The Costs and Benefits of Development: The Transition From Crawling to Walking

Caregiver encouragement to act on objects is related with crawling infants' receptive language

The progression from crawling to walking in infancy is associated with changes in infant language development. One possible explanation for such change is the infant's language environment. Prior research indicates that caregivers use more action directives with walking infants compared to crawling infants, but the relations of such parental speech with infant vocabulary is unknown. Here, we present findings from day-long home audio recordings (Study 1) and laboratory observations (Study 2) of same-aged crawling and walking infants to explore how caregiver language, specifically action directives, were associated with parent reported infant vocabulary size. Findings in both studies indicated that caregiver action directives were associated with crawling, but not walking infants' receptive vocabulary sizes. Specifically, action directives about objects occurring when the infant and caregiver were not jointly engaged were associated with higher receptive vocabulary scores for crawling infants, but no such pattern was found for walking infants. The replication of results in distinct samples with different research methodologies strengthens the findings. Taken together, these studies demonstrate that caregiver social engagement specific to infant motoric development is related with infant language learning.

The development of gait and mobility: Form and function in infant locomotion

The development of locomotion can be described by its form (i.e., gait) and its function (i.e., mobility). Both aspects of locomotion improve with experience. Traditional treatises on infant locomotion focus on form by describing an orderly progression of postural and locomotor milestones en route to characteristic patterns of crawling and walking gait. We provide a traditional treatment of gait by describing developmental antecedents of and improvements in characteristic gait patterns, but we highlight important misconceptions inherent in the notion of "milestones". Most critically, we argue that the prevailing focus on gait and milestones fails to capture the true essence of locomotion-functional mobility to engage with the world. Thus, we also describe the development of mobility, including the use of mobility aids for support and propulsion. We illustrate how infants find individual solutions for mobility and how the ability to move cascades into other domains of development. Finally, we show how an integration of gait and mobility provides insights into the psychological processes that make locomotion functional. This article is categorized under: Psychology > Motor Skill and Performance Psychology > Development and Aging.

Locomotor-cognitive dual-tasking in children with developmental coordination disorder

Introduction

Children with Developmental Coordination Disorder (DCD) demonstrate deficits in predictive motor control and aspects of cognitive control compared with their typically developing (TD) peers. Adjustment to dynamic environments depends on both aspects of control and the deficits for children with DCD may constrain their ability to perform daily actions that involve dual-tasking. Under the assumption that motor-cognitive integration is compromised in children with DCD, we examined proportional dual-task costs using a novel locomotor-cognitive dual-task paradigm that enlisted augmented reality. We expect proportional dual-task performance costs to be greater for children with DCD compared to their TD peers.

Methods

Participants were 34 children aged 6-12 years (16 TD, 18 DCD) who walked along a straight 12 m path under single- and dual-task conditions, the cognitive task being visual discrimination under simple or complex stimulus conditions presented via augmented reality. Dual-task performance was measured in two ways: first, proportional dual-task costs (pDTC) were computed for cognitive and gait outcomes and, second, within-trial costs (p-WTC) were measured as the difference on gait outcomes between pre- and post-stimulus presentation.

Results

On measures of pDTC, TD children increased their double-limb support time when walking in response to a dual-task, while the children with DCD increased their locomotor velocity. On p-WTC, both groups increased their gait variability (step length and step width) when walking in response to a dual-task, of which the TD group had a larger proportional change than the DCD group. Greater pDTCs on motor rather than cognitive outcomes were consistent across groups and method of dual-task performance measurement.

Discussion

Contrary to predictions, our results failed to support dramatic differences in locomotor-cognitive dual-task performance between children with DCD and TD, with both groups tending to priorities the cognitive over the motor task. Inclusion of a within-trial calculation of dual-task interference revealed an expectancy effect for both groups in relation to an impending visual stimulus. It is recommended that dual-task paradigms in the future continue to use augmented reality to present the cognitive task and consider motor tasks of sufficient complexity to probe the limits of performance in children with DCD.

Open Science Considerations for Descriptive Research in Developmental Science

Descriptive developmental research seeks to document, describe, and analyze the conditions under which infants and children live and learn. Here, we articulate how open-science practices can be incorporated into descriptive research to increase its transparency, reliability, and replicability. To date, most open-science practices have been oriented toward experimental rather than descriptive studies, and it can be confusing to figure out how to translate open-science practices (e.g., preregistration) for research that is more descriptive in nature. We discuss a number of unique considerations for descriptive developmental research, taking inspiration from existing open-science practices and providing examples from recent and ongoing studies. By embracing a scientific culture where descriptive research and open science coexist productively, developmental science will be better positioned to generate comprehensive theories of development and understand variability in development across communities and cultures.

Slower pace in early walking onset is related to communication, motor skills, and adaptive function in autistic toddlers

The onset of walking is a major developmental milestone in early childhood and is critical to the development of language and social communication. Delays in walking have been described in individuals with ASD. Yet, less is known about the quality of early gait development in toddlers with ASD and the relationship to motor skills, social communication, and language. Quantitative measures of locomotion can improve our ability to evaluate subtle and specific motor differences in toddlers with ASD and their relationship to other developmental domains. We used quantitative gait analysis to evaluate locomotion in toddlers with ASD (n = 51) and compared these data to a reference chronological aged (CA) and mental aged (MA) matched typically developing (TD) cohort (n = 45). We also examined the relationship of quantitative gait metrics to developmental measures among toddlers with ASD. We found that although toddlers with ASD achieved a typical age range of walking onset, they exhibited a pattern of slower pace compared to the TD cohort when matched by CA and MA. We also found that slower measures of pace were associated with lower developmental scores of communication, motor skills, and adaptive function. Our findings improve characterization of locomotion in toddlers with ASD and the relationship of motor skills to other developmental domains.

Early Mobility and Crawling: Beliefs and Practices of Pediatric Physical Therapists in the United States

PURPOSE

To characterize beliefs of pediatric physical therapists (PTs) in the United States regarding the role of crawling in infant development and clinical practice.

METHODS

Pediatric PTs reported their beliefs about early mobility and crawling, clinical approaches related to early mobility and crawling, and agreement with the removal of crawling from the Centers for Disease Control and Prevention (CDC)'s updated developmental milestone checklists in an online survey. Analyses examined associations between information sources and beliefs, between beliefs and clinical approaches, and between beliefs and CDC update opinions.

RESULTS

Most participants believed that crawling was important (92%) and linked to a variety of positive developmental outcomes (71%-99%) and disagreed with its removal from the CDC checklists (79%). Beliefs were linked with clinical approaches focused on promoting crawling and discouraging other forms of mobility.

CONCLUSIONS

Further research is needed to determine whether pediatric PTs' beliefs and clinical practices are supported by evidence.

Within arms reach: Physical proximity shapes mother-infant language exchanges in real-time

During everyday interactions, mothers and infants achieve behavioral synchrony at multiple levels. The ebb-and-flow of mother-infant physical proximity may be a central type of synchrony that establishes a common ground for infant-mother interaction. However, the role of proximity in language exchanges is relatively unstudied, perhaps because structured tasks-the common setup for observing infant-caregiver interactions-establish proximity by design. We videorecorded 100 mothers (U.S. Hispanic N = 50, U.S. Non-Hispanic N = 50) and their 13- to 23-month-old infants during natural activity at home (1-to-2 h per dyad), transcribed mother and infant speech, and coded proximity continuously (i.e., infants and mother within arms reach). In both samples, dyads entered proximity in a bursty temporal pattern, with bouts of proximity interspersed with bouts of physical distance. As hypothesized, Non-Hispanic and Hispanic mothers produced more words and a greater variety of words when within arms reach than out of arms reach. Similarly, infants produced more utterances that contained words when close to mother than when not. However, infants babbled equally often regardless of proximity, generating abundant opportunities to play with sounds. Physical proximity expands opportunities for language exchanges and infants' communicative word use, although babies accumulate massive practice babbling even when caregivers are not proximal.

"Go, go, go!" Mothers' verbs align with infants' locomotion

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.

Infant Communication Across the Transition to Walking: Developmental Cascades Among Infant Siblings of Children with Autism

New motor skills can shape how infants communicate with their caregivers. For example, learning to walk allows infants to move faster and farther than they previously could, in turn allowing them to approach their caregivers more frequently to gesture or vocalize. Does the link between walking and communication differ for infants later diagnosed with autism spectrum disorder (ASD), whose communicative and motor development differs from their neurotypically developing peers? We prospectively followed two groups of infants longitudinally during the transition from crawling to walking: (1) N = 25 infants with no family history of ASD; and (2) N = 91 infants with an older sibling with ASD. Fifteen infants were later diagnosed with ASD, and 26 infants showed a language delay (but did not receive an ASD diagnosis). After learning to walk, infants without ASD or language delay showed considerable changes in their communication: They gestured more frequently, and increasingly coordinated their gestures and vocalizations with locomotion (e.g., by approaching a caregiver and showing a toy). Infants with language delay showed similar but attenuated growth in their communication. However, infants later diagnosed with ASD did not display enhanced communication after they began to walk.

Long-form recording of infant body position in the home using wearable inertial sensors

Long-form audio recordings have had a transformational effect on the study of infant language acquisition by using mobile, unobtrusive devices to gather full-day, real-time data that can be automatically scored. How can we produce similar data in service of measuring infants' everyday motor behaviors, such as body position? The aim of the current study was to validate long-form recordings of infant position (supine, prone, sitting, upright, held by caregiver) based on machine learning classification of data from inertial sensors worn on infants' ankles and thighs. Using over 100 h of video recordings synchronized with inertial sensor data from infants in their homes, we demonstrate that body position classifications are sufficiently accurate to measure infant behavior. Moreover, classification remained accurate when predicting behavior later in the session when infants and caregivers were unsupervised and went about their normal activities, showing that the method can handle the challenge of measuring unconstrained, natural activity. Next, we show that the inertial sensing method has convergent validity by replicating age differences in body position found using other methods with full-day data captured from inertial sensors. We end the paper with a discussion of the novel opportunities that long-form motor recordings afford for understanding infant learning and development.

Gahvora cradling in Tajikistan: Cultural practices and associations with motor development

In Tajikistan, infants are bound supine in a "gahvora" cradle that severely restricts movement. Does cradling affect motor development and body growth? In three studies (2013-2018), we investigated associations between time in the gahvora (within days and across age) and motor skills and flattened head dimensions in 8-24-month-old Tajik infants (N = 269, 133 girls, 136 boys)) and 4.3-5.1-year-old children (N = 91, 53 girls, 38 boys). Infants had later motor onset ages relative to World Health Organization standards and pronounced brachycephaly; cradling predicted walk onset age and the proficiency of sitting, crawling, and walking. By 4-5 years, children's motor skills were comparable with US norms. Cultural differences in early experiences offer a unique lens onto developmental processes and equifinality in development.

The Mental Models Training App: Enhancing verbal reasoning through a cognitive training mobile application

Introduction

Reasoning is a complex form of human cognition whose nature has long been debated. While a number of neurocognitive mechanisms for deductive reasoning have been offered, one of the most prominent accounts is Mental Model Theory (MMT). According to MMT, humans are able to manipulate and represent information for reasoning and problem solving by leveraging the brain’s evolved visuospatial resources. Thus, when solving deductive reasoning problems, reasoners build “mental models” of the essential pieces of information conveyed in the premises, with their relations to each other represented spatially—even when the information contained within a reasoning problem is not intrinsically spatial. Crucially, taking a spatially-based approach, such as building mental models, supports higher accuracy on deductive reasoning problems. However, no study has empirically tested whether explicitly training this mental modeling ability leads to improved deductive reasoning performance.

Method

Therefore, we designed the Mental Models Training App, a cognitive training mobile application which requires participants to complete increasingly difficult reasoning problems while using an external mental modeling tool. In this preregistered study (https://osf.io/4b7kn), we conducted a between-subjects experiment (N = 301) which compared the Mental Models Training App to 3 distinct control conditions in order to examine which specific components (if any) of the training were causally responsible for improved reasoning performance.

Results

Results demonstrate that, when compared to a passive control condition, the Mental Models Training App led to improvements in adults’ verbal deductive reasoning performance both during and after the training intervention. However, contrary to our preregistered hypotheses, the training-induced improvements were not significantly larger than the effects of the active control conditions—one which included adaptive practice of the reasoning problems, and one which included adaptive practice as well as a spatial alphabetization control task.

Discussion

Therefore, while the present results demonstrate the ability of the Mental Models Training App to enhance verbal deductive reasoning, they do not support the hypothesis that directly training participants mental modeling ability yields improved performance beyond the effects of adaptive practice of reasoning. Future research should examine the long-term effects of repeated usage of the Mental Models Training App, as well as transfer effects to other forms of reasoning. Finally, we present the Mental Models Training App as a free mobile application available on the Apple App store (https://apps.apple.com/us/app/mental-models-training/id1664939931), in the hope that this translational research may be utilized by the general public to improve their reasoning ability.

Improving access to assessments of early motor development in local languages: polish adaptation of the Early Motor Questionnaire

A child's motor development progresses very dynamically. It is crucial to develop freely available parent-report measures of motor development that can be easily used globally to measure motor skills and identify children in need of interventions. This paper presents the adaptation and validation of the Early Motor Questionnaire, which consists of gross motor (GM), fine motor (FM), and perception-action integration (PA) subscales, to the Polish language (EMQ-PL). Study 1 (online, cross-sectional, N = 640) assessed psychometric properties of the EMQ-PL and its value in identifying children referred to physiotherapy. Results reveal excellent psychometric properties of the EMQ-PL and differences in GM and total age-independent scores between children that were and were not referred for physiotherapy. Study 2 (in-person assessment, longitudinal, N = 100) showed high correlations of GM and total scores with Alberta Infant Motor Scale.

CONCLUSION

Overall, the EMQ can be easily adapted to local languages and has the potential for use as a screening tool in global health contexts.

WHAT IS KNOWN

• Parent-report questionnaires - especially those available free of charge - can potentially improve the rapid assessment of motor skills in young children worldwide. • Translation, adaptation and validation of freely available parent-report measures of motor development to local languages are important for local populations.

WHAT IS NEW

• Early Motor Questionnaire can be easily adapted to local languages and has the potential for use as a screening tool in global health contexts. • The polish version of the Early Motor Questionnaire has excellent psychometric properties and highly correlates with infants' age and Alberta Infant Motor Scale scores.

Infant locomotion shapes proximity to adults during everyday play in the U.S

Learning to walk expands infants' access to the physical environment and prompts changes in their communicative behaviors. However, little is known about whether walking also shapes infants' proximity to their adult social partners during everyday activities at home. Here we followed 89 infants (42 boys, 47 girls; 92% White, not Hispanic or Latino) longitudinally and documented connections between infant locomotion and infant-adult proximity on two timescales: (1) across developmental time, by comparing data from a session when infants could only crawl to a later session when they could walk (M walk onset = 12.15 months, range = 8-15); and (2) in real time, by testing whether the amount of time that infants spent in motion (regardless of their locomotor status) related to their interpersonal distance to adults. The developmental transition to walking corresponded to a significant, but modest, decrease in infant-adult proximity. Infants' moment-to-moment locomotion, however, was strongly related to patterns of interpersonal distance: infants who spent more time in motion spent less time near adults and instigated more proximity transitions, resulting in shorter and more dispersed bouts of proximity throughout sessions. Findings shed new light on how infants' motor achievements can reverberate across other domains of development, and how changes in infant development that researchers often observe over months arise from infants' moment-to-moment experiences.

Locomotion development and infants' object interaction in a day‐care environment

This longitudinal study examined the relationship between the development of locomotion and infants' interaction with others involving objects. Observations took place in a multi-person situation-a day-care class-for one-year-old infants for 1 year. The study participants were 13 infants and 7 caregivers (all Japanese). Frequencies of infants' manual contact with objects and moving before contact with them did not differ according to locomotion developmental level. However, infants who began walking engaged in more social interactions than those who were cruising or crawling. Throughout all locomotor developmental periods, social interactions increased in frequency when more caregivers were present. As infants began to walk, they moved more prior to social interactions, had more frequent bidirectional and triadic social interactions, and moved and interacted more often with others during a single object episode. These results suggest that crawlers' engagement with objects is relatively object-oriented, while for walkers, locomotion seems to be driven by social stimuli. Infants who have begun to walk moved among caregivers and peers in a multi-person environment and developed more elaborated social interactions through objects.

"Learn the Signs. Act Early.": Updates and Implications for Physical Therapists

PURPOSE

In early 2022, the Centers for Disease Control and Prevention (CDC) updated their developmental surveillance milestone checklists. The purpose of this article is to clarify and interpret the updates from a physical therapist perspective and to discuss implications of the new milestones for physical therapists.

SUMMARY OF KEY POINTS

The CDC's updated checklists provide clear, consistent, easy to use, and evidence-based developmental milestones to prompt discussion with families. The new checklists do not represent a lowering of standards and will likely increase, not decrease, referrals for screening, evaluation, and services. Crawling has been removed from the milestone checklists, as the current evidence suggests that crawling is highly variable and not essential for development.

CONCLUSIONS AND RECOMMENDATIONS FOR CLINICAL PRACTICE

The updated milestone checklists will facilitate bringing vital services to children who need them. Physical therapists should support our primary care colleagues in implementing this useful program.

Early development in autism: How developmental cascades help us understand the emergence of developmental differences

Many theories of autism spectrum disorder (ASD) focus on a single system or factor as an explanatory mechanism for autism symptoms and behavior. However, there is growing recognition that ASD is a complex, multisystem neurodevelopmental condition with origins in prenatal life. Researchers therefore need a conceptual framework that allows examination of the interplay between multiple interacting domains and systems and the ways in which they extend their influence beyond the individual into the surrounding environment. The developmental cascades perspective suggests that even relatively small perturbations in early emerging behaviors in domains that are not traditionally linked may influence subsequent achievements across these areas. In this chapter, we illustrate how a developmental cascades framework can be used to inform the study of developmental differences. The developmental cascades perspective provides us with conceptual and methodological tools for considering how variation in children's real time behavior can provide new insights into sources of variation in their developmental trajectories and outcomes. It also suggests approaches for intervention that leverage targeted skills in novel ways, creating opportunities to support development in other domains and fine-tune caregiver behavior to create powerful moments for infant learning.

Infants exploring objects: A cascades perspective

Infants spend much of their time exploring objects (Herzberg et al., 2021), and object exploration is linked to learning and development in various domains (e.g., social, cognitive, motor). But how does exploration develop in the first place, and how, exactly, does exploration promote learning? One way to approach these process-oriented questions is with a developmental cascades perspective, which holds that new skills emerge from earlier-developing ones and that various interactions with people and objects accumulate over time to influence multiple domains of development (Masten & Cicchetti, 2010). In this chapter, we describe object exploration from a developmental cascades perspective. In Section 2, we describe typical and atypical trajectories of exploration behaviors, noting how these behaviors emerge from earlier-developing cognitive and motor skills. In Section 3, we discuss how object exploration opens the door for new types of learning opportunities. In Section 4, we discuss early experiences that may shape the development of object exploration. Altogether, we aim to convey that new developments in exploration skills are extensions of earlier-developing skills, and that seemingly insignificant exploratory behaviors (e.g., shaking a rattle) may result in numerous and varied consequences for the developing infant.

Cascades in action: How the transition to walking shapes caregiver communication during everyday interactions

New motor skills supply infants with new possibilities for action and have consequences for development in unexpected places. For example, the transition from crawling to walking is accompanied by gains in other abilities-better ways to move, see the world, and engage in social interactions (e.g., Adolph & Tamis-LeMonda, 2014). Do the developmental changes associated with walking extend to the communicative behaviors of caregivers? Thirty infants (14 boys, 16 girls; 93% White, not Hispanic or Latino) and their caregivers (84% held a college degree or higher) were observed during everyday activities at home during the two-month window surrounding the onset of walking (M infant age = 11.98 months, range = 8.74-14.86). Using a cross-domain coding system, we tracked change in the rates of co-occurrence between infants' locomotor actions and caregivers' concurrent language and gesture input. We examined these relations on two timescales-across developmental time, as infants transitioned from crawling to walking, and in real time based on moment-to-moment differences in infant posture. A consistent pattern of results emerged: compared to crawling, bouts of infant walking were more likely to co-occur with caregiver language and gestures that either requested or described movement or provided information about objects. An effect of infants' real-time behavior was also discovered, such that infants were more likely to hear language from their caregivers when they moved while upright compared to prone. Taken together, findings suggest that the emergence of walking reorganizes the infant-caregiver dyad and sets in motion a developmental cascade that shapes the communication caregivers provide. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A Contactless Method for Measuring Full-Day, Naturalistic Motor Behavior Using Wearable Inertial Sensors

How can researchers best measure infants' motor experiences in the home? Body position-whether infants are held, supine, prone, sitting, or upright-is an important developmental experience. However, the standard way of measuring infant body position, video recording by an experimenter in the home, can only capture short instances, may bias measurements, and conflicts with physical distancing guidelines resulting from the COVID-19 pandemic. Here, we introduce and validate an alternative method that uses machine learning algorithms to classify infants' body position from a set of wearable inertial sensors. A laboratory study of 15 infants demonstrated that the method was sufficiently accurate to measure individual differences in the time that infants spent in each body position. Two case studies showed the feasibility of applying this method to testing infants in the home using a contactless equipment drop-off procedure.

A comparison of young children's spatiotemporal gait measures in three common types of footwear with different sole hardness

BACKGROUND

It is unknown what the impact of sole hardness is on young children's gait. Yet, this feature is commonly marketed as having differing benefits for young children's walking and development.

RESEARCH QUESTION

What are the differences in spatiotemporal measures of gait during walking and running in three common types of young children's footwear with a soft sole, compared to a hard sole?

METHODS

The study used a quasi-experimental design, with the condition order randomised using a Latin square sequence. Forty-seven children were recruited (aged 2-4 years). Participants walked or ran the length of a GAITRite mat in a randomized order in a soft (Shore 48-53) or hard soled (Shore 60-65) sneaker, boot and sandal condition. Linear regression analyses were used to investigate the difference between footwear for the different gait parameters including velocity, cadence, step time, swing percentage, stance percentage, double support time and the toe in/out angle.

RESULTS

Children walked with a shorter stride length in the hard-soled sandals compared to the soft- soled sandals (p < 0.05). There were no other differences in spatiotemporal variables in the soft versus hard soled sandals during walking or running (p > 0.05). There were no differences in any spatiotemporal gait variables during walking or running in soft versus hard- soled runners and no differences in walking or running in soft versus hard-soled boots (p > 0.05).

SIGNIFICANCE

There were few differences in spatiotemporal parameters between soft and hard-soled footwear in both walking and running in three different types of footwear. This may be a positive finding for footwear designers and manufacturers, as a harder sole appeared to have limited impact on spatiotemporal gait parameters.

The Origins of Social Knowledge in Altricial Species

Human infants are altricial, born relatively helpless and dependent on parental care for an extended period of time. This protracted time to maturity is typically regarded as a necessary epiphenomenon of evolving and developing large brains. We argue that extended altriciality is itself adaptive, as a prolonged necessity for parental care allows extensive social learning to take place. Human adults possess a suite of complex social skills, such as language, empathy, morality, and theory of mind. Rather than requiring hardwired, innate knowledge of social abilities, evolution has outsourced the necessary information to parents. Critical information for species-typical development, such as species recognition, may originate from adults rather than from genes, aided by underlying perceptual biases for attending to social stimuli and capacities for statistical learning of social actions. We draw on extensive comparative findings to illustrate that, across species, altriciality functions as an adaptation for social learning from caregivers.

Communication changes when infants begin to walk

Learning to walk allows infants to travel faster and farther and explore more of their environments. In turn, walking may have a cascading effect on infants' communication and subsequent responses from caregivers. We tested for an inflection point-a dramatic shift in the developmental progression-in infant communication and caregiver responses when infants started walking. We followed 25 infants longitudinally over 7 months surrounding the onset of walking (mean walk onset age = 11.76 months, SD = 1.56). After learning to walk, the pace of gesture growth (but not vocalization growth) increased substantially, and infants increasingly coordinated gestures and vocalizations with locomotion (e.g., by walking to a caregiver and showing off a toy bear). Consequently, caregivers had more opportunities to respond contingently to their infants during walking months compared to crawling months (e.g., "What did you find? Is that your bear?"). Changes in communication were amplified for infants who began walking at older ages, compared to younger walkers. Findings suggest that learning to walk marks a point in development when infants actively communicate in new ways, and consequently elicit rich verbal input from caregivers.

Influence of enhanced nutrition and psychosocial stimulation in early childhood on cognitive functioning and psychological well-being in Guatemalan adults

Rationale

Early-life nutrition interventions in low and middle-income countries have demonstrated long-term benefits on cognitive skills, however, their influence on socioemotional outcomes has not been fully explored. Moreover, the mediating processes through which nutrition intervention effects operate and are maintained over time are understudied.

Methods

We followed-up a cohort of Guatemalan adults who participated as children in a community randomized food-supplementation trial. We examined associations of exposure to nutritional supplementation from conception to age 2 years with executive function (measured using three sub-tests of the NIH Toolbox Cognition Battery) and psychological well-being (measured using two sub-scales of the NIH Toolbox Emotion Battery) at ages 40–57 years (n = 1268). We used structural equation modeling to investigate the mediating role of psychosocial stimulation (measured in childhood using parent reports and ratings of home environments), cognitive ability (measured at ages 26–42 years using standardized tests), and executive function on the association of early-life exposure to nutritional supplementation with adult psychological well-being (n = 1640).

Results

We found positive but inconsistent associations of nutritional supplementation in childhood with executive function and psychological well-being in adulthood. Psychosocial stimulation, cognitive ability, and executive function did not mediate the association of early-life nutritional supplementation with adult psychological well-being. We found strong and positive associations of psychosocial stimulation in childhood with cognitive ability, executive function, and psychological well-being in adulthood. Moreover, we observed no interaction of exposure to nutritional supplementation and psychosocial stimulation in childhood with cognitive and psychological well-being outcomes in adulthood.

Conclusion

Our findings suggest that childhood nutrition interventions have long-lasting effects on cognitive ability and psychological well-being outcomes.

•

We assess the influence of early-life nutrition on neurodevelopmental outcomes.

•

We use a theoretical approach to examine mediators of the association.

•

We found no mediators of the association of early-life nutrition with adult psychological well-being.

•

Psychosocial stimulation is strongly associated with neurodevelopmental outcomes.

•

Improved child nutrition is positively associated with adult psychological well-being.

Particle Resuspension Dynamics in the Infant Near-Floor Microenvironment

Carpet dust contains microbial and chemical material that can impact early childhood health. Infants may be exposed to greater quantities of resuspended dust, given their close proximity to floor surfaces. Chamber experiments with a robotic infant were integrated with a material balance model to provide new fundamental insights into the size-dependency of infant crawling-induced particle resuspension and exposure. The robotic infant was exposed to resuspended particle concentrations from 10⁵ to 10⁶ m^-3 in the near-floor (NF) microzone during crawling, with concentrations generally decreasing following vacuum cleaning of the carpets. A pronounced vertical variation in particle concentrations was observed between the NF microzone and bulk air. Resuspension fractions for crawling are similar to those for adult walking, with values ranging from 10^-6 to 10^-1 and increasing with particle size. Meaningful amounts of dust are resuspended during crawling, with emission rates of 0.1 to 2 × 10⁴ μg h^-1. Size-resolved inhalation intake fractions ranged from 5 to 8 × 10³ inhaled particles per million resuspended particles, demonstrating that a significant fraction of resuspended particles can be inhaled. A new exposure metric, the dust-to-breathing zone transport efficiency, was introduced to characterize the overall probability of a settled particle being resuspended and delivered to the respiratory airways. Values ranged from less than 0.1 to over 200 inhaled particles per million settled particles, increased with particle size, and varied by over 2 orders of magnitude among 12 carpet types.

Anticipating future actions: Motor planning improves with age in wild bearded capuchin monkeys (Sapajus libidinosus)

Self-directed object manipulation tasks illuminate development of motor planning. Grasping strategies that lead to good object control to perform the following action(s) reveal second-order motor planning. Motor planning for efficient grips develops slowly in children. Age-related differences in other primates have been poorly investigated. Here, we investigated anticipatory motor planning of infant, juvenile and adult wild capuchin monkeys grasping a horizontally positioned stick baited to the left or right side (a version of the elevated spoon task). We recorded the grasps capuchins used to bring the baited end of the stick to the mouth. The percentage of efficient radial grips positively correlated with age and adults used efficient grips significantly more frequently than infants. Adult wild capuchins' use of radial grips was higher than that reported for adult captive capuchins in similar tasks, suggesting that experience throughout life may influence motor anticipation. Self-directed object manipulation tasks will be useful to compare this aspect of cognition across primates. A video abstract of this article can be viewed at https://youtu.be/a1Zbr_AQkb8.

Linear Growth Trajectories in Early Childhood and Adult Cognitive and Socioemotional Functioning in a Guatemalan Cohort

BACKGROUND

Growth faltering in early childhood is associated with poor human capital attainment, but associations of linear growth in childhood with executive and socioemotional functioning in adulthood are understudied.

OBJECTIVES

In a Guatemalan cohort, we identified distinct trajectories of linear growth in early childhood, assessed their predictors, and examined associations between growth trajectories and neurodevelopmental outcomes in adulthood. We also assessed the mediating role of schooling on the association of growth trajectories with adult cognitive outcomes.

METHODS

In 2017-2019, we prospectively followed 1499 Guatemalan adults who participated in a food supplementation trial in early childhood (1969-1977). We derived height-for-age sex-specific growth trajectories from birth to 84 mo using latent class growth analysis.

RESULTS

We identified 3 growth trajectories (low, intermediate, high) with parallel slopes and intercepts already differentiated at birth in both sexes. Children of taller mothers were more likely to belong to the high and intermediate trajectories [relative risk ratio (RRR): 1.21; 95% CI: 1.15, 1.26, and RRR: 1.11; 95% CI: 1.07, 1.15, per 1-cm increase in height, respectively] compared with the low trajectory. Children in the wealthiest compared with the poorest socioeconomic tertile were more likely to belong to the high trajectory compared with the low trajectory (RRR: 2.24; 95% CI: 1.29, 3.88). In males, membership in the high compared with low trajectory was positively associated with nonverbal fluid intelligence, working memory, inhibitory control, and cognitive flexibility at ages 40-57 y. Sex-adjusted results showed that membership in the high compared with low trajectory was positively associated with meaning and purpose scores at ages 40-57 y. Associations of intermediate compared with low growth trajectories with study outcomes were also positive but of lesser magnitude. Schooling partially mediated the associations between high and intermediate growth trajectories and measures of cognitive ability in adulthood.

CONCLUSIONS

Modifiable and nonmodifiable risk factors predicted growth throughout childhood. Membership in the high and intermediate growth trajectories was positively associated with adult cognitive and socioemotional functioning.

Effect of iron deficiency anemia on language development in preschool Egyptian children

BACKGROUND

Iron deficiency anemia (IDA) is the most common nutritional deficiency primarily in developing countries.

OBJECTIVE

This study evaluates the effect of IDA on language development in preschool children.

METHODOLOGY

The study is a multicenter, comparative cross-sectional study included 226 children between ages 4-6 years. The children were classified into two groups' anemic (patients) and non anemic (controls) according to the hemoglobin level. All anemic children subjected to complete iron study including; Serum iron, total iron binding capacity (TIBC), Serum ferritin level, to confirm the diagnosis of iron deficiency anemia. Cognitive assessment was done using the Arabic translation Stanford Binet intelligence scale, version four which comprised of four cognitive area scores; visual reasoning, verbal reasoning, quantitative reasoning and short-term memory. Measurement of IQ and mental age were calculated for each child. Language evaluation was done using the Arabic Language test. Receptive language quotient, expressive language quotient and total language quotient were calculated for each child.

RESULTS

122 children were anemic and 90 were non-anemic with hemoglobin level 10.65 and 11.96 g/dL, respectively (P < 0.000). Anemic children had significantly lower serum ferritin (p < 0.0001), and serum iron (p < 0.0001) compared to the controls. Both groups were matched as regards age, sex, socioeconomic levels and parental educational level. No significant differences observed regarding IQ, mental age, receptive, expressive and total language quotients between anemic and non-anemic children.

CONCLUSIONS

IDA does not seem to have an effect on language development in preschool Egyptian Children. Future large controlled studies with long follow-up time for the younger age group are needed to determine whether there are existent associations between IDA with language development.

Finding Structure in Time: Visualizing and Analyzing Behavioral Time Series

The temporal structure of behavior contains a rich source of information about its dynamic organization, origins, and development. Today, advances in sensing and data storage allow researchers to collect multiple dimensions of behavioral data at a fine temporal scale both in and out of the laboratory, leading to the curation of massive multimodal corpora of behavior. However, along with these new opportunities come new challenges. Theories are often underspecified as to the exact nature of these unfolding interactions, and psychologists have limited ready-to-use methods and training for quantifying structures and patterns in behavioral time series. In this paper, we will introduce four techniques to interpret and analyze high-density multi-modal behavior data, namely, to: (1) visualize the raw time series, (2) describe the overall distributional structure of temporal events (Burstiness calculation), (3) characterize the non-linear dynamics over multiple timescales with Chromatic and Anisotropic Cross-Recurrence Quantification Analysis (CRQA), (4) and quantify the directional relations among a set of interdependent multimodal behavioral variables with Granger Causality. Each technique is introduced in a module with conceptual background, sample data drawn from empirical studies and ready-to-use Matlab scripts. The code modules showcase each technique's application with detailed documentation to allow more advanced users to adapt them to their own datasets. Additionally, to make our modules more accessible to beginner programmers, we provide a "Programming Basics" module that introduces common functions for working with behavioral timeseries data in Matlab. Together, the materials provide a practical introduction to a range of analyses that psychologists can use to discover temporal structure in high-density behavioral data.

Exploring the Unmet Need for Technology to Promote Motor Ability in Children Younger Than 5 Years of Age: A Systematic Review

Objective

To (1) identify types of technology that promote motor ability in children younger than 5 years of age, (2) report on the type of support these devices provide, and (3) evaluate their potential for use in the community (outside of the laboratory or clinic).

Data Sources

A literature search of PubMed was conducted in February 2019 using specific terms, including child, rehabilitation, movement, and instrumentation.

Study Selection

The search yielded 451 peer-reviewed articles, which were screened by multiple reviewers. Articles that described the use of devices for the purpose of motor rehabilitation and/or assistance (regardless of device type or body part targeted) in the age range of 0-5 years were eligible for inclusion.

Data Extraction

In conformity with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, final stage data extraction consisted of full text readings where each article was reviewed twice by 3 independent reviewers.

Data Synthesis

About half of the devices available (46%) for children younger than 5 years of age are orthotics and corrective casting devices. There are more facilitative (ie, power mobility devices) than inhibitive (ie, casting) technologies being used. Approximately 60% of the devices are designed for use by a single body part. Walking is the most common motor skill addressed. Although most of the devices were used to some degree outside of the laboratory or clinic, most of the devices available are considered investigative and are not available for commercial purchase.

Conclusions

Many types of pediatric devices to assist movement exist, but the current scope of employed devices is limited. There is a need for developing technology that allows for, if not supports, high-dosage, early, and variable motor practice that can take place in community settings.

Where Infants Go: Real-Time Dynamics of Locomotor Exploration in Crawling and Walking Infants

Where do infants go? A longstanding assumption is that infants primarily crawl or walk to reach destinations viewed while stationary. However, many bouts of spontaneous locomotion do not end at new people, places, or things. Study 1 showed that half of 10- and 13-month-old crawlers' (N = 29) bouts end at destinations-more than previously found with walkers. Study 2 confirmed that, although infants do not commonly go to destinations, 12-month-old crawlers go to proportionally more destinations than age-matched walkers (N = 16). Head-mounted eye tracking revealed that crawlers and walkers mostly take steps in place while fixating something within reach. When infants do go to a destination, they take straight, short paths to a target fixated while stationary.

Making Sense of the World: Infant Learning From a Predictive Processing Perspective

For human infants, the first years after birth are a period of intense exploration-getting to understand their own competencies in interaction with a complex physical and social environment. In contemporary neuroscience, the predictive-processing framework has been proposed as a general working principle of the human brain, the optimization of predictions about the consequences of one's own actions, and sensory inputs from the environment. However, the predictive-processing framework has rarely been applied to infancy research. We argue that a predictive-processing framework may provide a unifying perspective on several phenomena of infant development and learning that may seem unrelated at first sight. These phenomena include statistical learning principles, infants' motor and proprioceptive learning, and infants' basic understanding of their physical and social environment. We discuss how a predictive-processing perspective can advance the understanding of infants' early learning processes in theory, research, and application.

Transition From Crawling to Walking Changes Gaze Communication Space in Everyday Infant-Parent Interaction

Acquisition of walking changes not only infants' locomotion itself but also infants' exploratory behavior and social interaction, such as gaze communication. To understand the ecological context in which gaze communication occurs and how it changes with walking development from the point of view of the spatial arrangement of infants, parents, and objects, we analyzed longitudinal data of daily eye contact scenes recorded from head-mounted eye trackers worn by parents as infants grew from 10 to 15.5 months, focusing on infant-parent distance and the number of objects between the dyad. A Bayesian state-space model revealed that the interpersonal distance at which infants initiated eye contact with their parents increased with the time ratio of walking to crawling. This result could not be explained by the developmental change in the amount of time that the infants were far from the parents, which is not limited to the gaze communication context. Moreover, the interpersonal distance at which the parents initiated eye contact with the infants did not increase with the time ratio of walking to crawling. The number of objects on the floor between infants and parents at the time of eye contact increased with interpersonal distance. Taken together, these results indicate that the transition from crawling to walking changes the ecological context in which infants initiate gaze communication to a visual environment characterized by a larger interpersonal distance and, therefore, more objects cluttered between the dyad. The present study has wider implications for the developmental change of shared attention in conjunction with walking development.

An Ecological Approach To Learning In (Not And) Development

The ecological approach is a framework for studying the behavior of animals in their environments. My version of an ecological approach focuses on learning in the context of development. I argue that the most important thing animals learn is behavioral flexibility. They must acquire the ability to flexibly guide their behavior from moment to moment in the midst of developmental changes in their bodies, brains, skills, and environments. They must select, modify, and create behaviors appropriate to the current situation. In essence, animals must learn how to learn. I describe the central concepts and empirical strategies for studying learning in development and use examples of infants coping with novel tasks to give a flavor of what researchers know and still must discover about the functions and processes of learning (to learn) in (not and) development.

Twelve-Month-Old Infants Respond to Speech About Absent Inaccessible Objects

This article investigated the interplay of 12-month-old infants' perception of affordances for locomotion and their ability to respond to the mention of hidden objects. In Experiment I, a toy was hidden in an ottoman that was placed on a cabinet out of infants' reach. Infants were more likely to look at, point to or approach the ottoman when there were stairs leading to it than when there were none. The stairs did not help infants respond by highlighting the target corner of the room (Experiment II) or by boosting their engagement with the study events (Experiment III). This suggests that infants' perception of the accessibility of the hiding location influences their ability to respond to speech about absent things.

A primal role for the vestibular sense in the development of coordinated locomotion

Mature locomotion requires that animal nervous systems coordinate distinct groups of muscles. The pressures that guide the development of coordination are not well understood. To understand how and why coordination might emerge, we measured the kinematics of spontaneous vertical locomotion across early development in zebrafish (Danio rerio) . We found that zebrafish used their pectoral fins and bodies synergistically during upwards swims. As larvae developed, they changed the way they coordinated fin and body movements, allowing them to climb with increasingly stable postures. This fin-body synergy was absent in vestibular mutants, suggesting sensed imbalance promotes coordinated movements. Similarly, synergies were systematically altered following cerebellar lesions, identifying a neural substrate regulating fin-body coordination. Together these findings link the vestibular sense to the maturation of coordinated locomotion. Developing zebrafish improve postural stability by changing fin-body coordination. We therefore propose that the development of coordinated locomotion is regulated by vestibular sensation.

Hand size underestimation grows during childhood

Cortical body size representations are distorted in the adult, from low-level motor and sensory maps to higher levels multisensory and cognitive representations. Little is known about how such representations are built and evolve during infancy and childhood. Here we investigated how hand size is represented in typically developing children aged 6 to 10. Participants were asked to estimate their hand size using two different sensory modalities (visual or haptic). We found a distortion (underestimation) already present in the youngest children. Crucially, such distortion increases with age and regardless of the sensory modality used to access the representation. Finally, underestimation is specific for the body as no bias was found for object estimation. This study suggests that the brain does not keep up with the natural body growth. However, since motor behavior nor perception were impaired, the distortion seems functional and/or compensated for, for proper interaction with the external environment.

The Relation Between Walking and Language in Infant Siblings of Children With Autism Spectrum Disorder

In typical development, walk onset is accompanied by increased language growth (e.g., Walle & Campos, 2014). The present study explored whether this relation may be disrupted in the infant siblings of children with autism spectrum disorder (ASD; heightened risk of receiving an ASD diagnosis; HR), a population exhibiting substantial variability in motor and language development (e.g., Gamliel, Yirmiya, & Sigman, 2007; Landa & Garrett-Mayer, 2006). Receptive and expressive language were examined across the transition to walking in three groups of HR infants (no diagnosis, language delay, and ASD; N = 91, 8-18 months) and in infants with no family history of ASD (N = 25; 9-15 months). Only infants with an eventual ASD diagnosis did not show increased language growth following walk onset.

From understanding others' needs to prosocial action: Motor and social abilities promote infants' helping

In the present study, we test the main hypothesis that infants' understanding of others' needs translates into helping behavior, when critical motor and social competencies have emerged, early in the second year. We assessed the understanding of others' needs in an eye-tracking paradigm and the helping behavior of 10- (n = 41) and 16-month-olds (n = 37). Furthermore, we assessed the motor and social abilities of 16-month-olds. Critically, while infants understood others' needs already at 10 months, fine motor and social interaction skills moderated the link between infants' prosocial understanding and helping behavior at 16 months. This provides first evidence that infants' helping behavior relates to their understanding of others' needs. Furthermore, we found that fine motor, gross motor, and social interaction skills predicted early helping behavior by themselves. These findings highlight that the emergence of infants' helping behavior is the result of a developmental system that includes infants' understanding of others' needs and also their motor and social competencies. The link between infants' understanding of others' needs and their early helpful actions provide further support for the prosocial nature of early helping behavior.

Navigation and the developing brain

As babies rapidly acquire motor skills that give them increasingly independent and wide-ranging access to the environment over the first two years of human life, they decrease their reliance on habit systems for spatial localization, switching to their emerging inertial navigation system and to allocentric frameworks. Initial place learning is evident towards the end of the period. From 3 to 10 years, children calibrate their ability to encode various sources of spatial information (inertial information, geometric cues, beacons, proximal landmarks and distal landmarks) and begin to combine cues, both within and across systems. Geometric cues are important, but do not constitute an innate and encapsulated module. In addition, from 3 to 10 years, children build the capacity to think about frames of reference different from their current one (i.e. to perform perspective taking). By around 12 years, we see adult-level performance and adult patterns of individual differences on cognitive mapping tasks requiring the integration of vista views of space into environmental space. These lines of development are continuous rather than stage-like. Spatial development builds on important beginnings in the neural systems of newborns, but changes in experience-expectant ways with motor development, action in the world and success–failure feedback. Human systems for integrating and manipulating spatial information also benefit from symbolic capacities and technological inventions.

Motor Development: Embodied, Embedded, Enculturated, and Enabling

Motor development and psychological development are fundamentally related, but researchers typically consider them separately. In this review, we present four key features of infant motor development and show that motor skill acquisition both requires and reflects basic psychological functions. ( a) Motor development is embodied: Opportunities for action depend on the current status of the body. ( b) Motor development is embedded: Variations in the environment create and constrain possibilities for action. ( c) Motor development is enculturated: Social and cultural influences shape motor behaviors. ( d) Motor development is enabling: New motor skills create new opportunities for exploration and learning that instigate cascades of development across diverse psychological domains. For each of these key features, we show that changes in infants' bodies, environments, and experiences entail behavioral flexibility and are thus essential to psychology. Moreover, we suggest that motor development is an ideal model system for the study of psychological development.

Different Dynamics of Sensory-Motor Development and Behavior During the Transitional Period in Puppies: Preliminary Results

Many studies have analyzed the behavior of puppies during their socialization period, while little attention has been paid to the transitional period, when vision and hearing develop. Here, we compared the average age of sensory and motor development, and the behavior among a total of 25 puppies. Each litter was videotaped during 1-hour daily sessions on postnatal days 10-21 and coded for the following mutually exclusive behavioral categories: sleeping, suckling and moving. The moving category included side-to-side head swinging, exploring, rolling and allogrooming. The opening of the eyelids, appearance of the startle response and ability to stand up with either the front or hind legs were identified. The duration and frequency of puppy behaviors varied significantly with breed and season of birth. Breed and gender differences in gross motor and sensory development were also observed. These findings may turn out to be crucial to enhance the welfare, standards of rearing, and behavioral interventions aimed at improving adaptability to novel stimuli in pet dogs.

Development (of Walking): 15 Suggestions

Although a fundamental goal of developmental science is to identify general processes of change, developmental scientists rarely generalize beyond their specific content domains. As a first step toward a more unified approach to development, we offer 15 suggestions gleaned from a century of research on infant walking. These suggestions collectively address the multi-leveled nature of change processes, cascades of real-time and developmental events, the diversity of developmental trajectories, inter- and intraindividual variability, starting and ending points of development, the natural input for learning, and the roles of body, environment, and sociocultural context. We argue that these 15 suggestions are not limited to motor development, and we encourage researchers to consider them within their own areas of research.

Push or Carry? Pragmatic Opportunities for Language Development in Strollers vs. Backpacks

Strollers and backpacks are employed early, frequently and throughout the first year, with parents overwhelmingly using strollers. However, because these transport modalities put infants in different proximities to caregivers, postures, and states of alertness, their use may translate to different opportunities that are of developmental consequence, particularly with regard to language. We used GoPro technology in a within subjects counter-balanced design to measure dyadic vocalizations in strollers and backpacks with 7-to-11-month-old infants. Parent-infant dyads (N=36), who regularly used both transport modes took two 8-minute walks in their own neighborhoods using their own carriers while wearing lightweight head-mounted GoPros. There was significantly more parent speech, infant vocalizations, dyadic conversations and infant-initiated speech in backpacks, as well as more head motion consistent with visual scanning by infants. Backpacks appear to be a practical way to encourage more engaging, language-enriched developmental opportunities in the critical first year.

Transitioning from level surface to stairs in children with and without Down syndrome: Locomotor adjustments during stair ascent

BACKGROUND

Children with Down syndrome (DS) often show underdeveloped motor ability and adaptation. Stair ascent is a common task to examine locomotor function and external ankle load is often used to perturb the stability of a system and observe the emergence of new patterns.

RESEARCH QUESTION

How do stair height and external ankle load affect locomotor adjustments in 5-to-11-year-old children with typical development (TD) and with DS during stair ascent?

METHODS

Fourteen children with DS and 14 age- and sex-matched children with TD participated in this study. They walked along a 5-m walkway and ascended 3-step staircases of different heights (low, moderate, and high) with or without ankle load. A 3D motion capture system was used for data collection. Dependent variables included stance time and toe-to-stair distance before stair ascent, and vertical toe clearance and horizontal toe velocity during stair ascent. Mixed ANOVAs with repeated measures were conducted for statistical analysis.

RESULTS

The DS group presented a longer stance time and a shorter toe-to-stair distance than the TD group before stair ascent. External ankle load affected, to a greater extent, the DS group than the TD group in stance time and toe-to-stair distance. During stair ascent, while the TD group generally maintained toe clearance and decreased horizontal toe velocity with the increase of stair height, the DS group decreased toe clearance and maintained horizontal toe velocity. Particularly, the DS group displayed a greater toe clearance than the TD group in the LS condition but a smaller toe clearance in the HS condition. In addition, external ankle load increased toe clearance and decreased horizontal toe velocity in both groups.

SIGNIFICANCE

Children with DS display underdeveloped locomotor adjustments during stair ascent. External ankle load appears to help the DS group regulate toe clearance and horizontal toe velocity for different stair heights.

Infant Motor Development in Autism Spectrum Disorder: A Synthesis and Meta-analysis

Studies of infant motor development in autism spectrum disorder (ASD) have increased in recent years. This article synthesized this literature through meta-analysis to assess (a) whether infant motor ability differs in ASD relative to neurotypical controls; and (b) whether motor ability and communication are related in infants with ASD. Study 1 aggregated data from 1,953 infants with ASD (ages 3.0-42.0 months), and Study 2 included 890 infants with ASD (age 6.0-42.9 months). Study 1 revealed that infant motor ability differed significantly in ASD compared with neurotypical infants-this difference was robust to variation in measurement and design. Furthermore, this group difference amplified as age increased. Study 2 indicated that within ASD, infant motor ability and communication are related.

Early human motor development: From variation to the ability to vary and adapt

This review summarizes early human motor development. From early fetal age motor behavior is based on spontaneous neural activity: activity of networks in the brainstem and spinal cord that is modulated by supraspinal activity. The supraspinal activity, first primarily brought about by the cortical subplate, later by the cortical plate, induces movement variation. Initially, movement variation especially serves exploration; its associated afferent information is primarily used to sculpt the developing nervous system, and less to adapt motor behavior. In the next phase, beginning at function-specific ages, movement variation starts to serve adaptation. In sucking and swallowing, this phase emerges shortly before term age. In speech, gross and fine motor development, it emerges from 3 to 4 months post-term onwards, i.e., when developmental focus in the primary sensory and motor cortices has shifted to the permanent cortical circuitries. With increasing age and increasing trial-and-error exploration, the infant improves its ability to use adaptive and efficicient forms of upright gross motor behavior, manual activities and vocalizations belonging to the native language.