Social touch alters newborn monkey behavior

In humans, infants respond positively to slow, gentle stroking—processed by C-tactile (CT) nerve fibers—by showing reductions in stress and increases in eye contact, smiling, and positive vocalizations. More frequent maternal touch is linked to greater activity and connectivity strength in social brain regions, and increases children’s attention to and learning of faces. It has been theorized that touch may prime children for social interactions and set them on a path towards healthy social cognitive development. However, less is known about the effects of touch on young infants’ psychological development, especially in the newborn period, a highly sensitive period of transition with rapid growth in sensory and social processing. It remains untested whether newborns can distinguish CT-targeted touch from other types of touch, or whether there are benefits of touch for newborns’ social, emotional, or cognitive development. In the present study, we experimentally investigated the acute effects of touch in newborn monkeys, a common model for human social development. Rhesus macaques (Macaca mulatta), like humans, are highly social, have complex mother-infant interactions with frequent body contact for the first weeks of life, making them an excellent model of infant sociality. Infant monkeys in the present study were reared in a neonatal nursery, enabling control over their early environment, including all caregiver interactions. One-week-old macaque infants (N = 27) participated in three 5-minute counter-balanced caregiver interactions, all with mutual gaze: stroking head and shoulders (CT-targeted touch), stroking palms of hands and soles of feet (Non-CT touch), or no stroking (No-touch). Immediately following the interaction, infants watched social and nonsocial videos and picture arrays including faces and objects, while we tracked their visual attention with remote eye tracking. We found that, during the caregiver interactions, infants behaved differently while being touched compared to the no-touch condition, irrespective of the body part touched. Most notably, in both touch conditions, infants exhibited fewer stress-related behaviors—self-scratching, locomotion, and contact time with a comfort object—compared to when they were not touched. Following CT-targeted touch, infants were faster to orient to the picture arrays compared to the other interaction conditions, suggesting CT-targeted touch may activate or prime infants’ attentional orienting system. In the No-touch condition infants attended longer to the nonsocial compared to the social video, possibly reflecting a baseline preference for nonsocial stimuli. In contrast, in both touch conditions, infants’ looked equally to the social and nonsocial videos, suggesting that touch may influence the types of visual stimuli that hold infants’ attention. Collectively, our results reveal that newborn macaques responded positively to touch, and touch appeared to influence some aspects of their subsequent attention, although we found limited evidence that these effects are mediated by CT fibers. These findings suggest that newborn touch may broadly support infants’ psychological development, and may have early evolutionary roots, shared across primates. This study illustrates the unique insight offered by nonhuman primates for exploring early infant social touch, revealing that touch may positively affect emotional and attentional development as early as the newborn period.     

Co-sleeping as a proximal context for infant development: The importance of physical touch

Co-sleeping is a complex familial phenomenon that has yet to be well understood by Western scientists. This paper provides an interdisciplinary review of research from anthropology, nursing, pediatrics, sociology, social work, public health, family studies, and psychology to focus on the role of physical touch in the context of co-sleeping, and how close physical contact in this context affects infants and their caregivers. Including an anthropological, evolutionary view of co-sleeping with other perspectives highlights it as an experience-expectant proximal context for infant growth and development. From this view, the importance of physical contact and touch in the nighttime caretaking microenvironment of co-sleeping becomes a central question, rather than an artifactual byproduct of “unhealthy” sleep arrangements. Rather than trying to eliminate co-sleeping, public health messages for parents would likely benefit from a more culturally-sensitive approach that focuses on advising how to co-sleep safely for families choosing it. For families trying to retain physical closeness between parent(s) and infants in the context of modern (especially Western) infant care practices that have reduced this physical contact, co-sleeping can be an important developmental context for encouraging and engaging in sensitive and responsive caregiving and providing a context for maternal-infant physiological synchrony and regulation.     

Experimental manipulation of emotion regulation changes mothers’ physiological and facial expressive responses to infant crying

This study examined whether instructing mothers to apply emotion regulation strategies can change mothers’ perception and reactivity to infant crying in an experimental within-subject design. Perception of crying, skin conductance level (SCL), facial expressivity, and intended caregiving responses to cry sounds were measured in mothers (N = 101, M = 30.88 years) who received suppression, reappraisal, and no emotion regulation instructions. Reappraisal resulted in lower SCL during exposure to crying and a less negative perception of crying compared to the suppression condition. In contrast, suppression resulted in increased facial expressions of sadness compared to the control condition. Thus, simple instructions on how to reframe thoughts about crying can change mothers’ perception of and reactivity to crying.     

Does category-training facilitate 11-month-olds’ acquisition of unfamiliar category-property associations?

The ability to form category-property links allows infants to extend a property from one category member to another. In two experiments, we examined whether orienting infants to the demands of the task, through categorization training, would facilitate 11-month-old infants’ category-property extensions when familiarized with a single exemplar of an unfamiliar animal category. In Experiment 1, 11-month-olds (N = 35) were trained with two familiar animal-sound pairings (i.e., dog-bark, cat-meow), familiarized with two unfamiliar animal-sound pairings and then tested on their learning and generalization of the unfamiliar animal-sound associations. Across two conditions, Experiment 2 familiarized 11-month-olds (N = 69) to one familiar (i.e., dog-bark) and one novel animal-sound pairing. Conditions differed in their presentation of familiarization trials (i.e., random or blocked). Infants were then tested on their learning and extension of the animal-sound associations. In both experiments, infants did not demonstrate learning of the original animal sound pairing, nor generalization of the sound property to new members of the animal categories. These results indicate that the two category training paradigms implemented in the current studies did not facilitate 11-month-olds’ ability to learn or generalize an unfamiliar animal-sound association, when familiarized with a single exemplar.     

The role of oxytocin in early mother-infant interactions: Variations in maternal affect attunement

The aim of the present research was to investigate the relationship between oxytocin and maternal affect attunement, as well as the role of affect attunement in the relationship between oxytocin and infant social engagement during early mother-infant interactions. Forty-three mother-infant dyads participated in the present study when infants were 4 months. They were observed during (1) a situation where no communication took place and (2) a natural interaction between mother and infant. During this procedure, three saliva samples from mothers and their infants were collected to determine their levels of oxytocin at different time points. Maternal affect attunement (maintaining attention, warm sensitivity) and infant interactive behaviors (gaze, positive, and negative affect) were coded during the natural interaction. Results indicated that overall maternal oxytocin functioning was negatively related to her warm sensitivity, while infant oxytocin reactivity together with maternal affect attunement were associated with infant positive social engagement with their mothers. Specifically, infant oxytocin reactivity was significantly related to their gazes at mother, but only for infants of highly attuned mothers. These results point to the complex role oxytocin plays in parent-infant interactions while emphasizing the need to analyze both overall oxytocin functioning as well as reactivity as different indices of human affiliative behavior.     

The BDNFval66met polymorphism and individual differences in temperament in 4-month-old infants: A pilot study

Individual differences in infants’ temperament are under genetic control. We investigated the association between brain-derived-neurotrophic-factor (BDNF_val66met) polymorphism and temperament in 63 full-term infants. Met-carriers (N = 25) had lower Regulatory capacities compared to val-homozygotes (N = 38). These findings suggest that the BDNF polymorphism affects early temperament individual differences.     

THE WORLDWIDE BURDEN OF INFANT MENTAL AND EMOTIONAL DISORDER: REPORT OF THE TASK FORCE OF THE WORLD ASSOCIATION FOR INFANT MENTAL HEALTH

Children worldwide experience mental and emotional disorders. Mental disorders occurring among young children, especially infants (birth –3 years), often go unrecognized. Prevalence rates are difficult to determine because of lack of awareness and difficulty assessing and diagnosing young children. Existing data, however, suggest that rates of disorders in young children are comparable to those of older children and adolescents (von Klitzing, Dohnert, Kroll, & Grube, 2015 ). The lack of widespread recognition of disorders of infancy is particularly concerning due to the unique positioning of infancy as foundational in the developmental process. Both the brain and behavior are in vulnerable states of development across the first 3 years of life, with potential for enduring deviations to occur in response to early trauma and deprivation. Intervention approaches for young children require sensitivity to their developmental needs within their families. The primacy of infancy as a time of unique foundational risks for disorder, the impact of trauma and violence on young children's development, the impact of family disruption on children's attachment, and existing literature on prevalence rates of early disorders are discussed. Finally, global priorities for addressing these disorders of infancy are highlighted to support prevention and intervention actions that may alleviate suffering among our youngest world citizens.     

Buddhist idealism and the problem of other minds

This essay is concerned with Indian Yogācāra philosophers’ treatment of the problem of other minds in the face of a threatened collapse into solipsism suggested by Vasubandhu’s epistemological argument for idealism. I discuss the attempts of Dharmakīrti and Ratnakīrti to address this issue, concluding that Dharmakīrti is best seen as addressing the epistemological problem of other minds and Ratnakīrti as addressing the conceptual problem of other minds.     

Three ideal observer models for rule learning in simple languages

Children learning the inflections of their native language show the ability to generalize beyond the perceptual particulars of the examples they are exposed to. The phenomenon of “rule learning”—quick learning of abstract regularities from exposure to a limited set of stimuli—has become an important model system for understanding generalization in infancy. Experiments with adults and children have revealed differences in performance across domains and types of rules. To understand the representational and inferential assumptions necessary to capture this broad set of results, we introduce three ideal observer models for rule learning. Each model builds on the next, allowing us to test the consequences of individual assumptions. Model 1 learns a single rule, Model 2 learns a single rule from noisy input, and Model 3 learns multiple rules from noisy input. These models capture a wide range of experimental results—including several that have been used to argue for domain-specificity or limits on the kinds of generalizations learners can make—suggesting that these ideal observers may be a useful baseline for future work on rule learning.     

Phonological priming and cohort effects in toddlers

Adult word recognition is influenced by prior exposure to phonologically or semantically related words (cup primes cat or plate) compared to unrelated words (door), suggesting that words are organised in the adult lexicon based on their phonological and semantic properties and that word recognition implicates not just the heard word, but also related words. We investigate the phonological organisation of the toddler lexicon with two experiments using a picture priming technique. Twenty-four month olds showed inhibition of target recognition in related primed trials compared to unrelated primed trials (Experiment 1) and also in related primed trials compared to unprimed trials (Experiment 2). Further analysis of children’s responding found that this inhibition effect was modulated by the cohort and neighbourhood size of the words tested. Overall, the results indicate a lexical basis for the reported effects and suggest that the phonological properties provide an organisational basis for words in the toddler lexicon.