Tuning the developing brain to emotional body expressions

Single point motion kinematics convey emotional signals in children and adults

This study investigates whether humans recognize different emotions conveyed only by the kinematics of a single moving geometrical shape and how this competence unfolds during development, from childhood to adulthood. To this aim, animations in which a shape moved according to happy, fearful, or neutral cartoons were shown, in a forced-choice paradigm, to 7- and 10-year-old children and adults. Accuracy and response times were recorded, and the movement of the mouse while the participants selected a response was tracked. Results showed that 10-year-old children and adults recognize happiness and fear when conveyed solely by different kinematics, with an advantage for fearful stimuli. Fearful stimuli were also accurately identified at 7-year-olds, together with neutral stimuli, while, at this age, the accuracy for happiness was not significantly different than chance. Overall, results demonstrates that emotions can be identified by a single point motion alone during both childhood and adulthood. Moreover, motion contributes in various measures to the comprehension of emotions, with fear recognized earlier in development and more readily even later on, when all emotions are accurately labeled.

Recognition of emotional body language from dyadic and monadic point-light displays in 5-year-old children and adults

Most child studies on emotion perception used faces and speech as emotion stimuli, but little is known about children's perception of emotions conveyed by body movements, that is, emotional body language (EBL). This study aimed to investigate whether processing advantages for positive emotions in children and negative emotions in adults found in studies on emotional face and term perception also occur in EBL perception. We also aimed to uncover which specific movement features of EBL contribute to emotion perception from interactive dyads compared with noninteractive monads in children and adults. We asked 5-year-old children and adults to categorize happy and angry point-light displays (PLDs), presented as pairs (dyads) and single actors (monads), in a button-press task. By applying representational similarity analyses, we determined intra- and interpersonal movement features of the PLDs and their relation to the participants' emotional categorizations. Results showed significantly higher recognition of happy PLDs in 5-year-olds and of angry PLDs in adults in monads but not in dyads. In both age groups, emotion recognition depended significantly on kinematic and postural movement features such as limb contraction and vertical movement in monads and dyads, whereas in dyads recognition also relied on interpersonal proximity measures such as interpersonal distance. Thus, EBL processing in monads seems to undergo a similar developmental shift from a positivity bias to a negativity bias, as was previously found for emotional faces and terms. Despite these age-specific processing biases, children and adults seem to use similar movement features in EBL processing.

Extending and refining the fearful ape hypothesis

The fearful ape hypothesis (FAH) presents an evolutionary-developmental framework stipulating that in the context of cooperative caregiving, unique to human great ape group life, heightened fearfulness was adaptive. This is because from early in human ontogeny fearfulness expressed and perceived enhanced care-based responding and cooperation with mothers and others. This response extends and refines the FAH by incorporating the commentaries' suggestions and additional lines of empirical work, providing a more comprehensive and nuanced version of the FAH. Specifically, it encourages and hopes to inspire cross-species and cross-cultural, longitudinal work elucidating evolutionary and developmental functions of fear in context. Beyond fear, it can be seen as a call for an evolutionary-developmental approach to affective science.

The discrimination of expressions in facial movements by infants: A study with point-light displays

Perceiving facial expressions is an essential ability for infants. Although previous studies indicated that infants could perceive emotion from expressive facial movements, the developmental change of this ability remains largely unknown. To exclusively examine infants' processing of facial movements, we used point-light displays (PLDs) to present emotionally expressive facial movements. Specifically, we used a habituation and visual paired comparison (VPC) paradigm to investigate whether 3-, 6-, and 9-month-olds could discriminate between happy and fear PLDs after being habituated with a happy PLD (happy-habituation condition) or a fear PLD (fear-habituation condition). The 3-month-olds discriminated between the happy and fear PLDs in both the happy- and fear-habituation conditions. The 6- and 9-month-olds showed discrimination only in the happy-habituation condition but not in the fear-habituation condition. These results indicated a developmental change in processing expressive facial movements. Younger infants tended to process low-level motion signals regardless of the depicted emotions, and older infants tended to process expressions, which emerged in familiar facial expressions (e.g., happy). Additional analyses of individual difference and eye movement patterns supported this conclusion. In Experiment 2, we concluded that the findings of Experiment 1 were not due to a spontaneous preference for fear PLDs. Using inverted PLDs, Experiment 3 further suggested that 3-month-olds have already perceived PLDs as face-like stimuli.

Seven-months-old infants show increased arousal to static emotion body expressions: Evidence from pupil dilation

Human body postures provide perceptual cues that can be used to discriminate and recognize emotions. It was previously found that 7-months-olds' fixation patterns discriminated fear from other emotion body expressions but it is not clear whether they also process the emotional content of those expressions. The emotional content of visual stimuli can increase arousal level resulting in pupil dilations. To provide evidence that infants also process the emotional content of expressions, we analyzed variations in pupil in response to emotion stimuli. Forty-eight 7-months-old infants viewed adult body postures expressing anger, fear, happiness and neutral expressions, while their pupil size was measured. There was a significant emotion effect between 1040 and 1640 ms after image onset, when fear elicited larger pupil dilations than neutral expressions. A similar trend was found for anger expressions. Our results suggest that infants have increased arousal to negative-valence body expressions. Thus, in combination with previous fixation results, the pupil data show that infants as young as 7-months can perceptually discriminate static body expressions and process the emotional content of those expressions. The results extend information about infant processing of emotion expressions conveyed through other means (e.g., faces).

Decoding functional brain networks through graph measures in infancy: The case of emotional faces

Graph measures represent an optimal way to investigate neural networks' organization, yet their application is still limited in developmental samples. To uncover the organization of 7-month-old infants' functional brain networks during an emotional perception task, we combined a decoding technique (i.e., Principal Component Regression) to graph metrics computation. Nodes' Within Module Degree Z Score (WMDZ) was computed as a measure of modular organization, and we decoded networks' functional organizations across EEG alpha and theta bands in response to static and dynamic facial expressions of emotions. We found that infants' brain topological activity differentiates between static and dynamic emotional faces due to the involvement of visual streams and sensorimotor areas, as often observed in adults. Moreover, network invariances point toward an already present rudimental network structure tuned to face processing already at 7-months of age. Overall, our results affirm the fruitfulness of the application of graph measures in developmental samples, due to their flexibility and the wealth of information they provide over infants' networks functional organization.

Age-of-actor effects in body expression recognition of children

Investigations of developmental trajectories for emotion recognition suggest that both face- and body expression recognition increases rapidly in early childhood and reaches adult levels of performance near the age of ten. So far, little is known about whether children's ability to recognise body expressions is influenced by the age of the person they are observing. This question is investigated here by presenting 119 children and 42 young adults with videos of children, young adults and older adults expressing emotions with their whole body. The results revealed an own-age advantage for children, reflected in adult-level accuracy for videos of children for most expressions but reduced accuracy for videos of older adults. Children's recognition of older adults' expressions was not correlated with children's estimated amount of contact with older adults. Support for potential influences of social biases on performance measures was minimal. The own-age advantage was explained in terms of children's reduced familiarity with body expressions of older adults due to aging related changes in the kinematics characteristics of movements and potentially due to stronger embodiment of other children's bodily movements.

Connecting inside out: Development of the social brain in infants and toddlers with a focus on myelination as a marker of brain maturation

Early childhood is a sensitive period for learning and social skill development. The maturation of cerebral regions underlying social processing lays the foundation for later social‐emotional competence. This study explored myelin changes in social brain regions and their association with changes in parent‐rated social‐emotional development in a cohort of 129 children (64 females, 0–36 months, 77 White). Results reveal a steep increase in myelination throughout the social brain in the first 3 years of life that is significantly associated with social‐emotional development scores. These findings add knowledge to the emerging picture of social brain development by describing neural underpinnings of human social behavior. They can contribute to identifying age‐/stage‐appropriate early life factors in this developmental domain.

Neural time course of pain observation in infancy

Perception of pain in others is of great evolutionary significance for the development of human empathy. However, infants' sensitivity to others' painful experiences has not been investigated so far. Here, we explored the neural time course of infants' processing of others' pain by measuring event-related brain potentials (ERPs) while 6-month-old infants observed a painful tactile stimulation directed towards the eye and a neutral tactile stimulation on the eyebrow. We analyzed both the Negative Central (Nc) and the later Late Positive Potential (LPP) ERP components, indexing respectively attention allocation and cognitive evaluation of perceptual stimuli. Results showed that observing painful touch elicits a mid-latency Nc (300-500 ms) over the right fronto-central site, which is greater in amplitude as compared to neutral touch. A divergent activity was also visible in the centro-parietal early (550-750 ms) and late (800-1000 ms) LPP, showing increased amplitudes in response to neutral compared to painful touch. The cognitive evaluation of painful stimuli, reflected by the LPP, might thus not be fully developed at 6 months of age, as adults typically show a larger LPP in response to painful as compared to neutral stimuli. Overall, infants show early attentional attuning to others' pain. This early sensitivity to others' painful tactile experiences might form a prerequisite for the development of human empathy.

Look up to the body: An eye-tracking investigation of 7-months-old infants' visual exploration of emotional body expressions

The human body is an important source of information to infer a person's emotional state. Research with adult observers indicate that the posture of the torso, arms and hands provide important perceptual cues for recognising anger, fear and happy expressions. Much less is known about whether infants process body regions differently for different body expressions. To address this issue, we used eye tracking to investigate whether infants' visual exploration patterns differed when viewing body expressions. Forty-eight 7-months-old infants were randomly presented with static images of adult female bodies expressing anger, fear and happiness, as well as an emotionally-neutral posture. Facial cues to emotional state were removed by masking the faces. We measured the proportion of looking time, proportion and number of fixations, and duration of fixations on the head, upper body and lower body regions for the different expressions. We showed that infants explored the upper body more than the lower body. Importantly, infants at this age fixated differently on different body regions depending on the expression of the body posture. In particular, infants spent a larger proportion of their looking times and had longer fixation durations on the upper body for fear relative to the other expressions. These results extend and replicate the information about infant processing of emotional expressions displayed by human bodies, and they support the hypothesis that infants' visual exploration of human bodies is driven by the upper body.

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.

Expanding Simulation Models of Emotional Understanding: The Case for Different Modalities, Body-State Simulation Prominence, and Developmental Trajectories

Recent models of emotion recognition suggest that when people perceive an emotional expression, they partially activate the respective emotion in themselves, providing a basis for the recognition of that emotion. Much of the focus of these models and of their evidential basis has been on sensorimotor simulation as a basis for facial expression recognition - the idea, in short, that coming to know what another feels involves simulating in your brain the motor plans and associated sensory representations engaged by the other person's brain in producing the facial expression that you see. In this review article, we argue that simulation accounts of emotion recognition would benefit from three key extensions. First, that fuller consideration be given to simulation of bodily and vocal expressions, given that the body and voice are also important expressive channels for providing cues to another's emotional state. Second, that simulation of other aspects of the perceived emotional state, such as changes in the autonomic nervous system and viscera, might have a more prominent role in underpinning emotion recognition than is typically proposed. Sensorimotor simulation models tend to relegate such body-state simulation to a subsidiary role, despite the plausibility of body-state simulation being able to underpin emotion recognition in the absence of typical sensorimotor simulation. Third, that simulation models of emotion recognition be extended to address how embodied processes and emotion recognition abilities develop through the lifespan. It is not currently clear how this system of sensorimotor and body-state simulation develops and in particular how this affects the development of emotion recognition ability. We review recent findings from the emotional body recognition literature and integrate recent evidence regarding the development of mimicry and interoception to significantly expand simulation models of emotion recognition.

Motion or emotion: Infants discriminate emotional biological motion based on low-level visual information

Infants' ability to discriminate emotional facial expressions and tones of voice is well-established, yet little is known about infant discrimination of emotional body movements. Here, we asked if 10-20-month-old infants rely on high-level emotional cues or low-level motion related cues when discriminating between emotional point-light displays (PLDs). In Study 1, infants viewed 18 pairs of angry, happy, sad, or neutral PLDs. Infants looked more at angry vs. neutral, happy vs. neutral, and neutral vs. sad. Motion analyses revealed that infants preferred the PLD with more total body movement in each pairing. Study 2, in which infants viewed inverted versions of the same pairings, yielded similar findings except for sad-neutral. Study 3 directly paired all three emotional stimuli in both orientations. The angry and happy stimuli did not significantly differ in terms of total motion, but both had more motion than the sad stimuli. Infants looked more at angry vs. sad, more at happy vs. sad, and about equally to angry vs. happy in both orientations. Again, therefore, infants preferred PLDs with more total body movement. Overall, the results indicate that a low-level motion preference may drive infants' discrimination of emotional human walking motions.

Changes in event-related brain responses and habituation during child development - A systematic literature review

OBJECTIVE

This systematic review highlights the influence of developmental changes of the central nervous system on habituation assessment during child development. Therefore, studies on age dependant changes in event-related brain responses as well as studies on behavioural and neurophysiological habituation during child development are compiled and discussed.

METHODS

Two PubMed searches with terms "(development evoked brain response (fetus OR neonate OR children) (electroencephalography OR magnetoencephalography))" and with terms "(psychology habituation (fetal OR neonate OR children) (human brain))" were performed to identify studies on developmental changes in event-related brain responses as well as habituation studies during child development.

RESULTS

Both search results showed a wide diversity of subjects' ages, stimulation protocols and examined behaviour or components of event-related brain responses as well as a demand for more longitudinal study designs.

CONCLUSIONS

A conclusive statement about clear developmental trends in event-related brain responses or in neurophysiological habituation studies is difficult to draw. Future studies should implement longitudinal designs, combination of behavioural and neurophysiological habituation measurement and more complex habituation paradigms to assess several habituation criteria.

SIGNIFICANCE

This review emphasizes that event-related brain responses underlie certain changes during child development which should be more considered in the context of neurophysiological habituation studies.

'Something in the way you move': Infants are sensitive to emotions conveyed in action kinematics

Body movements, as well as faces, communicate emotions. Research in adults has shown that the perception of action kinematics has a crucial role in understanding others' emotional experiences. Still, little is known about infants' sensitivity to body emotional expressions, since most of the research in infancy focused on faces. While there is some first evidence that infants can recognize emotions conveyed in whole-body postures, it is still an open question whether they can extract emotional information from action kinematics. We measured electromyographic (EMG) activity over the muscles involved in happy (zygomaticus major, ZM), angry (corrugator supercilii, CS) and fearful (frontalis, F) facial expressions, while 11-month-old infants observed the same action performed with either happy or angry kinematics. Results demonstrate that infants responded to angry and happy kinematics with matching facial reactions. In particular, ZM activity increased while CS activity decreased in response to happy kinematics and vice versa for angry kinematics. Our results show for the first time that infants can rely on kinematic information to pick up on the emotional content of an action. Thus, from very early in life, action kinematics represent a fundamental and powerful source of information in revealing others' emotional state.

Development of body emotion perception in infancy: From discrimination to recognition

Research suggests that infants progress from discrimination to recognition of emotions in faces during the first half year of life. It is unknown whether the perception of emotions from bodies develops in a similar manner. In the current study, when presented with happy and angry body videos and voices, 5-month-olds looked longer at the matching video when they were presented upright but not when they were inverted. In contrast, 3.5-month-olds failed to match even with upright videos. Thus, 5-month-olds but not 3.5-month-olds exhibited evidence of recognition of emotions from bodies by demonstrating intermodal matching. In a subsequent experiment, younger infants did discriminate between body emotion videos but failed to exhibit an inversion effect, suggesting that discrimination may be based on low-level stimulus features. These results document a developmental change from discrimination based on non-emotional information at 3.5 months to recognition of body emotions at 5 months. This pattern of development is similar to face emotion knowledge development and suggests that both the face and body emotion perception systems develop rapidly during the first half year of life.

Neural correlates of infants' sensitivity to vocal expressions of peers

Responding to others' emotional expressions is an essential and early developing social skill among humans. Much research has focused on how infants process facial expressions, while much less is known about infants' processing of vocal expressions. We examined 8-month-old infants' processing of other infants' vocalizations by measuring event-related brain potentials (ERPs) to positive (infant laughter), negative (infant cries), and neutral (adult hummed speech) vocalizations. Our ERP results revealed that hearing another infant cry elicited an enhanced negativity (N200) at temporal electrodes around 200ms, whereas listening to another infant laugh resulted in an enhanced positivity (P300) at central electrodes around 300ms. This indexes that infants' brains rapidly respond to a crying peer during early auditory processing stages, but also selectively respond to a laughing peer during later stages associated with familiarity detection processes. These findings provide evidence for infants' sensitivity to vocal expressions of peers and shed new light on the neural processes underpinning emotion processing in infants.

Integrated Emotion Processing in Infancy: Matching of Faces and Bodies

Accurate assessment of emotion requires the coordination of information from different sources such as faces, bodies, and voices. Adults readily integrate facial and bodily emotions. However, not much is known about the developmental origin of this capacity. Using a familiarization paired-comparison procedure, 6.5-month-olds in the current experiments were familiarized to happy, angry, or sad emotions in faces or bodies and tested with the opposite image type portraying the familiar emotion paired with a novel emotion. Infants looked longer at the familiar emotion across faces and bodies (except when familiarized to angry images and tested on the happy/angry contrast). This matching occurred not only for emotions from different affective categories (happy, angry) but also within the negative affective category (angry, sad). Thus, 6.5-month-olds, like adults, integrate emotions from bodies and faces in a fairly sophisticated manner, suggesting rapid development of emotion processing early in life.

Age-congruency and contact effects in body expression recognition from point-light displays (PLD)

Recognition of older people’s body expressions is a crucial social skill. We here investigate how age, not just of the observer, but also of the observed individual, affects this skill. Age may influence the ability to recognize other people’s body expressions by changes in one’s own ability to perform certain action over the life-span (i.e., an own-age bias may occur, with best recognition for one’s own age). Whole body point light displays of children, young adults and older adults (>70 years) expressing six different emotions were presented to observers of the same three age-groups. Across two variations of the paradigm, no evidence for the predicted own-age bias (a cross-over interaction between one’s own age and the observed person’s age) was found. Instead, experience effects were found with children better recognizing older actors’ expressions of ‘active emotions,’ such as anger and happiness with greater exposure in daily life. Together, the findings suggest that age-related changes in one own’s mobility only influences body expression categorization in young children who interact frequently with older adults.

Further evidence of early development of attention to dynamic facial emotions: Reply to Grossmann and Jessen

Adults exhibit enhanced attention to negative emotions like fear, which is thought to be an adaptive reaction to emotional information. Previous research, mostly conducted with static faces, suggests that infants exhibit an attentional bias toward fearful faces only at around 7months of age. In a recent study (Journal of Experimental Child Psychology, 2016, Vol. 147, pp. 100-110), we found that 5-month-olds also exhibit heightened attention to fear when tested with dynamic face videos. This indication of an earlier development of an attention bias to fear raises questions about developmental mechanisms that have been proposed to underlie this function. However, Grossmann and Jessen (Journal of Experimental Child Psychology, 2016, Vol. 153, pp. 149-154) argued that this result may have been due to differences in the amount of movement in the videos rather than a response to emotional information. To examine this possibility, we tested a new sample of 5-month-olds exactly as in the original study (Heck, Hock, White, Jubran, & Bhatt, 2016) but with inverted faces. We found that the fear bias seen in our study was no longer apparent with inverted faces. Therefore, it is likely that infants' enhanced attention to fear in our study was indeed a response to emotions rather than a reaction to arbitrary low-level stimulus features. This finding indicates enhanced attention to fear at 5months and underscores the need to find mechanisms that engender the development of emotion knowledge early in life.

The association of temperament and maternal empathy with individual differences in infants' neural responses to emotional body expressions

We examined the role of infant temperament and maternal dispositional empathy in the neural processing of happy and fearful emotional body expressions in 8-month-old infants by measuring event-related brain potentials. Our results revealed that infants' tendency to approach novel objects and people was positively correlated with the neural sensitivity (attention allocation) to fearful expressions, while infant fearfulness was negatively correlated to the neural sensitivity to fearful expressions. Maternal empathic concern was associated with infants' neural discrimination between happy and fearful expression, with infants of more empathetically concerned mothers showing greater neural sensitivity (attention allocation) to fearful compared to happy expressions. It is critical that our results also revealed that individual differences in the sensitivity to emotional information are explained by an interaction between infant temperament and maternal empathic concern. Specifically, maternal empathy appears to impact infants' neural responses to emotional body expressions, depending on infant fearfulness. These findings support the notion that the way in which infants respond to emotional signals in the environment is fundamentally linked to their temperament and maternal empathic traits. This adds an early developmental neuroscience dimension to existing accounts of social-emotional functioning, suggesting a complex and integrative picture of why and how infants' emotional sensitivity varies.

The Development of Body Structure Knowledge in Infancy

Although we know much about the development of face processing, we know considerably less about the development of body knowledge-despite bodies also being significant sources of social information. One set of studies indicated that body structure knowledge is poor during the 1st year of life and spawned a model that posits that, unlike the development of face knowledge, which benefits from innate propensities and dedicated learning mechanisms, the development of body knowledge relies on general learning mechanisms and develops slowly. In this article, we review studies on infants' knowledge about the structure of bodies and their processing of gender and emotion that paint a different picture. Although questions remain, a general social cognition system likely engenders similar trajectories of development of knowledge about faces and bodies, and may equip developing infants with the capacity to obtain socially critical information from many sources.

Putting the face in context: Body expressions impact facial emotion processing in human infants

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Brain responses were measured by presenting emotional faces in the context of emotional bodies.

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ERP data showed that 8-month-old infants discriminate between facial expressions only when presented in the context of congruent body expressions.

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Neural evidence for the existence of context-sensitive facial emotion perception in infants.

Body expressions exert strong contextual effects on facial emotion perception in adults. Specifically, conflicting body cues hamper the recognition of emotion from faces, as evident on both the behavioral and neural level. We examined the developmental origins of the neural processes involved in emotion perception across body and face in 8-month-old infants by measuring event-related brain potentials (ERPs). We primed infants with body postures (fearful, happy) that were followed by either congruent or incongruent facial expressions. Our results revealed that body expressions impact facial emotion processing and that incongruent body cues impair the neural discrimination of emotional facial expressions. Priming effects were associated with attentional and recognition memory processes, as reflected in a modulation of the Nc and Pc evoked at anterior electrodes. These findings demonstrate that 8-month-old infants possess neural mechanisms that allow for the integration of emotion across body and face, providing evidence for the early developmental emergence of context-sensitive facial emotion perception.

Differential Susceptibility of the Developing Brain to Contextual Adversity and Stress

A swiftly growing volume of literature, comprising both human and animal studies and employing both observational and experimental designs, has documented striking individual differences in neurobiological sensitivities to environmental circumstances within subgroups of study samples. This differential susceptibility to social and physical environments operates bidirectionally, in both adverse and beneficial contexts, and results in a minority subpopulation with remarkably poor or unusually positive trajectories of health and development, contingent upon the character of environmental conditions. Differences in contextual susceptibility appear to emerge in early development, as the interactive and adaptive product of genetic and environmental attributes. This paper surveys what is currently known of the mechanisms or mediators of differential susceptibility, at the levels of temperament and behavior, physiological systems, brain circuitry and neuronal function, and genetic and epigenetic variation. It concludes with the assertion that differential susceptibility is inherently grounded within processes of biological moderation, the complexities of which are at present only partially understood.

Body maps in the infant brain

Researchers have examined representations of the body in the adult brain but relatively little attention has been paid to ontogenetic aspects of neural body maps in human infants. Novel applications of methods for recording brain activity in infants are delineating cortical body maps in the first months of life. Body maps may facilitate infants' registration of similarities between self and other - an ability that is foundational to developing social cognition. Alterations in interpersonal aspects of body representations might also contribute to social deficits in certain neurodevelopmental disorders.

Duration of exclusive breastfeeding is associated with differences in infants' brain responses to emotional body expressions

Much research has recognized the general importance of maternal behavior in the early development and programing of the mammalian offspring's brain. Exclusive breastfeeding (EBF) duration, the amount of time in which breastfed meals are the only source of sustenance, plays a prominent role in promoting healthy brain and cognitive development in human children. However, surprisingly little is known about the influence of breastfeeding on social and emotional development in infancy. In the current study, we examined whether and how the duration of EBF impacts the neural processing of emotional signals by measuring electro-cortical responses to body expressions in 8-month-old infants. Our analyses revealed that infants with high EBF experience show a significantly greater neural sensitivity to happy body expressions than those with low EBF experience. Moreover, regression analyses revealed that the neural bias toward happiness or fearfulness differs as a function of the duration of EBF. Specifically, longer breastfeeding duration is associated with a happy bias, whereas shorter breastfeeding duration is associated with a fear bias. These findings suggest that breastfeeding experience can shape the way in which infants respond to emotional signals.

Discrimination of fearful and happy body postures in 8-month-old infants: an event-related potential study

Responding to others' emotional body expressions is an essential social skill in humans. Adults readily detect emotions from body postures, but it is unclear whether infants are sensitive to emotional body postures. We examined 8-month-old infants' brain responses to emotional body postures by measuring event-related potentials (ERPs) to happy and fearful bodies. Our results revealed two emotion-sensitive ERP components: body postures evoked an early N290 at occipital electrodes and a later Nc at fronto-central electrodes that were enhanced in response to fearful (relative to happy) expressions. These findings demonstrate that: (a) 8-month-old infants discriminate between static emotional body postures; and (b) similar to infant emotional face perception, the sensitivity to emotional body postures is reflected in early perceptual (N290) and later attentional (Nc) neural processes. This provides evidence for an early developmental emergence of the neural processes involved in the discrimination of emotional body postures.