Is there a 'zone of eye contact' within the borders of the face?

Eye contact is a salient feature of everyday interactions, yet it is not obvious what the physical conditions are under which we feel that we have eye contact with another person. Here we measure the range of locations that gaze can fall on a person's face to elicit a sense of eye contact. Participants made judgements about eye contact while viewing rendered images of faces with finely-varying gaze direction at a close interpersonal distance (50 cm). The 'zone of eye contact' tends to peak between the two eyes and is often surprisingly narrower than the observer's actual eye region. Indeed, the zone tends to extend further across the face in height than in width. This shares an interesting parallel with the 'cyclopean eye' of visual perspective - our sense of looking out from a single point in space despite the physical separation of our two eyes. The distribution of eye-contact strength across the face can be modelled at the individual-subject level as a 2D Gaussian function. Perception of eye contact is more precise than the sense of having one's face looked at, which captures a wider range of gaze locations in both the horizontal and vertical dimensions, at least at the close viewing distance used in the present study. These features of eye-contact perception are very similar cross-culturally, tested here in Australian and Japanese university students. However, the shape and position of the zone of eye contact does vary depending on recent sensory experience: adaptation to faces with averted gaze causes a pronounced shift and widening of the zone across the face, and judgements about eye contact also show a positive serial dependence. Together, these results provide insight into the conditions under which eye contact is felt, with respect to face morphology, culture, and sensory context.

A sparkle in the eye: Illumination cues and lightness constancy in the perception of eye contact.

In social interactions, our sense of when we have eye contact with another person relies on the distribution of luminance across their eye region, reflecting the position of the darker iris within the lighter sclera of the human eye. This distribution of luminance can be distorted by the lighting conditions, consistent with the fundamental challenge that the visual system faces in distinguishing the nature of a surface from the pattern of light falling upon it. Here we perform a set of psychophysics experiments in human observers to investigate how illumination impacts on the perception of eye contact. First, we find that simple changes in the direction of illumination can produce systematic biases in our sense of when we have eye contact with another person. Second, we find that the visual system uses information about the lighting conditions to partially discount or 'explain away' the effects of illumination in this context, leading to a significantly more robust sense of when we have eye contact with another person. Third, we find that perceived eye contact is affected by specular reflections from the eye surface in addition to shading patterns, implicating eye glint as a potential cue to gaze direction. Overall, this illustrates how our interpretation of social signals relies on visual mechanisms that both compensate for the effects of illumination on retinal input and potentially exploit novel cues that illumination can produce.

Comprehensive assessment of handwashing and faecal contamination among elementary school children in an urban slum of Indonesia.

OBJECTIVE: Globally, the challenge of handwashing with soap (HWWS) still exists despite the importance of HWWS being shown previously. This study aimed to evaluate faecal contamination on the hands of children and to find factors related to faecal contamination from handwashing techniques, HWWS, knowledge and awareness of water, sanitation, and hygiene (WASH), and a comprehensive WASH index. METHODS: The study was conducted at two elementary schools with 169 children in a densely populated area of Bandung, Indonesia. The survey involved handwashing observation using a checklist, hand bacteria sampling and questionnaires. RESULTS: Most children (98.7%) had faecal contamination. Girls had significantly fewer Escherichia coli than boys (P < 0.05). Ability in handwashing techniques, HWWS, and knowledge and awareness of WASH were poor in the lower grades. Escherichia coli counts were negatively correlated with handwashing technique (r = -0.171, P < 0.05), HWWS (r = -0.225, P < 0.01) and the WASH index (r = -0.205, P < 0.05). CONCLUSIONS: Proper handwashing technique and HWWS at appropriate times can reduce faecal contamination. Moreover, it is important that both grade-based and gender-based handwashing education be considered in elementary school education.

OBJECTIF: A l'échelle mondiale, le défi du lavage des mains au savon (HWWS) existe toujours, en dépit de l'importance révélée de ce procédé. Cette étude visait à évaluer la contamination fécale sur les mains des enfants et à trouver des facteurs liés à la contamination fécale résultant des procédés de lavage des mains, du lavage des mains au savon, de la connaissance et de la sensibilisation à l'eau, aux sanitaires et à l'hygiène (WASH), ainsi qu'un indice WASH détaillé. MÉTHODES: L'étude a été menée dans deux écoles élémentaires avec 169 enfants dans une zone densément peuplée de Bandung, en Indonésie. L'enquête comprenait l'observation du lavage des mains à l'aide d'une liste de contrôle, un échantillonnage bactérien sur les mains et des questionnaires. RÉSULTATS: La plupart des enfants (98,7%) avaient une contamination fécale. Escherichia coli était nettement moins présent chez les filles que chez les garçons (p <0,05). L'aptitude dans les techniques de lavage des mains, le lavage des mains au savon, ainsi que la connaissance et la sensibilisation au WASH étaient faibles dans les classes inférieures. Les comptages d'E. Coli corrélaient négativement avec la technique de lavage des mains (r = -0,171 ; p <0,05), le lavage des mains au savon (r = 0,225 ; p <0,01) et l'indice WASH (r= - 0,205 ; p <0,05). CONCLUSIONS: Une technique de lavage des mains appropriée et un lavage des mains au savon à des moments opportuns peuvent réduire la contamination fécale. De plus, il est important de prendre en compte l'éducation au lavage des mains basée sur le niveau et le sexe dans l'enseignement primaire.

Risk Factors for Undernutrition and Diarrhea Prevalence in an Urban Slum in Indonesia: Focus on Water, Sanitation, and Hygiene.

Unsafe drinking water and poor sanitation and hygiene lead to deterioration of the child health condition in low- and middle-income countries. This study aimed to evaluate the nutritional and health status of children living in an urban slum and to clarify the factors contributing to undernutrition and diarrhea prevalence by focusing on water, sanitation, and hygiene from three viewpoints: household environments, child personal hygiene practices, and knowledge and awareness. The study was conducted at a preschool and two elementary schools in the densely populated area of Bandung, Indonesia. Participants were 228 pairs of children and their caretakers. The survey involved 1) anthropometric measurements (height and weight), 2) handwashing observation using a checklist, and 3) questionnaires. On multivariate logistic regression analysis, not using a towel for handwashing practices (adjusted odds ratio [AOR] = 2.37; 95% confidence interval [CI] = 1.13-4.96) was significantly associated with an increased risk of stunting. Regarding household environments, children from households using tap water as drinking water were significantly associated with an increased risk of stunting and thinness compared with households using tank water (AOR = 2.26; 95% CI = 1.03-4.93; and AOR = 2.88; 95% CI = 1.13-7.35, respectively). Moreover, children from households using open containers for water storage were significantly associated with an increased risk of diarrhea (AOR = 5.01; 95% CI = 1.08-23.15). Therefore, drinking water management at home and proper personal hygiene practices of children are important for maintaining and promoting child health in urban Indonesian slums.

Influence of head orientation on perceived gaze direction and eye-region information.

Using synthetic 3D head and eye models, we examined the relationship between perceived gaze direction and the information within the image eye region across changes in head orientation. For each stimulus head and eye orientation, we rendered gray-scale images with realistic pigmentation and shading, and two-tone images depicting the regions corresponding to the iris, pupil, or eye-opening. Behavioural experiments using the gray-scale images as stimuli showed that perceived gaze direction was more strongly biased opposite to head orientation (repulsive effect) in the far-eye visible condition than in the near-eye visible condition. This trend occurred regardless of whether or not the whole face was visible, suggesting that the repulsive effect arose based on eye-region information. Consistent with this, geometrical analysis of the image eye region using the two-tone images revealed that the relative position of the iris and pupil of the far eye shifted opposite to head orientation more than that of the near eye. In addition, our findings regarding the pattern of the influence of head orientation suggest that estimation of the relative iris/pupil position may be achieved through a process of amodal completion of the whole iris behind the eyelid. Additional geometrical analysis of simulated images revealed situations where a greater repulsive effect for the far eye, as found here, is likely to be observed.

Biases in perceiving gaze vergence.

The focus of another person's gaze is an important cue in social interactions, helping us to understand others' intentions, predict their behavior, and allocate our own attention appropriately. The perception of gaze vergence provides information about the distance at which another person is fixating, but has yet to receive much empirical attention. Here, we report that observers display systematic biases when perceiving others' gaze vergence and depth of fixation. Specifically, they perceive others as having convergent gaze and fixating at closer distances, especially when gaze is directed downward or observed under conditions of sensory uncertainty. These biases may reflect the predominance of convergent over divergent gaze in everyday social interactions and implicit knowledge of the physical structure of the environment, in which objects below our line of sight are typically closer. These findings demonstrate the sophistication of social vision, in which our visual perception of others is shaped by statistical regularities, and help to establish the perception of others' gaze vergence and fixation distance as a subject of psychological investigation. (PsycINFO Database Record

Testing the dual-route model of perceived gaze direction: Linear combination of eye and head cues.

We have recently proposed a dual-route model of the effect of head orientation on perceived gaze direction (Otsuka, Mareschal, Calder, & Clifford, 2014; Otsuka, Mareschal, & Clifford, 2015), which computes perceived gaze direction as a linear combination of eye orientation and head orientation. By parametrically manipulating eye orientation and head orientation, we tested the adequacy of a linear model to account for the effect of horizontal head orientation on perceived direction of gaze. Here, participants adjusted an on-screen pointer toward the perceived gaze direction in two image conditions: Normal condition and Wollaston condition. Images in the Normal condition included a change in the visible part of the eye along with the change in head orientation, while images in the Wollaston condition were manipulated to have identical eye regions across head orientations. Multiple regression analysis with explanatory variables of eye orientation and head orientation revealed that linear models account for most of the variance both in the Normal condition and in the Wollaston condition. Further, we found no evidence that the model with a nonlinear term explains significantly more variance. Thus, the current study supports the dual-route model that computes the perceived gaze direction as a linear combination of eye orientation and head orientation.

Wollaston's effect in infants: Do infants integrate eye and head information in gaze perception?

The current study examined infants' sensitivity to Wollaston's effect: When identical eyes are placed in differently angled faces, the perceived gaze direction shifts toward the orientation of the face such that physically, the direct gaze is perceived as averted toward the orientation of the face. Consistent with Wollaston's effect, we found that looking toward direct and averted gaze by 4- to 5- and 7- to 8-month-olds (n = 40) was affected by the head orientation context. These results demonstrate that infants aged 4 to 5 and 7 to 8 months integrate eye and head information to perceive another's gaze direction. In light of recent psychophysical findings, the current results suggest that the visual function supporting constant gaze perception across head rotation is already at work by 4 to 5 months of age.

Who are you expecting? Biases in face perception reveal prior expectations for sex and age.

A person's appearance contains a wealth of information, including indicators of their sex and age. Because first impressions can set the tone of subsequent relationships, it is crucial we form an accurate initial impression. Yet prior expectation can bias our decisions: Studies have reported biases to respond "male" when asked to report a person's sex from an image of their face and to place their age closer to their own. Perceptual expectation effects and cognitive response biases may both contribute to these inaccuracies. The current research used a Bayesian modeling approach to establish the perceptual biases involved when estimating the sex and age of an individual from their face. We demonstrate a perceptual bias for male and older faces evident under conditions of uncertainty. This suggests the well-established male bias is perceptual in origin and may be impervious to cognitive control. In comparison, the own age anchor effect is not operationalized at the perceptual level: The perceptual expectation is for a face of advanced age. Thus, distinct biases in the estimation of age operate at the perceptual and cognitive levels.

"Are you looking at me?" How children's gaze judgments improve with age.

Adults' judgments of another person's gaze reflect both sensory (e.g., perceptual) and nonsensory (e.g., decisional) processes. We examined how children's performance on a gaze categorization task develops over time by varying uncertainty in the stimulus presented to 6- to 11- year-olds (n = 57). We found that younger children responded "direct" over a wider range of gaze deviations. We also found that increasing uncertainty led to an increase in direct responses, across all age groups. A simple model to account for these data revealed that although younger children had a noisier sensory representation of the stimulus, most developmental changes in gaze were because of a change in children's response criteria (category boundaries). These results suggest that although the core mechanisms for gaze processing are already in place by the age of 6, their development continues across the whole of childhood. (PsycINFO Database Record

Face Orientation and Motion Differently Affect the Deployment of Visual Attention in Newborns and 4-Month-Old Infants.

Orienting visual attention allows us to properly select relevant visual information from a noisy environment. Despite extensive investigation of the orienting of visual attention in infancy, it is unknown whether and how stimulus characteristics modulate the deployment of attention from birth to 4 months of age, a period in which the efficiency in orienting of attention improves dramatically. The aim of the present study was to compare 4-month-old infants' and newborns' ability to orient attention from central to peripheral stimuli that have the same or different attributes. In Experiment 1, all the stimuli were dynamic and the only attribute of the central and peripheral stimuli to be manipulated was face orientation. In Experiment 2, both face orientation and motion of the central and peripheral stimuli were contrasted. The number of valid trials and saccadic latency were measured at both ages. Our results demonstrated that the deployment of attention is mainly influenced by motion at birth, while it is also influenced by face orientation at 4-month of age. These findings provide insight into the development of the orienting visual attention in the first few months of life and suggest that maturation may be not the only factor that determines the developmental change in orienting visual attention from birth to 4 months.

Gaze constancy in upright and inverted faces.

The dual-route model (Otsuka, Mareschal, Calder, & Clifford, 2014) posits that constancy in the perception of gaze direction across lateral head rotation depends on the integration of information from the eye region and information about head rotation. Incorporation of information about head rotation serves to compensate for the change in eye-region information when viewing a rotated head. We tested the ability of this model to predict the magnitude of Wollaston's effect: When eyes from a frontal pose are inserted into an angled face, the perceived direction of gaze appears attracted towards the direction of the head. The framework of the dual-route model explains Wollaston's effect as a result of the misapplication of this same integration operation without any change in eye-region information. To test this explanation, we compared the magnitude of the integration occurring for Wollaston's effect to that for normal faces. Here, participants performed categorical judgment of gaze direction across head rotation poses in three image conditions: normal face, eyes-only, and Wollaston. Integration of eye and head information was inferred by comparing the effect of pose between the eyes-only condition and the normal face condition, and by examining the effect of pose in the Wollaston condition. Consistent with the dual-route model, the magnitude of integration was similar between the normal face condition and the Wollaston condition. Further, upright and inverted faces yielded similar levels of gaze constancy, showing that the dual-route model applies to the perception of gaze direction in inverted faces as well as in upright faces.

A generalized tendency toward direct gaze with uncertainty.

Joint gaze behavior plays a crucial role in nonverbal communication and enhances group interactions. We recently reported that under conditions of uncertainty, observers assume that another person's (left/right averted) gaze is directed towards them, a prior for direct gaze. Given that people's gaze can deviate in many directions during social interactions, we developed a versatile method to examine how the influence of the prior for direct gaze varies across a range of gaze directions in both forward facing and rotated heads. We find that observers tend to report another's gaze along all axes as being more direct when uncertainty is introduced by adding noise to the stimulus. We also find that the influence of the prior is stronger in rotated heads than direct (forward) heads. This is consistent with the idea that, when uncertain, humans tend to judge gaze deviations as being directed at them, regardless of head rotation or axis of deviation.

The processing of faces across non-rigid facial transformation develops at 7 month of age: a fNIRS-adaptation study.

BACKGROUND: Using near-infrared spectroscopy (NIRS), our previous neural adaptation studies found that infants' bilateral temporal regions process facial identity (FiHN 5:153, 2011). In addition, we revealed that size-invariant processing of facial identity develops by 5 months of age (NR 23:984-988, 2012), while view-invariant processing develops around 7 months of age (FiHN 5:153, 2011). The aim in the current study was to examine whether infants' brains process facial identity across the non-rigid transformation of facial features by using the neural adaptation paradigm. We used NIRS to compare hemodynamic changes in the bilateral temporal areas of 5- to 6-month-olds and 7- to 8-month-olds during presentations of an identical face and of different faces. RESULTS: We found that (1) the oxyhemoglobin concentration around the T5 and T6 positions increased significantly during the presentation of different faces only in 7- to 8-month-olds and (2) 7- to 8-month-olds, but not 5- to 6-month-olds, showed attenuation in these channels to the presentation of the same face rather than to the presentation of different faces, regardless of non-rigid changes in facial features. CONCLUSIONS: Our results suggest that the processing of facial identity with non-rigid facial transformation develops around 7 months after birth.

Dual-route model of the effect of head orientation on perceived gaze direction.

Previous studies on gaze perception have identified 2 opposing effects of head orientation on perceived gaze direction-1 repulsive and the other attractive. However, the relationship between these 2 effects has remained unclear. By using a gaze categorization task, the current study examined the effect of head orientation on the perceived direction of gaze in a whole-head condition and an eye-region condition. We found that the perceived direction of gaze was generally biased in the opposite direction to head orientation (a repulsive effect). Importantly, the magnitude of the repulsive effect was more pronounced in the eye-region condition than in the whole-head condition. Based on these findings, we developed a dual-route model, which proposes that the 2 opposing effects of head orientation occur through 2 distinct routes. In the framework of this dual-route model, we explain and reconcile the findings from previous studies, and provide a functional account of attractive and repulsive effects and their interaction.

Temporal dynamics of spatial frequency processing in infants.

The current study examined the temporal dynamics of coarse and fine spatial information processing in 7- to 8-month-old infants. The ability to discriminate between spatially filtered images was assessed by measuring infants' spontaneous preference for a changing over no-changing image sequences. In Experiments 1 and 2, we found that infants were able to discriminate between low spatial frequency (LSF) image sequences at shorter durations (150 ms) than was the case with high spatial frequency (HSF) images (300 ms). When the LSF and HSF changes were pitted against each other in hybrid images containing both spatial frequencies (Experiment 3), the 7- to 8-month-old infants showed a preference for the LSF change across all tested durations (150 ms to 600 ms). However, infants' processing of hybrid image sequences was modulated both by changes in the relative contrast energy between LSFs and HSFs (Experiment 4), and image duration (Experiment 5). Finally, we found that in 12- to 13-month-old infants, the shift toward HSF dominance occurred at shorter duration than in 7- to 8-month-old infants (Experiment 6). Our findings are among the first to provide a temporal characterization of coarse-to-fine processing in infants' perception. Possible links to the development of specialized visual pathways are discussed.

Contrast reversal of the eyes impairs infants' face processing: a near-infrared spectroscopic study.

Human can easily detect other's eyes and gaze from early in life. Such sensitivity is supported by the contrast polarity of human eyes, which have a white sclera contrasting with the darker colored iris (Kobayashi & Kohshima, (1997). Nature, 387, 767-768; Kobayashi & Kohshima, (2001). Journal of Human Evolution, 40, 419-435). Recent studies suggest that the contrast polarity around the eyes plays an important role in infants' face processing. Newborns preferred upright face images to inverted ones in contrast-preserved faces, but not in contrast-reversed faces (Farroni et al., (2005). Proceedings of National Academy of Sciences of the United States of America, 102, p. 17245-17250). Seven- to 8-month-old infants failed to discriminate between faces when the contrast polarity of eyes was reversed (Otsuka et al., (2013). Journal of Experimental Child Psychology, 115, 598-606). Neuroimaging study with adults revealed that full-negative faces induced less activation in the right fusiform gyrus than either full-positive faces or negative faces with contrast-preserved eyes (Gilad et al., (2009). Proceedings of National Academy of Sciences of the United States of America, 106, p. 5353-5358). In the present study, we investigated whether contrast-reversed eyes diminish infants' brain activity related to face processing. We measured hemodynamic responses in the bilateral temporal area of 5- to 6-month-old infants. Their hemodynamic responses to faces with positive eyes and those with negative eyes were compared against the baseline activation during the presentation of object images. We found that the presentation of faces with positive eyes increased the concentration of oxy-Hb in the right temporal area and those of total-Hb in the bilateral temporal areas. No such change occurred for faces with negative eyes. Our results suggest the importance of contrast polarity of the eyes in the face-selective neural responses from early development.

Eye contrast polarity is critical for face recognition by infants.

Just as faces share the same basic arrangement of features, with two eyes above a nose above a mouth, human eyes all share the same basic contrast polarity relations, with a sclera lighter than an iris and a pupil, and this is unique among primates. The current study examined whether this bright-dark relationship of sclera to iris plays a critical role in face recognition from early in development. Specifically, we tested face discrimination in 7- and 8-month-old infants while independently manipulating the contrast polarity of the eye region and of the rest of the face. This gave four face contrast polarity conditions: fully positive condition, fully negative condition, positive face with negated eyes ("negative eyes") condition, and negated face with positive eyes ("positive eyes") condition. In a familiarization and novelty preference procedure, we found that 7- and 8-month-olds could discriminate between faces only when the contrast polarity of the eyes was preserved (positive) and that this did not depend on the contrast polarity of the rest of the face. This demonstrates the critical role of eye contrast polarity for face recognition in 7- and 8-month-olds and is consistent with previous findings for adults.

Size-invariant representation of face in infant brain: an fNIRS-adaptation study.

We studied whether 5-month-old to 8-month-old infants process faces in a size-invariant manner by applying the fNIRS-adaptation paradigm used in our previous study. We used near-infrared spectroscopy to measure hemodynamic responses in the temporal regions of infants' brains during the repeated presentation of an identical face and different faces while changing the size of the faces. As a result, we found that (a) the hemodynamic responses in the channels around the T5 and T6 positions increased significantly during the presentation of different faces and (b) the hemodynamic responses in these channels showed attenuation to the presentation of the same face compared with the presentation of different faces even when the size of the faces altered. Our findings indicated that infants could show adaptation to the same face despite size alterations and that this processing occurred in the bilateral temporal areas.

Molecular arrangement and assembly guided by hydrophobic cavities inside DNA.

DNA is a unique yet useful material to organize nanoscale molecular arrays along the helix axis. In this study, we demonstrate a useful approach for creating molecular arrays inside a double helical DNA. Our approach is based on a host-guest system. Introducing abasic sites into DNA afforded a hydrophobic cavity that serves as a host. A planar aromatic molecule (cationic perylenediimide, PDI) was used as the guest molecule. In an aqueous solution, the PDI molecules tend to aggregate with themselves due to the strong hydrophobicity. In the presence of DNA with the cavity, the binding of the PDI was found to site-specifically occur in the hydrophobic cavity. The unique assembly and arrangement for more than two PDI molecules was achieved by controlling the sizes and positions of the cavities. Our approach would provide a simple and convenient way to construct one-dimensional aromatic arrays in DNA.