Preterm birth is associated with an increased fundamental frequency of spontaneous crying in human infants at term-equivalent age.

早産児の泣きが伝えること -早期からの発達評価・支援に向けた取り組み-. 京都大学プレスリリース. 2014-08-21.Human infant crying has been researched as a non-invasive tool for assessing neurophysiological states at an early developmental stage. Little is known about the acoustic features of spontaneous cries in preterm infants, although their pain-induced cries are at a higher fundamental frequency (F0) before term-equivalent age. In this study, we investigated the effects of gestational age, body size at recording and intrauterine growth retardation (IUGR) on the F0 of spontaneous cries in healthy preterm and full-term infants at term-equivalent age. We found that shorter gestational age was significantly associated with higher F0, although neither smaller body size at recording nor IUGR was related to increased F0 in preterm infants. These findings suggest that the increased F0 of spontaneous cries is not caused by their smaller body size, but instead might be caused by more complicated neurophysiological states owing to their different intrauterine and extrauterine experiences

Visual attention during neonatal imitation in newborn macaque monkeys

Previous studies suggest that about 50% of rhesus macaque infants engage in neonatal imitation of facial gestures. Here we measured whether individual differences in newborn macaques' (n = 49) visual attention may explain why some infants imitate lipsmacking (LPS) and tongue protrusion (TP) gestures. LPS imitators, but not TP imitators, looked more to a human experimenter's face and to a control stimulus compared to nonimitators (p = .017). LPS imitation was equally accurate when infants were looking at faces and when they were looking away (p = .221); TP imitation was more accurate when infants were looking at faces (p = .001). Potentially, less attention is necessary for LPS imitation compared to TP imitation, as LPS is part of macaques' natural communicative repertoire. These findings suggest that facial gestures may differentially engage imitators and nonimitators, and infants' visual attention during neonatal assessments may uncover the conditions that support this skill

Face processing limitation to own species in primates: a comparative study in brown capuchins, Tonkean macaques and humans

Most primates live in social groups which survival and stability depend on individuals' abilities to create strong social relationships with other group members. The existence of those groups requires to identify individuals and to assign to each of them a social status. Individual recognition can be achieved through vocalizations but also through faces. In humans, an efficient system for the processing of own species faces exists. This specialization is achieved through experience with faces of conspecifics during development and leads to the loss of ability to process faces from other primate species. We hypothesize that a similar mechanism exists in social primates. We investigated face processing in one Old World species (genus Macaca) and in one New World species (genus Cebus). Our results show the same advantage for own species face recognition for all tested subjects. This work suggests in all species tested the existence of a common trait inherited from the primate ancestor: an efficient system to identify individual faces of own species only

Neonatal Oral Imitation in Patients with Severe Brain Damage

Background: Neonates reproduce facial movements in response to an adult model just after birth. This neonatal oral imitation usually disappears at about 2- to 3-months of age following the development of cortical control. There is controversy relating to the nature and neural basis of such neonatal imitation. To address this issue, we studied the relationship between oral imitation, primitive reflexes, and residual voluntary movement in patients with severe brain damage. Methods: Six male and six female patients with cerebral palsy, from 4 to 39 years, were included in this study. Oral imitation was examined when they were awake and looked at the experimenter. Patients were evaluated as performing oral imitation when they opened their mouth repeatedly without visual feedback regarding their own behavior in response to the experimenter’s oral movement. Tongue or lip protrusion was not examined because none of patients were able to do those behaviors due to their physical disability. Rooting and sucking reflexes were also investigated as representatives of primitive reflexes. Results: Six patients (50%) performed oral imitation. Mouth opening was not observed repeatedly in response to other facial expression without opening the mouth such as surprise or smile, excluding the possibility of nonspecific oral reaction. They exhibited little voluntary movement of their extremities. Half of them also manifested at least one primitive reflex. N

The Association Between Imitation Recognition and Socio-communicative Competencies in Chimpanzees (Pan troglodytes)

Imitation recognition provides a viable platform from which advanced social cognitive skills may develop. Despite evidence that non-human primates are capable of imitation recognition, how this ability is related to social cognitive skills is unknown. In this study, we compared imitation recognition performance, as indicated by the production of testing behaviors, with performance on a series of tasks that assess social and physical cognition in 49 chimpanzees. In the initial analyses, we found that males were more responsive than females to being imitated and engaged in significantly greater behavior repetitions and testing sequences. We also found that subjects who consistently recognized being imitated performed better on social but not physical cognitive tasks, as measured by the Primate Cognitive Test Battery. These findings suggest that the neural constructs underlying imitation recognition are likely associated with or among those underlying more general socio-communicative abilities in chimpanzees. Implications regarding how imitation recognition may facilitate other social cognitive processes, such as mirror self-recognition, are discussed

Neonatal Imitation in Rhesus Macaques

The emergence of social behaviors early in life is likely crucial for the development of mother–infant relationships. Some of these behaviors, such as the capacity of neonates to imitate adult facial movements, were previously thought to be limited to humans and perhaps the ape lineage. Here we report the behavioral responses of infant rhesus macaques (Macaca mulatta) to the following human facial and hand gestures: lip smacking, tongue protrusion, mouth opening, hand opening, and opening and closing of eyes (control condition). In the third day of life, infant macaques imitate lip smacking and tongue protrusion. On the first day of life, the model's mouth openings elicited a similar matched behavior (lip smacking) in the infants. These imitative responses are present at an early stage of development, but they are apparently confined to a narrow temporal window. Because lip smacking is a core gesture in face-to-face interactions in macaques, neonatal imitation may serve to tune infants' affiliative responses to the social world. Our findings provide a quantitative description of neonatal imitation in a nonhuman primate species and suggest that these imitative capacities, contrary to what was previously thought, are not unique to the ape and human lineage. We suggest that their evolutionary origins may be traced to affiliative gestures with communicative functions

Reciprocal face-to-face communication between rhesus macaque mothers and their newborn infants

Human mothers interact emotionally with their newborns through exaggerated facial expressions, speech, mutual gaze, and body contact, a capacity that has long been considered uniquely human (1–4). Current developmental psychological theories propose that this pattern of mother-infant exchange promotes the regulation of infant emotions (4–6) and serves as a precursor of more complex forms of social exchange including perspective-taking and empathy. Here we report that in rhesus macaques, mother-infant pairs also communicate intersubjectively using complex forms of emotional exchanges including exaggerated lipsmacking, sustained mutual gaze, mouth-mouth contacts, and neonatal imitation. Infant macaques solicit their mother’s affiliative responses and actively communicate to her. However, this form of communication disappears within the infant’s first month of life. Our data challenge the view that the mother-infant communicative system functions in order to sustain proximity and that infants are simply passive recipients in such interaction. Thus, emotional communication between mother and infant is not uniquely human. Instead, we can trace back to macaques the evolutionary foundation of those behaviors that are crucial for the establishment of a functional capacity to socially exchange with others

The Power of an Infant\u27s Smile: Maternal Physiological Responses to Infant Emotional Expressions

Infant emotional expressions, such as distress cries, evoke maternal physiological reactions. Most of which involve accelerated sympathetic nervous activity. Comparatively little is known about effects of positive infant expressions, such as happy smiles, on maternal physiological responses. This study investigated how physiological and psychological maternal states change in response to infants\u27 emotional expressions. Thirty first-time mothers viewed films of their own 6- to 7-month-old infants\u27 affective behavior. Each observed a video of a distress cry followed by a video showing one of two expressions (randomly assigned): a happy smiling face (smile condition) or a calm neutral face (neutral condition). Both before and after the session, participants completed a self-report inventory assessing their emotional states. The results of the self-report inventory revealed no effects of exposure to the infant videos. However, the mothers in the smile condition, but not in the neutral condition, showed deceleration of skin conductance. These findings demonstrate that the mothers who observed their infants smiling showed decreased sympathetic activity. We propose that an infant\u27s positive emotional expression may affect the branch of the maternal stress-response system that modulates the homeostatic balance of the sympathetic and parasympathetic nervous systems

The rapid development of explicit gaze judgment ability at 3 years

Two studies examined development of the ability to judge what another person is looking at. In Study 1, 54 2- to 4-year-olds judged where someone was looking in real-life, photograph, and drawing formats. A minority of 2-year-olds but a majority of older children passed all tasks, suggesting the ability arises around 3 years. Study 2 examined the fine-grained gaze judgment of 76 3- to 6-year-olds and 15 adults, using gaze differences of 10° and 15°. Development of gaze judgment was gradual, from chance at 3 years to near-adult level performance at 6 years. Although performance was better when a congruent head turn was included, 3-year-olds were still at chance on 10° head-turn trials. The findings suggest that the ability to explicitly judge gaze is novel at 3 years and develops slowly thereafter. It therefore does not develop out of earlier gaze-following. General implications for the evolution and development of gaze processing are discussed

Interindividual differences in neonatal limitation and the development of action chains in rhesus macaques

The capacity to imitate facial gestures is highly variable in rhesus macaques and this variability may be related to differences in specific neurobehavioral patterns of development. This study evaluated the differential neonatal imitative response of 41 macaques in relation to the development of sensory, motor, and cognitive skills throughout the 1st month of life. The results show that infants who imitate facial gestures display more developed skills in goal-directed movements (reaching–grasping and fine hand motor control) than non-imitators. These differences might reflect, at least in part, the differential maturation of motor chains in the parietal and motor cortices, which partly overlap with those of the mirror neuron system. Thus, neonatal imitation appears to be a predictor of future neurobehavioral development