Infants\' interactions with social partners are richly multimodal. Dyads respond to and coordinate their visual attention, gestures, vocalizations, speech, manual actions, and manipulations of objects. Although infants are typically described as active learners, previous experimental research has often focused on how infants learn from stimuli that is well-crafted by researchers. Recent research studying naturalistic, free-flowing interactions has explored the meaningful patterns in dyadic behavior that relate to language learning. Infants\' manual engagement and exploration of objects supports their visual attention, creates salient and diverse views of objects, and elicits labeling utterances from parents. In this chapter, we discuss how the cascade of behaviors created by infant multimodal attention plays a fundamental role in shaping their learning environment, supporting real-time word learning and predicting later vocabulary size. We draw from recent at-home and cross-cultural research to test the validity of our mechanistic pathway and discuss why hands matter so much for learning. Our goal is to convey the critical need for developmental scientists to study natural behavior and move beyond our \"tried-and-true\" paradigms, like screen-based tasks. By studying natural behavior, the role of infants\' hands in early language learning was revealed-though it was a behavior that was often uncoded, undiscussed, or not even allowed in decades of previous research. When we study infants in their natural environment, they can show us how they learn about and explore their world. Word learning is hands-on.

Many group-living animals coordinate social behaviours using contact calls, which can be produced for all group members or targeted at specific individuals. In the disc-winged bat, Thyroptera tricolor, group members use \'inquiry\' and \'response\' calls to coordinate daily movements into new roosts (furled leaves). Rates of both calls show consistent among-individual variation, but causes of within-individual variation remain unknown. Here, we tested whether disc-winged bats produce more contact calls towards group members with higher kinship or association. In 446 experimental trials, we recorded 139 random within-group pairs of one flying bat (producing inquiry calls for roost searching) and one roosting bat (producing response calls for roost advertising). Using generalized linear mixed-effect models (GLMM), we assessed how response and inquiry calling rates varied by sender, receiver, genetic kinship and co-roosting association rate. Calling rates varied consistently across senders but not by receiver. Response calling was influenced by inquiry calling rates, but neither calling rate was higher when the interacting pair had higher kinship or association. Rather than dyadic calling rates indicating within-group relationships, our findings are consistent with the hypothesis that bats produce contact calls to maintain contact with any or all individuals within a group while collectively searching for a new roost site. This article is part of the theme issue \'The power of sound: unravelling how acoustic communication shapes group dynamics\'.

In this study we introduce an innovative mathematical and statistical framework for the analysis of motion energy dynamics in psychotherapy sessions. Our method combines motion energy dynamics with coupled linear ordinary differential equations and a measurement error model, contributing new clinical parameters to enhance psychotherapy research. Our approach transforms raw motion energy data into an interpretable account of therapist-patient interactions, providing novel insights into the dynamics of these interactions. A key aspect of our framework is the development of a new measure of synchrony between the motion energies of therapists and patients, which holds significant clinical and theoretical value in psychotherapy. The practical applicability and effectiveness of our modelling and estimation framework are demonstrated through the analysis of real session data. This work advances the quantitative analysis of motion dynamics in psychotherapy, offering important implications for future research and therapeutic practice.

Romantic relationships are defined by emotion dynamics, or how the emotions of one partner at a single timepoint can affect their own emotions and the emotions of their partner at the next timepoint. Previous research has shown that the level of these emotion dynamics plays a role in determining the state and quality of the relationship. However, this research has not examined whether the estimated emotion dynamics change over time, and how the change in these dynamics might relate to relationship outcomes, despite changes in dynamics being likely to occur. We examined whether the magnitude of variation in emotion dynamics over time was associated with relationship outcomes in a sample of 148 couples. Time-varying vector autoregressive models were used to estimate the emotion dynamics for each couple, and the average and standard deviation of the dynamics over time was related to relationship quality and relationship dissolution 1-2 years later. Our results demonstrate that certain autoregressive and cross-lagged parameters do show significant variation over time, and that this variation is associated with relationship outcomes. Overall, this study demonstrates the importance of accounting for change in emotion dynamics over time, and the relevance of this change to the prediction of future outcomes.

The current study tests the Motivational Interviewing (MI) technical and relational hypotheses in a sample of Hispanic/Latinx adults (N = 276) who engage in heavy alcohol consumption. MI causal theory hypothesizes that therapist use of MI consistent skills (i.e., technical hypothesis) and embodiment of the MI Spirit (i.e., relational hypothesis) will elicit client change talk, which is a putative mechanism of positive client outcome after the session. We tested these associations in a rigorous parallel process latent growth curve mediation modeling framework. The data are from a completed randomized clinical trial of a culturally-adapted (CAMI) versus un-adapted MI targeting hazardous alcohol use and consequences. Results. The unconditional growth models for the mediator (i.e., proportion of change talk relative to sustain talk) and two study outcomes (i.e., percent of heavy drinking days; alcohol-related consequences) showed a linear effect over a 12-month period with a slower rate of growth at later timepoints. Contrary to expectations, the latent growth mediation models did not show relationships between MI-consistent skills (i.e., technical predictor) or latent MI Spirit (i.e., relational indicator) and the slope factor for proportion change talk. The slope factor for proportion change talk was also not associated with the slope factors for percent heavy drinking and consequences over follow-up. Conclusions. In this novel population for MI process analysis, the technical and relational hypotheses were not supported. Studies that are exploratory may be needed to further investigate the causal model in populations that are not often represented in MI process research.

Caregivers use a of combination labeling, pointing, object grasping, and gaze to communicate with infants about referents in their environment. By two years of age, children reliably use these referent-oriented cues to communicate and learn. While there is some evidence from lab-based studies that younger infants attend to and use referent-oriented cues during communication, some more naturalistic studies have found that in the first year of life, infants do not robustly leverage these cues during dyadic interactions. The current study examined parent and infant gaze, touching, pointing, and reaching to referents for a wide range of nouns, verbs, adjectives, and other early-learned words during 59 one-hour head-camera recordings sampled from one English-learning infants\' life between 6 and 12 months of age. We found substantial variability across individual words for all cues. Some variability was explained by referent concreteness and the grammatical category of the label. The parent\'s touching of labeled referents increased across months, suggesting that parent-infant-referent interactions may change with development. Future studies should investigate the trajectories of specific types of words and contexts, rather than attempting to discover possibly non-existent universal trajectories of parent and infant referent-oriented behaviors.

Sibling relationships provide unique social experiences that can vary across the lifespan. Early sibling social interactions (ESSI) have been associated with children\'s own relationship and developmental outcomes, highlighting the essential role that sibling encounters play, even from a young age. Understanding how these social exchanges occur and unfold and the range of opportunities they provide can shed light on critical aspects of early childhood development and family life. However, the methodological approach used in studying ESSI can influence our understanding of these early experiences. This systematic review aims to delineate the methodological framework adopted in observational studies of ESSI. Through a systematic search of psychology and domain-general databases until March 2023, we focused on studies that addressed bidirectional naturalistic interactions in young sibling dyads (at least one child aged 0-36 months). Of the 713 articles screened, only 63 met the inclusion criteria. Findings regarding three main issues are examined, including sample characteristics, study designs and procedures, and sibling interactive behaviours targeted. Previous research has focused on a diverse range of sibling behavioral exchanges, including cues of children\'s social skills and relationship quality within mainly ecological contexts. However, limitations in representativeness and standardization have been identified. Future studies should incorporate sequential analyses to fully comprehend the interactive nature of early sibling social encounters.

Caregivers often tailor their language to infants\' ongoing actions (e.g., \"are you stacking the blocks?\"). When infants develop new motor skills, do caregivers show concomitant changes in their language input? We tested whether the use of verbs that refer to locomotor actions (e.g., \"come,\" \"bring,\" \"walk\") differed for mothers of 13-month-old crawling (N = 16) and walking infants (N = 16), and mothers of 18-month-old experienced walkers (N = 16). Mothers directed twice as many locomotor verbs to walkers compared to same-age crawlers, but mothers\' locomotor verbs were similar for younger and older walkers. In real-time, mothers\' use of locomotor verbs was dense when infants were locomoting, and sparse when infants were stationary, regardless of infants\' crawler/walker status. Consequently, infants who spent more time in motion received more locomotor verbs compared to infants who moved less frequently. Findings indicate that infants\' motor skills guide their in-the-moment behaviors, which in turn shape the language they receive from caregivers. RESEARCH HIGHLIGHTS: Infants\' motor skills guide their in-the-moment behaviors, which in turn shape the language they receive from caregivers. Mothers directed more frequent and diverse verbs that referenced locomotion (e.g., \"come,\" \"go,\" \"bring\") to walking infants compared to same-aged crawling infants. Mothers\' locomotor verbs were temporally dense when infants locomoted and sparse when infants were stationary, regardless of whether infants could walk or only crawl.

BACKGROUND: Mealtime is a critical daily activity to ensure nutrition, hydration, function and socialisation. Interactions between staff and residents during mealtimes are complex and dynamic processes including verbal and/or nonverbal communication that can be positive/neutral or challenging. This study examined characteristics of and relationships between person-centred and task-centred care and positive/neutral and challenging mealtime behaviours in persons with dementia.
METHODS: This study was a secondary behavioural analyses of videotaped mealtime observations (n = 110) involving 42 unique staff-resident dyads (29 staff and 25 residents with dementia) in nine nursing homes. The refined Cue Utilization and Engagement in Dementia mealtime video-coding scheme was used to code videos during 2019-2020. Dependent variables representing resident mealtime behaviours included positive verbal behaviours, positive/neutral nonverbal behaviours, functional impairments (nonverbal) and resistive behaviours (verbal and nonverbal). Independent variables were staff person-centred and task-centred approaches (verbal and nonverbal). Relationships between resident mealtime behaviours and staff approaches were examined using bivariate analysis and logistic regression.
RESULTS: Staff person-centred verbal approaches were associated with resident positive verbal behaviours (OR = 1.38, 95% CI = 1.09-1.76), functional impairments (OR = 0.81, 95% CI = 0.66-1.00) and resistive behaviours (OR = 1.65, 95% CI = 1.18-2.31). Staff person-centred nonverbal approaches were associated with resident functional impairments (OR = 1.33, 95% CI = 1.02-1.74). Staff task-centred approaches were not associated with resident positive/neutral or challenging mealtime behaviours.
CONCLUSIONS: This study characterised staff approaches and resident behaviours during mealtime care and provided preliminary support on associations between staff person-centred approaches and resident positive and challenging behaviours. Person-centred mealtime care practice is recommended by focusing on support of common, challenging behaviours and reinforcement of positive behaviours with adequate consideration of individual needs and preferences.

Motivational interviewing (MI) theory and process research highlights the role of therapist technical and relational behaviors in predicting client in-session statements for or against behavior change (i.e., change and sustain talk, respectively). These client statements, in turn, have been shown to predict intervention outcomes. The current study examines sequential associations between therapist behaviors and client change and sustain talk in a sample of Latinx individuals who engage in heavy alcohol consumption.
Data are from a completed randomized clinical trial of a culturally adapted (CAMI) versus unadapted MI targeting alcohol use and consequences among Latinx individuals.
The study collected observational coding data with the Motivational Interviewing Skill Code (MISC 2.5, i.e., therapist behaviors and global ratings) and the Client Language Assessment - Proximal/Distal (CLA-PD, i.e., client language). Frequentist and Bayesian sequential analyses examined the relationship among nine different categories of therapist behaviors and three different categories of client language (i.e., change talk, sustain talk, neutral). We examined odds ratios and conditional probabilities for the direction, magnitude, and significance of the association between the use of MI technical behaviors and subsequent client statements about change. The study compared these same transitional associations between low/average (i.e., <4) and high (i.e., ≥4) MI Spirit sessions.
The pattern of results was replicated across both analytic frameworks. Questions and reflections about change talk versus sustain talk versus neutral statements showed greater odds of predicting the intended client response (i.e., change talk, sustain talk, neutral, respectively) compared to other possible client responses. Conditional probabilities for these transitions were high, ranging from 0.55 to.88. The magnitude of certain technical transitions significantly differed between low/average and high MI Spirit sessions.
Analyses supported the hypothesized associations between therapist use of technical MI behaviors and client change language within this Latinx sample. Analyses of MI Spirit as a moderator of these transitions showed partial support.