Endogenous Control and Reward-based Mechanisms Shape Infants' Attention Biases to Caregiver Faces.

Infants rely on developing attention skills to identify relevant stimuli in their environments. Although caregivers are socially rewarding and a critical source of information, they are also one of many stimuli that compete for infants' attention. Young infants preferentially hold attention on caregiver faces, but it is unknown whether they also preferentially orient to caregivers and the extent to which these attention biases reflect reward-based attention mechanisms. To address these questions, we measured 4- to 10-month-old infants' (N = 64) frequency of orienting and duration of looking to caregiver and stranger faces within multi-item arrays. We also assessed whether infants' attention to these faces related to individual differences in Surgency, an indirect index of reward sensitivity. Although infants did not show biased attention to caregiver versus stranger faces at the group level, infants were increasingly biased to orient to stranger faces with age and infants with higher Surgency scores showed more robust attention orienting and attention holding biases to caregiver faces. These effects varied based on the selective attention demands of the task, suggesting that infants' attention biases to caregiver faces may reflect both developing attention control skills and reward-based attention mechanisms.

Outcome of creating clustering nursing care and healing environment on premature infants' behavioural outcomes.

We conducted a quasi-experimental study in two neonatal intensive care units (NICUs) from January to July 2021, focusing on the effects of clustering nursing care and creating a healing environment on premature infants' behavioural outcomes. The study included 106 infants, with 53 in both the study and control groups. Significant improvements were observed in organisation state/sleep and responsiveness/interaction domains in the study group, along with shorter hospital stays and greater weight gain on discharge. These findings highlight the positive impact of targeted interventions on premature infants' developmental outcomes, emphasising the need for comprehensive care strategies in NICU settings.

What we don't know about what babies know: Reconsidering psychophysics, exploration, and infant behavior.

Researchers must infer "what babies know" based on what babies do. Thus, to maximize information from doing, researchers should use tasks and tools that capture the richness of infants' behaviors. We clarify Gibson's views about the richness of infants' behavior and their exploration in the service of guiding action - what Gibson called "learning about affordances."

Infant attachment does not depend on neonatal amygdala and hippocampal structure and connectivity.

Infant attachment is an antecedent of later socioemotional abilities, which can be adversely affected by preterm birth. The structural integrity of amygdalae and hippocampi may subserve attachment in infancy. We aimed to investigate associations between neonatal amygdalae and hippocampi structure and their whole-brain connections and attachment behaviours at nine months of age in a sample of infants enriched for preterm birth. In 133 neonates (median gestational age 32 weeks, range 22.14-42.14), we calculated measures of amygdala and hippocampal structure (volume, fractional anisotropy, mean diffusivity, neurite dispersion index, orientation dispersion index) and structural connectivity, and coded attachment behaviours (distress, fretfulness, attentiveness to caregiver) from responses to the Still-Face Paradigm at nine months. After multiple comparisons correction, there were no significant associations between neonatal amygdala or hippocampal structure and structural connectivity and attachment behaviours: standardised ß values - 0.23 to 0.18, adjusted p-values > 0.40. Findings indicate that the neural basis of infant attachment in term and preterm infants is not contingent on the structure or connectivity of the amygdalae and hippocampi in the neonatal period, which implies that it is more widely distributed in early life and or that network specialisation takes place in the months after hospital discharge.

Neonatal neurobehavior associated with developmental changes from age 2 to 3 in very preterm infants.

OBJECTIVE: Understand how high-risk infants' development changes over time. Examine whether NICU Network Neurobehavioral Scale (NNNS) profiles are associated with decrements in developmental outcomes between ages 2 and 3 years in infants born very preterm. STUDY DESIGN: The Neonatal Outcomes for Very preterm Infants (NOVI) cohort is a multisite prospective study of 704 preterm infants born <30 weeks' gestation across nine university and VON affiliated NICUs. Data included infant neurobehavior measured by NNNS profiles at NICU discharge and the Bayley Scales of Infant and Toddler Development (BSID-III) at ages 2 and 3 years. Generalized estimating equations tested associations between NNNS profiles and BSID-III composite score changes between ages 2 and 3 years. RESULTS: The final study sample included 433 infants with mean gestational age of 27 weeks at birth. Infants with dysregulated NNNS profiles were more likely to have decreases in BSID-III Cognitive (OR = 2.66) and Language scores (OR = 2.53) from age 2 to 3 years compared to infants with more well-regulated neurobehavioral NNNS profiles. Further, infants with more well-regulated NNNS profiles were more likely to have increases in BSID-III Cognitive scores (OR = 2.03), rather than no change, compared to infants with dysregulated NNNS profiles. CONCLUSIONS AND RELEVANCE: Prior to NICU discharge, NNNS neurobehavioral profiles identified infants at increased risk for developing later language and cognitive challenges. Findings suggests that neonatal neurobehavior provides a unique, clinically significant contribution to the evaluation of very preterm infants to inform treatment planning for the most vulnerable.

Caregiver reactions to babbling organize turn-taking interactions: Facilitative effects of vocal versus non-vocal responses.

Turn-taking interactions are foundational to the development of social, communicative, and cognitive skills. In infants, vocal turn-taking experience is predictive of infants' socioemotional and language development. However, different forms of turn-taking interactions may have different effects on infant vocalizing. It is presently unknown how caregiver vocal, non-vocal and multimodal responses to infant vocalizations compare in extending caregiver-infant vocal turn-taking bouts. In bouts that begin with an infant vocalization, responses that maintain versus change the communicative modality may differentially affect the likelihood of further infant vocalizing. No studies have examined how caregiver response modalities that either matched or differed from the infant acoustic (vocal) modality might affect the temporal structure of vocal turn-taking beyond the initial serve-and-return exchanges. We video-recorded free-play sessions of 51 caregivers with their 9-month-old infants. Caregivers responded to babbling most often with vocalizations. In turn, caregiver vocal responses were significantly more likely to elicit subsequent infant babbling. Bouts following an initial caregiver vocal response contained significantly more turns than those following a non-vocal or multimodal response. Thus prelinguistic turn-taking is sensitive to the modality of caregivers' responses. Future research should investigate if such sensitivity is grounded in attentional constraints, which may influence the structure of turn-taking interactions.

Developmental cascades of vocal turn-taking connect prelinguistic vocalizing with early language.

Conversational turn-taking is ubiquitously found in caregiver-infant interactions, and robustly predictive of infant communicative development. Over the first year, infants take quick adult-like vocal turns with caregivers. Many studies have documented the consistency of caregiver responsiveness and its influence on infant rapid language growth. However, few have examined how caregiver responsiveness facilitates extended vocal turn-taking in real-time with infants over the first year. The influence of prelinguistic vocal turn-taking on the emergence of language has also been under-investigated. We analyzed free-play sessions of 30 caregivers and their infants at both 5 and 10 months, and obtained infant language outcomes at 18 months. We examined the developmental consistency (group-level continuity and dyad-order stability) and change of infant volubility, caregiver responses to babbling in vocal, non-vocal and multimodal modalities, and the influence of modality on caregiver-infant vocal turn-taking. Caregiver contingent responsiveness to infant babbling at 5 months predicted vocal turn-taking at 10 months. Developmental increases in prelinguistic vocalizing and vocal turn-taking from 5 to 10 months predicted infant language outcomes at 18 months. At both 5 and 10 months, caregiver vocal responses were more effective in extending turn-taking than non-vocal or multimodal responses. In summary, prelinguistic vocal turn-taking, facilitated by caregiver vocal responsiveness, is positively related to the emergence of early language.

Masked or not, I smile to you: Exploring full-term and preterm infants' social smiles to adults wearing a protective facemask.

The early emergence of social smiles is an important milestone of infants' socio-emotional development. Our aim was to assess how the use of protective facemasks by adults affects the display of social smiles in preterm (PT) and full-term (FT) infants at 3 months (corrected age for prematurity). We enrolled 30 FT and 30 PT infants (gestational age ≤ 32 weeks). Infants' social smiles displays were assessed at 2-3-month-age (corrected) across a three-episode (masked mother; unmasked mother; masked adult female stranger) videotaped interactive task. During each episode, the adult was instructed to maintain specific facial expressions (happy-smiling, sad-frowning, neutral-unresponsive) for 15 second windows and then instructed to interact spontaneously for 45 s (of which the first 15 s were coded). FT and PT infants did not differ in the display of social smiles. In both groups, social smiles were mostly exhibited in response to happy/smiling and spontaneously interacting partners. Overall, no effect of wearing a protective facemask emerged. The use of protective facemasks did not result in a lower display of social smiles. The findings suggest that FT and PT might be equally sensitive to their adult interactive partners in terms of social smiles displays at 2-3-month-age.

Variations in infants' physical and social environments shape spontaneous locomotion.

Independent locomotion is associated with a range of positive developmental outcomes, but unlike cognitive, linguistic, and social skills, acquiring motor skills requires infants to generate their own input for learning. We tested factors that shape infants' spontaneous locomotion by observing forty 12- to 22-month-olds (19 girls, 21 boys) during free play. Infants were recruited from the New York City area, and caregivers reported that 25 infants were White, six were Asian, four were Black, and five had multiple races; four were Hispanic or Latino. All infants played in four conditions: two environmental conditions (gross-motor toys, fine-motor toys) crossed with two social conditions (alone, together with a caregiver). Infants moved more in the gross-motor toy conditions than in the fine-motor toy conditions. However, the effect of playing with a caregiver differed by toy condition. In the gross-motor toy conditions, playing with a caregiver did not affect how much infants moved, but in the fine-motor toy conditions, playing with a caregiver further depressed infant locomotion. Infants with more walking experience moved more with gross-motor toys but not with fine-motor toys. Differences in the amount of locomotion between conditions were related to how infants used toys and the interactions between infants and caregivers. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The breadth and specificity of 18-month-old's infant-initiated interactions in naturalistic home settings.

Infants actively initiate social interactions aiming to elicit different types of responses from other people. This study aimed to document a variety of communicative interactions initiated by 18-month-old Turkish infants from diverse SES (N = 43) with their caregivers in their natural home settings. The infant-initiated interactions such as use of deictic gestures (e.g., pointing, holdouts), action demonstrations, vocalizations, and non-specific play actions were coded from video recordings and classified into two categories as need-based and non-need-based. Need-based interactions were further classified as a) biological (e.g., feeding); b) socio-emotional (e.g., cuddling), and non-need-based interactions (i.e., communicative intentions) were coded as a) expressive, b) requestive; c) information/help-seeking; d) information-giving. Infant-initiated non-need-based (88%) interactions were more prevalent compared to need-based interactions (12%). Among the non-need-based interactions, 50% aimed at expressing or sharing attention or emotion, 26% aimed at requesting an object or an action, and 12% aimed at seeking information or help. Infant-initiated information-giving events were rare. We further investigated the effects of familial SES and infant sex, finding no effect of either on the number of infant-initiated interactions. These findings suggest that at 18 months, infants actively communicate with their social partners to fulfil their need-based and non-need-based motivations using a wide range of verbal and nonverbal behaviors, regardless of their sex and socio-economic background. This study thoroughly characterizes a wide and detailed range of infant-initiated spontaneous communicative bids in hard-to-access contexts (infants' daily lives at home) and with a traditionally underrepresented non-WEIRD population.

Infant sustained attention differs by context and social content in the first 2 years of life.

Sustained attention (SA) is an endogenous form of attention that emerges in infancy and reflects cognitive engagement and processing. SA is critical for learning and has been measured using different methods during screen-based and interactive contexts involving social and nonsocial stimuli. How SA differs by measurement method, context, and stimuli across development in infancy is not fully understood. This 2-year longitudinal study examines attention using one measure of overall looking behavior and three measures of SA-mean look duration, percent time in heart rate-defined SA, and heart rate change during SA-in N = 53 infants from 1 to 24 months across four unique task conditions: social videos, nonsocial videos, social interactions (face-to-face play), and nonsocial interactions (toy engagement). Results suggest that developmental changes in attention differ by measurement method, task context (screen or interaction), and task stimulus (social or nonsocial). During social interactions, overall looking and look durations declined after age 3-4 months, whereas heart rate-defined attention measures remained stable. All SA measures were greater for videos than for live interaction conditions throughout the first 6 months, but SA to social and nonsocial stimuli within each task context were equivalent. In the second year of life, SA measured with look durations was greater for social videos compared to other conditions, heart rate-defined SA was greater for social videos compared to nonsocial interactions, and heart rate change during SA was similar across conditions. Together, these results suggest that different measures of attention to social and nonsocial stimuli may reflect unique developmental processes and are important to compare and consider together, particularly when using infant attention as a marker of typical or atypical development. RESEARCH HIGHLIGHTS: Attention measure, context, and social content uniquely differentiate developmental trajectories of attention in the first 2 years of life. Overall looking to caregivers during dyadic social interactions declines significantly from 4 to 6 months of age while sustained attention (SA) to caregivers remains stable. Heart rate-defined SA generally differentiates stimulus context where infants show greater SA while watching videos than while engaging with toys.

Building language learning: Relations between infant attention and social contingency in the first year of life.

In Western societies, social contingency, or prompt and meaningful back-and-forth exchanges between infant and caregiver, is a powerful feature of the early language environment. Research suggests that infants with better attentional skills engage in more social contingency during interactions with adults and, in turn, social contingency supports infant attention. This reciprocity is theorized to build infant language skills as the adult capitalizes on and extends the infant's attention during socially contingent interactions. Using data from 104 infants and caregivers, this paper tests reciprocal relations between infant attention and social contingency at 6- and 12-months and the implications for infant vocabulary at 18-months. Infant attentional skills to social (women speaking) and nonsocial (objects dropping) events were assessed, and social contingency was examined during an 8-minute toy play interaction with a caregiver. Child receptive and expressive vocabulary was measured by caregiver-report. Both social and nonsocial attentional skills related to engagement in social contingency during caregiver-infant interaction, though only models that included social attention and social contingency predicted vocabulary. These findings provide empirical evidence for the proposed reciprocal relations between infant attention and social contingency as well as how they relate to later language.

It's You and Me: Infants' cross-modal communicative signals and mother-infant interactive behavior predict infant regulatory patterns in the still-face paradigm at 3 months.

Infant regulatory behavior develops since birth and impacts their early social interactions. Infants differ in the relative coherence and incoherence of their cross-modal communicative signals during en-face infant-caregiver interactions. We expand this research by evaluating whether different infant regulatory patterns observed during the Face-to-Face Still-Face (FFSF) at 3 months are associated with the coherence or incoherence of infants' cross-modal communicative behaviors during en-face interactions or with multiple dimensions of mother-infant interactive behavior during free-play. Analyses were based on data collected from 100 mother-infant dyads from urban, working- and middle-class backgrounds in Portugal who were videotaped during the FFSF and free play at 3 months. Results confirm that infants' different regulatory behavior patterns in the FFSF at 3 months are associated with the coherence and incoherence of their cross-modal interactive behaviors and specific aspects of mother-infant interaction. Infants with a Social-Positive oriented regulatory pattern during the FFSF displayed more coherent and less incoherent communicative behaviors with their mothers and were more cooperative during free play. In turn, their mothers were more sensitive. Our findings support the perspective that infants' regulatory behavior strategies in the context of caregiver regulatory support and sensitivity are likely to increase dyadic correspondence and infant ability to engage with the world.

Real-time teaching and learning: Caregivers teaching infants to descend stairs.

Learning to descend stairs requires motor and cognitive capacities on the part of infants and opportunities for practice and assurance of safety offered by caregivers. The American Academy of Pediatrics prescribes the age strategy to teach toddlers to safely descend stairs but without much consideration for individual differences in infants' skills or caregivers' techniques. The purpose of this study was to observe the natural ways in which caregivers teach infants to descend stairs at home and the extent to which infants abide. Of particular interest was to examine the dynamic nature of caregivers' teaching and infants' learning over the session with attention to individual differences. Dyads (N = 59) were videorecorded on Zoom for 10 min interacting on stairs at home in the United States, Brazil, Canada, Italy, and Spain. Infants (n = 30 girls, 29 boys; 13-month-olds ± 1 week) were novice walkers (M = 2.04 months walking experience). Caregivers used a variety of teaching strategies and focused on "backing" and "scooting." Infants were more likely to heed caregivers' guidance when caregivers provided hands-on support and verbal encouragement suggesting infants were engaged and responsive to caregivers' overtures. Infants' walking experience predicted change in descent strategy over the session. Although infants did not show evidence of learning over the session, consistent caregiver instruction suggested caregivers were persistent, if not effective, teachers. Teaching and learning motor skills in a potentially risky task creates a unique opportunity for interaction, allowing infants and caregivers to learn from one another. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Disinhibited attachment behavior among infants reared at home: Relations to maternal severe mental illness and personality disorder symptoms.

Disinhibited attachment behavior (DAB) among infants is persistent and associated with behavioral and relational problems throughout childhood and adolescence. Little is known about risk factors for DAB among infants reared at home, although studies have linked DAB with maternal psychiatric hospitalization and maternal borderline personality disorder. The aim of the current study was to further assess the association between DAB, maternal severe mental illness (SMI; schizophrenia, bipolar disorder, and depression), and maternal PD symptoms. Ninety-three mothers and their infants participated in the study: 46.2% with SMI and 53.8% with no-diagnosis. During pregnancy, mothers were assessed on the Structured Clinical Interview for DSM-5 and the Standardized Assessment of Personality Abbreviated Scale a validated measure of personality disorder (PD) symptoms. Infants were assessed for DAB at 1 year of age using the rating of infant stranger engagement, assessed during the strange situation procedure. Infants of mothers with clinical levels of PD symptoms were significantly more likely to display DAB (OR = 3.44) compared to infants of mothers without clinical levels of PD symptoms. Maternal SMI was not significantly associated with infant DAB. Because most mothers with clinical levels of PD symptoms also had comorbid diagnoses in this study, further work is needed to evaluate the role of comorbidity. These results add to the emerging literature indicating that maternal personality symptoms may be a risk factor for indiscriminate forms of attachment behavior among home-reared infants. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Let's make music as we normally do: A systematic review of how early natural musical interactions between infant and caregiver have been studied in research.

Musical interactions between babies and their primary caregivers are very frequent during the early years of life and their impact on dyadic interaction and infants' development has garnered significant attention in recent literature. However, the difficulties that natural observations entail have meant that research often carries out methodological manipulations that have a significant impact on the phenomenon studied. In order to clarify how to investigate best natural musical interactions and the information that these can provide, we have carried out a systematic review to analyze the proposed scenarios and the variables analyzed in the studies published on such interactions between main caregivers and babies under three years old. We have screened 971 articles and yielded 27. We have found a higher prevalence in the literature of studies on singing interactions, between mothers and babies under 12 months of age. We have also been able to identify two extremes in terms of methodological structuring of natural interactions. Regarding the analysis variables, a few behaviors are repeated throughout the studies, being emotions, rhythmic behaviors and characterizations of the vocal emissions common between parents and babies. Synchrony is the dyadic variable with the most weight and also one of the preferred focuses of interest in the most recent literature that has undergone a shift of focus from characterization of musical interactions to the search for the mechanisms that underlie and make them specific.

The violation-of-expectation paradigm: A conceptual overview.

For over 35 years, the violation-of-expectation paradigm has been used to study the development of expectations in the first 3 years of life. A wide range of expectations has been examined, including physical, psychological, sociomoral, biological, numerical, statistical, probabilistic, and linguistic expectations. Surprisingly, despite the paradigm's widespread use and the many seminal findings it has contributed to psychological science, so far no one has tried to provide a detailed and in-depth conceptual overview of the paradigm. Here, we attempted to do just that. We first focus on the rationale of the paradigm and discuss how it has evolved over time. We then show how improved descriptions of infants' looking behavior, together with the addition of a rich panoply of brain and behavioral measures, have helped deepen our understanding of infants' responses to violations. Next, we review the paradigm's strengths and limitations. Finally, we end with a discussion of challenges that have been leveled against the paradigm over the years. Through it all, our goal was twofold. First, we sought to provide psychologists and other scientists interested in the paradigm with an informed and constructive analysis of its theoretical origins and development. Second, we wanted to take stock of what the paradigm has revealed to date about how infants reason about events, and about how surprise at unexpected events, in or out of the laboratory, can lead to learning, by prompting infants to revise their working model of the world. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Pandemic beyond the virus: maternal COVID-related postnatal stress is associated with infant temperament.

BACKGROUND: Studies have shown that infant temperament varies with maternal psychosocial factors, in utero illness, and environmental stressors. We predicted that the pandemic would shape infant temperament through maternal SARS-CoV-2 infection during pregnancy and/or maternal postnatal stress. To test this, we examined associations among infant temperament, maternal prenatal SARS-CoV-2 infection, maternal postnatal stress, and postnatal COVID-related life disruptions. METHODS: We tested 63 mother-infant dyads with prenatal maternal SARS-CoV-2 infections and a comparable group of 110 dyads without infections. To assess postnatal maternal stress, mothers completed the Perceived Stress Scale 4 months postpartum and an evaluation of COVID-related stress and life disruptions 6 months postpartum. Mothers reported on infant temperament when infants were 6-months-old using the Infant Behavior Questionnaire-Revised (IBQ-R) Very Short Form. RESULTS: Maternal SARS-CoV-2 infection during pregnancy was not associated with infant temperament or maternal postnatal stress. Mothers with higher self-reported postnatal stress rated their infants lower on the Positive Affectivity/Surgency and Orienting/Regulation IBQ-R subscales. Mothers who reported greater COVID-related life disruptions rated their infants higher on the Negative Emotionality IBQ-R subscale. CONCLUSIONS: Despite no effect of prenatal maternal SARS-CoV-2 infection, stress and life disruptions incurred by the COVID-19 pandemic were associated with infant temperament at 6-months. IMPACT: SARS-CoV-2 infection during pregnancy is not associated with postnatal ratings of COVID-related life disruptions, maternal stress, or infant temperament. Postnatal ratings of maternal stress during the COVID-19 pandemic are associated with normative variation in maternal report of infant temperament at 6 months of age. Higher postnatal ratings of maternal stress are associated with lower scores on infant Positive Affectivity/Surgency and Orienting/Regulation at 6 months of age. Higher postnatal ratings of COVID-related life disruptions are associated with higher scores on infant Negative Emotionality at 6 months of age.

Interactional preludes to infants' affective climax - Mother-infant interaction around infant smiling in two cultures.

Due to limited research on cross-cultural similarities and differences in the development of infant smiling, the main goals of this study were to analyze, first, the development of infants' bouts of intense smiling during their third month and, second, the interactional preludes to infants' affective climax in two cultural contexts, namely Kichwa families from the Ecuadorian Andes region and educated urban middle-class families from Münster, Germany, which differ concerning their cultural models on infant smiling. Based on a longitudinal, naturalistic study design, mother-infant interaction in Kichwa (n = 10) and Münster (n = 10) families was analyzed when infants were 9 and 13 weeks old. Following a mixed methods approach, a quantitative analysis of infant smiling based on a 1-second interval-coding approach showed that there was a significant increase in infants' high-intensity positive affect from 9 to 13 weeks in the Münster, but not the Kichwa sample, leading to significant cross-cultural differences at 13 weeks. Complementarily, the qualitative analysis of the interactional preludes to the 66 infants' affective climaxes at 13 weeks identified two main patterns that characterized the dynamic that resulted in high-intensity positive affect and that were similar across the two cultural contexts: the first was intense and multimodal stimulation with repetition and theme variation, and the second was positively tuned and mutually contingent responsiveness, often in the form of prolonged proto-conversations between mother and infant. Overall, this open approach converged on key mechanisms underlying infant smiling, namely infants' experience of mastery based on effortful assimilation or self-efficacy, which was embedded in episodes of intersubjective coordination. Overall, these results suggest universality without uniformity; that is, similar interactional mechanisms are associated with high-intense positivity in infants, while the episodes are co-constructed differently in different dyads and high-intense positivity varies in significance and frequency across cultures.

The Bidirectional View of Mother-Infant Interaction by Gaze and Facial Affect. / Anne-Bebek Etkilesimine Çift-Yönlü Bakis Açisi: Bakis ve Yüz Duygulanimi.

OBJECTIVE: The aim of this research was to assess gaze behaviors and facial affect expressions in mother-infant interaction within the frame of self-contingency and interactive contingency, reflecting self-regulation and interactive regulation, respectively. In Model 1, second-by-second changing gaze behaviors (on partner's face/off partner's face) and in Model 2, facial affect expressions (from positive to negative) were examined. Self-contingency reflects the variability or stability in gaze directions and facial affect expressions in each partner. Interactive contingency reflects the degree of mother-infant gaze and facial affect attunement or interactive regulation relative to each other. METHOD: Sample was composed of 56 healthy mother-infant dyads. All infants were 4 months old, and mean maternal age was 29.61 (SD=3.71). Mother-infant interactions were filmed at the lab. Interactions were coded second-by-second for mother-infant gaze behaviors and facial affect expressions with video microanalysis method. The analysis method was multilevel-multivariate time series analysis. RESULTS: According to Model 1-2, mother-infant gaze behaviors and facial affect expressions were neither too stable nor too variable, rather, the change in gaze behaviors and facial affect expressions in each partner showed predictable patterns. Mothers regulated their gaze behaviors and facial affect expressions in relation to that of their infants. Infants regulated their facial affect expressions in relation to their mothers' facial affect expressions, but infant gaze interactive contingency to mother gaze was marginally significant. CONCLUSION: In interactions, infants and mothers regulate the rhythms of their own behavior and at the same time contingently coordinate with that of the partner. This bi-directionally regulating environment is the foundation of infants' relationship expectations and bio-socialbehavioral regulation capacity, which may be related to psychopathology in future.