Preference for human eyes in human infants

Sensorimotor regulation of facial expression - An untouched frontier

Facial expression is a critical form of nonverbal social communication which promotes emotional exchange and affiliation among humans. Facial expressions are generated via precise contraction of the facial muscles, guided by sensory feedback. While the neural pathways underlying facial motor control are well characterized in humans and primates, it remains unknown how tactile and proprioceptive information reaches these pathways to guide facial muscle contraction. Thus, despite the importance of facial expressions for social functioning, little is known about how they are generated as a unique sensorimotor behavior. In this review, we highlight current knowledge about sensory feedback from the face and how it is distinct from other body regions. We describe connectivity between the facial sensory and motor brain systems, and call attention to the other brain systems which influence facial expression behavior, including vision, gustation, emotion, and interoception. Finally, we petition for more research on the sensory basis of facial expressions, asserting that incomplete understanding of sensorimotor mechanisms is a barrier to addressing atypical facial expressivity in clinical populations.

Maximizing valid eye-tracking data in human and macaque infants by optimizing calibration and adjusting areas of interest

Remote eye tracking with automated corneal reflection provides insights into the emergence and development of cognitive, social, and emotional functions in human infants and non-human primates. However, because most eye-tracking systems were designed for use in human adults, the accuracy of eye-tracking data collected in other populations is unclear, as are potential approaches to minimize measurement error. For instance, data quality may differ across species or ages, which are necessary considerations for comparative and developmental studies. Here we examined how the calibration method and adjustments to areas of interest (AOIs) of the Tobii TX300 changed the mapping of fixations to AOIs in a cross-species longitudinal study. We tested humans (N = 119) at 2, 4, 6, 8, and 14 months of age and macaques (Macaca mulatta; N = 21) at 2 weeks, 3 weeks, and 6 months of age. In all groups, we found improvement in the proportion of AOI hits detected as the number of successful calibration points increased, suggesting calibration approaches with more points may be advantageous. Spatially enlarging and temporally prolonging AOIs increased the number of fixation-AOI mappings, suggesting improvements in capturing infants' gaze behaviors; however, these benefits varied across age groups and species, suggesting different parameters may be ideal, depending on the population studied. In sum, to maximize usable sessions and minimize measurement error, eye-tracking data collection and extraction approaches may need adjustments for the age groups and species studied. Doing so may make it easier to standardize and replicate eye-tracking research findings.

The importance of awareness in face processing: A critical review of interocular suppression studies

Human faces convey essential information for understanding others' mental states and intentions. The importance of faces in social interaction has prompted suggestions that some relevant facial features such as configural information, emotional expression, and gaze direction may promote preferential access to awareness. This evidence has predominantly come from interocular suppression studies, with the most common method being the Breaking Continuous Flash Suppression (bCFS) procedure, which measures the time it takes different stimuli to overcome interocular suppression. However, the procedures employed in such studies suffer from multiple methodological limitations. For example, they are unable to disentangle detection from identification processes, their results may be confounded by participants' response bias and decision criteria, they typically use small stimulus sets, and some of their results attributed to detecting high-level facial features (e.g., emotional expression) may be confounded by differences in low-level visual features (e.g., contrast, spatial frequency). In this article, we review the evidence from the bCFS procedure on whether relevant facial features promote access to awareness, discuss the main limitations of this very popular method, and propose strategies to address these issues.

The adaptive significance of human scleral brightness: an experimental study

Homogeneously depigmented sclerae have long been proposed to be uniquely human-an adaptation to enable cooperative behaviour by facilitating interpersonal coordination through gaze following. However, recent evidence has shown that deeply pigmented sclerae also afford gaze following if surrounding a bright iris. Furthermore, while current scleral depigmentation is clearly adaptive in modern humans, it is less clear how the evolutionarily intermediate stages of scleral pigmentation may have been adaptive. In sum, it is unclear why scleral depigmentation became the norm in humans, while not so in sister species like chimpanzees, or why some extant species display intermediate degrees of pigmentation (as our ancestors presumably did at some point). We created realistic facial images of 20 individually distinct hominins with diverse facial morphologies, each face in the (i) humanlike bright sclera and (ii) generalised apelike dark sclera version. Participants in two online studies rated the bright-sclera hominins as younger, healthier, more attractive and trustworthy, but less aggressive than the dark-sclera hominins. Our results support the idea that the appearance of more depigmented sclerae promoted perceived traits that fostered trust, increasing fitness for those individuals and resulting in depigmentation as a fixed trait in extant humans.

Gaze direction and face orientation modulate perceptual sensitivity to faces under interocular suppression

Faces convey information essential for social interaction. Their importance has prompted suggestions that some facial features may be processed unconsciously. Although some studies have provided empirical support for this idea, it remains unclear whether these findings were due to perceptual processing or to post-perceptual decisional factors. Evidence for unconscious processing of facial features has predominantly come from the Breaking Continuous Flash Suppression (b-CFS) paradigm, which measures the time it takes different stimuli to overcome interocular suppression. For example, previous studies have found that upright faces are reported faster than inverted faces, and direct-gaze faces are reported faster than averted-gaze faces. However, this procedure suffers from important problems: observers can decide how much information they receive before committing to a report, so their detection responses may be influenced by differences in decision criteria and by stimulus identification. Here, we developed a new procedure that uses predefined exposure durations, enabling independent measurement of perceptual sensitivity and decision criteria. We found higher detection sensitivity to both upright and direct-gaze (compared to inverted and averted-gaze) faces, with no effects on decisional factors. For identification, we found both greater sensitivity and more liberal criteria for upright faces. Our findings demonstrate that face orientation and gaze direction influence perceptual sensitivity, indicating that these facial features may be processed unconsciously.

Visual perspective-taking in complex natural scenes

Studies of visual perspective-taking have shown that adults can rapidly and accurately compute their own and other peoples’ viewpoints, but they experience difficulties when the two perspectives are inconsistent. We tested whether these egocentric (i.e., interference from one’s own perspective) and altercentric biases (i.e., interference from another person’s perspective) persist in ecologically valid complex environments. Participants (N = 150) completed a dot-probe visual perspective-taking task, in which they verified the number of discs in natural scenes containing real people, first only according to their own perspective and then judging both their own and another person’s perspective. Results showed that the other person’s perspective did not disrupt self perspective-taking judgements when the other perspective was not explicitly prompted. In contrast, egocentric and altercentric biases were found when participants were prompted to switch between self and other perspectives. These findings suggest that altercentric visual perspective-taking can be activated spontaneously in complex real-world contexts, but is subject to both top-down and bottom-up influences, including explicit prompts or salient visual stimuli.

Automatic gaze to the nose region cannot be inhibited during observation of facial expression in Eastern observers

Humans can extract a great deal of information about others very quickly. This is partly because the face automatically captures observers' attention. Specifically, the eyes can attract overt attention. Although it has been reported that not only the eyes but also the nose can capture initial oculomotor movement in Eastern observers, its generalizability remains unknown. In this study, we applied the "don't look" paradigm wherein participants are asked not to fixate on a specific facial region (i.e., eyes, nose, and mouth) during an emotion recognition task with upright (Experiment 1) and inverted (Experiment 2) faces. In both experiments, we found that participants were less able to inhibit the initial part of their fixations to the nose, which can be interpreted as the nose automatically capturing attention. Along with previous studies, our overt attention tends to be attracted by a part of the face, which is the nose region in Easterner observers.

When novelty prevails on familiarity: Visual biases for child versus infant faces in 3.5- to 12-month-olds

The current study examined the influence of everyday perceptual experience with infant and child faces on the shaping of visual biases for faces in 3.5-, 6-, 9-, and 12-month-old infants. In Experiment 1, infants were presented with pairs of photographs of unfamiliar child and infant faces. Four groups with differential experience with infant and child faces were composed from parents' reports of daily exposure with infants and children (no experience, infant face experience, child face experience, and both infant and child face experience) to assess influence of experience on face preferences. Results showed that infants from all age groups displayed a bias for the novel category of faces in relation to their previous exposure to infant and child faces. In Experiment 2, this pattern of visual attention was reversed in infants presented with pictures of personally familiar child faces (i.e., older siblings) compared with unfamiliar infant faces, especially in older infants. These results suggest that allocation of attention for novelty can supersede familiarity biases for faces depending on experience and highlight that multiple factors drive infant visual behavior in responding to the social world.

Differential sensitivity to species- and race-based information in the development of attention orienting and attention holding face biases in infancy

Experience-based biases in face processing can reflect both attention orienting biases that support efficient selection of faces from competing stimuli and attention holding biases that allow for detailed encoding of selected faces. It is well established that infants demonstrate both species- and race-based biases in attention holding. Fewer studies have found species-based, but not race-based, orienting biases in infancy but these studies examined species- and race-based biases separately and measured overall orienting without examining attention to distractors. The present study directly compared 6- and 11-month-old infants' species- and race-based biases in attention holding and orienting to faces. We measured infants' duration of looking and frequency/speed of orienting to own-race, other-race, and monkey faces in multi-item search arrays, and their frequency of orienting to faces and distractors during search. Infants showed expected species- and race-based biases in attention holding but only a species-based bias in overall orienting. However, they also showed reduced orienting to salient distractors in the context of own-race faces. These results suggest that orienting mechanisms mediating face selection are robustly driven by species information while orienting to faces versus distractors during search may also reflect prior learning about frequently experienced own-race faces.

Face detection in 2- to 6-month-old infants is influenced by gaze direction and species

Humans detect faces efficiently from a young age. Face detection is critical for infants to identify and learn from relevant social stimuli in their environments. Faces with eye contact are an especially salient stimulus, and attention to the eyes in infancy is linked to the emergence of later sociality. Despite the importance of both of these early social skills-attending to faces and attending to the eyes-surprisingly little is known about how they interact. We used eye tracking to explore whether eye contact influences infants' face detection. Longitudinally, we examined 2-, 4-, and 6-month-olds' (N = 65) visual scanning of complex image arrays with human and animal faces varying in eye contact and head orientation. Across all ages, infants displayed superior detection of faces with eye contact; however, this effect varied as a function of species and head orientation. Infants were more attentive to human than animal faces and were more sensitive to eye and head orientation for human faces compared to animal faces. Unexpectedly, human faces with both averted heads and eyes received the most attention. This pattern may reflect the early emergence of gaze following-the ability to look where another individual looks-which begins to develop around this age. Infants may be especially interested in averted gaze faces, providing early scaffolding for joint attention. This study represents the first investigation to document infants' attention patterns to faces systematically varying in their attentional states. Together, these findings suggest that infants develop early, specialized functional conspecific face detection.

Eye Tracking Abnormalities in School-Aged Children With Strabismus and With and Without Amblyopia

PURPOSE

To detect eye tracking abnormalities in children with strabismus in the absence or presence of amblyopia.

METHODS

A total of 100 patients aged 7 to 17 years were enrolled prospectively for 2 years from the pediatric ophthalmology clinic of the American University of Beirut Medical Center: 50 children with strabismus (including 24 with amblyopia) and 50 age- and gender-matched controls. Eye tracking with different paradigms was performed.

RESULTS

Mean age was 10.66 ± 2.90 years in the strabismus group and 10.02 ± 2.75 years in the control group. Demographic characteristics were similar with respect to vision, gender, and refraction. Four paradigms were tested using the eye tracker: (1) distance/near paradigm: patients with strabismus showed a lower fixation count and longer fixation at both distances and a tendency for decreased latency and percentage of fixation in distant elements; (2) reading paradigm: the strabismus group had a higher fixation count and duration, especially those without amblyopia; (3) location identification paradigm: strabismus group without amblyopia fixated less and with shorter duration on the most flagrant element; and (4) video paradigm: no differences in eye movements were noted.

CONCLUSIONS

Significant eye movement deficits were demonstrated in patients with strabismus compared to controls while reading text and identifying prominent elements in a crowded photograph. This was significant in the non-amblyopic subgroup. [J Pediatr Ophthalmol Strabismus. 2019;56(5):297-304.].

How Infants' Arousal Influences Their Visual Search

The influence of arousal on visual attention was examined in 6.5-month-old infants (N = 42) in the context of a visual search task. Phasic increases in arousal were induced with brief sounds and measured with pupil dilation. Evidence was found for an inverted U-shaped relation between pupil dilation amplitude and visual orienting, with highest likelihood of a target fixation at intermediate levels of arousal. Effects were similar for facial stimuli and simple objects. Together, these results contribute to our understanding of the relation between arousal and attention in infancy. The study also demonstrates that infants have a bias to orient to human eyes, even when presented in isolation.

Neural correlates of attentional capture by stimuli previously associated with social reward

Our attention is strongly influenced by reward learning. Stimuli previously associated with monetary reward have been shown to automatically capture attention in both behavioral and neurophysiological studies. Stimuli previously associated with positive social feedback similarly capture attention; however, it is unknown whether such social facilitation of attention relies on similar or dissociable neural systems. Here, we used the value-driven attentional capture paradigm in an fMRI study to identify the neural correlates of attention to stimuli previously associated with social reward. The results reveal learning-dependent priority signals in the contralateral visual cortex, posterior parietal cortex, and caudate tail, similar to studies using monetary reward. An additional priority signal was consistently evident in the right middle frontal gyrus (MFG). Our findings support the notion of a common neural mechanism for directing attention on the basis of selection history that generalizes across different types of reward.

Attention to the face is characterised by a difficult to inhibit first fixation to the eyes

The eyes are preferentially attended over other facial features and recent evidence suggests this bias is difficult to suppress. To further examine the automatic and volitional nature of this bias for eye information, we used a novel prompting face recognition paradigm in 41 adults and measured the location of their first fixations, overall dwell time and behavioural responses. First, patterns of eye gaze were measured during a free-viewing forced choice face recognition paradigm. Second, the task was repeated but with prompts to look to either the eyes or the mouth. Participants showed significantly more first fixations to the eyes than mouth, both when prompted to look at the eyes and when prompted to look at the mouth. The pattern of looking to the eyes when prompted was indistinguishable from the unprompted condition in which participants were free to look where they chose. Notably, the dwell time data demonstrated that the eye bias did not persist over the entire presentation period. Our results suggest a difficult-to-inhibit bias to initially orient to the eyes, which is superseded by volitional, top-down control of eye gaze. Further, the amount of looking to the eyes is at a maximum level spontaneously and cannot be enhanced by explicit instructions.

Social Environment and Epigenetics

Our social environment, from the microscopic to the macro-social, affects us for the entirety of our lives. One integral line of research to examine how interpersonal and societal environments can get "under the skin" is through the lens of epigenetics. Epigenetic mechanisms are adaptations made to our genome in response to our environment which include tags placed on and removed from the DNA itself to how our DNA is packaged, affecting how our genes are read, transcribed, and interact. These tags are affected by social environments and can persist over time; this may aid us in responding to experiences and exposures, both the enriched and the disadvantageous. From memory formation to immune function, the experience-dependent plasticity of epigenetic modifications to micro- and macro-social environments may contribute to the process of learning from comfort, pain, and stress to better survive in whatever circumstances life has in store.

Fearful but not happy expressions boost face detection in human infants

Human adults show an attentional bias towards fearful faces, an adaptive behaviour that relies on amygdala function. This attentional bias emerges in infancy between 5 and 7 months, but the underlying developmental mechanism is unknown. To examine possible precursors, we investigated whether 3.5-, 6- and 12-month-old infants show facilitated detection of fearful faces in noise, compared to happy faces. Happy or fearful faces, mixed with noise, were presented to infants (N = 192), paired with pure noise. We applied multivariate pattern analyses to several measures of infant looking behaviour to derive a criterion-free, continuous measure of face detection evidence in each trial. Analyses of the resulting psychometric curves supported the hypothesis of a detection advantage for fearful faces compared to happy faces, from 3.5 months of age and across all age groups. Overall, our data show a readiness to detect fearful faces (compared to happy faces) in younger infants that developmentally precedes the previously documented attentional bias to fearful faces in older infants and adults.

The Eyes as Windows Into Other Minds

Eyes have been shown to play a key role during human social interactions. However, to date, no comprehensive cross-discipline model has provided a framework that can account for uniquely human responses to eye cues. In this review, I present a framework that brings together work on the phylogenetic, ontogenetic, and neural bases of perceiving and responding to eyes. Specifically, I argue for a two-process model: a first process that ensures privileged attention to information encoded in the eyes and is important for the detection of other minds and a second process that permits the decoding of information contained in the eyes concerning another person's emotional and mental states. To some degree, these processes are unique to humans, emerge during different times in infant development, can be mapped onto distinct but interconnected brain regions, and likely serve critical functions in facilitating cooperative interactions in humans. I also present evidence to show that oxytocin is a key modulator of sensitive responding to eye cues. Viewing eyes as windows into other minds can therefore be considered a hallmark feature of human social functioning deeply rooted in our biology.

Developmental changes in social attention and oxytocin levels in infants and children

Oxytocin (OT) signalling represents one of the most critical systems involved in human social behaviour. Although several studies have examined the relationship between social functioning and peripheral OT levels, the association between OT and the development of social attention has not been well studied. Therefore, we investigated the developmental relationship between gaze fixation for social cues and OT levels during young childhood. We examined visual attention using an eye tracking system in infants and children (5-90 months of age) and measured the concentration of OT in saliva samples. We observed a negative association between age and both attention toward social cues and salivary OT levels, and a positive association between age and attention for non-social cues. We also observed that salivary OT levels were modulated by polymorphisms in oxytocin receptor (OXTR) rs53576. Our results suggest that there is an age-dependent association between visual attention for social cues and OT levels in infants and children, and that the development of visual attention to the eyes as social cues is associated with both OXTR polymorphisms and OT levels. Such findings indicate that OT and OXTR status may provide insight into the atypical development of social attention in infants and young children.

Face recognition impairment in small for gestational age and preterm children

BACKGROUND

Infants born prematurely or with low birth weight are at increased risk of visual perceptual impairment. Face recognition is a high-order visual ability important for social development, which has been rarely assessed in premature or low birth weight children.

AIMS

To evaluate the influence of prematurity and low birth weight on face recognition skills.

METHODS

Seventy-seven children were evaluated as part of a prospective cohort study. They were divided into premature and term birth cohorts. Children with a birth weight below the 10th centile were considered small for gestational age. All children underwent a full ophthalmologic assessment and evaluation of face recognition skills using the Facial Memory subtest from the Test of Memory and Learning.

RESULTS

Premature infants scored worse on immediate face recognition compared to term infants. However, after adjusting for birth weight, prematurity was not associated with worse outcomes. Independent of gestational age, outcomes of low birth weight children were worse than those of appropriate birth weight children, for immediate face recognition (odds ratio [OR], 5.14; 95% confidence interval [CI], 1.32-21.74) and for face memory (OR, 4.48; 95% CI, 1.14-16.95).

CONCLUSIONS

Being born small for gestational age is associated with suboptimal face recognition skills, even in children without major neurodevelopmental problems.

Multiple Measures of Fixation on Social Content in Infancy: Evidence for a Single Social Cognitive Construct?

The preference of infants to fixate on social information in a stimulus is well known. We examine how this preference manifests across a series of free-viewing tasks using different stimulus types. Participants were thirty typically developing infants. We measured eye movements when viewing isolated faces, faces alongside objects in a grid, and faces naturally presented in photographed scenes. In each task, infants fixated social content for longer than nonsocial content. Social preference scores representing distribution of fixation to social versus general image content were highly correlated and thus combined into a single composite measure, which was independent of demographic and behavioral measures. We infer that multiple eye-tracking tasks can be used to generate a composite measure of social preference in infancy. This approach may prove useful in the early characterization of developmental disabilities.

Three-month-old infants' sensitivity to horizontal information within faces

Horizontal information is crucial to face processing in adults. Yet the ontogeny of this preferential type of processing remains unknown. To clarify this issue, we tested 3-month-old infants' sensitivity to horizontal information within faces. Specifically, infants were exposed to the simultaneous presentation of a face and a car presented in upright or inverted orientation while their looking behavior was recorded. Face and car images were either broadband (UNF) or filtered to only reveal horizontal (H), vertical (V) or this combined information (HV). As expected, infants looked longer at upright faces than at upright cars, but critically, only when horizontal information was preserved in the stimulus (UNF, HV, H). These results first indicate that horizontal information already drives upright face processing at 3 months of age. They also recall the importance, for infants, of some facial features, arranged in a top-heavy configuration, particularly revealed by this band of information. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 536-542, 2016.

Efficient human face detection in infancy

Adults detect conspecific faces more efficiently than heterospecific faces; however, the development of this own-species bias (OSB) remains unexplored. We tested whether 6- and 11-month-olds exhibit OSB in their attention to human and animal faces in complex visual displays with high perceptual load (25 images competing for attention). Infants (n = 48) and adults (n = 43) passively viewed arrays containing a face among 24 non-face distractors while we measured their gaze with remote eye tracking. While OSB is typically not observed until about 9 months, we found that, already by 6 months, human faces were more likely to be detected, were detected more quickly (attention capture), and received longer looks (attention holding) than animal faces. These data suggest that 6-month-olds already exhibit OSB in face detection efficiency, consistent with perceptual attunement. This specialization may reflect the biological importance of detecting conspecific faces, a foundational ability for early social interactions.

Developmental changes in face visual scanning in autism spectrum disorder as assessed by data-based analysis

Individuals with autism spectrum disorder (ASD) present reduced visual attention to faces. However, contradictory conclusions have been drawn about the strategies involved in visual face scanning due to the various methodologies implemented in the study of facial screening. Here, we used a data-driven approach to compare children and adults with ASD subjected to the same free viewing task and to address developmental aspects of face scanning, including its temporal patterning, in healthy children, and adults. Four groups (54 subjects) were included in the study: typical adults, typically developing children, and adults and children with ASD. Eye tracking was performed on subjects viewing unfamiliar faces. Fixations were analyzed using a data-driven approach that employed spatial statistics to provide an objective, unbiased definition of the areas of interest. Typical adults expressed a spatial and temporal strategy for visual scanning that differed from the three other groups, involving a sequential fixation of the right eye (RE), left eye (LE), and mouth. Typically developing children, adults and children with autism exhibited similar fixation patterns and they always started by looking at the RE. Children (typical or with ASD) subsequently looked at the LE or the mouth. Based on the present results, the patterns of fixation for static faces that mature from childhood to adulthood in typical subjects are not found in adults with ASD. The atypical patterns found after developmental progression and experience in ASD groups appear to remain blocked in an immature state that cannot be differentiated from typical developmental child patterns of fixation.

Face perception and processing in early infancy: inborn predispositions and developmental changes

From birth it is critical for our survival to identify social agents and conspecifics. Among others stimuli, faces provide the required information. The present paper will review the mechanisms subserving face detection and face recognition, respectively, over development. In addition, the emergence of the functional and neural specialization for face processing as an experience-dependent process will be documented. Overall, the present work highlights the importance of both inborn predispositions and the exposure to certain experiences, shortly after birth, to drive the system to become functionally specialized to process faces in the first months of life.

Evolutionary relevance and experience contribute to face discrimination in infant macaques (Macaca mulatta)

In human children and adults, familiar face types-typically own-age and own-species faces-are discriminated better than other face types; however, human infants do not appear to exhibit an own-age bias, but instead better discriminate adult faces, which they see more often. There are two possible explanations for this pattern: Perceptual attunement, which predicts advantages in discrimination for the most-experienced face types; additionally or alternatively, there may be an experience-independent bias for infants to discriminate own-species faces, an adaptation for evolutionarily relevant faces. These possibilities have not been disentangled in studies thus far, which did not control infants' early experiences with faces. In the present study, we tested these predictions in infant macaques (Macaca mulatta) reared under controlled environments, not exposed to adult conspecifics. We measured newborns' (15-25 days; n = 27) and 6- to 7-month-olds' (n = 35) discrimination of human and macaque faces of three ages-young infants, old infants, and adults-in a visual paired comparison task. We found that 6- to 7-month-olds were the best at discriminating adult macaque faces; however, in the first few seconds of looking, additionally discriminated familiar face types-same-aged peer and adult human faces-highlighting the importance of experience with certain face categories. The present data suggest that macaque infants possess both experience-independent and experientially tuned face biases. In human infants, early face skills may likewise be driven by both experience and evolutionary relevance; future studies should consider both of these factors.

Can human eyes prevent perceptual narrowing for monkey faces in human infants?

Perceptual narrowing has been observed in human infants for monkey faces: 6-month-olds can discriminate between them, whereas older infants from 9 months of age display difficulty discriminating between them. The difficulty infants from 9 months have processing monkey faces has not been clearly identified. It could be due to the structural characteristics of monkey faces, particularly the key facial features that differ from human faces. The current study aimed to investigate whether the information conveyed by the eyes is of importance. We examined whether the presence of Caucasian human eyes in monkey faces allows recognition to be maintained in 6-month-olds and facilitates recognition in 9- and 12-month-olds. Our results revealed that the presence of human eyes in monkey faces maintains recognition for those faces at 6 months of age and partially facilitates recognition of those faces at 9 months of age, but not at 12 months of age. The findings are interpreted in the context of perceptual narrowing and suggest that the attenuation of processing of other-species faces is not reversed by the presence of human eyes.

Photographic but not line-drawn faces show early perceptual neural sensitivity to eye gaze direction

Our brains readily decode facial movements and changes in social attention, reflected in earlier and larger N170 event-related potentials (ERPs) to viewing gaze aversions vs. direct gaze in real faces (Puce et al., 2000). In contrast, gaze aversions in line-drawn faces do not produce these N170 differences (Rossi et al., 2014), suggesting that physical stimulus properties or experimental context may drive these effects. Here we investigated the role of stimulus-induced context on neurophysiological responses to dynamic gaze. Sixteen healthy adults viewed line-drawn and real faces, with dynamic eye aversion and direct gaze transitions, and control stimuli (scrambled arrays and checkerboards) while continuous electroencephalographic (EEG) activity was recorded. EEG data from 2 temporo-occipital clusters of 9 electrodes in each hemisphere where N170 activity is known to be maximal were selected for analysis. N170 peak amplitude and latency, and temporal dynamics from Event-Related Spectral Perturbations (ERSPs) were measured in 16 healthy subjects. Real faces generated larger N170s for averted vs. direct gaze motion, however, N170s to real and direct gaze were as large as those to respective controls. N170 amplitude did not differ across line-drawn gaze changes. Overall, bilateral mean gamma power changes for faces relative to control stimuli occurred between 150–350 ms, potentially reflecting signal detection of facial motion. Our data indicate that experimental context does not drive N170 differences to viewed gaze changes. Low-level stimulus properties, such as the high sclera/iris contrast change in real eyes likely drive the N170 changes to viewed aversive movements.

Current Understanding of What Infants See

The current understanding of what infants see varies greatly among healthcare and education specialists. Even among ophthalmologists and pediatric neurologists in charge of clinical examinations of infants, opinions vary on what infants perceive, recognize, and use for communication and learning. It is, therefore, of interest to review publications from several specialties to learn whether new information is available on the development of visual functions and use of vision. Ten percent of total publications on this subject are reviewed here based on the usefulness of their content for improving early diagnosis and intervention of vision disorders in infants.