Searching for a perceived stare in the crowd

Gaze direction can be represented in terms not only of local-feature information (ie the location of the pupil in the eye socket), but also of an emergent property---whether the perceived gaze direction is straight or averted. To examine whether this emergent property is preferentially accessed when searching for an oddly directed gaze, we experimentally manipulated the local-feature information and the emergent property independently, in order to investigate the influences of both types of information on visual searches for an oddly directed gaze. We found that the primary determinant of search efficiency was not the local-feature information of eye region, but the emergent property--the perceived direction of the gaze. This finding is consistent with the idea that important social signals are recognised primarily by their emergent properties.     

威胁相关面孔表情对眼睛注视方向知觉的影响

以往研究发现眼睛注视方向知觉受面孔表情的影响,愤怒面孔相较于恐惧面孔更倾向被判断为看着观察者。虽然研究者对此提出了不同的解释,但目前尚不清楚愤怒和恐惧表情在注视方向知觉中的这种差异影响到底来自于面孔的结构信息还是物理特征信息。本研究采用注视方向辨别任务,计算直视知觉范围（The Cone of Direct Gaze,CoDG）为因变量,分别以直立,倒置及模糊图片为实验材料,试图通过分离面孔结构信息和物理特征信息,对以上问题进行探讨。结果发现在保留面孔全部信息的情况下（实验1）愤怒面孔的CoDG大于恐惧面孔;在破坏结构信息加工,只保留特征信息加工的情况下（实验2））愤怒和恐惧表情在直视知觉范围上的差异消失了;在削弱物理特征信息加工,保留结构信息加工的情况下（实验3）二者在CoDG上的差异又复现。本研究结果说明不同威胁性面孔表情对眼睛注视知觉的影响主要来自于二者在与情绪意义相关的结构信息加工上的不同,而二者非低级的物理信息上的差异,支持信号共享假说和情绪评价假说对威胁性面孔表情与注视方向整合加工解释的理论基础。     

Configural processing in the perception of eye-gaze direction

Traditional accounts of gaze perception emphasise the geometric or configural cues present in the eye; the position of the iris in relation to the corner of the eye, for example. This kind of geometric account has been supported, in part, by findings that gaze judgments are impaired in faces rotated through 180 degrees, a manipulation known to disrupt the processing of relations between facial elements. However, studies involving this manipulation have confounded inversion of the face context with inversion of the eye region. The effects of inversion might therefore have been caused by a disruption of the computation of gaze direction from the eye region itself and/or a disruption of the influence that face context might exert on gaze processing. In the experiment reported here we independently manipulated eye orientation and the orientation of the face context, and measured participants' sensitivity to gaze direction. Performance was severely affected by inversion of the eyes, regardless of the orientation of the face, whereas face inversion had no significant effect on gaze sensitivity. Previous reports of a face-inversion effect on gaze perception can therefore be attributed to inversion of the eye region itself which, we suggest, disrupts some form of configural or relational processing that is normally involved in the computation of eye-gaze direction.     

Gaze cueing as a function of perceived gaze direction

Previous studies have found that attention is automatically oriented in the direction of other people's gaze. This study directly investigated whether the perceiving gaze direction modulates the orienting of observers' attention. Gaze perception was manipulated by changing the face context (head orientation) of the gaze cue: the perceived gaze angle was increased (or decreased) when the head and gaze are congruent (or incongruent), while the local‐feature information of the eye region was preserved for all stimuli. The results showed that gaze‐cueing effects were enhanced when the perceived gaze direction was averted more toward left or right, and reduced when the perceived gaze direction was closer to direct gaze. The results suggest that gaze‐cueing effects are based on mechanisms specialized for gaze perception, and the magnitude of gaze‐cueing effects was probably a function of the perceived gaze direction.     

Gaze behavior during urban cycling: Effects of subjective risk perception and vista space properties

In this research, we investigate how gaze behavior during urban cycling is affected by subjective risk perception and the local spatial configuration. For this purpose, participants cycled at five defined test locations while wearing a mobile eye tracking system. Next to the fixation duration, we extracted sight vector lengths (i.e., the distance between the current body location and the gaze location) and gaze angles (i.e., the degree to which the gaze deviates from the current travel direction). Concerning risk perception, participants provided a hazard estimate for each test location, as well as information about specific areas they experienced as dangerous. This information was aggregated into a local hazard level across all participants. Finally, the vista space (i.e., the space visible from the current position during a fixation) was quantified via isovist analysis. The results imply that spatially open locations, extending about equally into all directions, increase the level of perceived risk. Depending on the local spatial properties, participants also gaze into different directions, rather than further ahead and into their travel direction. Higher cycling experience and greater familiarity with a location enabled a more foresighted and focused gaze behavior. Our findings underline the importance to provide cyclists not only with enough space and with unobstructed views, but also to limit the space they are required to distribute their attention to.     

Contrast polarity of eyes modulates gaze‐cueing effect1

Two experiments using a modified Posner‐type visual cueing paradigm tested the prediction that detecting the darker region of the eyes of another's gaze triggers a reflexive orienting of the observer in the direction of the gaze. A target was presented in the left or right visual‐field following a gaze‐cue with positive or negative‐image polarity (Experiment 1). In Experiment 2, the polarity of the eyes was manipulated independently of the negative polarity of the face (eye‐positive or eye‐negative‐image polarity conditions). The results showed that the response to the target presented at the side the eyes gazed toward was faster than for the target presented at the other side in the positive polarity condition (Experiment 1), whereas, in the negative polarity condition, the gaze‐cuing effect was not found. In Experiment 2, in the eye‐negative condition, a reversed gaze‐cueing effect appeared, whereas in the eye‐positive polarity condition, a typical gaze‐cueing effect was obtained. These findings suggested that the reflexive orienting of the observer shifts toward the position indicated by the darker region of the other's eyes.     

Vertical gaze direction and the resting posture of the eyes

With horizontal gaze, the resting posture of binocular vergence typically corresponds to a distance of about 1 m. The effect of vertical direction of gaze on this basic resting posture was investigated. The dark vergence of twenty-four subjects was measured while they fixated a dim monocular light-point at vertical directions ranging from -45 degree (lowered) to +30 degrees (elevated). In one condition, gaze was varied by changes in eye position with the head held upright; in a second condition, gaze was varied by changes in head inclination with the eyes held in constant (horizontal) position with respect to the head. In both conditions, dark vergence shifted in the convergent (nearer) direction with lowered gaze and in the divergent (farther) direction with elevated gaze. The effect of varied eye inclination was larger, more variable across subjects, and more stable over time than that of varied head inclination. These findings indicate that multiple mechanisms contribute to gaze-related variations of the resting posture of the eyes. They may help to explain the variations of space perception and visual fatigue that are observed with different gaze inclinations.     

What are you looking at? Acuity for triadic eye gaze

The authors measured observers' ability to determine direction of gaze toward an object in space. In Experiment 1, they determined the difference threshold for determining whether a live "looker" was looking to the left or right of a target point. Acuity for eye direction was quite high (approximately 30 s arc). Viewing the movement of the looker's eyes did not improve acuity. When one of the looker's eyes was occluded, the observers' acuity was disrupted and their point of subjective equality was shifted away from the exposed eye. Experiment 2 was a replication of Experiment 1, but digitized gaze displays were used. The results of Experiment 3 showed that the acuity for direction of gaze depended on the position of the looker's target. Overall, the results indicated that humans are highly sensitive to gaze direction and that information from both eyes is used to determine direction of regard.     

Facial expressions modulate the gaze orienting effect on sound localization judgement

Recent studies have shown that cueing eye gaze can affect the processing of visual information, and this phenomenon is called the gaze-orienting effect (visual-GOE). Emerging evidence has shown that the cueing eye gaze also affects the processing of auditory information (auditory-GOE). However, it is unclear whether the auditory-GOE is modulated by emotion. We conducted three behavioural experiments to investigate whether cueing eye gaze influenced the orientation judgement to a sound, and whether the effect was modulated by facial expressions. The current study set four facial expressions (angry, fearful, happy, and neutral), manipulated the display type of facial expressions, and changed the sequence of gaze and emotional expressions. Participants were required to judge the sound orientation after facial expressions and gaze cues. The results showed that the orientation judgement of sound was influenced by gaze direction in all three experiments, and the orientation judgement of sound was faster when the face was oriented to the target location (congruent trials) than when the face was oriented away from the target location (incongruent trials). The modulation of emotion on auditory-GOE was observed only when gaze shifted followed by facial expression (Exp3); the auditory-GOE was significantly greater for angry faces than for neutral faces. These findings indicate that auditory-GOE as a social phenomenon exists widely, and the effect was modulated by facial expression. Gaze shift before the presentation of emotion was the key influencing factor for the emotional modulation in an auditory target gaze-orienting task. Our findings suggest that the integration of facial expressions and eye gaze was context-dependent.     

头部朝向在社会性注意转移中的作用

注视指向是非常重要的社会性注意线索,但是在日常情境中,注视指向往往伴随着头部朝向信息,而且两者都包含空间指向信息.已有研究发现头部朝向会影响注视指向知觉的速度和准确性,为注视指向提供参照系,进而会影响注视指向诱发的社会性注意.头部朝向和注视指向加工的神经机制也存在着广泛的重合.因此,除眼睛注视以外,头部朝向也是建构和完善基于心理模型的社会性注意机制的一个关键因素.未来的研究应关注头部朝向与眼睛注视指向共同影响注意转移的作用机制,并且从功能整合的角度开展神经机制研究.     

Regarding Scenes

ABSTRACT— When we view the visual world, our eyes flit from one location to another about three times each second. These frequent changes in gaze direction result from very fast saccadic eye movements. Useful visual information is acquired only during fixations, periods of relative gaze stability. Gaze control is defined as the process of directing fixation through a scene in real time in the service of ongoing perceptual, cognitive, and behavioral activity. This article discusses current approaches and new empirical findings that are allowing investigators to unravel how human gaze control operates during active real-world scene perception.     

Perception of gaze direction based on luminance ratio

Changing the luminance of one side of the sclera induces an apparent shift of the perceived direction of gaze toward the darker side of the sclera (Ando, 2002 Perception 31 657-674). However, when both the sclera and the skin surrounding it were darkened simultaneously as if by a cast shadow, the apparent direction of gaze shifted less than when only the sclera was darkened. The results suggest that one mechanism for gaze judgment is based on a simple analysis of the local luminance ratio between the eye and the surrounding region.     

眼睛注视线索提示效应: 内源性注意还是外源性注意?

采用改进的Posner视-空间线索提示范式, 对眼睛注视线索提示效应(eyes gaze cueing effect)的加工机制进行了探讨。实验一考察注视提示线索对空间Stroop效应的影响; 实验二考察注视提示线索对特征抽取和特征整合的影响。实验结果显示: 注视线索提示有效时的空间Stroop效应显著大于提示无效的情景; 在单一特征搜索与特征联合搜索任务中, 注视线索提示效应无差别。这说明, 注视线索通过在头脑里形成空间方位表征诱导注意转移; 注视线索通过影响特征抽取、而非特征整合阶段, 对客体加工产生易化。本研究支持注视线索提示效应属于内源性注意的观点。     

Infants perceiving and acting on the eyes: tests of an evolutionary hypothesis

It has been hypothesized that an evolutionarily ancient mechanism underlies the ability of human infants to detect and act upon the direction of eye gaze of another human face. However, the evidence from behavioral studies with infants is also consistent with a more domain-general system responsive to the lateral motion of stimuli regardless of whether or not eyes are involved. To address this issue three experiments with 4-month-old infants are reported that utilize a standard face-cueing paradigm. In the first experiment an inverted face was used to investigate whether the motion of the pupils elicits the cueing effect regardless of the surrounding face context. In the second experiment pupil motion and eye gaze direction were opposed, allowing us to assess their relative importance. In a third experiment, a more complex gaze shift sequence allowed us to analyse the importance of beginning with a period of mutual gaze. Overall, the results were consistent with the importance of the perceived direction of motion of pupils. However, to be effective in cueing spatial locations this motion needs to be preceded by a period of direct mutual gaze (eye contact). We suggest that evolution results in information-processing biases that shape and constrain the outcome of individual development to eventually result in adult adaptive specializations.     

A role for eyebrows in regulating the visibility of eye gaze direction

The human eye is unique amongst those of primates in having white sclera against which the dark iris is clearly visible. This high-contrast structure makes the gaze direction of a human potentially easily perceptible to others. For a social creature such as a human, the ability to perceive the direction of another's gaze may be very useful, since gaze usually signals attention. We report data showing that the accuracy of gaze deviation detection is independent of viewing distance up to a certain critical distance, beyond which it collapses. This is, of itself, surprising since most visual tasks are performed better at closer viewing distances. Our data also show that the critical distance, but not accuracy, is affected by the position of the eyebrows so that lowering the eyebrows reduces the critical distance. These findings show that mechanisms exist by which humans could expand or restrict the availability of their gaze direction to others. A way to regulate the availability of the gaze direction signal could be an advantage. We show that an interpretation of eyebrow function in these terms provides a novel explanation for several well-known eyebrow actions, including the eyebrow flash.     

A role for eyebrows in regulating the visibility of eye gaze direction

The human eye is unique amongst those of primates in having white sclera against which the dark iris is clearly visible. This high-contrast structure makes the gaze direction of a human potentially easily perceptible to others. For a social creature such as a human, the ability to perceive the direction of another's gaze may be very useful, since gaze usually signals attention. We report data showing that the accuracy of gaze deviation detection is independent of viewing distance up to a certain critical distance, beyond which it collapses. This is, of itself, surprising since most visual tasks are performed better at closer viewing distances. Our data also show that the critical distance, but not accuracy, is affected by the position of the eyebrows so that lowering the eyebrows reduces the critical distance. These findings show that mechanisms exist by which humans could expand or restrict the availability of their gaze direction to others. A way to regulate the availability of the gaze direction signal could be an advantage. We show that an interpretation of eyebrow function in these terms provides a novel explanation for several well-known eyebrow actions, including the eyebrow flash.     

The whereabouts of visual attention: Involuntary attentional bias toward the default gaze direction

This study proposed and verified a new hypothesis on the relationship between gaze direction and visual attention: attentional bias by default gaze direction based on eye-head coordination. We conducted a target identification task in which visual stimuli appeared briefly to the left and right of a fixation cross. In Experiment 1, the direction of the participant’s head (aligned with the body) was manipulated to the left, front, or right relative to a central fixation point. In Experiment 2, head direction was manipulated to the left, front, or right relative to the body direction. This manipulation was based on results showing that bias of eye position distribution was highly correlated with head direction. In both experiments, accuracy was greater when the target appeared at a position where the eyes would potentially be directed. Consequently, eye–head coordination influences visual attention. That is, attention can be automatically biased toward the location where the eyes tend to be directed.     

Exploiting human sensitivity to gaze for tracking the eyes

Given the prevalence, quality, and low cost of web cameras, along with the remarkable human sensitivity to gaze, we examined the accuracy of eye tracking using only a web camera. Participants were shown webcamera recordings of a person’s eyes moving 1°, 2°, or 3° of visual angle in one of eight radial directions (north, northeast, east, southeast, etc.), or no eye movement occurred at all. Observers judged whether an eye movement was made and, if so, its direction. Our findings demonstrate that for all saccades of any size or direction, observers can detect and discriminate eye movements significantly better than chance. Critically, the larger the saccade, the better the judgments, so that for eye movements of 3°, people can tell whether an eye movement occurred, and where it was going, at about 90% or better. This simple methodology of using a web camera and looking for eye movements offers researchers a simple, reliable, and cost-effective research tool that can be applied effectively both in studies where it is important that participants maintain central fixation (e.g., covert attention investigations) and in those where they are free or required to move their eyes (e.g., visual search).     

Effects of head orientation on gaze perception: How positive congruency effects can be reversed

Several past studies have considered how perceived head orientation may be combined with perceived gaze direction in judging where someone else is attending. In three experiments we tested the impact of different sources of information by examining the role of head orientation in gaze-direction judgements when presenting: (a) the whole face; (b) the face with the nose masked; (c) just the eye region, removing all other head-orientation cues apart from some visible part of the nose; or (d) just the eyes, with all parts of the nose masked and no head orientation cues present other than those within the eyes themselves. We also varied time pressure on gaze direction judgements. The results showed that gaze judgements were not solely driven by the eye region. Gaze perception can also be affected by parts of the head and face, but in a manner that depends on the time constraints for gaze direction judgements. While “positive” congruency effects were found with time pressure (i.e., faster left/right judgements of seen gaze when the seen head deviated towards the same side as that gaze), the opposite applied without time pressure.     

Effects of direct and averted gaze on the subsequent saccadic response

The saccadic latency to visual targets is susceptible to the properties of the currently fixated objects. For example, the disappearance of a fixation stimulus prior to presentation of a peripheral target shortens saccadic latencies (the gap effect). In the present study, we investigated the influences of a social signal from a facial fixation stimulus (i.e., gaze direction) on subsequent saccadic responses in the gap paradigm. In Experiment 1, a cartoon face with a direct or averted gaze was used as a fixation stimulus. The pupils of the face were unchanged (overlap), disappeared (gap), or were translated vertically to make or break eye contact (gaze shift). Participants were required to make a saccade toward a target to the left or the right of the fixation stimulus as quickly as possible. The results showed that the gaze direction influenced saccadic latencies only in the gaze shift condition, but not in the gap or overlap condition; the direct-to-averted gaze shift (i.e., breaking eye contact) yielded shorter saccadic latencies than did the averted-to-direct gaze shift (i.e., making eye contact). Further experiments revealed that this effect was eye contact specific (Exp. 2) and that the appearance of an eye gaze immediately before the saccade initiation also influenced the saccadic latency, depending on the gaze direction (Exp. 3). These results suggest that the latency of target-elicited saccades can be modulated not only by physical changes of the fixation stimulus, as has been seen in the conventional gap effect, but also by a social signal from the attended fixation stimulus.