The slow emergence of gaze- and point-following: A longitudinal study of infants from 4 to 12 months

Acquisition of visual attention-following skills, notably gaze- and point-following, contributes to infants' ability to share attention with caregivers, which in turn contributes to social learning and communication. However, the development of gaze- and point-following in the first 18 months remains controversial, in part because of different testing protocols and standards. To address this, we longitudinally tested N = 43 low-risk, North American middle-class infants' tendency to follow gaze direction, pointing gestures, and gaze-and-point combinations. Infants were tested monthly from 4 to 12 months of age. To control motivational differences, infants were taught to expect contingent reward videos in the target locations. No-cue trials were included to estimate spontaneous target fixation rates. A comparison sample (N = 23) was tested at 9 and 12 months to estimate practice effects. Results showed gradual increases in both gaze- and point-following starting around 7 months, and modest month-to-month individual stability from 8 to 12 months. However, attention-following did not exceed chance levels until after 6 months. Infants rarely followed cues to locations behind them, even at 12 months. Infants followed combined gaze-and-point cues more than gaze alone, and followed points at intermediate levels (not reliably different from the other cues). The comparison group's results showed that practice effects did not explain the age-related increase in attention-following. The results corroborate and extend previous findings that North American middle-class infants' attention-following in controlled laboratory settings increases slowly and incrementally between 6 and 12 months of age. RESEARCH HIGHLIGHTS: A longitudinal experimental study documented the emergence and developmental trajectories of North American middle-class infants' visual attention-following skills, including gaze-following, point-following, and gaze-and-point-following. A new paradigm controlled for factors including motivation, attentiveness, and visual-search baserates. Motor development was ruled out as a predictor or limiter of the emergence of attention-following. Infants did not follow attention reliably until after 6 months, and following increased slowly from 7 to 12 months. Infants' individual trajectories showed modest month-to-month stability from 8 to 12 months of age.

Remote, tablet-based assessment of gaze following: a nationwide infant twin study

Introduction

Much of our understanding of infant psychological development relies on an in-person, laboratory-based assessment. This limits research generalizability, scalability, and equity in access. One solution is the development of new, remotely deployed assessment tools that do not require real-time experimenter supervision.

Methods

The current nationwide (Sweden) infant twin study assessed participants remotely via their caregiver's tablets (N = 104, ages 3 to 17 months). To anchor our findings in previous research, we used a gaze-following task where experimental and age effects are well established.

Results

Closely mimicking results from conventional eye tracking, we found that a full head movement elicited more gaze following than isolated eye movements. Furthermore, predictably, we found that older infants followed gaze more frequently than younger infants. Finally, while we found no indication of genetic contributions to gaze-following accuracy, the latency to disengage from the gaze cue and orient toward a target was significantly more similar in monozygotic twins than in dizygotic twins, an indicative of heritability.

Discussion

Together, these results highlight the potential of remote assessment of infants' psychological development, which can improve generalizability, inclusion, and scalability in developmental research.

Individual differences in gaze-cuing effect are associated with facial emotion recognition and social conformity

Spontaneous gaze following and the concomitant joint attention enable us to share representations of the world with others, which forms a foundation of a broad range of social cognitive processes. Although this form of social orienting has long been suggested as a critical starting point for the development of social and communicative behavior, there is limited evidence directly linking it to higher-level social cognitive processes among healthy adults. Here, using a gaze-cuing paradigm, we examined whether individual differences in gaze following tendency predict higher-order social cognition and behavior among healthy adults. We found that individuals who showed greater gaze-cuing effect performed better in recognizing others' emotion and had greater tendency to conform with group opinion. These findings provide empirical evidence supporting the fundamental role of low-level socio-attentional processes in human sociality.

Inferential eye movement control while following dynamic gaze

Attending to other people's gaze is evolutionary important to make inferences about intentions and actions. Gaze influences covert attention and triggers eye movements. However, we know little about how the brain controls the fine-grain dynamics of eye movements during gaze following. Observers followed people's gaze shifts in videos during search and we related the observer eye movement dynamics to the time course of gazer head movements extracted by a deep neural network. We show that the observers' brains use information in the visual periphery to execute predictive saccades that anticipate the information in the gazer's head direction by 190-350ms. The brain simultaneously monitors moment-to-moment changes in the gazer's head velocity to dynamically alter eye movements and re-fixate the gazer (reverse saccades) when the head accelerates before the initiation of the first forward gaze-following saccade. Using saccade-contingent manipulations of the videos, we experimentally show that the reverse saccades are planned concurrently with the first forward gaze-following saccade and have a functional role in reducing subsequent errors fixating on the gaze goal. Together, our findings characterize the inferential and functional nature of social attention's fine-grain eye movement dynamics.

Can the robot "see" what I see? Robot gaze drives attention depending on mental state attribution

Mentalizing, where humans infer the mental states of others, facilitates understanding and interaction in social situations. Humans also tend to adopt mentalizing strategies when interacting with robotic agents. There is an ongoing debate about how inferred mental states affect gaze following, a key component of joint attention. Although the gaze from a robot induces gaze following, the impact of mental state attribution on robotic gaze following remains unclear. To address this question, we asked forty-nine young adults to perform a gaze cueing task during which mental state attribution was manipulated as follows. Participants sat facing a robot that turned its head to the screen at its left or right. Their task was to respond to targets that appeared either at the screen the robot gazed at or at the other screen. At the baseline, the robot was positioned so that participants would perceive it as being able to see the screens. We expected faster response times to targets at the screen the robot gazed at than targets at the non-gazed screen (i.e., gaze cueing effect). In the experimental condition, the robot's line of sight was occluded by a physical barrier such that participants would perceive it as unable to see the screens. Our results revealed gaze cueing effects in both conditions although the effect was reduced in the occluded condition compared to the baseline. These results add to the expanding fields of social cognition and human-robot interaction by suggesting that mentalizing has an impact on robotic gaze following.

Interpersonal matching of autistic trait levels in typically developed individuals is associated with spontaneous gaze following and initiation during face-to-face social interaction

OBJECTIVES

People with autism spectrum disorders (ASD) usually exhibit typical behaviours and thoughts that are called autistic traits. Autistic traits are widely and continuously distributed among typically developed (TD) and ASD populations. Previous studies have found that people with ASD have difficulty in following the eye gaze of social peers. However, it remains unknown whether TD adults with high or low autistic traits also differ in spontaneous gaze following and initiation in face-to-face social interactions. To fill this gap, this study used a novel and naturalistic gaze-cueing paradigm to examine this research question.

DESIGN

A 4 (group: high-high, high-low, low-high or low-low autistic traits) × 3 (congruency: congruent, neutral, or incongruent) mixed-measures design was used.

METHODS

Typically developed adults who were high or low in autistic traits completed a visual search task while a confederate who was high or low in autistic traits sat facing them. Critically, the match of autistic traits within a participant-confederate pair was manipulated. The confederate gazed at (congruent) or away from (incongruent) the location of the target prior to the appearance of the target. Participants were not explicitly instructed to follow the confederate's gaze.

RESULTS

Autistic traits were associated with spontaneous gaze following and initiation in face-to-face social interactions. Specifically, only when both the participant and confederate were low in autistic traits did the incongruent gaze cues of confederates interfere with the participants' responses.

CONCLUSIONS

Autistic traits impeded gaze following and initiation by TD adults. This study has theoretical and practical implications regarding autistic trait-induced social deficits and indicates a new approach for social skill interventions.

A frontoparietal network for volitional control of gaze following

Gaze following is a major element of non-verbal communication and important for successful social interactions. Human gaze following is a fast and almost reflex-like behaviour, yet it can be volitionally controlled and suppressed to some extent if inappropriate or unnecessary, given the social context. In order to identify the neural basis of the cognitive control of gaze following, we carried out an event-related fMRI experiment, in which human subjects' eye movements were tracked while they were exposed to gaze cues in two distinct contexts: A baseline gaze following condition in which subjects were instructed to use gaze cues to shift their attention to a gazed-at spatial target and a control condition in which the subjects were required to ignore the gaze cue and instead to shift their attention to a distinct spatial target to be selected based on a colour mapping rule, requiring the suppression of gaze following. We could identify a suppression-related blood-oxygen-level-dependent (BOLD) response in a frontoparietal network comprising dorsolateral prefrontal cortex (dlPFC), orbitofrontal cortex (OFC), the anterior insula, precuneus, and posterior parietal cortex (PPC). These findings suggest that overexcitation of frontoparietal circuits in turn suppressing the gaze following patch might be a potential cause of gaze following deficits in clinical populations.

Social engagement revealed by gaze following in third-party observers of simulated social conflict

Humans and non-human primates can allocate visual attention to areas of high interest in their visual field based on the behaviors of their social partners. Allocation of attention is particularly important for third-party observers of social interactions. By following the gaze of interacting individuals, the observer can obtain information about the mental states, emotions, and intentions of others. We presented three adult monkeys (Macaca mulatta) with videos of simulated social interactions and quantified their eye movements to determine which observed behaviors were most conducive to gaze following. Social interactions were simulated by juxtaposing two videos depicting a threatening and an appeasing individual facing each other, with the timing of the facial and bodily displays adjusted to mimic an exchange of social signals. Socially meaningful facial displays combined with full body movements significantly enhanced the probability of gaze following and joint attention. Despite the synthetic nature of these interactions, the facial and bodily displays of the submissive individual elicited significantly more joint-attention than gaze-following saccades, suggesting a preferential allocation of attention to the recipients of threatening displays. Temporal alignment of gaze following and joint attention to the frames of each video showed numerous clusters of significant increases in the frequency of these saccades. These clusters suggest that some videos contained signals that can induce a quasi-automatic redirection of the observer's attention. However, these saccades occurred only on a fraction of the viewings, and we have documented large inter-individual variations. All viewers produced sequences of joint attention saccades (check-backs) shifting their attention between the two monkeys as though monitoring the simulated emitting-receiving cycle of social signals. These sequences reflect the viewer's interest in monitoring the ongoing exchange of agonistic and affiliative displays. It appears that in macaque monkeys, the scanpaths of third-party observers of simulated social interactions are informed by social-cognitive processes suggestive of mentalizing.

Physiological arousal explains infant gaze following in various social contexts

Gaze following (GF) is fundamental to central aspects of human sociocognitive development, such as acquiring language and cultural learning. Studies have shown that infant GF is not a simple reflexive orientation to an adult's eye movement. By contrast, infants adaptively modulate GF behaviour depending on the social context. However, arguably, the neurophysiological mechanisms underlying contextual modulation of GF remain somewhat unexplored. In this study, we tested the proposition about whether the contextual modulation of infant GF is mediated by the infant's heart rate (HR), which indicates the infant's physiological arousal. Forty-one 6- to 9-month-old infants participated in this study, and infants observed either a reliable face, which looked towards the location of an object, or an unreliable face, which looked away from the location of an object. Thereafter, the infants watched a video of the same model making eye contact or not making any ostensive signals, before shifting their gaze towards one of the two objects. We revealed that reliability and eye contact acted independently to increase HR, which then fully mediates the effects of these social cues on the frequency of GF. Results suggest that each social cue independently enhances physiological arousal, which then accumulatively predicts the likelihood of infant GF behaviour.

Physiological arousal explains infant gaze following in various social contexts

Gaze following (GF) is fundamental to central aspects of human sociocognitive development, such as acquiring language and cultural learning. Studies have shown that infant GF is not a simple reflexive orientation to an adult's eye movement. By contrast, infants adaptively modulate GF behaviour depending on the social context. However, arguably, the neurophysiological mechanisms underlying contextual modulation of GF remain somewhat unexplored. In this study, we tested the proposition about whether the contextual modulation of infant GF is mediated by the infant's heart rate (HR), which indicates the infant's physiological arousal. Forty-one 6- to 9-month-old infants participated in this study, and infants observed either a reliable face, which looked towards the location of an object, or an unreliable face, which looked away from the location of an object. Thereafter, the infants watched a video of the same model making eye contact or not making any ostensive signals, before shifting their gaze towards one of the two objects. We revealed that reliability and eye contact acted independently to increase HR, which then fully mediates the effects of these social cues on the frequency of GF. Results suggest that each social cue independently enhances physiological arousal, which then accumulatively predicts the likelihood of infant GF behaviour.

Improving Eye Contact and Gaze Following in Children with Autism Spectrum Disorder: Systematic Withdrawal of Stimulus Prompts and Tangible Reinforcers

The purpose of this study was to investigate the effects of a procedure involving systematic withdrawal of stimulus prompts and tangible reinforcers on the acquisition, maintenance, and generalization of eye contact and gaze following for two children with ASD in China. Two boys with ASD (5-6 years of age) participated. A concurrent multiple probe design across behaviors and participants was used. Results indicate that the procedure effectively established eye contact and gaze following for both children. Generalization to new instructors occurred in the free play setting, and the acquired behaviors were maintained for 1 month following training. Eye contact was maintained with social consequences for one child; the other child required tokens along with social consequences to maintain eye contact. Social consequences were sufficient to maintain gaze following for both children.

Infants Learn to Follow Gaze in Stages: Evidence Confirming a Robotic Prediction

Gaze following is an early-emerging skill in infancy argued to be fundamental to joint attention and later language development. However, how gaze following emerges is a topic of great debate. Representational theories assume that in order to follow adults’ gaze, infants must have a rich sensitivity to adults’ communicative intention from birth. In contrast, learning-based theories hold that infants may learn to gaze follow based on low-level social reinforcement, without the need to understand others’ mental states. Nagai et al. (2006) successfully taught a robot to gaze follow through social reinforcement and found that the robot learned in stages: first in the horizontal plane, and later in the vertical plane—a prediction that does not follow from representational theories. In the current study, we tested this prediction in an eye-tracking paradigm. Six-month-olds did not follow gaze in either the horizontal or vertical plane, whereas 12-month-olds and 18-month-olds only followed gaze in the horizontal plane. These results confirm the core prediction of the robot model, suggesting that children may also learn to gaze follow through social reinforcement coupled with a structured learning environment.

What gaze adds to arrows: Changes in attentional response to gaze versus arrows in childhood and adolescence

From early ages, gaze acts as a cue to infer the interests, behaviours, thoughts and emotions of social partners. Despite sharing attentional properties with other non-social directional stimuli, such as arrows, gaze produces unique effects. A spatial interference task revealed this dissociation. The direction of arrows was identified faster on congruent than on incongruent direction-location trials. Conversely, gaze produced a reversed congruency effect (RCE), with faster identifications on incongruent than congruent trials. To determine the emergence of these gaze-specific attentional mechanisms, 214 Spanish children (4-17 years) divided into 6 age groups, performed the aforementioned task across three experiments. Results showed stimulus-specific developmental trajectories. Whereas the standard effect of arrows was unaffected by age, gaze shifted from an arrow-like effect at age 4 to a gaze-specific RCE at age 12. The orienting mechanisms shared by gaze and arrows are already present in 4-year olds and, throughout childhood, gaze becomes a special social cue with additional attentional properties. Besides orienting attention to a direction, as arrows would do, gaze might orient attention towards a specific object that would be attentionally selected. Such additional components may not fully develop until adolescence. Understanding gaze-specific attentional mechanisms may be crucial for children with atypical socio-cognitive development.

What are you looking at? Gaze following with and without target objects in ASD and typical development

LAY ABSTRACT

During the first year of life, infants start to align their attention with that of other people. This ability is called joint attention and facilitates social learning and language development. Although children with autism spectrum disorder (ASD) are known to engage less in joint attention compared to other children, several experimental studies have shown that they follow other's gaze (a requirement for visual joint attention) to the same extent as other children. In this study, infants' eye movements were measured at age 10, 14, and 18 months while watching another person look in a certain direction. A target object was either present or absent in the direction of the other person's gaze. Some of the infants were at elevated likelihood of ASD, due to having an older autistic sibling. At age 3 years, infants were assessed for a diagnosis of ASD. Results showed that infants who met diagnostic criteria at 3 years followed gaze to the same extent as other infants. However, they then looked back at the model faster than typically developing infants when no target object was present. When a target object was present, there was no difference between groups. These results may be in line with the view that directly after gaze following, infants with later ASD are less influenced by other people's gaze when processing the common attentional focus. The study adds to our understanding of both the similarities and differences in looking behaviors between infants who later receive an ASD diagnosis and other infants.

Do the Eyes Have It? A Systematic Review on the Role of Eye Gaze in Infant Language Development

Eye gaze is a ubiquitous cue in child–caregiver interactions, and infants are highly attentive to eye gaze from very early on. However, the question of why infants show gaze-sensitive behavior, and what role this sensitivity to gaze plays in their language development, is not yet well-understood. To gain a better understanding of the role of eye gaze in infants' language learning, we conducted a broad systematic review of the developmental literature for all studies that investigate the role of eye gaze in infants' language development. Across 77 peer-reviewed articles containing data from typically developing human infants (0–24 months) in the domain of language development, we identified two broad themes. The first tracked the effect of eye gaze on four developmental domains: (1) vocabulary development, (2) word–object mapping, (3) object processing, and (4) speech processing. Overall, there is considerable evidence that infants learn more about objects and are more likely to form word–object mappings in the presence of eye gaze cues, both of which are necessary for learning words. In addition, there is good evidence for longitudinal relationships between infants' gaze following abilities and later receptive and expressive vocabulary. However, many domains (e.g., speech processing) are understudied; further work is needed to decide whether gaze effects are specific to tasks, such as word–object mapping or whether they reflect a general learning enhancement mechanism. The second theme explored the reasons why eye gaze might be facilitative for learning, addressing the question of whether eye gaze is treated by infants as a specialized socio-cognitive cue. We concluded that the balance of evidence supports the idea that eye gaze facilitates infants' learning by enhancing their arousal, memory, and attentional capacities to a greater extent than other low-level attentional cues. However, as yet, there are too few studies that directly compare the effect of eye gaze cues and non-social, attentional cues for strong conclusions to be drawn. We also suggest that there might be a developmental effect, with eye gaze, over the course of the first 2 years of life, developing into a truly ostensive cue that enhances language learning across the board.

The development of gaze following in monolingual and bilingual infants: A multi-laboratory study

Determining the meanings of words requires language learners to attend to what other people say. However, it behooves a young language learner to simultaneously encode relevant non-verbal cues, for example, by following the direction of their eye gaze. Sensitivity to cues such as eye gaze might be particularly important for bilingual infants, as they encounter less consistency between words and objects than monolingual infants, and do not always have access to the same word-learning heuristics (e.g., mutual exclusivity). In a preregistered study, we tested the hypothesis that bilingual experience would lead to a more pronounced ability to follow another's gaze. We used a gaze-following paradigm developed by Senju and Csibra (Current Biology, 18, 2008, 668) to test a total of 93 6- to 9-month-old and 229 12- to 15-month-old monolingual and bilingual infants, in 11 laboratories located in 8 countries. Monolingual and bilingual infants showed similar gaze-following abilities, and both groups showed age-related improvements in speed, accuracy, frequency, and duration of fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations to on-screen objects, whether or not they were cued by the actor. These results suggest that gaze sensitivity is a fundamental aspect of development that is robust to variation in language exposure.

Measuring sensitivity to eye gaze cues in naturalistic scenes: Presenting the eye gaze FoCuS database

OBJECTIVES

The ability to process information about eye gaze and its use for nonverbal communication is foundational to human social interactions. We developed and validated a database of stimuli that are optimized to investigate the perception and referential understanding of shifts in eye gaze.

METHODS

The 245 Gaze Perception stimuli are digital photographs that test the ability to estimate and interpret eye gaze trajectory. The 82 Gaze Following stimuli are digital videos that measure the ability to follow and interpret eye gaze shifts online. Both stimuli were designed for a 4-alternative forced choice paradigm (4AFC) in which the participant identifies the gazed-at object.

RESULTS

Each stimulus was validated by independent raters and only included if the endorsement of the correct item was ≥75%. Finally, we provided timestamps for 19 40-second video segments from adolescent-oriented entertainment movies that are matched on several factors. These segments involve social interactions with eye gaze shifts and can be used to measure visual social attention.

CONCLUSIONS

This database will be an excellent resource for researchers interested in studying the developmental, behavioral, and/or neural mechanisms supporting the perception and interpretation of eye gaze cues.

Gaze Following in Ungulates: Domesticated and Non-domesticated Species Follow the Gaze of Both Humans and Conspecifics in an Experimental Context

Gaze following is the ability to use others' gaze to obtain information about the environment (e.g., food location, predators, and social interactions). As such, it may be highly adaptive in a variety of socio-ecological contexts, and thus be widespread across animal taxa. To date, gaze following has been mostly studied in primates, and partially in birds, but little is known on the gaze following abilities of other taxa and, especially, on the evolutionary pressures that led to their emergence. In this study, we used an experimental approach to test gaze following skills in a still understudied taxon, ungulates. Across four species (i.e., domestic goats and lamas, and non-domestic guanacos and mouflons), we assessed the individual ability to spontaneously follow the gaze of both conspecifics and human experimenters in different conditions. In line with our predictions, species followed the model's gaze both with human and conspecific models, but more likely with the latter. Except for guanacos, all species showed gaze following significantly more in the experimental conditions (than in the control ones). Despite the relative low number of study subjects, our study provides the first experimental evidence of gaze following skills in non-domesticated ungulates, and contributes to understanding how gaze following skills are distributed in another taxon-an essential endeavor to identify the evolutionary pressures leading to the emergence of gaze following skills across taxa.

Deixis, Meta-Perceptive Gaze Practices, and the Interactional Achievement of Joint Attention

The paper investigates the use of gaze along with deictics and embodied pointing to accomplish reference and joint attention in naturally occurring social interaction. It assumes that deixis, in its primordial use in face-to-face interaction, is an embodied phenomenon that involves gestural pointing as well as visual perception, thus giving rise to recurring gaze practices of the participants. The analysis draws on a model of the interactional organization of deictic reference and joint attention that serves as a sequential framework for investigating the functions of eye gaze. The analysis focuses on two meta-perceptive practices: gaze following and gaze monitoring. It shows that the use of these practices in naturally occurring social activities is context dependent, positionally sensitive, tied to participant roles, and temporally fine-tuned to the stream of the participants' verbal and embodied conduct. The sequential analysis of these practices further documents that meta-perceptive gaze practices contribute to the constitution of joint attention as mutually known by the participants. The data for this study were recorded with two pairs of mobile eye tracking glasses and an external camera. Methodologically situated within the framework of conversation analysis and interactional linguistics where video recording is used, the study breaks new ground by employing a technology almost exclusively applied in experimental frameworks to record ordinary social activities "in the wild." In striving for ecologically valid and precise eye gaze data, it also contributes to a refinement of concepts developed in experimental paradigms by adapting them to qualitative research within the field of multimodal conversation analysis and interactional linguistics.

Frontal, Parietal, and Temporal Brain Areas Are Differentially Activated When Disambiguating Potential Objects of Joint Attention

Humans establish joint attention with others by following the other's gaze. Previous work has suggested that a cortical patch (gaze-following patch, GFP) close to the posterior superior temporal sulcus (pSTS) may serve as a link between the extraction of the other's gaze direction and the resulting shifts of attention, mediated by human lateral intraparietal area (hLIP). However, it is not clear how the brain copes with situations in which information on gaze direction alone is insufficient to identify the target object because more than one may lie along the gaze vector. In this fMRI study, we tested human subjects on a paradigm that allowed the identification of a target object based on the integration of the other's gaze direction and information provided by an auditory cue on the relevant object category. Whereas the GFP activity turned out to be fully determined by the use of gaze direction, activity in hLIP reflected the total information needed to pinpoint the target. Moreover, in an exploratory analysis, we found that a region in the inferior frontal junction (IFJ) was sensitive to the total information on the target. An examination of the BOLD time courses in the three identified areas suggests functionally complementary roles. Although the GFP seems to primarily process directional information stemming from the other's gaze, the IFJ may help to analyze the scene when gaze direction and auditory information are not sufficient to pinpoint the target. Finally, hLIP integrates both streams of information to shift attention to distinct spatial locations.

Social and emotional contexts predict the development of gaze following in early infancy

The development of gaze following begins in early infancy and its developmental foundation has been under heavy debate. Using a longitudinal design (N = 118), we demonstrate that attachment quality predicts individual differences in the onset of gaze following, at six months of age, and that maternal postpartum depression predicts later gaze following, at 10 months. In addition, we report longitudinal stability in gaze following from 6 to 10 months. A full path model (using attachment, maternal depression and gaze following at six months) accounted for 21% of variance in gaze following at 10 months. These results suggest an experience-dependent development of gaze following, driven by the infant's own motivation to interact and engage with others (the social-first perspective).

How accurate are autistic adults and those high in autistic traits at making face-to-face line-of-sight judgements?

LAY ABSTRACT

In order to effectively understand and consider what others are talking about, we sometimes need to follow their line-of-sight to the location at which they are looking, as this can provide important contextual information regarding what they are saying. If we are not able to follow other people's line-of-sight, this could result in social communication difficulties. Here we tested how effectively autistic and neurotypical adults are at following a social partner's line-of-sight during a face-to-face task. In a first study, completed by 14 autistic adult participants of average to above-average verbal ability and 14 neurotypical adult participants, we found that all participants were able to effectively follow the social partner's line-of-sight. We also found that participants tended to be as effective at making these judgements from both a brief, 1s, glance or a long, 5s, stare. However, autistic adults were less accurate, on average, than neurotypical adults overall. In a second study, a separate group of 65 neurotypical adults completed the same line-of-sight judgement task to investigate whether task performance was related to individual variation in self-reported autistic traits. This found that the amount of self-reported autistic traits was not at all related to people's ability to accurately make line-of-sight judgements. This research isolates and furthers our understanding of an important component part of the social communication process and assesses it in a real-world context.

What leads to coordinated attention in parent-toddler interactions? Children's hearing status matters

Coordinated attention between children and their parents plays an important role in their social, language, and cognitive development. The current study used head-mounted eye-trackers to investigate the effects of children's prelingual hearing loss on how they achieve coordinated attention with their hearing parents during free-flowing object play. We found that toddlers with hearing loss (age: 24-37 months) had similar overall gaze patterns (e.g., gaze length and proportion of face looking) as their normal-hearing peers. In addition, children's hearing status did not affect how likely parents and children attended to the same object at the same time during play. However, when following parents' attention, children with hearing loss used both parents' gaze directions and hand actions as cues, whereas children with normal hearing mainly relied on parents' hand actions. The diversity of pathways leading to coordinated attention suggests the flexibility and robustness of developing systems in using multiple pathways to achieve the same functional end.

Learning Process of Gaze Following: Computational Modeling Based on Reinforcement Learning

Many studies have explored factors which influence gaze-following behavior of young infants. However, the results of empirical studies were inconsistent, and the mechanism underlying the contextual modulation of gaze following remains unclear. In order to provide valuable insight into the mechanisms underlying gaze following, we conducted computational modeling using Q-learning algorithm and simulated the learning process of infant gaze following to suggest a feasible model. In Experiment 1, we simulated how communicative cues and infant internal states affect the learning process of gaze following. The simulation indicated that the model in which communicative cues enhance infant internal states is the most feasible to explain the infant learning process. In Experiment 2, we simulated how individual differences in motivation for communication affect the learning process. The results showed that low motivation for communication can delay the learning process and decrease the frequency of gaze following. These simulations suggest that communicative cues may enhance infants' internal states and promote the development of gaze following. Also, initial social motivation may affect the learning process of social behaviors in the long term.

Enhanced gaze-following behavior in Deaf infants of Deaf parents

Gaze following plays a role in parent-infant communication and is a key mechanism by which infants acquire information about the world from social input. Gaze following in Deaf infants has been understudied. Twelve Deaf infants of Deaf parents (DoD) who had native exposure to American Sign Language (ASL) were gender-matched and age-matched (±7 days) to 60 spoken-language hearing control infants. Results showed that the DoD infants had significantly higher gaze-following scores than the hearing infants. We hypothesize that in the absence of auditory input, and with support from ASL-fluent Deaf parents, infants become attuned to visual-communicative signals from other people, which engenders increased gaze following. These findings underscore the need to revise the 'deficit model' of deafness. Deaf infants immersed in natural sign language from birth are better at understanding the signals and identifying the referential meaning of adults' gaze behavior compared to hearing infants not exposed to sign language. Broader implications for theories of social-cognitive development are discussed. A video abstract of this article can be viewed at https://youtu.be/QXCDK_CUmAI.

Are Horses (Equus caballus) Sensitive to Human Emotional Cues?

Emotions are important for social animals because animals' emotions function as beneficial cues to identify valuable resources such as food or to avoid danger by providing environmental information. Emotions also enable animals to predict individuals' behavior and determine how to behave in a specific context. Recently, several studies have reported that dogs are highly sensitive to not only conspecific but also human emotional cues. These studies suggest that domestication may have affected such sensitivity. However, there are still few studies that examine whether other domesticated animals, in addition to dogs, exhibit sensitivity to human emotional cues. In this study, we used a gaze-following task to investigate whether horses (Equus caballus) are sensitive to human emotional cues (happy, neutral, disgust) and if they adjust their behavior accordingly. In the study, the experimenter suddenly turned her head to either right or left and showed emotional cues. The results revealed that horses significantly decreased the frequency with which they followed the experimenter's gaze and the total looking time during the gaze-emotional cue presentation in the Disgust condition compared to the Neutral condition. These results suggest the possibility that horses are sensitive to human emotional cues and behave on the basis of the meaning implied by negative human emotional cues.

Gaze Following and Attention to Objects in Infants at Familial Risk for ASD

Reduced gaze following has been associated previously with lower language scores in children with autism spectrum disorder (ASD). Here, we use eye-tracking in a controlled experimental setting to investigate whether gaze following and attention distribution during a word learning task associate with later developmental and clinical outcomes in a population of infants at familial risk for ASD. Fifteen-month-old infants (n = 124; n = 101 with familial risk) watched an actress repeatedly gaze toward and label one of two objects present in front of her. We show that infants who later developed ASD followed gaze as frequently as typically developing peers but spent less time engaged with either object. Moreover, more time spent on faces and less on objects was associated with lower concurrent or later verbal abilities, but not with later symptom severity. No outcome group showed evidence for word learning. Thus, atypical distribution of attention rather than poor gaze following is a limiting factor for language development in infants at familial risk for ASD.

Seeing minds in others: Mind perception modulates low-level social-cognitive performance and relates to ventromedial prefrontal structures

In social interactions, we rely on nonverbal cues like gaze direction to understand the behavior of others. How we react to these cues is affected by whether they are believed to originate from an entity with a mind, capable of having internal states (i.e., mind perception). While prior work has established a set of neural regions linked to social-cognitive processes like mind perception, the degree to which activation within this network relates to performance in subsequent social-cognitive tasks remains unclear. In the current study, participants performed a mind perception task (i.e., judging the likelihood that faces, varying in physical human-likeness, have internal states) while event-related fMRI was collected. Afterwards, participants performed a social attention task outside the scanner, during which they were cued by the gaze of the same faces that they previously judged within the mind perception task. Parametric analyses of the fMRI data revealed that activity within ventromedial prefrontal cortex (vmPFC) was related to both mind ratings inside the scanner and gaze-cueing performance outside the scanner. In addition, other social brain regions were related to gaze-cueing performance, including frontal areas like the left insula, dorsolateral prefrontal cortex, and inferior frontal gyrus, as well as temporal areas like the left temporo-parietal junction and bilateral temporal gyri. The findings suggest that functions subserved by the vmPFC are relevant to both mind perception and social attention, implicating a role of vmPFC in the top-down modulation of low-level social-cognitive processes.

Variability of signal sequences in turn-taking exchanges induces agency attribution in 10.5-mo-olds

Infants' sensitivity to contingent reactivity as an indicator of intentional agency has been demonstrated by numerous referential gaze-following studies. Here we propose that variability of signal sequences in a turn-taking exchange provides an informative cue for infants to recognize interactions that may involve communicative information transfer between agents. Our experiment demonstrates that based on the abstract structural cue of variability of exchanged signal sequences, 10.5-mo-olds gaze-followed an entity's subsequent object-orienting action to fixate the same object. This gaze-following effect did not depend on the specific acoustic features of the sound signals produced. However, no orientation following to target was induced when the exchanged signal sequences were identical, or when only a single entity produced the variable sound sequences. These results demonstrate infants' early sensitivity to detect signal variability in turn-taking interactions as a relevant feature of communicative information transfer, which induces them to attribute intentional agency and communicative abilities to the participating entities. However, when no variability was present in the exchanged signals, or when the variable signal sequences were produced by a single entity alone, infants showed no evidence of attributing agency. In sum, we argue that perceiving contingent turn-taking exchange of variable signal sequences induce 10.5-mo-old preverbal infants to recognize such interactions as potentially involving communicative information transmission and attribute agency to the participating entities even if both the entities and the signals they produce are unfamiliar to them.

Physiological arousal predicts gaze following in infants

According to the natural pedagogy theory, infant gaze following is based on an understanding of the communicative intent of specific ostensive cues. However, it has remained unclear how eye contact affects this understanding and why it induces gaze following behaviour. In this study, we examined infant arousal in different gaze following contexts and whether arousal levels during eye contact predict gaze following. Twenty-five infants, ages 9-10 months participated in this study. They watched a video of an actress gazing towards one of two objects and then either looking directly into the camera to make eye contact or not showing any communicative intent. We found that eye contact led to an elevation in the infants' heart rates (HRs) and that HR during eye contact was predictive of later gaze following. Furthermore, increases in HR predicted gaze following whether it was accompanied by communicative cues or not. These findings suggest that infant gaze following behaviour is associated with both communicative cues and physiological arousal.

Gaze-Following and Reaction to an Aversive Social Interaction Have Corresponding Associations with Variation in the OXTR Gene in Dogs but Not in Human Infants

It has been suggested that dogs' remarkable capacity to use human communicative signals lies in their comparable social cognitive skills; however, this view has been questioned recently. The present study investigated associations between oxytocin receptor gene (OXTR) polymorphisms and social behavior in human infants and dogs with the aim to unravel potentially differential mechanisms behind their responsiveness to human gaze. Sixteen-month-old human infants (N = 99) and adult Border Collie dogs (N = 71) participated in two tasks designed to test (1) their use of gaze-direction as a cue to locate a hidden object, and (2) their reactions to an aversive social interaction (using the still face task for children and a threatening approach task for dogs). Moreover, we obtained DNA samples to analyze associations between single nucleotide polymorphisms (SNP) in the OXTR (dogs: -213AG, -94TC, -74CG, rs8679682, children: rs53576, rs1042778, rs2254298) and behavior. We found that OXTR genotype was significantly associated with reactions to an aversive social interaction both in dogs and children, confirming the anxiolytic effect of oxytocin in both species. In dogs, the genotypes linked to less fearful behavior were associated also with a higher willingness to follow gaze whereas in children, OXTR gene polymorphisms did not affect gaze following success. This pattern of gene-behavior associations suggests that for dogs the two situations are more alike (potentially fear-inducing or competitive) than for human children. This raises the possibility that, in contrast to former studies proposing human-like cooperativeness in dogs, dogs may perceive human gaze in an object-choice task in a more antagonistic manner than children.

Gaze Following is Related to the Broader Autism Phenotype in a Sex-Specific Way: Building the Case for Distinct Male and Female Autism Phenotypes

The search for a female autism phenotype is difficult, given the low diagnostic rates in females. Here, we studied potential sex differences in a core feature of autism, difficulty with eye gaze processing, among typically developing individuals who vary in the broad autism phenotype, which includes autistic-like traits that are common, continuously distributed, and similarly heritable in males and females. Participants viewed complex images of an actor in a naturalistic scene looking at one of many possible objects and had to identify the target gazed-at object. Among males, those high in autistic-like traits exhibited worse eye gaze following performance than did those low in these traits. Among females, eye gaze following behavior did not vary with autistic-like traits. These results suggest that deficient eye gaze following behavior is part of the broader autism phenotype for males, but may not be a part of the female autism phenotype.

Incubation environment impacts the social cognition of adult lizards

Recent work exploring the relationship between early environmental conditions and cognition has shown that incubation environment can influence both brain anatomy and performance in simple operant tasks in young lizards. It is currently unknown how it impacts other, potentially more sophisticated, cognitive processes. Social-cognitive abilities, such as gaze following and social learning, are thought to be highly adaptive as they provide a short-cut to acquiring new information. Here, we investigated whether egg incubation temperature influenced two aspects of social cognition, gaze following and social learning in adult reptiles (Pogona vitticeps). Incubation temperature did not influence the gaze following ability of the bearded dragons; however, lizards incubated at colder temperatures were quicker at learning a social task and faster at completing that task. These results are the first to show that egg incubation temperature influences the social cognitive abilities of an oviparous reptile species and that it does so differentially depending on the task. Further, the results show that the effect of incubation environment was not ephemeral but lasted long into adulthood. It could thus have potential long-term effects on fitness.

Hand-Eye Coordination Predicts Joint Attention

The present article shows that infant and dyad differences in hand-eye coordination predict dyad differences in joint attention (JA). In the study reported here, 51 toddlers ranging in age from 11 to 24 months and their parents wore head-mounted eye trackers as they played with objects together. We found that physically active toddlers aligned their looking behavior with their parent and achieved a substantial proportion of time spent jointly attending to the same object. However, JA did not arise through gaze following but rather through the coordination of gaze with manual actions on objects as both infants and parents attended to their partner's object manipulations. Moreover, dyad differences in JA were associated with dyad differences in hand following.

Saccades and smooth pursuit eye movements trigger equivalent gaze-cued orienting effects

Research has established that a perceived eye gaze produces a concomitant shift in a viewer's spatial attention in the direction of that gaze. The two experiments reported here investigate the extent to which the nature of the eye movement made by the gazer contributes to this orienting effect. On each trial in these experiments, participants were asked to make a speeded response to a target that could appear in a location toward which a centrally presented face had just gazed (a cued target) or in a location that was not the recipient of a gaze (an uncued target). The gaze cues consisted of either fast saccadic eye movements or slower smooth pursuit movements. Cued targets were responded to faster than uncued targets, and this gaze-cued orienting effect was found to be equivalent for each type of gaze shift both when the gazes were un-predictive of target location (Experiment 1) and counterpredictive of target location (Experiment 2). The results offer no support for the hypothesis that motion speed modulates gaze-cued orienting. However, they do suggest that motion of the eyes per se, regardless of the type of movement, may be sufficient to trigger an orienting effect.

Tolerant Barbary macaques maintain juvenile levels of social attention in old age, but despotic rhesus macaques do not

Complex social life is thought to be a major driver of complex cognition in primates, but few studies have directly tested the relationship between a given primate species' social system and their social cognitive skills. We experimentally compared life span patterns of a foundational social cognitive skill (following another's gaze) in tolerant Barbary macaques, Macaca sylvanus, and despotic rhesus macaques, Macaca mulatta. Semi-free-ranging monkeys (N = 80 individuals from each species) followed gaze more in test trials where an actor looked up compared to control trials. However, species differed in ontogenetic trajectories: both exhibited high rates of gaze following as juveniles, but rhesus monkeys exhibited declines in social attention with age, whereas Barbary macaques did not. This pattern indicates that developmental patterns of social attention vary with social tolerance, and that diversity in social behaviour can lead to differences in social cognition across primates.

Rhesus monkeys show human-like changes in gaze following across the lifespan

Gaze following, or co-orienting with others, is a foundational skill for human social behaviour. The emergence of this capacity scaffolds critical human-specific abilities such as theory of mind and language. Non-human primates also follow others' gaze, but less is known about how the cognitive mechanisms supporting this behaviour develop over the lifespan. Here we experimentally tested gaze following in 481 semi-free-ranging rhesus macaques (Macaca mulatta) ranging from infancy to old age. We found that monkeys began to follow gaze in infancy and this response peaked in the juvenile period-suggesting that younger monkeys were especially attuned to gaze information, like humans. After sexual maturity, monkeys exhibited human-like sex differences in gaze following, with adult females showing more gaze following than males. Finally, older monkeys showed reduced propensity to follow gaze, just as older humans do. In a second study (n = 80), we confirmed that macaques exhibit similar baseline rates of looking upwards in a control condition, regardless of age. Our findings indicate that-despite important differences in human and non-human primate life-history characteristics and typical social experiences-monkeys undergo robust ontogenetic shifts in gaze following across early development, adulthood and ageing that are strikingly similar to those of humans.

Where Is Your Attention? Assessing Individual Instances of Covert Attentional Orienting in Response to Gaze and Arrow Cues

Humans spontaneously follow where others are looking. However, recent investigations suggest such gaze-following behavior during natural interactions occurs relatively infrequently, only in about a third of available instances. Here we investigated if a similar frequency of orienting is also found in laboratory tasks that measure covert attentional orienting using manual responses. To do so, in two experiments, we analyzed responses from a classic gaze cuing task, with arrow cues serving as control stimuli. We reasoned that the proportions of attentional benefits and costs, defined as responses falling outside of 1 standard deviation of the average performance for the neutral condition, would provide a good approximation of individual instances of attentional shifts. We found that although benefits and costs occurred in less than half of trials, benefits emerged on a greater proportion of validly cued relative to invalidly cued trials. This pattern of data held across two different measures of neutral performance, as assessed by Experiments 1 and 2, as well as across the two cue types. These results suggest that similarly to gaze-following in naturalistic settings, covert orienting within the cuing task also appears to occur relatively infrequently.

Learning from where 'eye' remotely look or point: Impact on number line estimation error in adults

In this article, we present an investigation into the use of visual cues during number line estimation and their influence on cognitive processes for reducing number line estimation error. Participants completed a 0-1000 number line estimation task before and after a brief intervention in which they observed static-visual or dynamic-visual cues (control, anchor, gaze cursor, mouse cursor) and also made estimation marks to test effective number-target estimation. Results indicated that a significant pre-test to post-test reduction in estimation error was present for dynamic-visual cues of modelled eye-gaze and mouse cursor. However, there was no significant performance difference between pre- and post-test for the control or static anchor conditions. Findings are discussed in relation to the extent to which anchor points alone are meaningful in promoting successful segmentation of the number line and whether dynamic cues promote the utility of these locations in reducing error through attentional guidance.

Observing Third-Party Attentional Relationships Affects Infants' Gaze Following: An Eye-Tracking Study

Not only responding to direct social actions toward themselves, infants also pay attention to relevant information from third-party interactions. However, it is unclear whether and how infants recognize the structure of these interactions. The current study aimed to investigate how infants' observation of third-party attentional relationships influence their subsequent gaze following. Nine-month-old, 1-year-old, and 1.5-year-old infants (N = 72, 37 girls) observed video clips in which a female actor gazed at one of two toys after she and her partner either silently faced each other (face-to-face condition) or looked in opposite directions (back-to-back condition). An eye tracker was used to record the infants' looking behavior (e.g., looking time, looking frequency). The analyses revealed that younger infants followed the actor's gaze toward the target object in both conditions, but this was not the case for the 1.5-year-old infants in the back-to-back condition. Furthermore, we found that infants' gaze following could be negatively predicted by their expectation of the partner's response to the actor's head turn (i.e., they shift their gaze toward the partner immediately after they realize that the actor's head will turn). These findings suggested that the sensitivity to the difference in knowledge and attentional states in the second year of human life could be extended to third-party interactions, even without any direct involvement in the situation. Additionally, a spontaneous concern with the epistemic gap between self and other, as well as between others, develops by this age. These processes might be considered part of the fundamental basis for human communication.

Chimpanzee uses manipulative gaze cues to conceal and reveal information to foraging competitor

Tactical deception has been widely reported in primates on a functional basis, but details of behavioral mechanisms are usually unspecified. We tested a pair of chimpanzees (Pan troglodytes) in the informed forager paradigm, in which the subordinate saw the location of hidden food and the dominant did not. We employed cross-correlations to examine temporal contingencies between chimpanzees' behavior: specifically how the direction of the subordinate's gaze and movement functioned to manipulate the dominant's searching behavior through two tactics, withholding, and misleading information. In Experiment 1, not only did the informed subordinate tend to stop walking toward a single high value food, but she also refrained from gazing toward it, thus, withholding potentially revealing cues from her searching competitor. In a second experiment, in which a moderate value food was hidden in addition to the high value food, whenever the subordinate alternated her gaze between the dominant and the moderate value food, she often paused walking for 5 s; this frequently recruited the dominant to the inferior food, functioning as a "decoy." The subordinate flexibly concealed and revealed gaze toward a goal, which suggests that not only can chimpanzees use visual cues to make predictions about behavior, but also that chimpanzees may understand that other individuals can exploit their gaze direction. These results substantiate descriptive reports of how chimpanzees use gaze to manipulate others, and to our knowledge are the first quantitative data to identify behavioral mechanisms of tactical deception.

RESEARCH HIGHLIGHTS

Cross correlations show a subordinate chimpanzee tactically deceived a dominant by not gazing toward a valuable food (withholding), and recruiting to a "decoy" food (misleading). Chimpanzees understand that others can exploit their gaze direction.

Monkeys head-gaze following is fast, precise and not fully suppressible

Human eye-gaze is a powerful stimulus, drawing the observer's attention to places and objects of interest to someone else ('eye-gaze following'). The largely homogeneous eyes of monkeys, compromising the assessment of eye-gaze by conspecifics from larger distances, explain the absence of comparable eye-gaze following in these animals. Yet, monkeys are able to use peer head orientation to shift attention ('head-gaze following'). How similar are monkeys' head-gaze and human eye-gaze following? To address this question, we trained rhesus monkeys to make saccades to targets, either identified by the head-gaze of demonstrator monkeys or, alternatively, identified by learned associations between the demonstrators' facial identities and the targets (gaze versus identity following). In a variant of this task that occurred at random, the instruction to follow head-gaze or identity was replaced in the course of a trial by the new rule to detect a change of luminance of one of the saccade targets. Although this change-of-rule rendered the demonstrator portraits irrelevant, they nevertheless influenced performance, reflecting a precise redistribution of spatial attention. The specific features depended on whether the initial rule was head-gaze or identity following: head-gaze caused an insuppressible shift of attention to the target gazed at by the demonstrator, whereas identity matching prompted much later shifts of attention, however, only if the initial rule had been identity following. Furthermore, shifts of attention prompted by head-gaze were spatially precise. Automaticity and swiftness, spatial precision and limited executive control characterizing monkeys' head-gaze following are key features of human eye-gaze following. This similarity supports the notion that both may rely on the same conserved neural circuitry.

Male long-tailed macaques (Macaca fascicularis) understand the target of facial threat

The cognitive demands of group living have resulted in the development of social competences in a wide range of animal species. Primates are well aware of the complex social structure within their group and infer information about social status by observing interactions of others. A capacity used to infer this information, Visual Perspective Taking (VPT), is present in apes and in monkeys. However, it is unclear whether monkeys really understand that another individual is looking at a specific target. We investigated whether monkeys understand the target of attention of conspecifics using a new paradigm, based on expectancy violation. Subjects were exposed to pictures of scenes involving group members. These pictures either represented congruent (agonistic signals consistent with the dominance hierarchy) or incongruent (signals contradict the dominance hierarchy) social situations. The only difference between scenes concerned the looking direction, that is, the target of attention, and facial expression of the central monkey in the picture. Female subjects did not differ in their looking times to incongruent and congruent scenes, but results may be confounded by their longer looking times at scenes involving kin than non-kin. Male subjects looked significantly longer at incongruent than congruent scenes, suggesting that they understand the target of attention of other individuals. Alternative explanations involving simpler cognitive capacities were excluded. This implies that monkey species share social cognitive capacities underlying VPT with apes and humans. Am. J. Primatol. 78:720-730, 2016. © 2016 Wiley Periodicals, Inc.

The attracting power of the gaze of politicians is modulated by the personality and ideological attitude of their voters: a functional magnetic resonance imaging study

Observing someone rapidly moving their eyes induces reflexive shifts of overt and covert attention in the onlooker. Previous studies have shown that this process can be modulated by the onlooker's personality, as well as by the social features of the person depicted in the cued face. Here, we investigated whether an individual's preference for social dominance orientation, in-group perceived similarity (PS), and political affiliation of the cued-face modulated neural activity within specific nodes of the social attention network. During functional magnetic resonance imaging, participants were requested to perform a gaze-following task to investigate whether the directional gaze of various Italian political personages might influence the oculomotor behaviour of in-group or out-group voters. After scanning, we acquired measures of PS in personality traits with each political personage and preference for social dominance orientation. Behavioural data showed that higher gaze interference for in-group than out-group political personages was predicted by a higher preference for social hierarchy. Higher blood oxygenation level-dependent activity in incongruent vs. congruent conditions was found in areas associated with orienting to socially salient events and monitoring response conflict, namely the left frontal eye field, right supramarginal gyrus, mid-cingulate cortex and left anterior insula. Interestingly, higher ratings of PS with the in-group and less preference for social hierarchy predicted increased activity in the left frontal eye field during distracting gaze movements of in-group as compared with out-group political personages. Our results suggest that neural activity in the social orienting circuit is modulated by higher-order social dimensions, such as in-group PS and individual differences in ideological attitudes.

Training for eye contact modulates gaze following in dogs

Following human gaze in dogs and human infants can be considered a socially facilitated orientation response, which in object choice tasks is modulated by human-given ostensive cues. Despite their similarities to human infants, and extensive skills in reading human cues in foraging contexts, no evidence that dogs follow gaze into distant space has been found. We re-examined this question, and additionally whether dogs' propensity to follow gaze was affected by age and/or training to pay attention to humans. We tested a cross-sectional sample of 145 border collies aged 6 months to 14 years with different amounts of training over their lives. The dogs' gaze-following response in test and control conditions before and after training for initiating eye contact with the experimenter was compared with that of a second group of 13 border collies trained to touch a ball with their paw. Our results provide the first evidence that dogs can follow human gaze into distant space. Although we found no age effect on gaze following, the youngest and oldest age groups were more distractible, which resulted in a higher number of looks in the test and control conditions. Extensive lifelong formal training as well as short-term training for eye contact decreased dogs' tendency to follow gaze and increased their duration of gaze to the face. The reduction in gaze following after training for eye contact cannot be explained by fatigue or short-term habituation, as in the second group gaze following increased after a different training of the same length. Training for eye contact created a competing tendency to fixate the face, which prevented the dogs from following the directional cues. We conclude that following human gaze into distant space in dogs is modulated by training, which may explain why dogs perform poorly in comparison to other species in this task.

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We provide the first evidence that dogs can follow human gaze to distant space.

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There were no age effects on gaze following to human gaze cues.

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Gazing patterns of young and elderly dogs were influenced by higher distractibility.

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Training decreased dogs' gaze following and increased gaze to the human face.

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Dogs' tendency to follow human gaze is modulated by training for eye contact.

European starlings recognize the location of robotic conspecific attention

Looking where others are allocating attention can facilitate social interactions by providing information about objects or locations of interest. We asked whether European starlings follow the orientation behaviour of conspecifics owing to their highly gregarious behaviour. Starlings reoriented their attention to follow that of a robot around a barrier more often than when the robot's attention was directed elsewhere. This is the first empirical evidence of reorienting in response to conspecific attention in a songbird. Starlings may use this behaviour to obtain fine-tuned spatial information from conspecifics (e.g. direction of predator approach, spatial location of food patches), enhancing group cohesion.

Domain general learning: Infants use social and non-social cues when learning object statistics

Previous research has shown that infants can learn from social cues. But is a social cue more effective at directing learning than a non-social cue? This study investigated whether 9-month-old infants (N = 55) could learn a visual statistical regularity in the presence of a distracting visual sequence when attention was directed by either a social cue (a person) or a non-social cue (a rectangle). The results show that both social and non-social cues can guide infants' attention to a visual shape sequence (and away from a distracting sequence). The social cue more effectively directed attention than the non-social cue during the familiarization phase, but the social cue did not result in significantly stronger learning than the non-social cue. The findings suggest that domain general attention mechanisms allow for the comparable learning seen in both conditions.

Gorillas with white sclera: A naturally occurring variation in a morphological trait linked to social cognitive functions

Human eye morphology is considered unique among the primates in that humans possess larger width/height ratios (WHR), expose a greater amount of visible sclera (SSI; width of exposed eyeball/width of visible iris), and critically, have a white sclera due to a lack of pigmentation. White sclera in humans amplifies gaze direction, whereas the all-dark eyes of apes are hypothesized to conceal gaze from others. This study examines WHR and SSI in humans (N = 13) and gorillas (N = 85) engaged in direct and averted gazes and introduces a qualitative assessment of sclera color to evaluate variations in sclera pigmentation. The results confirm previous findings that humans possess a larger WHR than gorillas but indicate that humans and gorillas display similar amounts of visible sclera. Additionally, 72% (N = 124) of gorilla eyes in this sample deviated from the assumed all-dark eye condition. This questions whether gaze camouflage is the primary function of darkened sclera in non-human primates or whether other functional roles can be ascribed to the sclera, light or dark. We argue that white sclera evolved to amplify direct gazes in humans, which would have played a significant role in the development of ostensive communication, which is communication that both shows something and shows the intention to show something. We conclude that the horizontal elongation of the human eye, rather than sclera color, more reliably distinguishes human from great ape eyes, represented here by gorillas.

Complementary effects of gaze direction and early saliency in guiding fixations during free viewing

Gaze direction provides an important and ubiquitous communication channel in daily behavior and social interaction of humans and some animals. While several studies have addressed gaze direction in synthesized simple scenes, few have examined how it can bias observer attention and how it might interact with early saliency during free viewing of natural and realistic scenes. Experiment 1 used a controlled, staged setting in which an actor was asked to look at two different objects in turn, yielding two images that differed only by the actor's gaze direction, to causally assess the effects of actor gaze direction. Over all scenes, the median probability of following an actor's gaze direction was higher than the median probability of looking toward the single most salient location, and higher than chance. Experiment 2 confirmed these findings over a larger set of unconstrained scenes collected from the Web and containing people looking at objects and/or other people. To further compare the strength of saliency versus gaze direction cues, we computed gaze maps by drawing a cone in the direction of gaze of the actors present in the images. Gaze maps predicted observers' fixation locations significantly above chance, although below saliency. Finally, to gauge the relative importance of actor face and eye directions in guiding observer's fixations, in Experiment 3, observers were asked to guess the gaze direction from only an actor's face region (with the rest of the scene masked), in two conditions: actor eyes visible or masked. Median probability of guessing the true gaze direction within ±9° was significantly higher when eyes were visible, suggesting that the eyes contribute significantly to gaze estimation, in addition to face region. Our results highlight that gaze direction is a strong attentional cue in guiding eye movements, complementing low-level saliency cues, and derived from both face and eyes of actors in the scene. Thus gaze direction should be considered in constructing more predictive visual attention models in the future.