all conditions were perceived as unattractive, disharmonious, bizarre, and artificial. Expositions with audio speech increased the adequacy of evaluations under conditions of straight orientation. Practical significance. Digital collaging methods can significantly expand the capabilities of researchers in the field of interpersonal perception. Moreover, information technologies can expedite the creation of stimuli models for “impossible face” images, which are necessary for the further investigation of the human psyche in the course of communication.

Emotion lateralization in a graduated emotional chimeric face task: An online study.

To resolve inconsistencies in the literature regarding the dominance of the right cerebral hemisphere (RH) in emotional face perception, specifically investigating the role of the intensity of emotional expressions, different emotions, and conscious perception. The study used an online version of the well-established emotional chimeric face task (ECFT) in which participants judged which side of a chimeric face stimulus was more emotional. We tested the laterality bias in the ECFT across six basic emotions and experimentally modified the intensity of the emotional facial expression from neutral to fully emotional expressions, in incremental steps of 20%. The results showed an overall left hemiface bias across all emotions, supporting the RH hypothesis of emotional lateralization. However, the left hemiface bias decreased with decreasing intensity of the emotional facial expression. The results provide further support for the RH hypothesis and suggest that the RH dominance in emotional face perception may be affected by task difficulty and visual perception strategy. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Supplemental Material for Emotion Lateralization in a Graduated Emotional Chimeric Face Task: An Online Study

Supplemental Material for Emotion Lateralization in a Graduated Emotional Chimeric Face Task: An Online Study

Does face-selective cortex show a left visual field bias for centrally-viewed faces?

The left half of a centrally-viewed face contributes more strongly to recognition performance than the right. This left visual field (LVF) advantage is typically attributed to an untested assumption that face-selective cortex in the right hemisphere (RH) exhibits a contralateral bias, even for centrally-viewed faces. We tested the validity of this assumption using a behavioral measure of the LVF advantage and an fMRI experiment that measured laterality of face-selective cortex and neural contralateral bias. In the behavioral experiment, participants performed a chimeric face-matching task (Harrison and Strother, 2019). In the fMRI experiment, participants viewed chimeric faces comprised of face halves that either repeated or changed simultaneously in both hemifields, or repeated in one hemifield and changed in the other. This enabled us to measure lateralization of fMRI face-repetition suppression and hemifield-specific half-face sensitivity in face-selective cortex. We found that LVF bias in the fusiform face area (FFA) and right-lateralization of the FFA for changing versus repeated faces were both positively correlated with a behavioral measure of the LVF advantage for upright (but not inverted) faces. Results from regression analyses showed that LVF bias in the right FFA and FFA laterality make separable contributions to the prediction of our behavioral measure of the LVF bias for upright faces. Our results confirm a ubiquitous but previously untested assumption that RH superiority combined with contralateral bias in face-selective cortex explains the LVF advantage in face recognition. Specifically, our results show that neural LVF bias in the right FFA is sufficient to explain the relationship between FFA laterality and the perceptual LVF bias for centrally-viewed faces.

The left-side bias is not unique to own-race face processing.

Humans show a clear left-side bias in face processing. A chimeric face constructed with the left side (from the viewer's perspective) of a face and its mirror image is usually rated as more resemblant to the original face than a chimeric face constructed with the right side of the same face. Previous studies have characterized the left-side bias mainly with own-race faces, but it remains unclear whether this effect is race specific or if it reflects an universal visual expertise. One hundred and five Chinese students completed two versions of a chimeric face-identification task. The results revealed a significant left-side bias for both own-race (Chinese) and other-race (Caucasian) faces, suggesting that the left-side bias reflects an universal visual expertise in face processing.

Laterality and (in)visibility in emotional face perception: Manipulations in spatial frequency content.

It is widely agreed that hemispheric asymmetries in emotional face perception exist. However, the mechanisms underlying this lateralization are not fully understood. In the present study, we tested whether (a) these asymmetries are driven by the low spatial frequency content of images depicting facial expressions, and (b) whether the effects differed depending on whether the emotional facial expressions were clearly visible or hidden (i.e., embedded in low spatial frequencies). The manipulation sheds light on the contribution of cortical and subcortical routes to emotional processing mechanisms. We prepared both unfiltered (broadband) and hybrid faces. Within the latter, different bands of spatial frequency content from images of 2 different expressions were combined (i.e., low frequencies from an emotional image combined with high frequencies from a neutral image). We presented these broadband and hybrid images using the free-viewing emotional chimeric faces task (ECFT) in which 2 images are presented above and below fixation and asked participants to report which of the 2 mirror reversed images appeared more emotional. As predicted, the results showed that only broadband expressions produced the well-known left visual field/right hemisphere (LVF/RH) bias across all basic emotions. For hybrid images, only happiness revealed a significant LVF/RH bias. These results suggest that low spatial frequency content of emotional facial expressions, which activates the magnocellular pathway in subcortical structures and bypassing cortical visual processing, is not generally sufficient to induce an LVF bias under free-viewing conditions where participants deny explicitly seeing the emotion, suggesting that the LVF bias in ECFT is primarily cortically mediated. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Assessing the reliability of an online behavioural laterality battery: A pre-registered study

ABSTRACT Studies of cerebral lateralization often involve participants completing a series of perceptual tasks under laboratory conditions. This has constrained the number of participants recruited in such studies. Online testing can allow for much larger sample sizes but limits the amount of experimental control that is feasible. Here we considered whether online testing could give valid and reliable results on four tasks: a rhyme decision visual half-field task, a dichotic listening task, a chimeric faces task, and a finger tapping task. We recruited 392 participants, oversampling left-handers, who completed the battery twice. Three of the tasks showed evidence of both validity and reliability, insofar as they showed hemispheric advantages in the expected direction and test-retest reliability of at least r = .75. The reliability of the rhyme decision task was less satisfactory (r = .62). We also confirmed a prediction that extreme left-handers were more likely to depart from typical lateralization. Lateralization across the two language tasks (dichotic listening and rhyme judgement) was weakly correlated, but unrelated to lateralization on the chimeric faces task. We conclude that three of the tasks, dichotic listening, chimeric faces and finger tapping, show considerable promise for online evaluation of cerebral lateralization.

Exploring Consistency in Right Hemispheric Hypothesis and Valence Hypothesis for Perception of Emotions in Brain

The present study explores the consistency of two hemispheric hypotheses of the brain in perception of emotions: right hemisphere hypothesis, and valence hypothesis in the context of emotional intelligence, sex, and age using the sample of 323 participants. Unlike traditional procedures adopted for Chimeric face test, we developed a software for Chimeric face test with the help of APACHE 2.4 platform in PHP 5.2 application in i-7, 5th generation Intel core-based computer system with male and female faces reflecting four states of emotions—happy, fear, anger, and sad—to measure brain laterality. The level of emotional intelligence among participants is measured using Genos Emotional Intelligence test. By employing multivariate logistic regression analysis, the study reveals that the right hemisphere hypothesis is more dominant than the valence hypothesis in the sampled participants, and observes its dominance lucidly in males. Males with higher emotional intelligence have higher right hemisphere hypothesis responses whereas age has no significant impact on its validation. Valence hypothesis has no impact due to emotional intelligence, sex, or age. For female participants, the presence of the valence hypothesis is not observed, and higher emotional intelligence suggests fewer right hemisphere hypothesis responses.

Assessing the presence of face biases by means of anorthoscopic perception

Anorthoscopy is a presentation mode in which an image is shown sliding behind a slit-shaped aperture, so that it is visible only part by part and never in its entirety. With the aims to assess (1) whether the processing of complex stimuli (faces) correctly occurs in anorthoscopy, and (2) whether the Own-Gender Bias (OGB: the better recognition of stimuli belonging to the same gender of the observer: faster and more accurate) and the Left-Face Bias (LFB: the preference to analyze the left half of the face) occur in such a part by part presentation, we presented female and male faces as whole stimuli (Experiment 1) and in anorthoscopy (Experiments 2 and 3), as well as female/male chimeric faces (Experiment 4), during a gender categorization task. Experiment 1 confirmed that participants correctly categorized the gender of faces, but the OGB was not found. In Experiments 2 and 3 we manipulated the direction (Experiment 2: upward/downward; Experiment 3: leftward/rightward), the speed (slow and fast) of the sliding faces, and the width of the aperture (small and large). Both tasks revealed that facial gender was correctly categorized in anorthoscopy. The OGB was found, but only for males/females in Experiments 2/3, respectively. In Experiment 4 the LFB emerged only in the tachistoscopic session, suggesting that this perceptual bias does not extend to anorthoscopy.

White matter correlates of hemi-face dominance in happy and sad expression.

The neural underpinnings of human emotional expression are thought to be unevenly distributed among the two brain hemispheres. However, little is known on the anatomy supporting this claim, particularly in the cerebral white matter. Here, we explored the relationship between hemi-face dominance in emotional expression and cerebral white matter asymmetries in 33 healthy participants. Measures of emotional expression were derived from pictures of the participant's faces in a 'happy smiling' and a 'sad frowning' conditions. Chimeric faces were constructed by mirroring right and left hemi-faces, as done in previous studies, resulting in a left mirrored and right mirrored chimeric face per picture. To gain measures of hemi-face dominance per participant, a jury of 20 additional participants rated which chimeric face shows the higher intensity of emotional expressivity, by marking a 155mm line between the two versions. Measures of the asymmetry of the uncinate, the cingulum and the three branches of superior longitudinal fasciculi were derived from diffusion-weighted imaging tractography dissections. Group effect analyses indicated that the degree of asymmetry in emotional expression was not as prominent as reported in the literature and showed a large inter-individual variability. The degree of asymmetry in emotional expression was, however, significantly associated with the asymmetries in connective properties of the fronto-temporal and fronto-parietal tracts, specifically the uncinate fasciculus and the first branch of the superior longitudinal fasciculus. Therefore, this result raises novel hypotheses on the relationship of specific white matter tracts and emotional expression, especially their role in mood disorders.

MUL-TIBIOMETRIC PATTERN RETRIEVAL USING INDEX CODE TO IMPROVE RESPONSE TIME

In a biometric identification system, the identity corresponding to the input data (probe) is typically determined by comparing it against the templates of all identities in a database (gallery). Exhaustive matching against a large number of identities increases the response time of the system and may also reduce the accuracy of identification. Onaway to reduce the response time is by designing biometric templates that allow for rapid matching, as in the case of Iris Codes. An alternative approach is to limit the number of identities against which matching is performed based on criteria that are fast to evaluate. We propose a method for generating fixed-length codes for indexing biometric databases. An index code is constructed by computing match scores between a biometric image and a fixed set of reference images. Candidate identities are retrieved based on the similarity between the index code of the probe image and those of the identities in the database. The proposed technique can be easily extended to retrieve pertinent identities from multimodal databases. Experiments on a chimeric face and fingerprint bimodal database resulted in an 84% average reduction in the search space at a hit rate of 100%. These results suggest that the proposed indexing scheme has the potential to substantially reduce the response time without compromising the accuracy of identification.

HEMIFACIAL ASYMMETRIES IN AGE PERCEPTION: THE LEFT CHEEK LOOKS OLDER FOR FEMALES, BUT NOT MALES

The left hemiface expresses emotion more intensely than the right. Because emotional expressions contract the facial muscles and wrinkle the skin, theoretically the left hemiface’s greater expressivity should prompt more pronounced expression lines and wrinkles on the left than right side of the face. As wrinkles are the most salient age cue, we investigated whether the left hemiface consequently appears older than the right. Two hundred and sixty participants (F=148; M=112) viewed booklets containing pairs of left-left and right-right chimeric faces of eight models (M=F). For each trial participants were asked to make a two alternative forced choice response indicating which image looked older. Results confirmed a left cheek bias, with participants more likely to select left-left than right-right chimeras. Whilst participant gender did not influence perceptions, model gender predicted cheek selections: responses to female models drive the overall left cheek bias. The left cheek (56.8%) appeared older than the right cheek (43.2%) for female models, whereas there was little difference in perceived age between male models' left (50.8%) and right (49.2%) cheeks. Given that youth influences perceptions of female beauty, these findings complement previous research and offer a potential explanation for why the left side of females’ faces are judged less attractive: the right cheek appears younger.

Does right hemisphere superiority sufficiently explain the left visual field advantage in face recognition?

The tendency to perceive the identity of the left half of a centrally viewed face more strongly than that of the right half is associated with visual processing of faces in the right hemisphere (RH). Here we investigate conditions under which this well-known left visual field (LVF) half-face advantage fails to occur. Our findings challenge the sufficiency of its explanation as a function of RH specialization for face processing coupled with LVF-RH correspondence. In two experiments we show that the LVF half-face advantage occurs for normal faces and chimeric faces composed of different half-face identities. In a third experiment, we show that face inversion disrupts the LVF half-face advantage. In two additional experiments we show that half-faces viewed in isolation or paired with inverted half-faces fail to show the LVF advantage. Consistent with previous explanations of the LVF half-face advantage, our findings suggest that the LVF half-face advantage reflects RH superiority for processing faces and direct transfer of LVF face information to visual cortex in the RH. Critically, however, our findings also suggest the operation of a third factor, which involves the prioritization of face-processing resources to the LVF, but only when two upright face-halves compete for these resources. We therefore conclude that RH superiority alone does not suffice to explain the LVF advantage in face recognition. We also discuss the implications of our findings for specialized visual processing of faces by the right hemisphere, and we distinguish LVF advantages for faces viewed centrally and peripherally in divided field studies.

Lateralization of facial emotion processing and facial mimicry

ABSTRACT The two halves of the brain are believed to play different roles in emotional processing. In studies involving chimeric faces, emotional expressions in the left visual field are more strongly perceived as emotional than those in the right visual field. Notably, the role of facial mimicry has not been studied in relation to hemispheric lateralization. In the current study, which used a novel stimulus set of chimeric faces, we proposed and found that emotional intensity judgments replicate the left visual field bias for facial expressions of emotions. While a general facial mimicry effect to the chimeric faces occurred for the corrugator muscle, these mimicry effects were not related to the visual field bias. The results suggest that encoding the emotionality of another person’s facial expression might occur independent from the mere mimicry of the facial expression itself.

The depth and breadth of multiple perceptual asymmetries in right handers and non-right handers

ABSTRACTSeveral non-verbal perceptual and attentional processes have been linked with specialization of the right cerebral hemisphere. Given that most people have a left hemispheric specialization for language, it is tempting to assume that functions of these two classes of dominance are related. Unfortunately, such models of complementarity are notoriously hard to test. Here we suggest a method which compares frequency of a particular perceptual asymmetry with known frequencies of left hemispheric language dominance in right-handed and non-right handed groups. We illustrate this idea using the greyscales and colourscales tasks, chimeric faces, emotional dichotic listening, and a consonant–vowel dichotic listening task. Results show a substantial “breadth” of leftward bias on the right hemispheric tasks and rightward bias on verbal dichotic listening. Right handers and non-right handers did not differ in terms of proportions of people who were left biased for greyscales/colourscales. Support for reduced typical biases in non-right handers was found for chimeric faces and for CV dichotic listening. Results are discussed in terms of complementary theories of cerebral asymmetries, and how this type of method could be used to create a taxonomy of lateralized functions, each categorized as related to speech and language dominance, or not.

Baboon (Papio anubis) chimeric face processing by human (Homo sapiens) judges: Influence of stimuli complexity on the perception of oro-facial asymmetries.

Two methodologies have traditionally been used to measure hemispheric specialization for perception and expression of emotions in human and nonhuman primates. The first refers to objective measures, that is, measures of area and length of facial features, and the second concerns subjective "measures," that is, assessment of chimeric faces by human judges. We proposed a refined approach to the subjective assessment of hemispheric specializations, which aims at delimiting methodological issues in the study of orofacial asymmetries. The study focused on a baboon threat orofacial expression, which has led to discordant results according to the methodology used (Wallez & Vauclair, 2011, 2013). We presented human participants with two sets of chimeric stimuli varying the regions of the face likely to be processed. The whole face set was composed of classical chimeric faces, and the upper face set was made of chimeric faces for which the lower part was blurred. The purpose of this new procedure was to shed light on the perception process of baboon faces by human participants during a free-viewing chimeric task. Results showed a concomitant influence of the chimera structure depending on the order of the presentation of the set, revealing a training effect in our human judges. These factors combined together allowed the appearance of an overall left-left chimeric choice by human judges (i.e., which indicates a right hemisphere involvement in baboon threat expression). These findings bring novel insights into the study of orofacial asymmetries in nonhuman primates by human judgments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Left-Side Bias Is Observed in Sequential Matching Paradigm for Face Processing.

The left-side bias refers to how a chimeric face is created from the left side of a face (from the viewer’s perspective) and its mirror image are considered more similar to the original face than a chimeric face created from the right side of the same face and its mirror image. Previous studies investigated the left-side bias by using the chimeric stimuli task, where the original face and chimeric face were presented simultaneously. However, it remains unclear whether left-side bias effect is observed when the original face and chimeric face are presented sequentially. We completed two experiments using the sequential matching paradigm to investigate this issue. The results from both Experiment 1 and 2 showed that participants judged the identical proportion of the left chimeric face and original face was significantly higher than that of the right chimeric face and original face, which implies that the left-side bias effect can be observed in the sequential matching paradigm for face processing.

Emotional facedness in Parkinson's disease.

People with Parkinson's disease (PD) have a deficit of facial expression. Previous studies indicate that hemispheric dominance for emotional processing can give rise to an asymmetric pattern of facial expression of emotion. In this study, we aimed to evaluate possible asymmetry in facial emotion expressivity in PD. Twenty PD patients and twenty healthy controls were video-recorded while posing the 6 basic emotions. The most expressive pictures were derived from the videos and chimeric faces were created. Nine healthy raters were asked to judge which of the two chimeras looked more expressive. Chosen responses, reaction times and confidence levels were the main outcome measures. We evaluated possible differences in these measures within each group and between groups (PD, healthy controls). We assessed possible correlations between a global facial laterality index (pooling all emotions together) as well as facial laterality indexes for each emotion and the body laterality index, accounting for the predominant side of limb bradykinesia in patients. There was no difference in outcome measures when evaluating the two hemifaces within PD patients and healthy controls or between the two groups (all Ps > 0.05). In PD patients there was a correlation between the global facial laterality index and the body laterality index (R = - 0.39, P = 0.01), suggesting that the most expressive hemiface corresponded to the less affected body side. The results of our study do not support the hypothesis of hemisphere predominance in regulating facial emotion expressions and provides novel information on altered facial emotion expression in PD.