Newborns' face recognition: role of inner and outer facial features

An Eye-Tracking Study on Six Early Social-Emotional Abilities in Children Aged 1 to 3 Years

BACKGROUND

The experimental evaluation of young children's socio-emotional abilities is limited by the lack of existing specific measures to assess this population and by the relative difficulty for researchers to adapt measures designed for the general population.

METHODS

This study examined six early social-emotional abilities in 86 typically developing children aged 1 to 3 years using an eye-tracking-based experimental paradigm that combined visual preference tasks adapted from pre-existing infant studies.

OBJECTIVES

The aim of this study is to obtain developmental norms in six early social-emotional abilities in typical children aged 1 to 3 years that would be promising for an understanding of disorders of mental development. These developmental standards are essential to enable comparative assessments with children with atypical development, such as children with Profound Intellectual and Multiple Disabilities (PIMD).

RESULTS

The participants had greater spontaneous visual preferences for biological (vs. non-biological) motion, socially salient (vs. non-social) stimuli, the eye (vs. mouth) area of emotional expressions, angry (vs. happy) faces, and objects of joint attention (vs. non-looked-at ones). Interestingly, although the prosocial (vs. antisocial) scene of the socio-moral task was preferred, both the helper and hinderer characters were equally gazed at. Finally, correlational analyses revealed that performance was neither related to participants' age nor to each other (dismissing the hypothesis of a common underpinning process).

CONCLUSION

Our revised experimental paradigm is possible in infants aged 1 to 3 years and thus provides additional scientific proof on the direct assessment of these six socio-emotional abilities in this population.

The development of upright face perception depends on evolved orientation-specific mechanisms and experience

Here we examine whether our impressive ability to perceive upright faces arises from evolved orientation-specific mechanisms, our extensive experience with upright faces, or both factors. To do so, we tested Claudio, a man with a congenital joint disorder causing his head to be rotated back so that it is positioned between his shoulder blades. As a result, Claudio has seen more faces reversed in orientation to his own face than matched to it. Controls exhibited large inversion effects on all tasks, but Claudio performed similarly with upright and inverted faces in both detection and identity-matching tasks, indicating these abilities are the product of evolved mechanisms and experience. In contrast, he showed clear upright superiority when detecting "Thatcherized" faces (faces with vertically flipped features), suggesting experience plays a greater role in this judgment. Together, these findings indicate that both evolved orientation-specific mechanisms and experience contribute to our proficiency with upright faces.

How do human newborns come to understand the multimodal environment?

For a long time, newborns were considered as human beings devoid of perceptual abilities who had to learn with effort everything about their physical and social environment. Extensive empirical evidence gathered in the last decades has systematically invalidated this notion. Despite the relatively immature state of their sensory modalities, newborns have perceptions that are acquired, and are triggered by, their contact with the environment. More recently, the study of the fetal origins of the sensory modes has revealed that in utero all the senses prepare to operate, except for the vision mode, which is only functional starting from the first minutes after birth. This discrepancy between the maturation of the different senses leads to the question of how human newborns come to understand our multimodal and complex environment. More precisely, how the visual mode interacts with the tactile and auditory modes from birth. After having defined the tools that newborns use to interact with other sensory modalities, we review studies across different fields of research such as the intermodal transfer between touch and vision, auditory-visual speech perception, and the existence of links between the dimensions of space, time, and number. Overall, evidence from these studies supports the idea that human newborns are spontaneously driven, and cognitively equipped, to link information collected by the different sensory modes in order to create a representation of a stable world.

Face shape processing via visual-to-auditory sensory substitution activates regions within the face processing networks in the absence of visual experience

Previous evidence suggests that visual experience is crucial for the emergence and tuning of the typical neural system for face recognition. To challenge this conclusion, we trained congenitally blind adults to recognize faces via visual-to-auditory sensory-substitution (SDD). Our results showed a preference for trained faces over other SSD-conveyed visual categories in the fusiform gyrus and in other known face-responsive-regions of the deprived ventral visual stream. We also observed a parametric modulation in the same cortical regions, for face orientation (upright vs. inverted) and face novelty (trained vs. untrained). Our results strengthen the conclusion that there is a predisposition for sensory-independent and computation-specific processing in specific cortical regions that can be retained in life-long sensory deprivation, independently of previous perceptual experience. They also highlight that if the right training is provided, such cortical preference maintains its tuning to what were considered visual-specific face features.

Superior neural individuation of mother's than stranger's faces by five months of age

Human adults are better at recognizing different views of a given face as belonging to the same person when that person is familiar rather than unfamiliar. To clarify the developmental origin of this well-established phenomenon, one group of five-month-olds (N = 22) was presented with pictures of four different unfamiliar female faces at a fixed rate (6 Hz, 166 msec stimulus onset asynchrony), interrupted every 5th stimulus (1.2 Hz) by either their mother's face (mother oddball condition) or, in different stimulation sequences, a stranger's face (stranger oddball condition). In another group of five-month-olds (N = 17), stimulation sequences were reversed such that their mothers' or a given stranger's face were repeated at 6 Hz and interrupted every 5 stimuli by pictures of different female faces (mother standard, stranger standard conditions, respectively). Twelve variable images of each identity served as stimulus material. Besides clear frequency-tagged EEG responses at the 6 Hz stimulation rate over the medial occipital region in all conditions, significant activity at 1.2 Hz and harmonics (2.4 Hz, etc.) was observed in this region, reflecting selective responses to facial identity across changes of views. This effect was strongest when the mother's face was immediately repeated at every stimulation cycle (mother standard). Overall, these observations point to an early developmental advantage of identifying a familiar face presented from different views during immediate stimulus repetition.

Mouth Movements as Possible Cues of Social Interest at Birth: New Evidences for Early Communicative Behaviors

Previous studies evidenced that different interactive contexts modulate the visual attention of newborns. In the present study, we investigated newborns' motor feedback as an additional cue to neonates' expression of interest. Using videos of interactive faces and a familiarization-test procedure, three different groups of newborns were assigned to three different conditions (i.e., one condition with a talking face during familiarization and silently moving faces at test, silently moving/silently moving condition, or talking/static condition). Following studies on neonatal imitation, mouth movements were analyzed as indicators of social interest. We expected the occurrence of mouth movements in the newborns to differ according to different conditions: (a) whether or not the face in front of them was talking and (b) if the person had been already seen or was new. Results revealed that a talking face elicited more motor feedback from the newborns than a silent one and that there was no difference in front of the familiar face or the novel one. Finally, frequencies of mouth movements were greater, and latencies of appearance of the first mouth movement were shorter, in front of a static vs. a dynamic face. These results are congruent with the idea of the existence of "a sense" for interaction at birth, and therefore new approaches in newborn studies are discussed.

Effects of Emotional Expression on Face Recognition May Be Accounted for by Image Similarity

We examined the degree to which differences in face recognition rates across emotional expression conditions varied concomitantly with differences in mean objective image similarity. Effects of emotional expression on face recognition performance were measured via an old/new recognition paradigm in which stimuli at both learning and testing had happy, neutral, and angry expressions. Results showed an advantage for faces learned with neutral expressions, as well as for angry faces at testing. Performance data was compared to three quantitative image-similarity indices. Findings showed that mean human performance was strongly correlated with mean image similarity, suggesting that the former may be at least partly explained by the latter. Our findings sound a cautionary note regarding the necessity of considering low-level stimulus properties as explanations for findings that otherwise may be prematurely attributed to higher order phenomena such as attention or emotional arousal.

Eye-tracking-based experimental paradigm to assess social-emotional abilities in young individuals with profound intellectual and multiple disabilities

Individuals with Profound Intellectual and Multiple Disabilities (PIMD) experience a combination of severe cognitive and motor impairments frequently associated with additional sensory deficits and numerous medical disorders. The purpose of the present study was to propose an experimental paradigm based on eye-tracking that combines various pre-existing tasks from infancy research as an assessment tool. This would enable the investigation of social-emotional abilities in nine young individuals with PIMD through their visual preferences for different types of stimuli. The first objective was to test the feasibility of this paradigm, by expecting individuals to look more at the tasks’ presentation screen than elsewhere during its implementation. The second objective was to investigate whether PIMD individuals exhibit visual preferences for (a) biological (vs. non-biological) motion, (b) socially salient (vs. non-social) scenes, (c) the facial area of the eyes (vs. the mouth), (d) happy (vs. angry) faces, (e) objects of joint attention (vs. non-looked at ones), and for (f) prosocial (vs. anti-social) behaviors similar to those of a control group of typically developing children aged two years on average. Overall, the feasibility of this paradigm proved to be good, resulting in high individual looking rates that were not affected by the presentation or the content of the tasks. Analyses of individual social-emotional abilities, supported by the visual preference patterns of each PIMD individual, firstly revealed strong—but expected—variability both within and between subjects, and secondly highlighted some individual task-specific abilities although few similarities between these individual results and those of the control group were found. These findings underline the great relevance of using this type of paradigm for assessing PIMD individuals and thus contribute to a better understanding of their social and emotional development.

Distorting Face Representations in Newborn Brains

What role does experience play in the development of face recognition? A growing body of evidence indicates that newborn brains need slowly changing visual experiences to develop accurate visual recognition abilities. All of the work supporting this "slowness constraint" on visual development comes from studies testing basic-level object recognition. Here, we present the results of controlled-rearing experiments that provide evidence for a slowness constraint on the development of face recognition, a prototypical subordinate-level object recognition task. We found that (1) newborn chicks can rapidly develop view-invariant face recognition and (2) the development of this ability relies on experience with slowly moving faces. When chicks were reared with quickly moving faces, they built distorted face representations that largely lacked invariance to viewpoint changes, effectively "breaking" their face recognition abilities. These results provide causal evidence that slowly changing visual experiences play a critical role in the development of face recognition, akin to basic-level object recognition. Thus, face recognition is not a hardwired property of vision but is learned rapidly as the visual system adapts to the temporal structure of the animal's visual environment.

Individually distinctive features facilitate numerical discrimination of sets of objects in domestic chicks

Day-old domestic chicks approach the larger of two groups of identical objects, but in a 3 vs 4 comparison, their performance is random. Here we investigated whether adding individually distinctive features to each object would facilitate such discrimination. Chicks reared with 7 objects were presented with the operation 1 + 1 + 1 vs 1 + 1 + 1 + 1. When objects were all identical, chicks performed randomly, as expected (Experiment 1). In the remaining experiments, objects differed from one another due to additional features. Chicks succeeded when those features were differently oriented segments (Experiment 2) but failed when the features were arranged to depict individually different face-like displays (Experiment 3). Discrimination was restored if the face-like stimuli were presented upside-down, disrupting global processing (Experiment 4). Our results support the claim that numerical discrimination in 3 vs 4 comparison benefits from the presence of distinctive features that enhance object individuation due to individual processing. Interestingly, when the distinctive features are arranged into upright face-like displays, the process is susceptible to global over local interference due to configural processing. This study was aimed at assessing whether individual object processing affects numerical discrimination. We hypothesise that in humans similar strategies aimed at improving performance at the non-symbolic level may have positive effects on symbolic mathematical abilities.

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.

Universal Mechanisms and the Development of the Face Network: What You See Is What You Get

Our assignment was to review the development of the face-processing network, an assignment that carries the presupposition that a face-specific developmental program exists. We hope to cast some doubt on this assumption and instead argue that the development of face processing is guided by the same ubiquitous rules that guide the development of cortex in general.

A critical period for faces: Other-race face recognition is improved by childhood but not adult social contact

Poor recognition of other-race faces is ubiquitous around the world. We resolve a longstanding contradiction in the literature concerning whether interracial social contact improves the other-race effect. For the first time, we measure the age at which contact was experienced. Taking advantage of unusual demographics allowing dissociation of childhood from adult contact, results show sufficient childhood contact eliminated poor other-race recognition altogether (confirming inter-country adoption studies). Critically, however, the developmental window for easy acquisition of other-race faces closed by approximately 12 years of age and social contact as an adult — even over several years and involving many other-race friends — produced no improvement. Theoretically, this pattern of developmental change in plasticity mirrors that found in language, suggesting a shared origin grounded in the functional importance of both skills to social communication. Practically, results imply that, where parents wish to ensure their offspring develop the perceptual skills needed to recognise other-race people easily, childhood experience should be encouraged: just as an English-speaking person who moves to France as a child (but not an adult) can easily become a native speaker of French, we can easily become “native recognisers” of other-race faces via natural social exposure obtained in childhood, but not later.

Attention during Visual Preference Tasks: Relation to Caregiving and Face Recognition

This research examined how caregiver experience (female primary caregiver or distributed caregiving with mom and dad) influenced 10-, 14-, and 16-month-olds' visual preferences and attention toward internal facial features of female-male face pairs, and how these behaviors related to novelty preferences in a face recognition task and speed and accuracy on a visual search task. In the visual preference task, infants visually preferred male faces, regardless of caregiver experience. Despite similarities in visual preferences, infants' attention toward females and males' internal facial features was related for infants with distributed caregiving only. Infants' performance across face processing tasks most often correlated for those with female primary caregivers. Results further our understanding of how infants with female primary caregivers display specialized processing of female faces, and how infants with distributed caregiving show similarities in their attention to female and male facial features.

A face is more than just the eyes, nose, and mouth: fMRI evidence that face-selective cortex represents external features

What is a face? Intuition, along with abundant behavioral and neural evidence, indicates that internal features (e.g., eyes, nose, mouth) are critical for face recognition, yet some behavioral and neural findings suggest that external features (e.g., hair, head outline, neck and shoulders) may likewise be processed as a face. Here we directly test this hypothesis by investigating how external (and internal) features are represented in the brain. Using fMRI, we found highly selective responses to external features (relative to objects and scenes) within the face processing system in particular, rivaling that observed for internal features. We then further asked how external and internal features are represented in regions of the cortical face processing system, and found a similar division of labor for both kinds of features, with the occipital face area and posterior superior temporal sulcus representing the parts of both internal and external features, and the fusiform face area representing the coherent arrangement of both internal and external features. Taken together, these results provide strong neural evidence that a "face" is composed of both internal and external features.

Judging Others by Your Own Standards: Attractiveness of Primate Faces as Seen by Human Respondents

The aspects of facial attractiveness have been widely studied, especially within the context of evolutionary psychology, which proposes that aesthetic judgements of human faces are shaped by biologically based standards of beauty reflecting the mate quality. However, the faces of primates, who are very similar to us yet still considered non-human, remain neglected. In this paper, we aimed to study the facial attractiveness of non-human primates as judged by human respondents. We asked 286 Czech respondents to score photos of 107 primate species according to their perceived "beauty." Then, we analyzed factors affecting the scores including morphology, colors, and human-likeness. We found that the three main primate groups were each scored using different cues. The proportions of inner facial features and distinctiveness are cues widely reported to affect human facial attractiveness. Interestingly, we found that these factors also affected the attractiveness scores of primate faces, but only within the Catarrhines, i.e., the primate group most similar to humans. Within this group, human-likeness positively affected the attractiveness scores, and facial extremities such as a prolonged nose or exaggerated cheeks were considered the least attractive. On the contrary, the least human-like prosimians were scored as the most attractive group. The results are discussed in the context of the "uncanny valley," the widely discussed empirical rule.

Adults’ Markers of Face Processing Are Present at Age 6 and Are Interconnected Along Development

Recent studies on the development of face processing argue for a late, quantitative, domain-specific development of face processing, and face memory in particular. Most previous findings were based on separately tracking the developmental course of face perception skills, comparing performance across different age groups. Here, we adopted a different approach studying the mechanisms underlying the development of face processing by focusing on how different face skills are interrelated over the years (age 6 to adulthood). Specifically, we examined correlations within and between different categories of tasks: face domain-specific skills involving face recognition based on long-term representations (famous face), and short-term memory retention (Cambridge Face Memory Test), perceptual face-specific marker (inversion effect), global effects in scene perception (global–local task), and the perception of facial expressions. Factor analysis revealed that face identity skills have a similar pattern of interrelations throughout development, identifying two factors: a face domain-specific factor comprising adultlike markers of face processing and a general factor incorporating related, but nonspecific perceptual skills. Domain-specific age-related changes in face recognition entailing short- and long-term retention of face representations were observed, along with mature perceptual face-specific markers and more general perceptual effects predicting face perception skills already at age 6. The results suggest that the domain-specific changes in face processing are unlikely to result from developmental changes in perceptual skills driving face recognition. Instead, development may either involve improvement in the ability to retain face representations in memory or changes in the interactions between the perceptual representations of faces and their representations in long-term memory.

Are 6-month-old human infants able to transfer emotional information (happy or angry) from voices to faces? An eye-tracking study

The present study examined whether 6-month-old infants could transfer amodal information (i.e. independently of sensory modalities) from emotional voices to emotional faces. Thus, sequences of successive emotional stimuli (voice or face from one sensory modality -auditory- to another sensory modality -visual-), corresponding to a cross-modal transfer, were displayed to 24 infants. Each sequence presented an emotional (angry or happy) or neutral voice, uniquely, followed by the simultaneous presentation of two static emotional faces (angry or happy, congruous or incongruous with the emotional voice). Eye movements in response to the visual stimuli were recorded with an eye-tracker. First, results suggested no difference in infants’ looking time to happy or angry face after listening to the neutral voice or the angry voice. Nevertheless, after listening to the happy voice, infants looked longer at the incongruent angry face (the mouth area in particular) than the congruent happy face. These results revealed that a cross-modal transfer (from auditory to visual modalities) is possible for 6-month-old infants only after the presentation of a happy voice, suggesting that they recognize this emotion amodally.

Seeing faces is necessary for face-domain formation

Here we report that monkeys raised without exposure to faces did not develop face domains, but did develop domains for other categories and did show normal retinotopic organization, indicating that early face deprivation leads to a highly selective cortical processing deficit. Therefore, experience must be necessary for the formation (or maintenance) of face domains. Gaze tracking revealed that control monkeys looked preferentially at faces, even at ages prior to the emergence of face domains, but face-deprived monkeys did not, indicating that face looking is not innate. A retinotopic organization is present throughout the visual system at birth, so selective early viewing behavior could bias category-specific visual responses toward particular retinotopic representations, thereby leading to domain formation in stereotyped locations in inferotemporal cortex, without requiring category-specific templates or biases. Thus, we propose that environmental importance influences viewing behavior, viewing behavior drives neuronal activity, and neuronal activity sculpts domain formation.

Recognition of human faces by dogs (Canis familiaris) requires visibility of head contour

Researchers have suggested that dogs are able to recognise human faces, but conclusive evidence has yet to be found. Experiment 1 of this study investigated whether dogs can recognise humans using visual information from the face/head region, and whether this also occurs in conditions of suboptimal visibility of the face. Dogs were presented with their owner's and a stranger's heads, protruding through openings of an apparatus in opposite parts of the experimental setting. Presentations occurred in conditions of either optimal or suboptimal visibility; the latter featured non-frontal orientation, uneven illumination and invisibility of outer contours of the heads. Instances where dogs approached their owners with a higher frequency than predicted by chance were considered evidence of recognition. This occurred only in the optimal condition. With a similar paradigm, Experiment 2 investigated which of the alterations in visibility that characterised the suboptimal condition accounted for dogs' inability to recognise owners. Dogs approached their owners more frequently than predicted by chance if outer head contours were visible, but not if heads were either frontally oriented or evenly illuminated. Moreover, male dogs were slightly better at recognition than females. These findings represent the first clear demonstration that dogs can recognise human faces and that outer face elements are crucial for such a task, complementing previous research on human face processing in dogs. Parallels with face recognition abilities observed in other animal species, as well as with human infants, point to the relevance of these results from a comparative standpoint.

Intact word processing in developmental prosopagnosia

A wealth of evidence from behavioural, neuropsychological and neuroimaging research supports the view that face recognition is reliant upon a domain-specific network that does not process words. In contrast, the recent many-to-many model of visual recognition posits that brain areas involved in word and face recognition are functionally integrated. Developmental prosopagnosia (DP) is characterised by severe deficits in the recognition of faces, which the many-to-many model predicts should negatively affect word recognition. Alternatively, domain-specific accounts suggest that impairments in face and word processing need not go hand in hand. To test these possibilities, we ran a battery of 7 tasks examining word processing in a group of DP cases and controls. One of our prosopagnosia cases exhibited a severe reading impairment with delayed response times during reading aloud tasks, but not lexical decision tasks. Overall, however, we found no evidence of global word processing deficits in DP, consistent with a dissociation account for face and word processing.

Prevalence of Face Recognition Deficits in Middle Childhood

Approximately 2–2.5% of the adult population is believed to show severe difficulties with face recognition, in the absence of any neurological injury—a condition known as developmental prosopagnosia (DP). However, to date no research has attempted to estimate the prevalence of face recognition deficits in children, possibly because there are very few child-friendly, well-validated tests of face recognition. In the current study, we examined face and object recognition in a group of primary school children (aged 5–11 years), to establish whether our tests were suitable for children and to provide an estimate of face recognition difficulties in children. In Experiment 1 ( n = 184), children completed a pre-existing test of child face memory, the Cambridge Face Memory Test–Kids (CFMT-K), and a bicycle test with the same format. In Experiment 2 ( n = 413), children completed three-alternative forced-choice matching tasks with faces and bicycles. All tests showed good psychometric properties. The face and bicycle tests were well matched for difficulty and showed a similar developmental trajectory. Neither the memory nor the matching tests were suitable to detect impairments in the youngest groups of children, but both tests appear suitable to screen for face recognition problems in middle childhood. In the current sample, 1.2–5.2% of children showed difficulties with face recognition; 1.2–4% showed face-specific difficulties—that is, poor face recognition with typical object recognition abilities. This is somewhat higher than previous adult estimates: It is possible that face matching tests overestimate the prevalence of face recognition difficulties in children; alternatively, some children may “outgrow” face recognition difficulties.

Developing the Own-Race Advantage in 4-, 6-, and 9-Month-Old Taiwanese Infants: A Perceptual Learning Perspective

Previous infant studies on the other-race effect have favored the perceptual narrowing view, or declined sensitivities to rarely exposed other-race faces. Here we wish to provide an alternative possibility, perceptual learning, manifested by improved sensitivity for frequently exposed own-race faces in the first year of life. Using the familiarization/visual-paired comparison paradigm, we presented 4-, 6-, and 9-month-old Taiwanese infants with oval-cropped Taiwanese, Caucasian, Filipino faces, and each with three different manipulations of increasing task difficulty (i.e., change identity, change eyes, and widen eye spacing). An adult experiment was first conducted to verify the task difficulty. Our results showed that, with oval-cropped faces, the 4 month-old infants could only discriminate Taiwanese "change identity" condition and not any others, suggesting an early own-race advantage at 4 months. The 6 month-old infants demonstrated novelty preferences in both Taiwanese and Caucasian "change identity" conditions, and proceeded to the Taiwanese "change eyes" condition. The 9-month-old infants demonstrated novelty preferences in the "change identity" condition of all three ethnic faces. They also passed the Taiwanese "change eyes" condition but could not extend this refined ability of detecting a change in the eyes for the Caucasian or Philippine faces. Taken together, we interpret the pattern of results as evidence supporting perceptual learning during the first year: the ability to discriminate own-race faces emerges at 4 months and continues to refine, while the ability to discriminate other-race faces emerges between 6 and 9 months and retains at 9 months. Additionally, the discrepancies in the face stimuli and methods between studies advocating the narrowing view and those supporting the learning view were discussed.

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

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

Many faces, one rule: the role of perceptual expertise in infants' sequential rule learning

Rule learning is a mechanism that allows infants to recognize and generalize rule-like patterns, such as ABB or ABA. Although infants are better at learning rules from speech vs. non-speech, rule learning can be applied also to frequently experienced visual stimuli, suggesting that perceptual expertise with material to be learned is critical in enhancing rule learning abilities. Yet infants' rule learning has never been investigated using one of the most commonly experienced visual stimulus category available in infants' environment, i.e., faces. Here, we investigate 7-month-olds' ability to extract rule-like patterns from sequences composed of upright faces and compared their results to those of infants who viewed inverted faces, which presumably are encountered far less frequently than upright faces. Infants were habituated with face triads in either an ABA or ABB condition followed by a test phase with ABA and ABB triads composed of faces that differed from those showed during habituation. When upright faces were used, infants generalized the pattern presented during habituation to include the new face identities showed during testing, but when inverted faces were presented, infants failed to extract the rule. This finding supports the idea that perceptual expertise can modulate 7-month-olds' abilities to detect rule-like patterns.

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

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

Evolutionary Psychology as a Metatheory for the Social Sciences: How to Gather Interdisciplinary Evidence for a Psychological Adaptation

Evolutionary psychology has been proposed as a new metatheory for the social sciences ( Buss, 1995 ). Evolutionary psychology is an approach that emphasizes the evolutionary background of psychological phenomena (e.g., cognition, motivation, perception), with the expectation that knowledge about this background enhances our understanding of the working of the present human mind. This proposal has met with both enthusiasm and criticism. An important criticism is that it is hard, if possible at all, to find empirical evidence for a hypothesized psychological adaptation. This criticism has been addressed with the proposal to build a nomological network of evidence around a hypothesized psychological adaptation ( Schmitt & Pilcher, 2004 ). In this article, we show that it is possible to use this nomological network of evidence to support the hypothesis that face recognition is an adaptation. We reviewed the literature on face recognition from different disciplines (psychology, medicine, neuroscience, genetics, primatology, and anthropology) and conclude that there is an extensive network of evidence for the proposed hypothesis. We argue that building a nomological network of evidence is a promising way to address several criticisms of evolutionary psychology, and that such a network can serve as a metatheoretical framework for the social sciences.

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

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

Effects of visual expertise on a novel eye-size illusion: implications for holistic face processing

We examined the effect of visual experience on the magnitude of a novel eye-size illusion: when the size of a face's frame is increased or decreased but eye size is unchanged, observers judge the size of the eyes to be different from that in the original face frame. In the current study, we asked Chinese and Caucasian participants to judge eye size in different pairs of faces and measured the magnitude of the illusion when the faces were own- or other-age (adult vs. infant faces) and when the faces were own- or other-race (Chinese vs. Caucasian faces). We found an other-age effect and an other-race effect with the eye-size illusion: The illusion was more pronounced with own-race and own-age faces than with other-race and other-age faces. These findings taken together suggest that visual experience with faces influences the magnitude of this novel illusion. Extensive experience with certain face categories strengthens the illusion in the context of these categories, but lack of it reduces the magnitude of the illusion. Our results further imply that holistic processing may play an important role in engendering the eye-size illusion.

Eye tracking reveals a crucial role for facial motion in recognition of faces by infants

Current knowledge about face processing in infancy comes largely from studies using static face stimuli, but faces that infants see in the real world are mostly moving ones. To bridge this gap, 3-, 6-, and 9-month-old Asian infants (N = 118) were familiarized with either moving or static Asian female faces, and then their face recognition was tested with static face images. Eye-tracking methodology was used to record eye movements during the familiarization and test phases. The results showed a developmental change in eye movement patterns, but only for the moving faces. In addition, the more infants shifted their fixations across facial regions, the better their face recognition was, but only for the moving faces. The results suggest that facial movement influences the way faces are encoded from early in development.

Face and body recognition show similar improvement during childhood

Adults are proficient in extracting identity cues from faces. This proficiency develops slowly during childhood, with performance not reaching adult levels until adolescence. Bodies are similar to faces in that they convey identity cues and rely on specialized perceptual mechanisms. However, it is currently unclear whether body recognition mirrors the slow development of face recognition during childhood. Recent evidence suggests that body recognition develops faster than face recognition. Here we measured body and face recognition in 6- and 10-year-old children and adults to determine whether these two skills show different amounts of improvement during childhood. We found no evidence that they do. Face and body recognition showed similar improvement with age, and children, like adults, were better at recognizing faces than bodies. These results suggest that the mechanisms of face and body memory mature at a similar rate or that improvement of more general cognitive and perceptual skills underlies improvement of both face and body recognition.

Face recognition in schizophrenia disorder: A comprehensive review of behavioral, neuroimaging and neurophysiological studies

Facial emotion processing has been extensively studied in schizophrenia patients while general face processing has received less attention. The already published reviews do not address the current scientific literature in a complete manner. Therefore, here we tried to answer some questions that remain to be clarified, particularly: are the non-emotional aspects of facial processing in fact impaired in schizophrenia patients? At the behavioral level, our key conclusions are that visual perception deficit in schizophrenia patients: are not specific to faces; are most often present when the cognitive (e.g. attention) and perceptual demands of the tasks are important; and seems to worsen with the illness chronification. Although, currently evidence suggests impaired second order configural processing, more studies are necessary to determine whether or not holistic processing is impaired in schizophrenia patients. Neural and neurophysiological evidence suggests impaired earlier levels of visual processing, which might involve the deficits in interaction of the magnocellular and parvocellular pathways impacting on further processing. These deficits seem to be present even before the disorder out-set. Although evidence suggests that this deficit may be not specific to faces, further evidence on this question is necessary, in particularly more ecological studies including context and body processing.

Limitations of a habituation task to demonstrate discrimination of natural signals in songbirds

The habituation-dishabituation (HDH) paradigm is a common method used to examine animal cognition. Recent studies reported that spontaneous vocalizations could be used as an index of song familiarity and novelty in songbirds. However, these studies assigned only a few stimulus sets for all subjects, which might cause pseudoreplication. Therefore, we examined universality and general applicability of this method in Bengalese finches using a variety of stimulus sets. Seven unfamiliar conspecific songs were collected as a stimulus pool and a habituation song was randomly chosen for each subject. The subject was exposed to the habituation song repeatedly over 2h. During the test phase, the habituation song and a novel song randomly chosen from the stimulus pool were presented. We compared the degree of increase in call production during playback of those two songs. Although the degree was greater for the novel song compared with the habituation song in some birds, the trend was not consistent across all stimulus sets tested in these birds. Our results show that the HDH paradigm is not suitable to test song discrimination in songbirds unless precautions are taken to increase external validity by utilizing a variety of stimulus sets for each subject.

Suprasegmental information affects processing of talking faces at birth

From birth, newborns show a preference for faces talking a native language compared to silent faces. The present study addresses two questions that remained unanswered by previous research: (a) Does the familiarity with the language play a role in this process and (b) Are all the linguistic and paralinguistic cues necessary in this case? Experiment 1 extended newborns' preference for native speakers to non-native ones. Given that fetuses and newborns are sensitive to the prosodic characteristics of speech, Experiments 2 and 3 presented faces talking native and nonnative languages with the speech stream being low-pass filtered. Results showed that newborns preferred looking at a person who talked to them even when only the prosodic cues were provided for both languages. Nonetheless, a familiarity preference for the previously talking face is observed in the "normal speech" condition (i.e., Experiment 1) and a novelty preference in the "filtered speech" condition (Experiments 2 and 3). This asymmetry reveals that newborns process these two types of stimuli differently and that they may already be sensitive to a mismatch between the articulatory movements of the face and the corresponding speech sounds.

Discrimination of biomechanically possible and impossible hand movements at birth

The development of human body perception has long been investigated, but little is known about its early origins. This study focused on how a body part highly relevant to the human species, namely the hand, is perceived a few days after birth. Using a preferential-looking paradigm, 24- to 48-hr-old newborns watched biomechanically possible and impossible dynamic hand gestures (Experiment 1, N = 15) and static hand postures (Experiment 2, N = 15). In Experiment 1, newborns looked longer at the impossible, compared to the possible, hand movement, whereas in Experiment 2 no visual preference emerged. These findings suggest that early in life the representation of the human body may be shaped by sensory-motor experience.

Infant perceptual development for faces and spoken words: an integrated approach

There are obvious differences between recognizing faces and recognizing spoken words or phonemes that might suggest development of each capability requires different skills. Recognizing faces and perceiving spoken language, however, are in key senses extremely similar endeavors. Both perceptual processes are based on richly variable, yet highly structured input from which the perceiver needs to extract categorically meaningful information. This similarity could be reflected in the perceptual narrowing that occurs within the first year of life in both domains. We take the position that the perceptual and neurocognitive processes by which face and speech recognition develop are based on a set of common principles. One common principle is the importance of systematic variability in the input as a source of information rather than noise. Experience of this variability leads to perceptual tuning to the critical properties that define individual faces or spoken words versus their membership in larger groupings of people and their language communities. We argue that parallels can be drawn directly between the principles responsible for the development of face and spoken language perception.

Part-based and configural processing of owner's face in dogs

Dogs exhibit characteristic looking patterns when looking at human faces but little is known about what the underlying cognitive mechanisms are and how much these are influenced by individual experience. In Experiment 1, seven dogs were trained in a simultaneous discrimination procedure to assess whether they could discriminate a) the owner's face parts (eyes, nose or mouth) presented in isolation and b) whole faces where the same parts were covered. Dogs discriminated all the three parts of the owner's face presented in isolation, but needed fewer sessions to reach the learning criterion for the eyes than for both nose and mouth. Moreover, covering the eyes region significantly disrupted face discriminability compared to the whole face condition while such difference was not found when the nose or mouth was hidden. In Experiment 2, dogs were presented with manipulated images of the owner's face (inverted, blurred, scrambled, grey-scale) to test the relative contribution of part-based and configural processing in the discrimination of human faces. Furthermore, by comparing the dogs enrolled in the previous experiment and seven ‘naïve’ dogs we examined if the relative contribution of part-based and configural processing was affected by dogs' experience with the face stimuli. Naïve dogs discriminated the owner only when configural information was provided, whereas expert dogs could discriminate the owner also when part-based processing was necessary. The present study provides the first evidence that dogs can discriminate isolated internal features of a human face and corroborate previous reports of salience of the eyes region for human face processing. Although the reliance on part-perception may be increased by specific experience, our findings suggest that human face discrimination by dogs relies mainly on configural rather than on part-based elaboration.

Female face preference in 4-month-olds: the importance of hairline

At 3-4 months of age, infants respond to gender information in human faces. Specifically, young infants display a visual preference toward female over male faces. In three experiments, using a visual preference task, we investigated the role of hairline information in this bias. In Experiment 1, we presented male and female composite faces with similar hairstyles to 4-month-olds and observed a preference for female faces. In Experiment 2, the faces were presented, but in this instance, without hairline cues, and the preference was eliminated. In Experiment 3, using the same cropping to eliminate hairline cues, but with feminized female faces and masculinized male faces, infants' preference toward female faces was still not in evidence. The findings show that hairline information is important in young infants' preferential orientation toward female faces.

Integration of internal and external facial features in 8- to 10-year-old children and adults

Investigation of whole-part and composite effects in 4- to 6-year-old children gave rise to claims that face perception is fully mature within the first decade of life (Crookes & McKone, 2009). However, only internal features were tested, and the role of external features was not addressed, although external features are highly relevant for holistic face perception (Sinha & Poggio, 1996; Axelrod & Yovel, 2010, 2011). In this study, 8- to 10-year-old children and adults performed a same-different matching task with faces and watches. In this task participants attended to either internal or external features. Holistic face perception was tested using a congruency paradigm, in which face and non-face stimuli either agreed or disagreed in both features (congruent contexts) or just in the attended ones (incongruent contexts). In both age groups, pronounced context congruency and inversion effects were found for faces, but not for watches. These findings indicate holistic feature integration for faces. While inversion effects were highly similar in both age groups, context congruency effects were stronger for children. Moreover, children's face matching performance was generally better when attending to external compared to internal features. Adults tended to perform better when attending to internal features. Our results indicate that both adults and 8- to 10-year-old children integrate external and internal facial features into holistic face representations. However, in children's face representations external features are much more relevant. These findings suggest that face perception is holistic but still not adult-like at the end of the first decade of life.