Differences in the perception of direct gaze between the externally and internally rotated eye.

The perception of direct gaze provides multiple benefits for the observer. Previous studies have investigated how the information from both eyes is used to estimate gaze direction, showing that the perception of gaze direction differs when only the externally rotated eye versus only the internally rotated eye is visible. We examined the width and center of the area of direct gaze by presenting the observers with either the externally or internally rotated eye, or both eyes with the task to judge whether a computer avatar is looking at them. Two experiments yield evidence for a wider area of direct gaze for the externally rotated eye (around 6°) than for the internally rotated eye (around 4°). The area of direct gaze for both eyes was found to be the same as for the internally rotated eye, but smaller than for the externally rotated eye. When both eyes were present, our results indicate that the perception of direct gaze is more likely to follow the internally rotated eye. The discussion substantiates a new generalization that observers base their judgments on the more rotated eye, which can differ due to angle kappa and vergence, in our study it is the internally rotated eye.

Are the directions of both eyes integrated before or after the perception of direct gaze? Evidence from simulated mild strabismus.

The cone of gaze is a looker's range of gaze directions that is accepted as direct by an observer. The present research asks how the condition of mild strabismus, that is, when the two eyes point in slightly different directions, influences the cone of gaze. Normally, both eyes are rotated in a coordinated manner such that both eyes are directed to the same fixation point. With strabismus, there are two fixation points, and, therefore, two directions into which the two eyes point. This raises the question of the direction and the shape (i.e., width) of the gaze cone. Two experiments are conducted with simulated mild strabismus. Three conditions are tested, the two strabismic conditions of esotropia, and exotropia and one orthotropic (nonstrabismic) condition. Results show that the direction of the gaze cone is roughly the average of the directions of the two eyes. Furthermore, the width of the gaze cone is not affected by simulated strabismus and is thus the same for the strabismic and the orthotropic conditions. The results imply a model where at first the direction of gaze based on both eyes is perceived, and where the gaze cone is implied on the basis of the combined gaze direction.

How vergence influences the perception of being looked at.

Perceiving other people's direct gaze is important for many areas of everyday activity. For horizontal and vertical eye movements, the area of being looked at, known as the cone of gaze, has been well explored. Previous research has shown a range of eye rotations (up to eccentricities of 4°-9°) that people accept as direct gaze. Vergence is an important cue for perceiving the depth of fixation. This study examines the range of vergence angles that support the perception of being looked at. In two experiments, observers adjusted the degree of vergence of the lookers' eyes until they felt just (not) looked at. The first experiment also asked to adjust the point of being exactly looked at, which was 0° (parallel eyes). The thresholds of being just (not) looked at were around 4.5° of convergence and 2.5° divergence, which results in a depth of 7° of vergence. This depth was replicated in Experiment 2, while the thresholds of convergence (3.5°) and divergence (3.5°) slightly differ from Experiment 1. The results indicate a consistent area of vergences being accepted as direct gaze, yielding first-time evidence for a third dimension-the depth dimension-of direct gaze.

Examining Gaze Cone Shape and Size.

Another person's looking behavior is used by observers to judge gaze direction and fixation points. An important task in this context is the judgement of direct gaze, that is, the perception of being looked at. The cone of gaze can be defined as the range of fixation points that support direct gaze. The cone concept implies that this range lawfully increases with distance, but that the cone angle is constant. The present experiment tested the concept with a larger number and a more extended range of distances than previously done, and took care of possible directional errors. The gaze cone was found to be roughly linear, and stable between 1.6 m and 7.9 m - an almost perfect cone. The mean cone size subtended 5.2° in diameter when averaged over ascending and descending series. Measures differed, however, in ascending and descending series, consistent with a conservative bias. Also, the variability of judgements increased slightly with distance. Results are discussed considering whether cone size is actually smaller than often reported in the literature.

Measuring the emotion-specificity of rapid stimulus-driven attraction of attention to fearful faces: evidence from emotion categorization and a comparison with disgusted faces.

In the current study, we tested whether a fear advantage-rapid attraction of attention to fearful faces that is more stimulus-driven than to neutral faces-is emotion specific. We used a cueing task with face cues preceding targets. Cues were non-predictive of the target locations. In two experiments, we found enhanced cueing of saccades towards the targets with fearful face cues than with neutral face cues: Saccades towards targets were more efficient with cues and targets at the same position (under valid conditions) than at opposite positions (under invalid conditions), and this cueing effect was stronger with fearful than with neutral face cues. In addition, this cueing effect difference between fearful and neutral faces was absent with inverted faces as cues, indicating that the fear advantage is face-specific. We also show that emotion categorization of the face cues mirrored these effects: Participants were better at categorizing face cues as fearful or neutral with upright than with inverted faces (Experiment 1). Finally, in alternative blocks including disgusted faces instead of fearful faces, we found more similar cueing effects with disgusted faces and neutral faces, and with upright and inverted faces (Experiment 2). Jointly, these results demonstrate that the fear advantage is emotion-specific. Results are discussed in light of evolutionary explanations of the fear advantage.

New task-new results? How the gaze cone is influenced by the method of measurement.

Perceiving direct gaze - the perception of being looked at - is important in everyday life. The gaze cone is a concept to define the area in which observers perceive gaze as direct. The most frequently used methods to measure direct gaze threshold fall into two broad groups: First, a variant of the method of constant stimuli, firstly introduced by Gibson and Pick (The American Journal of Psychology, 76, 386-394, 1963). Second, a variant of the method of adjustment, firstly introduced by Gamer and Hecht (Journal of Experimental Psychology: Human Perception and Performance, 33, 705-715, 2007). Previous studies found a considerable range of thresholds, and although some influences on thresholds are already known (uncertainty, clinical groups), thresholds often vary for no apparent reason. Another important method is a triadic gaze-perception task, which usually finds triadic gaze direction judgments to be overestimated. In two experiments, we compare the method of adjustment with the method of constant stimuli. Experiment 1 additionally examines the influence of the overestimation effect found in the triadic task. Results indicate that thresholds are larger when measured by the method of adjustment than by constant stimuli. Furthermore, Experiment 1 finds a nonlinear overestimation factor, indicating that gaze directions near 0° are less overestimated than larger eccentricities. Correcting the thresholds with individually obtained overestimation factors widens the gaze cone but does not eliminate the average difference between the methods of adjustments and constant stimuli.

Alerting effects require the absence of surprise.

Ongoing actions are interrupted for a brief period of time whenever salient and expectancy-discrepant stimuli (surprise stimuli) interfere with the present task set. By contrast, salient stimuli (alerting cues) preceding targets can facilitate behaviour by reducing time to initiate actions. Both phenomena seem to be at odds with each other as actions are either impaired or facilitated. Therefore, in the present study, we asked how surprise and alerting effects interact. In two experiments, participants performed choice reaction tasks without any prior knowledge of the impending alerting cue. After a baseline period of trials without an alerting cue, the alerting cue was presented for the first time. It was found that the initial presentation of the alerting cue significantly slowed down reaction times. However, after just a single trial this impairment went away. This reveals that the beneficial effects of alerting for action presuppose that alerting cues are expected and represented in the top-down task set. As such, the present findings challenge the standard view of phasic alerting as a bottom-up and entirely stimulus-driven phenomenon.

Which processes dominate visual search: Bottom-up feature contrast, top-down tuning or trial history?

Previous research has identified three mechanisms that guide visual attention: bottom-up feature contrasts, top-down tuning, and the trial history (e.g., priming effects). However, only few studies have simultaneously examined all three mechanisms. Hence, it is currently unclear how they interact or which mechanisms dominate over others. With respect to local feature contrasts, it has been claimed that a pop-out target can only be selected immediately in dense displays when the target has a high local feature contrast, but not when the displays are sparse, which leads to an inverse set-size effect. The present study critically evaluated this view by systematically varying local feature contrasts (i.e., set size), top-down knowledge, and the trial history in pop-out search. We used eye tracking to distinguish between early selection and later identification-related processes. The results revealed that early visual selection was mainly dominated by top-down knowledge and the trial history: When attention was biased to the target feature, either by valid pre-cueing (top-down) or automatic priming, the target could be localised immediately, regardless of display density. Bottom-up feature contrasts only modulated selection when the target was unknown and attention was biased to the non-targets. We also replicated the often-reported finding of reliable feature contrast effects in the mean RTs, but showed that these were due to later, target identification processes (e.g., in the target dwell times). Thus, contrary to the prevalent view, bottom-up feature contrasts in dense displays do not seem to directly guide attention, but only facilitate nontarget rejection, probably by facilitating nontarget grouping.

Of toothy grins and angry snarls--open mouth displays contribute to efficiency gains in search for emotional faces.

The emotional face-in-a-crowd effect is widely cited, but its origin remains controversial, particularly with photorealistic stimuli. Recently, it has been suggested that one factor underlying the guidance of attention by a photorealistic emotional face in visual search might be the visibility of teeth, a hypothesis, however, that has not been studied systematically to date. The present experiments manipulate the visibility of teeth experimentally and orthogonally to facial emotion. Results suggest that much of the face-in-a-crowd effect with photorealistic emotional faces is due to visible teeth, and that the visibility of teeth can create a search advantage for either a happy or an angry target face when teeth visibility and facial emotion are confounded. Further analyses clarify that the teeth visibility primarily affects the speed with which neutral crowds are scanned, shedding new light on the mechanism that evokes differences in search efficiency for different emotional expressions.

Perception of direct gaze in a video-conference setting: the effects of position and size.

A common problem in video conferences is gaze direction. In face-to-face communication, it is common that speaker and listener intermittently look at each other. In a video-conference setting, where multiple participants are on the screen, things are complicated and not necessarily optimal. If the listener feels looked at when the speaker looks into the camera, how tolerant is the listener for slight deviations? And does this depend on the position of the speaker's tile on the screen, or the size of the tile? In a first experiment, participants from a student population judged whether they are looked at, while vertical gaze direction of the looker was varied. Furthermore, the position of the tile on the screen varied. The results showed that a slightly upward directed gaze was optimal for the direct gaze judgment, with a width of ± 4 degrees. Optimal gaze direction was somewhat higher for tiles at the bottom of the screen. A second experiment tested the effect of size on the perception of horizontal gaze directions. Size was found to increase the gaze cone. The paper concludes with some recommendations for a setup of video conference systems, optimized for perceived gaze contact.

Urbanicity-Perspectives from Neuroscience and Public Health: A Scoping Review.

Urban residency is associated with exposure to environmental factors, which can influence health in many ways. Neuroscientific research, as well as Public Health research, aim towards broadening evidence in the field of Urban Health. However, it is unclear whether the association between urban living and mental illnesses is causal rather than explainable by other selective effects. This review seeks to gather information on the current evidence regarding urban living and neurological outcomes to demonstrate how Public Health and Neuroscience could complement each other in the field of Urban Health. A scoping review was conducted in four electronic databases according to the PRISMA-statement guidelines. 25 empirical studies were included. Outcomes such as schizophrenia and psychotic disorders, social and cognitive functioning were scrutinised. Evidence was found for alteration of brain functioning and brain structure. Most studies researching cognitive functioning or cognitive decline displayed possible protective effects of urban living compared to rural living. The different study designs in Public Health and Neuroscience could profit from each other. Although the comparability of studies is limited by the inconsistent assessments of urbanity. Synergies and potentials to combine aspects of Public Health and Neuroscience in the field of Urban Health to improve population health became apparent.

More efficient visual search for happy faces may not indicate guidance, but rather faster distractor rejection: Evidence from eye movements and fixations.

The visual search paradigm has been used in emotion research to examine the relation between facial expressions of emotion and attention. Here, the better performance in a search for one facial expression category (e.g., a happy face) compared to a second category (e.g., an angry face) has been often interpreted as indicating better guidance of attention. Better guidance of attention in turn indicates that some aspect of the facial expression can be used preattentively, that is, while focused attention is directed elsewhere in the visual field. This view has been criticized because better performance may also mean better distractor rejection independently of guidance. The present study uses eye tracking to disentangle the two variables. The results show better search performance with a happy than angry face as the target. Facial emotion also influenced the time the eyes fixated a stimulus (dwelling), but not guidance related variables of search performance. A linear regression moreover showed that dwelling accounted for large amounts of variance in the overall search times. Overall, the results present clear-cut evidence that differential search performance does not need to indicate differential guidance, but may also be explained by postselective factors that influence the dwelling on stimuli. The broader implication of this demonstration is that results from the visual search paradigm have to be interpreted with caution, and that better search performance cannot be directly interpreted as an indicator of preattentive guidance of attention. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Dwelling on simple stimuli in visual search.

Research and theories on visual search often focus on visual guidance to explain differences in search. Guidance is the tuning of attention to target features and facilitates search because distractors that do not show target features can be more effectively ignored (skipping). As a general rule, the better the guidance is, the more efficient search is. Correspondingly, behavioral experiments often interpreted differences in efficiency as reflecting varying degrees of attentional guidance. But other factors such as the time spent on processing a distractor (dwelling) or multiple visits to the same stimulus in a search display (revisiting) are also involved in determining search efficiency. While there is some research showing that dwelling and revisiting modulate search times in addition to skipping, the corresponding studies used complex naturalistic and category-defined stimuli. The present study tests whether results from prior research can be generalized to more simple stimuli, where target-distractor similarity, a strong factor influencing search performance, can be manipulated in a detailed fashion. Thus, in the present study, simple stimuli with varying degrees of target-distractor similarity were used to deliver conclusive evidence for the contribution of dwelling and revisiting to search performance. The results have theoretical and methodological implications: They imply that visual search models should not treat dwelling and revisiting as constants across varying levels of search efficiency and that behavioral search experiments are equivocal with respect to the responsible processing mechanisms underlying more versus less efficient search. We also suggest that eye-tracking methods may be used to disentangle different search components such as skipping, dwelling, and revisiting.

Novelty competes with saliency for attention.

A highly debated question in attention research is to what extent attention is biased by bottom-up factors such as saliency versus top-down factors as governed by the task. Visual search experiments in which participants are briefly familiarized with the task and then see a novel stimulus unannounced and for the first time support yet another factor, showing that novel and surprising features attract attention. In the present study, we tested whether gaze behavior as an indicator for attentional prioritization can be predicted accurately within displays containing both salient and novel stimuli by means of a priority map that assumes novelty as an additional source of activation. To that aim, we conducted a visual search experiment where a color singleton was presented for the first time in the surprise trial and manipulated the color-novelty of the remaining non-singletons between participants. In one group, the singleton was the only novel stimulus ("one-new"), whereas in another group, the non-singleton stimuli were likewise novel ("all-new"). The surprise trial was always target absent and designed such that top-down prioritization of any color was unlikely. The results show that the singleton in the all-new group captured the gaze less strongly, with more early fixations being directed to the novel non-singletons. Overall, the fixation pattern can accurately be explained by noisy priority maps where saliency and novelty compete for gaze control.

Visual search for facial expressions of emotions: a comparison of dynamic and static faces.

A number of past studies have used the visual search paradigm to examine whether certain aspects of emotional faces are processed preattentively and can thus be used to guide attention. All these studies presented static depictions of facial prototypes. Emotional expressions conveyed by the movement patterns of the face have never been examined for their preattentive effect. The present study presented for the first time dynamic facial expressions in a visual search paradigm. Experiment 1 revealed efficient search for a dynamic angry face among dynamic friendly faces, but inefficient search in a control condition with static faces. Experiments 2 to 4 suggested that this pattern of results is due to a stronger movement signal in the angry than in the friendly face: No (strong) advantage of dynamic over static faces is revealed when the degree of movement is controlled. These results show that dynamic information can be efficiently utilized in visual search for facial expressions. However, these results do not generally support the hypothesis that emotion-specific movement patterns are always preattentively discriminated.

The Mona Lisa Illusion-Scientists See Her Looking at Them Though She Isn't.

If the person depicted in an image gazes at the camera or painter, a viewer perceives this as being gazed at. The viewers' perception holds irrespectively of their position relative to image. This is the Mona Lisa effect named after the subject of Leonardo's famous painting La Gioconda. The effect occurs reliably but was not tested with Mona Lisa herself. Remarkably, viewers judged Mona Lisa's gaze as directed to their right-hand side irrespectively of the image zoom, its horizontal position on screen, and the distance of the ruler that was used for measuring the gaze direction.

The Cognitive-Evolutionary Model of Surprise: A Review of the Evidence.

Research on surprise relevant to the cognitive-evolutionary model of surprise proposed by Meyer, Reisenzein, and Schützwohl (1997) is reviewed. The majority of the assumptions of the model are found empirically supported. Surprise is evoked by unexpected (schema-discrepant) events and its intensity is determined by the degree if schema-discrepancy, whereas the novelty and the valence of the eliciting events probably do not have an independent effect. Unexpected events cause an automatic interruption of ongoing mental processes that is followed by an attentional shift and attentional binding to the events, which is often followed by causal and other event analysis processes and by schema revision. The facial expression of surprise postulated by evolutionary emotion psychologists has been found to occur rarely in surprise, for as yet unknown reasons. A physiological orienting response marked by skin conductance increase, heart rate deceleration, and pupil dilation has been observed to occur regularly in the standard version of the repetition-change paradigm of surprise induction, but the specificity of these reactions as indicators of surprise is controversial. There is indirect evidence for the assumption that the feeling of surprise consists of the direct awareness of the schema-discrepancy signal, but this feeling, or at least the self-report of surprise, is also influenced by experienced interference. In contrast, facial feedback probably does contribute substantially to the feeling of surprise and the evidence for the hypothesis that surprise is affected by the difficulty of explaining an unexpected event is, in our view, inconclusive. Regardless of how the surprise feeling is constituted, there is evidence that it has both motivational and informational effects. Finally, the prediction failure implied by unexpected events sometimes causes a negative feeling, but there is no convincing evidence that this is always the case, and we argue that even if it were so, this would not be a sufficient reason for regarding this feeling as a component, rather than as an effect of surprise.

Dwelling on distractors varying in target-distractor similarity.

Present day models of visual search focus on explaining search efficiency by visual guidance: The target guides attention to the target's position better in more efficient than in less efficient search. The time spent processing the distractor, however, is set to a constant in these models. In contrast to this assumption, recent studies found that dwelling on distractors is longer in more inefficient search. Previous experiments in support of this contention all presented the same distractors across all conditions, while varying the targets. While this procedure has its virtues, it confounds the manipulation of search efficiency with target type. Here we use the same targets over the entire experiment, while varying search efficiency by presenting different types of distractors. Eye fixation behavior was used to infer the amount of distractor dwelling, skipping, and revisiting. The results replicate previous results, with similarity affecting dwelling, and dwelling in turn affecting search performance. A regression analysis confirmed that variations in dwelling account for a large amount of variance in search speed, and that the similarity effect in dwelling accounts for the similarity effect in overall search performance.

Spatio-temporal dynamics of action-effect associations in oculomotor control.

While there is ample evidence that actions are guided by anticipating their effects (ideomotor control) in the manual domain, much less is known about the underlying characteristics and dynamics of effect-based oculomotor control. Here, we address three open issues. 1) Is action-effect anticipation in oculomotor control reflected in corresponding spatial saccade characteristics in inanimate environments? 2) Does the previously reported dependency of action latency on the temporal effect delay (action-effect interval) also occur in the oculomotor domain? 3) Which temporal effect delay is optimally suited to develop strong action-effect associations over time in the oculomotor domain? Participants executed left or right free-choice saccades to peripheral traffic lights, causing an (immediate or delayed) action-contingent light switch in the upper vs. lower part of the traffic light. Results indicated that saccades were spatially shifted toward the location of the upcoming change, indicating anticipation of the effect (location). Saccade latency was affected by effect delay, suggesting that corresponding time information is integrated into event representations. Finally, delayed (vs. immediate) effects were more effective in strengthening action-effect associations over the course of the experiment, likely due to greater saliency of perceptual changes occurring during target fixation as opposed to changes during saccades (saccadic suppression). Overall, basic principles underlying ideomotor control appear to generalize to the oculomotor domain.

Search asymmetries with real faces: testing the anger-superiority effect.

The anger-superiority hypothesis states that angry faces are detected more efficiently than friendly faces. Previously research used schematized stimuli, which minimizes perceptual confounds, but violates ecological validity. The authors argue that a confounding of appearance and meaning is unavoidable and even unproblematic if real faces are presented. Four experiments tested carefully controlled photos in a search-asymmetry design. Experiments 1 and 2 revealed more efficient detection of an angry face among happy faces than vice versa. Experiment 3 indicated that the advantage was due to the mouth, but not to the eyes, and Experiment 4, using upright and inverted thatcherized faces, suggests a perceptual basis. The results are in line with a sensory-bias hypothesis that facial expressions evolved to exploit extant capabilities of the visual system.