Left gaze bias in humans, rhesus monkeys and domestic dogs

While viewing faces, human adults often demonstrate a natural gaze bias towards the left visual field, that is, the right side of the viewee’s face is often inspected first and for longer periods. Using a preferential looking paradigm, we demonstrate that this bias is neither uniquely human nor limited to primates, and provide evidence to help elucidate its biological function within a broader social cognitive framework. We observed that 6-month-old infants showed a wider tendency for left gaze preference towards objects and faces of different species and orientation, while in adults the bias appears only towards upright human faces. Rhesus monkeys showed a left gaze bias towards upright human and monkey faces, but not towards inverted faces. Domestic dogs, however, only demonstrated a left gaze bias towards human faces, but not towards monkey or dog faces, nor to inanimate object images. Our findings suggest that face- and species-sensitive gaze asymmetry is more widespread in the animal kingdom than previously recognised, is not constrained by attentional or scanning bias, and could be shaped by experience to develop adaptive behavioural significance.     

面孔参照或观察者参照：性别二态线索、面孔吸引力与表情对正视面孔偏好的影响

本研究探讨了性别二态线索、面孔吸引力和表情对正视面孔偏好的影响。实验1基于面孔参照,被试普遍偏好正视面孔;相对男性化/厌恶和生气/低吸引力的面孔,被试更偏好女性化/高兴和中性/高吸引力的正视面孔;实验2基于观察者参照,总体并未表现出正视偏好;对低吸引力/中性表情/男性化面孔更偏好斜视面孔。     

Rapid detection of person information in a naturalistic scene

A preferential-looking paradigm was used to investigate how gaze is distributed in naturalistic scenes. Two scenes were presented side by side: one contained a single person (person-present) and one did not (person-absent). Eye movements were recorded, the principal measures being the time spent looking at each region of the scenes, and the latency and location of the first fixation within each trial. We studied gaze patterns during free viewing, and also in a task requiring gender discrimination of the human figure depicted. Results indicated a strong bias towards looking to the person-present scene. This bias was present on the first fixation after image presentation, confirming previous findings of ultra-rapid processing of complex information. Faces attracted disproportionately many fixations, the preference emerging in the first fixation and becoming stronger in the following ones. These biases were exaggerated in the gender-discrimination task. A tendency to look at the object being fixated by the person in the scene was shown to be strongest at a slightly later point in the gaze sequence. We conclude that human bodies and faces are subject to special perceptual processing when presented as part of a naturalistic scene.     

Factors contributing to individual differences in facial expression categorisation

Individuals vary in perceptual accuracy when categorising facial expressions, yet it is unclear how these individual differences in non-clinical population are related to cognitive processing stages at facial information acquisition and interpretation. We tested 104 healthy adults in a facial expression categorisation task, and correlated their categorisation accuracy with face-viewing gaze allocation and personal traits assessed with Autism Quotient, anxiety inventory and Self-Monitoring Scale. The gaze allocation had limited but emotion-specific impact on categorising expressions. Specifically, longer gaze at the eyes and nose regions were coupled with more accurate categorisation of disgust and sad expressions, respectively. Regarding trait measurements, higher autistic score was coupled with better recognition of sad but worse recognition of anger expressions, and contributed to categorisation bias towards sad expressions; whereas higher anxiety level was associated with greater categorisation accuracy across all expressions and with increased tendency of gazing at the nose region. It seems that both anxiety and autistic-like traits were associated with individual variation in expression categorisation, but this association is not necessarily mediated by variation in gaze allocation at expression-specific local facial regions. The results suggest that both facial information acquisition and interpretation capabilities contribute to individual differences in expression categorisation within non-clinical populations.     

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.     

Gaze behaviour in hereditary prosopagnosia

Prosopagnosia is the inability to recognize someone by the face alone in the absence of sensory or intellectual impairment. In contrast to the acquired form of prosopagnosia we studied the congenital form. Since we could recently show that this form is inherited as a simple monogenic trait we called it hereditary form. To determine whether not only face recognition and neuronal processing but also the perceptual acquisition of facial information is specific to prosopagnosia, we studied the gaze behaviour of four hereditary prosopagnosics in comparison to matched control subjects. This rarely studied form of prosopagnosia ensures that deficits are limited to face recognition. Whereas the control participants focused their gaze on the central facial features, the hereditary prosopagnosics showed a significantly different gaze behaviour. They had a more dispersed gaze and also fixated external facial features. Thus, the face recognition impairment of the hereditary prosopagnosics is reflected in their gaze behaviour.     

Perceptual biases in processing facial identity and emotion

Normal observers demonstrate a bias to process the left sides of faces during perceptual judgments about identity or emotion. This effect suggests a right cerebral hemisphere processing bias. To test the role of the right hemisphere and the involvement of configural processing underlying this effect, young and older control observers and patients with right hemisphere damage completed two chimeric faces tasks (emotion judgment and face identity matching) with both upright and inverted faces. For control observers, the emotion judgment task elicited a strong left-sided perceptual bias that was reduced in young controls and eliminated in older controls by face inversion. Right hemisphere damage reversed the bias, suggesting the right hemisphere was dominant for this task, but that the left hemisphere could be flexibly recruited when right hemisphere mechanisms are not available or dominant. In contrast, face identity judgments were associated most clearly with a vertical bias favouring the uppermost stimuli that was eliminated by face inversion and right hemisphere lesions. The results suggest these tasks involve different neurocognitive mechanisms. The role of the right hemisphere and ventral cortical stream involvement with configural processes in face processing is discussed.     

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.     

The development of same and different judgments

Junior kindergarten children, third-grade children, and college students were given a simultaneous pattern discrimination task, with simple and complex patterns, under either unlimited or limited (150 msec) viewing time. Under unlimited viewing, RTs to same patterns were faster than to different patterns for younger children and older males. Under limited viewing, same and different RTs were equivalent, but more errors were made in judging different patterns by all age groups. The RTs were longer to complex than to simple patterns, but the increase was differentially less for the youngest Ss, especially on same pairs. Since this age difference was found under both limited and unlimited viewing, it was not attributable to age differences in perceptual scanning strategies. The same-different asymmetry in RT under unlimited viewing and in error rate under limited viewing confirms across a wide age range previous findings with adults using codable stimuli. A two-process model for same and different judgments appears to be required, although young children may have had a response bias for same in Expt II.     

Building biases in infancy: the influence of race on face and voice emotion matching

Early in the first year of life infants exhibit equivalent performance distinguishing among people within their own race and within other races. However, with development and experience, their face recognition skills become tuned to groups of people they interact with the most. This developmental tuning is hypothesized to be the origin of adult face processing biases including the other-race bias. In adults the other-race bias has also been associated with impairments in facial emotion processing for other-race faces. The present investigation aimed to show perceptual narrowing for other-race faces during infancy and to determine whether the race of a face influences infants' ability to match emotional sounds with emotional facial expressions. Behavioral (visual-paired comparison; VPC) and electrophysiological (event-related potentials; ERPs) measures were recorded in 5-month-old and 9-month-old infants. Behaviorally, 5-month-olds distinguished faces within their own race and within another race, whereas 9-month-olds only distinguish faces within their own race. ERPs were recorded while an emotion sound (laughing or crying) was presented prior to viewing an image of a static African American or Caucasian face expressing either a happy or a sad emotion. Consistent with behavioral findings, ERPs revealed race-specific perceptual processing of faces and emotion/sound face congruency at 9 months but not 5 months of age. In addition, from 5 to 9 months, the neural networks activated for sound/face congruency were found to shift from an anterior ERP component (Nc) related to attention to posterior ERP components (N290, P400) related to perception.     

How does reading direction modulate perceptual asymmetry effects?

Left-side bias effects refer to a bias towards the left side of the stimulus/space in perceptual/visuospatial judgments, and are argued to reflect dominance of right hemisphere processing. It remains unclear whether reading direction can also account for the bias effect. Previous studies comparing readers of languages read from left to right with those read from right to left (e.g., French vs. Hebrew) have obtained inconsistent results. As a language that can be read from left to right or from right to left, Chinese provides a unique opportunity for a within-culture examination of reading direction effects. Chinese participants performed a perceptual judgment task (with both face and Chinese character stimuli; Experiment 1) and two visuospatial attention tasks (the greyscales and line bisection tasks; Experiment 2) once before and once after a reading task, in which they read Chinese passages either from left to right or from right to left for about 20 min. After reading from right to left, participants showed significantly reduced left-side bias in Chinese character perceptual judgments but not in the other three tasks. This effect suggests that the role of reading direction on different forms of left-side bias may differ, and its modulation may be stimulus-specific.     

知觉负载对负性分心面孔的知觉加工和记忆的影响

本研究采用视觉搜索和意外再认记忆任务,结合事件相关电位技术,考察知觉负载对负性分心面孔的知觉加工和记忆的影响。在视觉搜索任务中,行为上恐惧分心面孔在高负载下干扰任务。ERP结果上,恐惧比中性分心面孔诱发更大的N170和N250;在低负载下恐惧比中性分心面孔诱发更大的N700,在高负载下没有差异。在意外再认记忆中,个体对低负载下的恐惧分心面孔表现出记忆。这些结果说明负性分心物在早期是自动化加工;晚期加工受知觉负载的调节,负载越低对负性分心物的过滤越少,存在对负性分心物的记忆偏向。     

On the perceptual specificity of memory representations

The present paradigm involved manipulating the congruency of the perceptual processing during the study and test phases of a recognition memory task. During each trial, a gaze-contingent window was used to limit the stimulus display to a region either inside or outside a 10° square centred on the participant's point of gaze, constituting the Central and Peripheral viewing modes respectively. The window position changed in real time in concert with changes in gaze position. Four experiments documented better task performance when viewing modes at encoding and retrieval matched than when they mismatched (i.e., perceptual specificity effects). Viewing mode congruency effects were demonstrated with both verbal and non-verbal stimuli. The present research is motivated and discussed in terms of theoretical views proposed in the 1970s including the levels-of-processing framework and the proceduralist viewpoint. In addition, implications for current processing and multiple systems views of memory are outlined.     

On the perceptual specificity of memory representations

The present paradigm involved manipulating the congruency of the perceptual processing during the study and test phases of a recognition memory task. During each trial, a gaze-contingent window was used to limit the stimulus display to a region either inside or outside a 10 degrees square centred on the participant's point of gaze, constituting the Central and Peripheral viewing modes respectively. The window position changed in real time in concert with changes in gaze position. Four experiments documented better task performance when viewing modes at encoding and retrieval matched than when they mismatched (i.e., perceptual specificity effects). Viewing mode congruency effects were demonstrated with both verbal and non-verbal stimuli. The present research is motivated and discussed in terms of theoretical views proposed in the 1970s including the levels-of-processing framework and the proceduralist viewpoint. In addition, implications for current processing and multiple systems views of memory are outlined.     

知觉场理论对面孔知觉年龄偏差效应的解释

使用融合面孔范式和倒置面孔范式来研究面孔知觉的年龄偏差效应,检验知觉场能否作为面孔整体加工的指标,并以此发展年龄偏差的整体加工解释。结果发现：（1）成人和儿童在加工正立面孔时的知觉场均大于加工倒置面孔时的知觉场;（2）在加工正立面孔时,成人加工本年龄面孔比加工他年龄面孔的知觉场更大。上述结果表明：（1）知觉场大小可以作为面孔整体加工的指标,且受面孔朝向的影响;（2）知觉场假设可以解释面孔的年龄偏差效应。     

知觉场理论对面孔知觉年龄偏差效应的解释

使用融合面孔范式和倒置面孔范式来研究面孔知觉的年龄偏差效应,检验知觉场能否作为面孔整体加工的指标,并以此发展年龄偏差的整体加工解释。结果发现：（1）成人和儿童在加工正立面孔时的知觉场均大于加工倒置面孔时的知觉场;（2）在加工正立面孔时,成人加工本年龄面孔比加工他年龄面孔的知觉场更大。上述结果表明：（1）知觉场大小可以作为面孔整体加工的指标,且受面孔朝向的影响;（2）知觉场假设可以解释面孔的年龄偏差效应。     

拥挤感启动对威胁性表情识别知觉敏感性的影响

为了考察拥挤感启动对威胁性面部表情识别的影响,以28名大学生为被试,进行不同拥挤启动条件下的愤怒-中性和恐惧-中性表情识别任务。信号检测论分析发现,拥挤感启动降低了愤怒表情识别的辨别力,不影响其判断标准,也不影响恐惧表情识别的辨别力和判断标准;主观报告的愤怒表情强度在拥挤感启动条件下显著高于非拥挤条件,恐惧、中性表情强度则不受拥挤感启动的影响。结果表明,拥挤感启动使人们辨别愤怒表情的知觉敏感性下降。     

Does perceived direct gaze boost detection in adults and children with and without autism? The stare-in-the-crowd effect revisited

This study extended that of von Grünau and Anston (1995) and explored whether perceived direct gaze is easily detected by individuals with and without autism, utilizing a visual-search paradigm. Participants detected target faces with either direct gaze or averted gaze. Laterally averted faces were used to eliminate the involvement of lower perceptual characteristics such as symmetry, which were inherent with the “straight gaze” used by von Grünau and Anston. Both typically developed adults and children detected targets with direct gaze more quickly than those with averted gaze, but face inversion distorted this asymmetrical performance, suggesting the contribution of configurative facial processing. In contrast, children with autism were not affected by the gaze direction presented by realistic facial stimuli. They were, however, faster to detect straight gaze defined solely by local features, which suggests that their impairment might be specific to the detection of direct gaze presented within a facial context.