The perception of biological motion by human infants

Neural processing of bottom-up perception of biological motion under attentional load

Considering its importance for one's survival and social significance, biological motion (BM) perception is assumed to occur automatically. Previous behavioral results showed that task-irrelevant BM in the periphery interfered with task performance at the fovea. Under selective attention, BM perception is supported by a network of regions including the occipito-temporal (OTC), parietal, and premotor cortices. Retinotopy studies that use BM stimulus showed distinct maps for its processing under and away from selective attention. Based on these findings, we investigated how bottom-up perception of BM would be processed in the human brain under attentional load when it was shown away from the focus of attention as a task-irrelevant stimulus. Participants (N = 31) underwent an fMRI study in which they performed an attentionally demanding visual detection task at the fovea while intact or scrambled point light displays of BM were shown at the periphery. Our results showed the main effect of attentional load in fronto-parietal regions and both univariate activity maps and multivariate pattern analysis results support the attentional load modulation on the task-irrelevant peripheral stimuli. However, this effect was not specific to intact BM stimuli and was generalized to motion stimuli as evidenced by the motion-sensitive OTC involvement during the presence of dynamic stimuli in the periphery. These results confirm and extend previous work by showing that task-irrelevant distractors can be processed by stimulus-specific regions when there are enough attentional resources available. We discussed the implications of these results for future studies.

Skill and experience impact neural activity during global and local biological motion processing

During biological motion perception, individuals with perceptual experience learn to use more global processing, simultaneously extracting information from multiple body segments. Less experienced observers may use more local processing of individual body segments. The parietal lobe (e.g., alpha and beta power) has been shown to be critical to global and local static stimulus perception. Therefore, in this paper, we examined how skill impacts motion processing by assessing behavioral and neural responses to degrading global or local motion information for soccer penalty kicks. Skilled (N = 21) and less skilled (N = 19) soccer players anticipated temporally occluded videos of penalty kicks under normal, blurred (degraded local information), or spatially occluded (hips-only; degraded global information) viewing conditions. EEG was used to measure parietal alpha and beta power. Skilled players outperformed less skilled players, albeit both skill groups were less accurate in the blurred and hips-only conditions. Skilled performers showed significant decreases in bilateral parietal beta power in the hips-only condition, suggesting a greater reliance on global motion information under normal viewing conditions. Additionally, the hips-only condition elicited significantly greater beta relative to alpha power (beta - alpha), lower beta power, and lower alpha power than the control condition for both skill groups, suggesting spatial occlusion elicited a shift towards more local processing. Our novel findings demonstrate that skill and experience impact how motion is processed.

Recognition of humans from biological motion in infants

Infant studies have suggested that the detection of biological motion (BM) might be an innate capacity, based on newborns' spontaneous preference for BM. However, it is unclear if, like adults, infants recognize humans from BM and are able to build the representation of bodies and faces. To address this issue, we tested whether exposure to BM influences subsequent face recognition in 3- to 8-month-old infants. After familiarization with a point-light walker (PLW) of either a female or a male, the infant's preference for female and male faces was measured. If infants can build the representation of not only the body but also the face from PLWs, the familiarization effect of gender induced by the PLW might be generalized to faces. We found that infants at 7 to 8 months looked for longer at the face whose gender was opposite to that of the PLW, whereas 3- to 4- and 5- to 6-month-old infants did not. These results suggest that infants can access the representation of humans from BM and extract gender, which is shared across bodies and faces, from at least 7 to 8 months of age.

Finding Structure in Modern Dance

Research has shown that both adults and children organize familiar activity into discrete units with consistent boundaries, despite the dynamic, continuous nature of everyday experiences. However, less is known about how observers segment unfamiliar event sequences. In the current study, we took advantage of the novelty that is inherent in modern dance. Modern dance features natural human motion but does not contain canonical goals-therefore, observers cannot recruit prior goal-related knowledge to segment it. Our main aims were to identify whether observers segment modern dance into the steps intended by the dancers, and what types of cues contribute to segmentation under these circumstances. Experiment 1 used a classic event segmentation task and found that adults were able to consistently identify only a few of the dancers' intended steps. Experiment 2 tested adults in an offline labeling task. Results showed that steps which could more easily be labeled offline in Experiment 2 were more likely to be segmented online in Experiment 1.

Perceiving animacy from kinematics: visual specification of life-likeness in simple geometric patterns

Since the seminal work of Heider and Simmel, and Michotte's research, many studies have shown that, under appropriate conditions, displays of simple geometric shapes elicit rich and vivid impressions of animacy and intentionality. The main purpose of this review is to emphasize the close relationship between kinematics and perceived animacy by showing which specific motion cues and spatiotemporal patterns automatically trigger visual perceptions of animacy and intentionality. The animacy phenomenon has been demonstrated to be rather fast, automatic, irresistible, and highly stimulus-driven. Moreover, there is growing evidence that animacy attributions, although usually associated with higher-level cognition and long-term memory, may reflect highly specialized visual processes that have evolved to support adaptive behaviors critical for survival. The hypothesis of a life-detector hardwired in the perceptual system is also supported by recent studies in early development and animal cognition, as well as by the issue of the "irresistibility" criterion, i.e., the persistence of animacy perception in adulthood even in the face of conflicting background knowledge. Finally, further support for the hypothesis that animacy is processed in the earliest stages of vision comes from recent experimental evidence on the interaction of animacy with other visual processes, such as visuomotor performance, visual memory, and speed estimation. Summarizing, the ability to detect animacy in all its nuances may be related to the visual system's sensitivity to those changes in kinematics - considered as a multifactorial relational system - that are associated with the presence of living beings, as opposed to the natural, inert behavior of physically constrained, form-invariant objects, or even mutually independent moving agents. This broad predisposition would allow the observer not only to identify the presence of animates and to distinguish them from inanimate, but also to quickly grasp their psychological, emotional, and social characteristics.

Gravity-Dependent Animacy Perception in Zebrafish

Biological motion (BM), depicted by a handful of point lights attached to the major joints, conveys rich animacy information, which is significantly disrupted if BM is shown upside down. This well-known inversion effect in BM perception is conserved in terrestrial vertebrates and is presumably a manifestation of an evolutionarily endowed perceptual filter (i.e., life motion detector) tuned to gravity-compatible BM. However, it remains unknown whether aquatic animals, living in a completely different environment from terrestrial animals, perceive BM in a gravity-dependent manner. Here, taking advantage of their typical shoaling behaviors, we used zebrafish as a model animal to examine the ability of teleosts to discriminate between upright (gravity-compatible) and inverted (gravity-incompatible) BM signals. We recorded their swimming trajectories and quantified their preference based on dwelling time and head orientation. The results obtained from three experiments consistently showed that zebrafish spent significantly more time swimming in proximity to and orienting towards the upright BM relative to the inverted BM or other gravity-incompatible point-light stimuli (i.e., the non-BM). More intriguingly, when the recorded point-light video clips of fish were directly compared with those of human walkers and pigeons, we could identify a unique and consistent pattern of accelerating movements in the vertical (gravity) direction. These findings, to our knowledge, demonstrate for the first time the inversion effect in BM perception in simple aquatic vertebrates and suggest that the evolutionary origin of gravity-dependent BM processing may be traced back to ancient aquatic animals.

Human (but not animal) motion can be recognized at first sight - After treatment for congenital blindness

The long-standing nativist vs. empiricist debate asks a foundational question in epistemology - does our knowledge arise through experience or is it available innately? Studies that probe the sensitivity of newborns and patients recovering from congenital blindness are central in informing this dialogue. One of the most robust sensitivities our visual system possesses is to 'biological motion' - the movement patterns of humans and other vertebrates. Various biological motion perception skills (such as distinguishing between movement of human and non-human animals, or between upright and inverted human movement) become evident within the first months of life. The mechanisms of acquiring these capabilities, and specifically the contribution of visual experience to their development, are still under debate. We had the opportunity to directly examine the role of visual experience in biological motion perception, by testing what level of sensitivity is present immediately upon onset of sight following years of congenital visual deprivation. Two congenitally blind patients who underwent sight-restorative cataract-removal surgery late in life (at the ages of 7 and 20 years) were tested before and after sight restoration. The patients were shown displays of walking humans, pigeons, and cats, and asked to describe what they saw. Visual recognition of movement patterns emerged immediately upon eye-opening following surgery, when the patients spontaneously began to identify human, but not animal, biological motion. This recognition ability was evident contemporaneously for upright and inverted human displays. These findings suggest that visual recognition of human motion patterns may not critically depend on visual experience, as it was evident upon first exposure to un-obstructed sight in patients with very limited prior visual exposure, and furthermore, was not limited to the typical (upright) orientation of humans in real-life settings.

Modulation of biological motion perception in humans by gravity

The human visual perceptual system is highly sensitive to biological motion (BM) but less sensitive to its inverted counterpart. This perceptual inversion effect may stem from our selective sensitivity to gravity-constrained life motion signals and confer an adaptive advantage to creatures living on Earth. However, to what extent and how such selective sensitivity is shaped by the Earth’s gravitational field is heretofore unexplored. Taking advantage of a spaceflight experiment and its ground-based analog via 6° head-down tilt bed rest (HDTBR), we show that prolonged microgravity/HDTBR reduces the inversion effect in BM perception. No such change occurs for face perception, highlighting the particular role of gravity in regulating kinematic motion analysis. Moreover, the reduced BM inversion effect is associated with attenuated orientation-dependent neural responses to BM rather than general motion cues and correlated with strengthened functional connectivity between cortical regions dedicated to visual BM processing (i.e., pSTS) and vestibular gravity estimation (i.e., insula). These findings suggest that the neural computation of gravity may act as an embodied constraint, presumably implemented through visuo-vestibular interaction, to sustain the human brain’s selective tuning to life motion signals.

Utilizing spaceflight and its ground-based analog, the authors show how the Earth’s gravity sustains the human brain’s orientation-dependent sensitivity to biological motion signals based on neural computations of visual and vestibular gravitational cues.

Three Months-Old' Preferences for Biological Motion Configuration and Its Subsequent Decline

To perceive, identify and understand the action of others, it is essential to perceptually organize individual and local moving body parts (such as limbs) into the whole configuration of a human body in action. Configural processing-processing the relations among features or parts of a stimulus-is a fundamental ability in the perception of several important social stimuli, such as faces or biological motion. Despite this, we know very little about how human infants develop the ability to perceive and prefer configural relations in biological motion. We present two preferential looking experiments (one cross-sectional and one longitudinal) measuring infants' preferential attention between a coherent motion configuration of a person walking vs. a scrambled point-light walker (i.e., a stimulus in which all configural relations were removed, thus, in which the perception of a person is impossible). We found that three-month-old infants prefer a coherent point-light walker in relation to a scrambled display, but both five- and seven-month-old infants do not show any preference. We discuss our findings in terms of the different perceptual, attentional, motor, and brain processes available at each age group, and how they dynamically interact with selective attention toward the coherent and socially relevant motion of a person walking during our first year of life.

Posterior brain sensorimotor recruitment for inhibition of delayed responses in children

Inhibitory control, the ability to suppress irrelevant thoughts or actions, is central to cognitive and social development. Protracted maturation of frontal brain networks has been reported as a major restraint for this ability, yet, young children, when motivated, successfully inhibit delayed responses. A better understanding of the age-dependent neural inhibitory mechanism operating during the awaiting-to-respond window in children may elucidate this conundrum. We recorded ERPs from children and parental adults to a visual-spatial working memory task with delayed responses. Cortical activation elicited during the first 1000 ms of the awaiting-to-respond window showed, as predicted by prior studies, early inhibitory effects in prefrontal ERPs (P200, 160-260 ms) associated with top-down attentional-biasing, and later effects in parietal/occipital ERPs (P300, 270-650 ms) associated with selective inhibition of task-irrelevant stimuli/responses and recurrent memory retrieval. Children successfully inhibited delayed responses and performed with a high level of accuracy (often over 90%), although, the prefrontal P200 displayed reduced amplitude and uniformly delayed peak latency, suggesting low efficacy of top-down attentional-biasing. P300, however, with no significant age-contrasts in latency was markedly elevated in children over the occipital/inferior parietal regions, with effects stronger in younger children. These results provide developmental evidence supporting the sensorimotor recruitment model of visual-spatial working memory relying on the occipital/parietal regions of the early maturing dorsal-visual network. The evidence is in line with the concept of age-dependent variability in the recruitment of cognitive inhibitory networks, complementing the former predominant focus on frontal lobes.

Infant perception of causal motion produced by humans and inanimate objects

Both the movements of people and inanimate objects are intimately bound up with physical causality. Furthermore, in contrast to object movements, causal relationships between limb movements controlled by humans and their body displacements uniquely reflect agency and goal-directed actions in support of social causality. To investigate the development of sensitivity to causal movements, we examined the looking behavior of infants between 9 and 18 months of age when viewing movements of humans and objects. We also investigated whether individual differences in gender and gross motor functions may impact the development of the visual preferences for causal movements. In Experiment 1, infants were presented with walking stimuli showing either normal body translation or a "moonwalk" that reversed the horizontal motion of body translations. In Experiment 2, infants were presented with unperformable actions beyond infants' gross motor functions (i.e., long jump) either with or without ecologically valid body displacement. In Experiment 3, infants were presented with rolling movements of inanimate objects that either complied with or violated physical causality. We found that female infants showed longer looking times to normal walking stimuli than to moonwalk stimuli, but did not differ in their looking time to movements of inanimate objects and unperformable actions. In contrast, male infants did not show sensitivity to causal movement for either category. Additionally, female infants looked longer at social stimuli of human actions than male infants. Under the tested circumstances, our findings indicate that female infants have developed a sensitivity to causal consistency between limb movements and body translations of biological motion, only for actions with previous visual and motor exposures, and demonstrate a preference toward social information.

Social cognition in individuals born preterm

Faces hold a substantial value for effective social interactions and sharing. Covering faces with masks, due to COVID-19 regulations, may lead to difficulties in using social signals, in particular, in individuals with neurodevelopmental conditions. Daily-life social participation of individuals who were born preterm is of immense importance for their quality of life. Here we examined face tuning in individuals (aged 12.79 ± 1.89 years) who were born preterm and exhibited signs of periventricular leukomalacia (PVL), a dominant form of brain injury in preterm birth survivors. For assessing the face sensitivity in this population, we implemented a recently developed experimental tool, a set of Face-n-Food images bordering on the style of Giuseppe Arcimboldo. The key benefit of these images is that single components do not trigger face processing. Although a coarse face schema is thought to be hardwired in the brain, former preterms exhibit substantial shortages in the face tuning not only compared with typically developing controls but also with individuals with autistic spectrum disorders. The lack of correlations between the face sensitivity and other cognitive abilities indicates that these deficits are domain-specific. This underscores impact of preterm birth sequelae for social functioning at large. Comparison of the findings with data in individuals with other neurodevelopmental and neuropsychiatric conditions provides novel insights into the origins of deficient face processing.

Intuitive sociology

How do humans intuitively understand the structure of their society? How should psychologists study people's commonsense understanding of societal structure? The present chapter seeks to address both of these questions by describing the domain of "intuitive sociology." Drawing primarily from empirical research focused on how young children represent and reason about social groups, we propose that intuitive sociology consists of three core phenomena: social types (the identification of relevant groups and their attributes); social value (the worth of different groups); and social norms (shared expectations for how groups ought to be). After articulating each component of intuitive sociology, we end the chapter by considering both the emergence of intuitive sociology in infancy as well as transitions from intuitive to reflective representations of sociology later in life.

Learning non-adjacent rules and non-adjacent dependencies from human actions in 9-month-old infants

Seven month old infants can learn simple repetition patterns, such as we-fo-we, and generalize the rules to sequences of new syllables, such as ga-ti-ga. However, repetition rule learning in visual sequences seems more challenging, leading some researchers to claim that this type of rule learning applies preferentially to communicative stimuli. Here we demonstrate that 9-month-old infants can learn repetition rules in sequences of non-communicative dynamic human actions. We also show that when primed with these non-adjacent repetition patterns, infants can learn non-adjacent dependencies that involve memorizing the dependencies between specific human actions-patterns that prior research has shown to be difficult for infants in the visual domain and in speech. We discuss several possible mechanisms that account for the apparent advantage stimuli involving human action sequences has over other kinds of stimuli in supporting non-adjacent dependency learning. We also discuss possible implications for theories of language acquisition.

Infants' identification of gender in biological motion displays

Infants' knowledge of social categories, including gender-typed characteristics, is a vital aspect of social cognitive development. In the current study, we examined 9- to 12-month-old infants' understanding of the categories "male" and "female" by testing for gender matching in voices or faces with biological motion depicted in point light displays (PLDs). Infants did not show voice-PLD gender matching spontaneously (Experiment 1) or after "training" with gender-matching voice-PLD pairs (Experiment 2). In Experiment 3, however, infants were trained with gender-matching face-PLD pairs and we found that patterns of visual attention to top regions of PLD stimuli during training predicted gender matching of female faces and PLDs. Prior to the end of the first postnatal year, therefore, infants may begin to identify gender in human walk motions, and perhaps form social categories from biological motion.

Bird expertise does not increase motion sensitivity to bird flight motion

While motion information is important for the early stages of vision, it also contributes to later stages of object recognition. For example, human observers can detect the presence of a human, judge its actions, and judge its gender and identity simply based on motion cues conveyed in a point-light display. Here we examined whether object expertise enhances the observer's sensitivity to its characteristic movement. Bird experts and novices were shown point-light displays of upright and inverted birds in flight, or upright and inverted human walkers, and asked to discriminate them from spatially scrambled point-light displays of the same stimuli. While the spatially scrambled stimuli retained the local motion of each dot of the moving objects, it disrupted the global percept of the object in motion. To estimate a detection threshold in each object domain, we systematically varied the number of noise dots in which the stimuli were embedded using an adaptive staircase approach. Contrary to our predictions, the experts did not show disproportionately higher sensitivity to bird motion, and both groups showed no inversion cost. However, consistent with previous work showing a robust inversion effect for human motion, both groups were more sensitive to upright human walkers than their inverted counterparts. Thus, the result suggests that real-world experience in the bird domain has little to no influence on the sensitivity to bird motion and that birds do not show the typical inversion effect seen with humans and other terrestrial movement.

Newborns' sensitivity to speed changes as a building block for animacy perception

The human visual system can discriminate between animate beings vs. inanimate objects on the basis of some kinematic cues, such as starting from rest and speed changes by self-propulsion. The ontogenetic origin of such capability is still under debate. Here we investigate for the first time whether newborns manifest an attentional bias toward objects that abruptly change their speed along a trajectory as contrasted with objects that move at a constant speed. To this end, we systematically manipulated the motion speed of two objects. An object that moves with a constant speed was contrasted with an object that suddenly increases (Experiment 1) or with one that suddenly decreases its speed (Experiment 2). When presented with a single speed change, newborns did not show any visual preference. However, newborns preferred an object that abruptly increases and then decreases its speed (Experiment 3), but they did not show any visual preference for the reverse sequence pattern (Experiment 4). Overall, results are discussed in line with the hypothesis of the existence of attentional biases in newborns that trigger their attention towards some visual cues of motion that characterized animate perception in adults.

Comparable search efficiency for human and animal targets in the context of natural scenes

In a previous series of studies, we have shown that search for human targets in the context of natural scenes is more efficient than search for mechanical targets. Here we asked whether this search advantage extends to other categories of biological objects. We used videos of natural scenes to directly contrast search efficiency for animal and human targets among biological or nonbiological distractors. In visual search arrays consisting of two, four, six, or eight videos, observers searched for animal targets among machine distractors, and vice versa (Exp. 1). Another group searched for animal targets among human distractors, and vice versa (Exp. 2). We measured search slope as a proxy for search efficiency, and complemented the slope with eye movement measurements (fixation duration on the target, as well as the proportion of first fixations landing on the target). In both experiments, we observed no differences in search slopes or proportions of first fixations between any of the target-distractor category pairs. With respect to fixation durations, we found shorter on-target fixations only for animal targets as compared to machine targets (Exp. 1). In summary, we did not find that the search advantage for human targets over mechanical targets extends to other biological objects. We also found no search advantage for detecting humans as compared to other biological objects. Overall, our pattern of findings suggests that search efficiency in natural scenes, as elsewhere, depends crucially on the specific target-distractor categories.

Right STS responses to biological motion in infancy - An fNIRS study using point-light walkers

Biological motion perception-our capacity to perceive the intrinsic motion of humans and animals-has been implicated as a precursor of social development in infancy. In the adult brain, several biological motion neural correlates have been identified; of particular importance, the right posterior superior temporal sulcus (rpSTS). We present a study, conducted with fNIRS, which measured brain activations in infants' right posterior temporal region to point-light walkers, a standard stimulus category of biological motion perception studies. Seven-month-old infants (n = 23) participated in a within-subject blocked design with three experimental conditions and one baseline. Infants viewed: an intact upright point-light walker of a person approaching the observer; the same point-light walker stimulus but inverted; and a selected frame from the point-light walker stimulus, approaching the viewer at constant velocity with no articulated motion, close to object motion. We found activations for both the upright and the inverted point-light walkers. The rigid moving point-light walker frame did not elicit any response consistent with a functional activation in this region. Our results suggest that biological motion is processed differently in the right middle posterior temporal cortex in infancy, and that articulated motion is a critical feature in biological motion processing at this early age.

Gender Perception From Gait: A Comparison Between Biological, Biomimetic and Non-biomimetic Learning Paradigms

This paper explores in parallel the underlying mechanisms in human perception of biological motion and the best approaches for automatic classification of gait. The experiments tested three different learning paradigms, namely, biological, biomimetic, and non-biomimetic models for gender identification from human gait. Psychophysical experiments with twenty-one observers were conducted along with computational experiments without applying any gender specific modifications to the models or the stimuli. Results demonstrate the utilization of a generic memory based learning system in humans for gait perception, thus reducing ambiguity between two opposing learning systems proposed for biological motion perception. Results also support the biomimetic nature of memory based artificial neural networks (ANN) in their ability to emulate biological neural networks, as opposed to non-biomimetic models. In addition, the comparison between biological and computational learning approaches establishes a memory based biomimetic model as the best candidate for a generic artificial gait classifier (83% accuracy, p < 0.001), compared to human observers (66%, p < 0.005) or non-biomimetic models (83%, p < 0.001) while adhering to human-like sensitivity to gender identification, promising potential for application of the model in any given non-gender based gait perception objective with superhuman performance.

Asymmetric visual representation of sex from human body shape

We efficiently infer others' states and traits from their appearance, and these inferences powerfully shape our social behaviour. One key trait is sex, which is strongly cued by the appearance of the body. What are the visual representations that link body shape to sex? Previous studies of visual sex judgment tasks find observers have a bias to report "male", particularly for ambiguous stimuli. This finding implies a representational asymmetry - that for the processes that generate a sex percept, the default output is "male", and "female" is determined by the presence of additional perceptual evidence. That is, female body shapes are positively coded by reference to a male default shape. This perspective makes a novel prediction in line with Treisman's studies of visual search asymmetries: female body targets should be more readily detected amongst male distractors than vice versa. Across 10 experiments (N = 32 each) we confirmed this prediction and ruled out alternative low-level explanations. The asymmetry was found with profile and frontal body silhouettes, frontal photographs, and schematised icons. Low-level confounds were controlled by balancing silhouette images for size and homogeneity, and by matching physical properties of photographs. The female advantage was nulled for inverted icons, but intact for inverted photographs, suggesting reliance on distinct cues to sex for different body depictions. Together, these findings demonstrate a principle of the perceptual coding that links bodily appearance with a significant social trait: the female body shape is coded as an extension of a male default. We conclude by offering a visual experience account of how these asymmetric representations arise in the first place.

Motion tracking in developmental research: Methods, considerations, and applications

In this chapter, we explore the use of motion tracking methodology in developmental research. With motion tracking, also called motion capture, human movements can be precisely recorded and analyzed. Motion tracking provides developmental researchers with objective measurements of motor and (socio-)cognitive development. It can further be used to create carefully-controlled stimuli videos and can offer means of measuring development outside of the lab. We discuss three types of motion tracking that lend themselves to developmental applications. First, marker-based systems track optical or electromagnetic markers or sensors placed on the body and offer high accuracy measurements. Second, markerless methods entail image processing of videos to track the movement of bodies without participants being hindered by physical markers. Third, inertial motion tracking measures three-dimensional movements and can be used in a variety of settings. The chapter concludes by examining three example topics from developmental literature in which motion tracking applications have contributed to our understanding of human development.

Biological Motion Perception in Huntington's Disease

BACKGROUND

The ability of healthy individuals to detect biological motion by using a small number of moving points is well established in animals and humans. Perception of human movements may depend on internal models that drive self-generated movements and influence motion discrimination (Reed CL et al. 1995 and 2007). As a person's motor repertoire deteriorates, the accuracy of these models may also decrease.

OBJECTIVE

Determine if people with symptomatic Huntington's disease (HD) have difficulty perceiving movements.

METHODS

In this study point-light displays were created with a Vicon Motion Capture System by recording one individual with (impaired) and one individual without (healthy) Parkinson's disease using a 13 joint marker set. Participants were asked to distinguish between three movements and determine if the movement was impaired or healthy. The ability of participants with and without HD to distinguish movement patterns and the time to perception were recorded.

RESULTS

Analyses found participants with HD had a decreased ability to correctly detect movements and point-light image type. The stair climbing motion showed the largest effect as participants with HD had more difficulty correctly identifying both the movement and whether it was impaired or healthy. In addition, the participants without HD showed an improvement as trials progressed which could not be observed in the HD cohort.

CONCLUSIONS

As people with symptomatic HD have difficulty perceiving movements further investigations using point-light displays should be done to determine if these impairments might serve as an easily administered, non-invasive marker of disease state.

Visual Perception in Autism Spectrum Disorder: A Review of Neuroimaging Studies

Although autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social impairments, patients with ASD frequently manifest atypical sensory behaviors. Recently, atypical sensory perception in ASD has received much attention, yet little is known about its cause or neurobiology. Herein, we review the findings from neuroimaging studies related to visual perception in ASD. Specifically, we examined the neural underpinnings of visual detection, motion perception, and face processing in ASD. Results from neuroimaging studies indicate that atypical visual perception in ASD may be influenced by attention or higher order cognitive mechanisms, and atypical face perception may be affected by disrupted social brain network. However, there is considerable evidence for atypical early visual processing in ASD. It is likely that visual perceptual abnormalities are independent of deficits of social functions or cognition. Importantly, atypical visual perception in ASD may enhance difficulties in dealing with complex and subtle social stimuli, or improve outstanding abilities in certain fields in individuals with Savant syndrome. Thus, future research is required to elucidate the characteristics and neurobiology of autistic visual perception to effectively apply these findings in the interventions of ASD.

Learning From Others: The Effects of Agency on Event Memory in Young Children

Little is known about the influence of social context on children's event memory. Across four studies, we examined whether learning that could occur in the absence of a person was more robust when a person was present. Three-year-old children (N = 125) viewed sequential events that either included or excluded an acting agent. In Experiment 1, children who viewed an agent recalled more than children who did not. Experiments 2a and 2b utilized an eye tracker to demonstrate this effect was not due to differences in attention. Experiment 3 used a combined behavioral and event-related potential paradigm to show that condition effects were present in memory-related components. These converging results indicate a particular role for social knowledge in supporting memory for events.

Anomalous Perception of Biological Motion in Autism: A Conceptual Review and Meta-Analysis

Despite its popularity, the construct of biological motion (BM) and its putative anomalies in autism spectrum disorder (ASD) are not completely clarified. In this article, we present a meta-analysis investigating the putative anomalies of BM perception in ASD. Through a systematic literature search, we found 30 studies that investigated BM perception in both ASD and typical developing peers by using point-light display stimuli. A general meta-analysis including all these studies showed a moderate deficit of individuals with ASD in BM processing, but also a high heterogeneity. This heterogeneity was explored in different additional meta-analyses where studies were grouped according to levels of complexity of the BM task employed (first-order, direct and instrumental), and according to the manipulation of low-level perceptual features (spatial vs. temporal) of the control stimuli. Results suggest that the most severe deficit in ASD is evident when perception of BM is serving a secondary purpose (e.g., inferring intentionality/action/emotion) and, interestingly, that temporal dynamics of stimuli are an important factor in determining BM processing anomalies in ASD. Our results question the traditional understanding of BM anomalies in ASD as a monolithic deficit and suggest a paradigm shift that deconstructs BM into distinct levels of processing and specific spatio-temporal subcomponents.

The two-process theory of biological motion processing

Perception, identification, and understanding of others' actions from motion information are vital for our survival in the social world. A breakthrough in the understanding of action perception was the discovery that our visual system is sensitive to human action from the sparse motion input of only a dozen point lights, a phenomenon known as biological motion (BM) processing. Previous psychological and computational models cannot fully explain the emerging evidence for the existence of BM processing during early ontogeny. Here, we propose a two-process model of the mechanisms underlying BM processing. We hypothesize that the first system, the 'Step Detector,' rapidly processes the local foot motion and feet-below-the-body information that is specific to vertebrates, is less dependent on postnatal learning, and involves subcortical networks. The second system, the 'Bodily Action Evaluator,' slowly processes the fine global structure-from-motion, is specific to conspecific, and dependent on gradual learning processed in cortical networks. This proposed model provides new insight into research on the development of BM processing.

Synchrony of Caresses: Does Affective Touch Help Infants to Detect Body-Related Visual-Tactile Synchrony?

Bodily self-awareness, that is the ability to sense and recognize our body as our own, involves the encoding and integration of a wide range of multisensory and motor signals. Infants’ abilities to detect synchrony and bind together sensory information in time and space critically contribute to the process of gradual bodily self-awareness. In particular, early tactile experiences may have a crucial role in promoting self-other differentiation and developing bodily self-awareness. More specifically affective touch, slow and gentle touch linked to the neurophysiologically specialized system of C-tactile afferents, provides both information about the body from within (interoception) and outside (exteroception), suggesting it may be a key component contributing to the experience of bodily self-awareness. The present study aimed to investigate the role of affective touch in the formation and modulation of body perception from the earliest stages of life. Using a preferential looking task, 5-month-old infants were presented with synchronous and asynchronous visuo–tactile body-related stimuli. The socio-affective valence of the tactile stimuli was manipulated by means of the velocity [CT-optimal (slow) touch vs. CT-suboptimal (fast) touch] and the source of touch (human hand vs. brush). For the first time, we show that only infants that were stroked using a brush at slow velocity displayed a preference for the visual–tactile synchronous video, suggesting that CT-optimal touch might help infants to detect body-related visual–tactile synchrony, independently from the source of touch. Our results are in line with findings from adults and indicate that affective touch might have a critical role in the early development of bodily self-awareness.

Visual development

The developing visual brain is an integrated system, linking analysis of the visual input to visuomotor control, visual cognition, and attention. Major points in human visual development are the presence of rudimentary pathways present at birth which can control fixation behavior, with subsequent development of specific functions. These functions include the emergence of cortical selectivity; the integration of local signals to provide global representations of motion, shape, and space; the development of visuomotor modules for eye movements, manual reaching, and locomotion; and the development of distinct attentional systems. Measures of these processes in infancy and early childhood can provide indicators of broader brain development in the at-risk child. A key system in development is the dorsal cortical stream. Measures of global motion processing, visuomotor actions, and attention suggest that this system is particularly vulnerable in children with a wide range of neurodevelopmental disorders. Early disorders of the eye (strabismus, cataract) reveal the level of plasticity in the developing visual system and the ways in which early experience can affect the course of functional development.

Relation Between Working Memory Capacity of Biological Movements and Fluid Intelligence

Studies have revealed that there is an independent buffer for holding biological movements (BM) in working memory (WM), and this BM-WM has a unique link to our social ability. However, it remains unknown as to whether the BM-WM also correlates to our cognitive abilities, such as fluid intelligence (Gf). Since BM processing has been considered as a hallmark of social cognition, which distinguishes from canonical cognitive abilities in many ways, it has been hypothesized that only canonical object-WM (e.g., memorizing color patches), but not BM-WM, emerges to have an intimate relation with Gf. We tested this prediction by measuring the relationship between WM capacity of BM and Gf. With two Gf measurements, we consistently found moderate correlations between BM-WM capacity, the score of both Raven's advanced progressive matrix (RAPM), and the Cattell culture fair intelligence test (CCFIT). This result revealed, for the first time, a close relation between WM and Gf with a social stimulus, and challenged the double-dissociation hypothesis for distinct functions of different WM buffers.

Experimental Evidence of Structural Representation of Hands in Early Infancy

Hands convey important social information, such as an individual's emotions, goals, and desires, are used to direct attention through pointing, and are a major organ for haptic perception. However, very little is known about infants' representation of human hands. In Experiment 1, infants tested in a familiarization/novelty preference task discriminated between images of intact hands and ones that contained first-order structure distortions (i.e., with locations of fingers altered to result in an unnatural configuration). In Experiment 2, infants tested in a spontaneous preference task exhibited a preference for scrambled hand images over intact images, indicating that 3.5-month-olds have gained sufficient sensitivity to the configural properties of hands to discriminate between intact versus scrambled images without any training in the laboratory. In both procedures, infants' performance was disrupted by inversion of images, suggesting that infants' performance in the upright conditions was not based on low-level features. These results indicate that sensitivity to the structure of hands develops early in life. This early development may lay the foundation for the development of the functional use of hand information for social communication.

Comparative thanatology, an integrative approach: exploring sensory/cognitive aspects of death recognition in vertebrates and invertebrates

Evolutionary thanatology benefits from broad taxonomic comparisons of non-human animals' responses to death. Furthermore, exploring the sensory and cognitive bases of these responses promises to allow classification of the underlying mechanisms on a spectrum from phylogenetically ancient to more derived traits. We draw on studies of perception and cognition in invertebrate and vertebrate taxa (with a focus on arthropods, corvids, proboscids, cetaceans and primates) to explore the cues that these animals use to detect life and death in others, and discuss proximate and ultimate drivers behind their capacities to do so. Parallels in thanatological behaviour exhibited by the last four taxa suggest similar sensory-cognitive processing rules for dealing with corpses, the evolution of which may have been driven by complex social environments. Uniting these responses is a phenomenon we term 'animacy detection malfunction', whereupon the corpse, having both animate and inanimate attributes, creates states of fear/curiosity manifested as approach/avoidance behaviours in observers. We suggest that integrating diverse lines of evidence (including the 'uncanny valley' effect originating from the field of robotics) provides a promising way to advance the field, and conclude by proposing avenues for future research.This article is part of the theme issue 'Evolutionary thanatology: impacts of the dead on the living in humans and other animals'.

Infant perception of sex differences in biological motion displays

We examined mechanisms underlying infants' ability to categorize human biological motion stimuli from sex-typed walk motions, focusing on how visual attention to dynamic information in point-light displays (PLDs) contributes to infants' social category formation. We tested for categorization of PLDs produced by women and men by habituating infants to a series of female or male walk motions and then recording posthabituation preferences for new PLDs from the familiar or novel category (Experiment 1). We also tested for intrinsic preferences for female or male walk motions (Experiment 2). We found that infant boys were better able to categorize PLDs than were girls and that male PLDs were preferred overall. Neither of these effects was found to change with development across the observed age range (∼4-18 months). We conclude that infants' categorization of walk motions in PLDs is constrained by intrinsic preferences for higher motion speeds and higher spans of motion and, relatedly, by differences in walk motions produced by men and women.

Reduced orienting to audiovisual synchrony in infancy predicts autism diagnosis at 3 years of age

BACKGROUND

Effective multisensory processing develops in infancy and is thought to be important for the perception of unified and multimodal objects and events. Previous research suggests impaired multisensory processing in autism, but its role in the early development of the disorder is yet uncertain. Here, using a prospective longitudinal design, we tested whether reduced visual attention to audiovisual synchrony is an infant marker of later-emerging autism diagnosis.

METHODS

We studied 10-month-old siblings of children with autism using an eye tracking task previously used in studies of preschoolers. The task assessed the effect of manipulations of audiovisual synchrony on viewing patterns while the infants were observing point light displays of biological motion. We analyzed the gaze data recorded in infancy according to diagnostic status at 3 years of age (DSM-5).

RESULTS

Ten-month-old infants who later received an autism diagnosis did not orient to audiovisual synchrony expressed within biological motion. In contrast, both infants at low-risk and high-risk siblings without autism at follow-up had a strong preference for this type of information. No group differences were observed in terms of orienting to upright biological motion.

CONCLUSIONS

This study suggests that reduced orienting to audiovisual synchrony within biological motion is an early sign of autism. The findings support the view that poor multisensory processing could be an important antecedent marker of this neurodevelopmental condition.

Perception of social interaction compresses subjective duration in an oxytocin-dependent manner

Communication through body gestures permeates our daily life. Efficient perception of the message therein reflects one’s social cognitive competency. Here we report that such competency is manifested temporally as shortened subjective duration of social interactions: motion sequences showing agents acting communicatively are perceived to be significantly shorter in duration as compared with those acting noncommunicatively. The strength of this effect is negatively correlated with one’s autistic-like tendency. Critically, intranasal oxytocin administration restores the temporal compression effect in socially less proficient individuals, whereas the administration of atosiban, a competitive antagonist of oxytocin, diminishes the effect in socially proficient individuals. These findings indicate that perceived time, rather than being a faithful representation of physical time, is highly idiosyncratic and ingrained with one’s personality trait. Moreover, they suggest that oxytocin is involved in mediating time perception of social interaction, further supporting the role of oxytocin in human social cognition.

Einstein once joked: “Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That’s relativity.” While it may not have helped explain the space-time continuum, his joke neatly captures how time can appear to pass at different rates. This perception depends in part on the sensory properties of the stimuli we are experiencing. Intense stimuli, such as bright and fast-moving objects, trigger stronger responses in the brain than less intense stimuli, and so we perceive them as longer lasting.

But what role do we, as the experiencers, play in how we perceive time? To find out, Liu, Yuan, Chen et al. showed volunteers pairs of movie clips, each featuring two human figures outlined by dots. In one clip, the two figures interacted socially, for example by passing an object between them. In the other, the two figures moved independently of each other. The volunteers had to decide which clip lasted longer.

The volunteers generally judged clips containing social interactions to be shorter than those without such interactions, even when this was not the case. Moreover, volunteers with better social skills tended to underestimate the length of the social interaction clips to a greater extent.

Previous studies have shown that people who are more social tend to have higher levels of a hormone called oxytocin in their blood. Oxytocin is sometimes referred to as the ‘love hormone’ because it promotes social behavior and bonding. Applying an oxytocin nasal spray to the volunteers who were less socially proficient caused them to perceive the social interaction clips as shorter than before. By contrast, socially proficient volunteers who used a nasal spray that blocks the effects of oxytocin perceived these clips as longer than they had done previously (although they still judged the clips to be shorter than videos that did not show people interacting).

The perception of time thus varies between people and may depend at least in part on personality. These results open up a new avenue for studying and manipulating how we process social situations. This could eventually benefit people who struggle with social interactions, such as those with autism spectrum disorders.

A Longitudinal Investigation of Preferential Attention to Biological Motion in 2- to 24-Month-Old Infants

Preferential attention to biological motion is an early-emerging mechanism of adaptive action that plays a critical role in social development. The present study provides a comprehensive longitudinal mapping of developmental change in preferential attention to biological motion in 116 infants at 7 longitudinal time points. Tested repeatedly from 2 until 24 months of age, results reveal that preferential attention to biological motion changes considerably during the first months of life. Previously reported preferences in both neonates and older infants are absent in the second month but do reemerge by month 3 and become increasingly pronounced during the subsequent two years. These results highlight the second month of life as a potentially critical transition period in social visual engagement.

Development of Social Working Memory in Preschoolers and Its Relation to Theory of Mind

Social working memory (WM) has distinct neural substrates from canonical cognitive WM (e.g., color). However, no study, to the best of our knowledge, has yet explored how social WM develops. The current study explored the development of social WM capacity and its relation to theory of mind (ToM). Experiment 1 had sixty-four 3- to 6-year-olds memorize 1-5 biological motion stimuli, the processing of which is considered a hallmark of social cognition. The social WM capacity steadily increased between 3- and 6-year-olds, with the increase between 4 and 5 years being sharp. Furthermore, social WM capacity positively predicted preschoolers' ToM scores, while nonsocial WM capacity did not; this positive correlation was particularly strong among 4-year-olds (Experiment 2, N = 144).

Visual Sonority Modulates Infants' Attraction to Sign Language

The infant brain may be predisposed to identify perceptually salient cues that are common to both signed and spoken languages. Recent theory based on spoken languages has advanced sonority as one of these potential language acquisition cues. Using a preferential looking paradigm with an infrared eye tracker, we explored visual attention of hearing 6- and 12-month-olds with no sign language experience as they watched fingerspelling stimuli that either conformed to high sonority (well-formed) or low sonority (ill-formed) values, which are relevant to syllabic structure in signed language. Younger babies showed highly significant looking preferences for well-formed, high sonority fingerspelling, while older babies showed no preference for either fingerspelling variant, despite showing a strong preference in a control condition. The present findings suggest babies possess a sensitivity to specific sonority-based contrastive cues at the core of human language structure that is subject to perceptual narrowing, irrespective of language modality (visual or auditory), shedding new light on universals of early language learning.

Links between action perception and action production in 10-week-old infants

In order to understand how experience of an action alters functional brain responses to visual information, we examined the effects of reflex walking on how 10-week-old infants processed biological motion. We gave experience of the reflex walk to half the participants, and did not give this experience to the other half of the sample. The participant's electrical brain activity in response to viewing upright and inverted walking and crawling movements indicated the detection of biological motion only for that group which experience the reflex walk, as evidenced by parietal electrode greater positivity for the upright than the inverted condition. This effect was observed only for the walking stimuli. This study suggests that parietal regions are associated with the perception of biological motion even at 9-11 weeks. Further, this result strongly suggests that experience refines the perception of biological motion and that at 10 weeks of age, the link between action perception and action production is tightly woven.