Motor training at 3 months affects object exploration 12 months later

Associating neuromotor outcomes at 12 months with wearable sensor measures collected during early infancy in rural Guatemala

BACKGROUND

Sensitive measures to predict neuromotor outcomes from data collected early in infancy are lacking. Measures derived from the recordings of infant movement using wearable sensors may be a useful new technique.

METHODS

We collected full-day leg movement of 41 infants in rural Guatemala across 3 visits between birth and 6 months of age using wearable sensors. Average leg movement rate and fuzzy entropy, a measure to describe the complexity of signals, of the leg movements' peak acceleration time series and the time series itself were derived. We tested the three measures for the predictability of infants' developmental outcome, Bayley Scales of Infant and Toddler Development III motor, language, or cognitive composite score assessed at 12 months of age. We performed quantile regressions with clustered standard errors, accounting for the multiple visits for each infant.

RESULTS

Fuzzy entropy was associated with the motor composite score at the 0.5 quantiles; this association was not found for the other two measures. Also, no leg movement characteristic was associated with language or cognitive composite scores.

CONCLUSION

We propose that the entropy of leg movement associated peak accelerations calculated from the wearable sensor data collected for a full-day can be considered as one predictor for infants' motor developmental outcome assessed with Bayley Scales of Infant and Toddler Development III at 12 months of age.

The Effect of Screen Habits and Alternative Activities on Tactile Exploration Skills in 6- to 36-Month-Old Toddlers

BACKGROUND/OBJECTIVES

With the rising ubiquity of digital media and screens in everyday life, toddlers are increasingly exposed to different screens from an early age (i.e., television, computer, tablet, phone). However, few studies have examined the effect of these screens on toddlers' perceptual development. Since tactile exploration skills are necessary for environmental discovery and overall development, the current research investigates the links between screen-use habits and the tactile exploration skills (with visual control) of 6- to 36-month-old toddlers.

METHODS

The study involved observing the interactions of 135 toddlers with various objects and assessing the complexity of their visuo-tactile exploration strategies through two original experimental tasks. Data concerning screen habits and other relevant factors, such as socio-economic level, were collected using a parental questionnaire.

RESULTS

Toddlers with greater screen exposure time demonstrated weaker tactile exploration skills and employed less age-appropriate exploration strategies. Socio-economic factors and parental engagement in alternative activities significantly influenced these developmental outcomes.

CONCLUSIONS

These findings emphasize the importance of reducing screen time and promoting interactive co-viewing and alternative activities to mitigate the negative effects of screen exposure. Further longitudinal research is needed to determine the long-term impacts of early screen exposure on tactile exploration and overall psychological development.

Language development in children's natural environments: People, places, and things

Our goal in this chapter is to describe young children's experiences with language by examining three domains-people, places, and things-that define and influence their language input. We highlight how features of each of these three domains could provide useful learning opportunities, as well as how differences in infants' and toddlers' experiences may affect their long-term language skills. However, we ultimately suggest that a full understanding of early environments must move beyond a focus on individual experiences and include the broader systems that shape young children's lives, including both tangible aspects of the environment, such as physical resources or locations, and more hidden factors, such as cultural considerations, community health, or economic constraints.

Biological and environmental factors may affect children's executive function through motor and sensorimotor development: Preterm birth and cerebral palsy

Disruptive biological and environmental factors may undermine the development of children's motor and sensorimotor skills. Since the development of cognitive skills, including executive function, is grounded in early motor and sensorimotor experiences, early delays or impairments in motor and sensorimotor processing often trigger dynamic developmental cascades that lead to suboptimal executive function outcomes. The purpose of this perspective paper is to link early differences in motor/sensorimotor processing to the development of executive function in children born preterm or with cerebral palsy. Uncovering such links in clinical populations would improve our understanding of developmental pathways and key motor and sensorimotor skills that are antecedent and foundational for the development of executive function. This knowledge will allow the refinement of early interventions targeting motor and sensorimotor skills with the goal of proactively improving executive function outcomes in at-risk populations.

How babies use their hands to learn about objects: Exploration, reach-to-grasp, manipulation, and tool use

Object play is essential for infant learning, and infants spend most of their day with objects. Young infants learn about objects and their properties through multimodal exploration facilitated by caregivers. They figure out how to transport their hands to where objects are, and how to grasp objects in increasingly complex ways. Building on earlier experiences, they learn how to use their hands collaboratively to act on objects, and how to use objects to act on other objects in instrumental ways. These changes in how infants use their hands occur during the most rapid period of motor development and may have important downstream implications for other domains. Recent research findings have established the importance of effective fine motor skills for later academic skills, yet our understanding of the factors that influence the early development of hand skills is sparse at best. Latest research on reaching, grasping, object manipulation, hands collaboration, and tool use is reviewed and connections among these developments are explained from the perspective of developmental cascades. This article is categorized under: Psychology > Motor Skill and Performance Psychology > Development and Aging.

Impact of Early Exposure to Play Materials on Motor Development in High-Risk Infants: A Randomised Controlled Trial

BACKGROUND

The purpose of this study was to determine the impact of early exposure to play materials on motor development in high-risk infants.

MATERIALS AND METHODS

A 1:1 parallel group randomised control study was conducted. A total of 36 participants were recruited, with 18 in each group. The intervention lasted 6 weeks for both groups, with follow-ups in the 2nd and 4th weeks. The Peabody Developmental Motor Scale 2nd Edition (PDMS-2) was used as an outcome measure. The data was analysed using the Likelihood Ratio test, Chi-square test, independent sample t-test, and paired t-test.

RESULTS

There was no difference between the groups except for the raw reflex scores (t = 3.29, p = 0.002), raw stationary scores (t = 4.26, p < 0.001), standard stationary scores (t = 2.57, p = 0.015), and Gross Motor Quotient (GMQ) (t = 3.275, p = 0.002). Statistical significance within the experimental group was observed in the raw reflex (t = -5.16, p < 0.001), stationary (t = -10.5, p < 0.001), locomotion (t = -5.67, p < 0.001), grasp (t = -4.68, p < 0.001), and visual motor (t = -5.03, p < 0.001) scores, as well as the standard stationary (t = -2.87, p = 0.010), locomotion (t = -3.43, p = 0.003), grasp (t = -3.28, p = 0.004), and visual motor (t = -5.03, p < 0.001) scores. Quotients were the GMQ (t = -7.31, p < 0.001), Total Motor Quotient (TMQ) (t = -5.71, p < 0.001), Fine Motor Quotient (FMQ) (t = -6.48, p < 0.001). Conclusions: The current study concludes that a six-week treatment of early exposure to age-appropriate toys is advantageous in enhancing motor development in high-risk neonates.

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.

Looking is not enough: Multimodal attention supports the real-time learning of new words

Most research on early language learning focuses on the objects that infants see and the words they hear in their daily lives, although growing evidence suggests that motor development is also closely tied to language development. To study the real-time behaviors required for learning new words during free-flowing toy play, we measured infants' visual attention and manual actions on to-be-learned toys. Parents and 12-to-26-month-old infants wore wireless head-mounted eye trackers, allowing them to move freely around a home-like lab environment. After the play session, infants were tested on their knowledge of object-label mappings. We found that how often parents named objects during play did not predict learning, but instead, it was infants' attention during and around a labeling utterance that predicted whether an object-label mapping was learned. More specifically, we found that infant visual attention alone did not predict word learning. Instead, coordinated, multimodal attention-when infants' hands and eyes were attending to the same object-predicted word learning. Our results implicate a causal pathway through which infants' bodily actions play a critical role in early word learning.

Unweighting infants reveals hidden motor skills

We investigated the role of rate limiting factors in development using walking as a model system. The achievement of bipedal posture and locomotion are among the most significant achievements in an infant's first year, with poor balance and weak muscles long proposed as the rate limiting factors. Compensating for either may reveal upright motor skill that has not yet emerged in the infant's natural repertoire. To probe this question, we unweighted prewalking infants and measured their performance in various standing and walking behaviors while unweighted compared to baseline. Our secondary objective was to determine if the influence of unweighting was related to infants' locomotor experience. Infants stood unsupported for longer durations with 20% or 40% unweighting. Infants took more independent steps and more steps with one hand held with 40% unweighting. No differences in transition to/from standing were observed. Locomotor experience was related to the influence of unweighting during cruising and walking with a push toy. This is the first report of more advanced motor skills-longer periods of unsupported standing and the emergence of independent walking-revealed by unweighting infants. We interpret our observations to suggest that the refinement of motor control needed to support bipedal posture and locomotion precedes the functional emergence of these skills in infants. In other words, the musculoskeletal components required for walking are slower to develop than the neurological factors - and consequently may be the rate limiters. We further suggest that training regimens including unweighting should be explored in infants with motor delays.

Sticky Mittens Training to Improve Reaching Skills and Manual Exploration of Full-Term and At-Risk Infants: A Systematic Review

AIM

To systematically review evidence of the effectiveness of sticky mittens training to improve reaching skills and manual exploration of full-term and at-risk infants and optimal training dosage.

METHODS

The Cochrane Collaboration and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guided this systematic review. The electronic search was performed from September 2017 to August 2021 on PubMed, Scopus, Science Direct, and Cochrane databases. Eligibility criteria followed PICO terms: clinical trials investigating the effects of sticky mittens training on reaching skills and manual exploration of full-term and at-risk infants. PEDro scale and GRADE assessed methodological quality and quality of evidence, respectively.

RESULTS

Eight studies (313 children) were included. Five studies found statistically significant differences between experimental and control groups (62.6%). One study presented high methodological quality. Evidence synthesis showed very low and low evidence of the beneficial effects of sticky mittens training in full-term and at-risk infants, respectively.

CONCLUSIONS

Findings suggest that sticky mittens training facilitates reaching skills and manual exploration. However, results should interpretation with caution because studies targeted full-term infants. Future research should focus on infants at risk or with motor impairments since sticky mittens training seems to show positive effects and is easy to apply.

Influences of Adult Gender and Parenthood on Adult-Child Interaction Style

Previous studies report differences between mothers and fathers during parent-child interactions. However, the origins of these differences remain unknown. We address this gap by examining the impact of adult gender and gender perceptions on adult-child interactions. Unlike previous studies, we observed both parent and non-parent adults during one-on-one interactions with a child. Further, for non-parent adults the child's identity was held constant while the child's assumed gender was actively manipulated using clothing cues. Results reveal systematic differences between parents and non-parents, but also between male and female adults in language quantity, quality, and engagement strategies during adult-child interactions. Adults' perceptions of gender roles partially explain these findings. In contrast, the child's gender did not impact adult-child interactions. Together, our results support the notion that male and female adults offer unique contributions to a child's development.

The Effect of START-Play Intervention on Reaching-Related Exploratory Behaviors in Children with Neuromotor Delays: A Secondary Analysis of a Randomized Controlled Trial

AIMS

Children with neuromotor delays are at risk for reaching and object exploration impairments, which may negatively affect their cognitive development and daily activity performance. This study evaluated the effectiveness of the Sitting Together And Reaching To Play (START-Play) intervention on reaching-related exploratory behaviors in children with neuromotor delays.

METHODS

In this randomized controlled clinical trial, 112 children (Mean = 10.80, SD = 2.59 months old at baseline) with motor delays were randomly assigned to receive START-Play intervention or usual care-early intervention. Performance for ten reaching-related exploratory behaviors was assessed at baseline and 1.5, 3, 6, 12 months post-baseline. Piecewise linear mixed-effects modeling was used to evaluate short- and long-term effects of the intervention.

RESULTS

Benefits of START-Play were observed for children with significant motor delays, but not for those with mild delays. START-Play was especially beneficial for children with significant motor delays who demonstrated early mastery in the reaching assessment (i.e., object contact ≥65% of the time within 3 months after baseline); these children showed greater improvements in manual, visual, and multimodal exploration, as well as intensity of exploration across time.

CONCLUSIONS

START-Play advanced the performance of reaching-related exploratory behaviors in children with significant motor delays.

Evaluation of a "tummy time" intervention to improve motor skills in infants after cardiac surgery

BACKGROUND

Infants who require open heart surgery are at increased risk for developmental delays including gross motor impairments which may have implications for later adaptive skills and cognitive performance. We sought to evaluate the feasibility and efficacy of a tummy time intervention to improve motor skill development in infants after cardiac surgery.

METHODS

Infants <4 months of age who underwent cardiac surgery were randomly assigned to tummy time with or without outpatient reinforcement or standard of care prior to hospital discharge. The Alberta Infant Motor Scale (AIMS) was administered to each infant prior to and 3 months after discharge. Groups were compared, and the association between parent-reported tummy time at home and change in motor scores at follow-up was examined.

RESULTS

Parents of infants (n = 64) who had cardiac surgery at a median age of 5 days were randomly assigned to tummy time instruction (n = 20), tummy time + outpatient reinforcement (n = 21) or standard of care (n = 23). Forty-nine (77%) returned for follow-up. At follow-up, reported daily tummy time was not significantly different between groups (p = 0.17). Fifteen infants had <15 minutes of tummy time daily. Infants who received >15 minutes of tummy time daily had a significantly greater improvement in motor scores than infants with <15 minutes of tummy time daily (p = 0.01).

CONCLUSION

In infants following cardiac surgery, <15 minutes of tummy time daily is associated with increased motor skill impairment. Further research is needed to elucidate the best strategies to optimise parental compliance with tummy time recommendations.

Effects of Early Motor Interventions on Gross Motor and Locomotor Development for Infants at-Risk of Motor Delay: A Systematic Review

Aim

To systematically examine the effect of early motor interventions on motor and locomotor development in infants <1 year of age with motor developmental disability or at risk of motor delay.

Methods

Pertinent literature from January 2000 to September 2021 was identified by searching the PubMed, Embase, Cochrane, Pedro and Web of Science databases. Selection criteria included interventions starting before 12 months corrected age. Methodological quality was assessed with AACPDM criteria, Mallen score and Cochrane risk of bias methodology. Evaluation procedure was performed using PRISMA protocol (PICO approach) and AMSTAR-2. This review was preregistered in PROSPERO (CRD42021286445).

Results

Ten articles met the inclusion criteria; seven had moderate to strong methodological quality. The interventions included treadmill training (n = 3), crawling training (n = 1), "tummy time" (n = 1), physical therapy with neonatal developmental program (n = 1) or Bobath approach (n = 1), treadmill training combined with active leg movements (n = 2) or Bobath physiotherapy (n = 1). The three key characteristics of effective interventions that emerged from the review were: (1) the infants' disability or risk of delay was well-defined; (2) the protocol was standardized and easy to replicate; (3) infants were required to make active movements.

Conclusion

There is an urgent need for additional high-quality studies on the effects of early motor interventions on the gross motor and locomotor development of infants with a range of disabilities or risks for delay. Suggestions for future research are outlined.

Effect of Contingency Paradigm-Based Interventions on Developmental Outcomes in Young Infants: A Systematic Review

PURPOSE

The purpose of this systematic review was to identify controlled trials evaluating the efficacy of contingency paradigm-based interventions to improve feeding, motor, or cognitive outcomes during the first year of life.

SUMMARY OF KEY POINTS

Seventeen studies, including 10 randomized controlled trials, incorporating contingency paradigm-based interventions were identified. Three of 3 trials reported improvements in nutritive sucking using pacifier-activated lullaby in preterm infants before term age. Seven of 12 trials reported improvements in reaching, manual exploration, and kicking behaviors in term and preterm infants; and 6 of 10 trials reported gains in early cognition using sticky mittens and contingent toys.

CONCLUSION AND RECOMMENDATIONS FOR CLINICAL PRACTICE

Contingency paradigm-based interventions can improve feeding outcomes in the neonatal intensive care unit in very preterm infants, and increase reaching, and perceptual-cognitive behaviors in term infants. Future research is needed to establish contingency paradigms as an effective early intervention strategy.

WHAT THIS ADDS TO THE EVIDENCE

This review synthesizes a body of literature on contingency paradigm-based interventions and highlights its potential paradigm-based interventions to improve developmental outcomes in infants.

From Hemispheric Asymmetry through Sensorimotor Experiences to Cognitive Outcomes in Children with Cerebral Palsy

Recent neuroimaging studies allowed us to explore abnormal brain structures and interhemispheric connectivity in children with cerebral palsy (CP). Behavioral researchers have long reported that children with CP exhibit suboptimal performance in different cognitive domains (e.g., receptive and expressive language skills, reading, mental imagery, spatial processing, subitizing, math, and executive functions). However, there has been very limited cross-domain research involving these two areas of scientific inquiry. To stimulate such research, this perspective paper proposes some possible neurological mechanisms involved in the cognitive delays and impairments in children with CP. Additionally, the paper examines the ways motor and sensorimotor experience during the development of these neural substrates could enable more optimal development for children with CP. Understanding these developmental mechanisms could guide more effective interventions to promote the development of both sensorimotor and cognitive skills in children with CP.

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.

A Pre-registered sticky mittens study: active training does not increase reaching and grasping in a swedish context

Several studies have previously investigated the effects of sticky mittens training on reaching and grasping development. However, recent critique casted doubts on the robustness of the motor effect of this training. The current study presents a pre-registered report that aimed to generalize these effects to Swedish infants. Three-month-old infants N = 96, 51 females, mostly White middle class in Uppsala, received daily, parent-led sticky mittens or observational training for 2 weeks or no training in 2019. Reaching and grasping abilities were assessed before and after training, using motion tracking and a 4-step reaching task. Sticky mittens training did not facilitate successful reaching. These results indicate that beneficial motor effects of sticky mittens training did not generalize to this sample.

Infant exuberant object play at home: Immense amounts of time-distributed, variable practice

Object play yields enormous benefits for infant development. However, little is known about natural play at home where most object interactions occur. We conducted frame-by-frame video analyses of spontaneous activity in two 2-h home visits with 13-month-old crawling infants and 13-, 18-, and 23-month-old walking infants (N = 40; 21 boys; 75% White). Regardless of age, for every infant and time scale, across 10,015 object bouts, object interactions were short (median = 9.8 s) and varied (transitions among dozens of toys and non-toys) but consumed most of infants' time. We suggest that infant exuberant object play-immense amounts of brief, time-distributed, variable interactions with objects-may be conducive to learning object properties and functions, motor skill acquisition, and growth in cognitive, social, and language domains.

Infant precursors of executive function in Down syndrome

BACKGROUND

Although early features of infant cognition are predictive of executive function (EF) in typically developing (TD) children, there is little information regarding the developmental origins of EF in neurogenetic conditions, such as Down syndrome (DS).

METHODS

The current study compared the performance of infants with and without DS on three dimensions that are hypothesised EF precursors: visual engagement, attention shifting and action planning. Additionally, the relationship between these EF precursors at Time 1 and EF performance at Time 2 (6 months later) was examined in the DS group. Participants were 36 infants with DS, M chronological age = 12.65 months, SD = 2.11; M developmental age = 8.84 months, SD = 2.22, and 36 TD infants, M chronological age = 8.62, SD = 3.06; M developmental age = 8.64 months, SD = 3.40.

RESULTS

Infants with DS visually engaged with objects for longer durations and demonstrated challenges with action planning compared with TD infants at Time 1. Attention shifting at Time 1 significantly predicted EF performance at Time 2 in the DS group.

CONCLUSIONS

This study provides evidence that an early atypical presentation of EF precursors is detectable during infancy in DS and is predictive of subsequent EF performance. These findings contribute to the identification of areas of early cognitive risk in DS and can inform future interventions in this population.

Early Motor Milestones in Infancy and Later Motor Impairments: A Population-Based Data Linkage Study

BACKGROUND

Developmental Coordination Disorder (DCD) is a neurodevelopmental condition with high prevalence. Early motor milestones are important markers to identify DCD. The current study aims to evaluate the association between the onset of crawling and independent walking and their transition pattern during infancy and later motor impairments.

METHODS

A total of 8,395 children aged 3-6 years old in China were included in the final analysis. A parent questionnaire was used to collect early milestone onset data. Children's motor performance was measured using the Movement Assessment Battery for Children-2nd edition (MABC-2). The association between motor milestones and motor impairment was analyzed using a multilevel regression model.

RESULTS

The result showed that a 1-month delay in crawling onset increased the risk of significant overall motor impairment by 5.3, and 14.0% when adjusting for child and family characteristics. A 1-month delay in walking onset increased the risk of significant overall motor, fine, gross, and balance impairment by 21.7, 8.3, 13.3, and 17.8%. A 1 month increase in the transition time from crawling to independent walking increased the risk of significant overall motor and gross motor impairment by 7.7 and 6.6%. These results were inconsistent across different age bands (each p < 0.05).

CONCLUSIONS

Our study indicates that even a mild delay in crawling and walking onsets in infancy increase the risk for subsequent motor impairments in childhood, and children with motor impairments revealed a different transition pattern from crawling to walking. The motor abilities of children with motor impairments can be observed to diverge from typically developing children as early as 6-8 months old. The findings can facilitate the early identification of motor impairments in children, and provide early signs to initiate intervention.

Young Children's Interactions with Objects: Play as Practice and Practice as Play

Objects permeate human culture and saturate the imagination. This duality offers both opportunity and challenge. Here we ask how young human children learn to exploit the immense potential afforded by objects that can exist simultaneously in both physical and imaginary realms. To this end, we advance a new framework that integrates the presently siloed literatures on manual skill and play development. We argue that developments in children's real and imagined use of objects are embodied, reciprocal and intertwined. Advances in one plane of action influence and scaffold advances in the other. Consistent with this unified framework, we show how real and imagined interactions with objects are characterized by developmental parallels in how children a) gradually move beyond objects' designed functions, b) extend beyond the self, and c) transcend the present to encompass future points in time and space. As well, we highlight how children's real and imagined interactions with objects are intertwined and reciprocally influence each other throughout development: Play engenders practice and skill in using objects, but just the same, practice using objects engenders advances in play. We close by highlighting the theoretical, empirical and translational implications of this embodied and integrated account of manual skill and play development.

Towards a Comprehensive View of Object-Oriented Play

The exploration and/or manipulation of objects and materials, referred to as object-oriented play (OOP), is one of the most prominent activities children engage in during early childhood. Especially within early childhood education, it is important to be able to assess and understand OOP, its developmental trajectory, and developmental value. This can support early childhood educators to successfully guide or enrich children’s OOP, so it becomes a context in which learning can take place. During the past decades, three dominant theoretical perspectives have explained and assessed certain (developmental) aspects of OOP: (1) genetic epistemology, (2) cultural historical psychology, and (3) evolutionary psychology. After reviewing the literature concerning OOP according to each theoretical perspective, this paper aims to synthesize these existing theories into a unified theoretical framework. This theoretical framework can be a starting point for future research on OOP in early childhood (education). We answer the following research questions: Q1. What are the defining labels and features of the exploration and/or manipulation of objects and materials by children in early childhood?; Q2. What is the developmental trajectory of the exploration and/or manipulation of objects and materials by children in early childhood?; Q3. What is the developmental value of the exploration and/or manipulation of objects and materials by children in early childhood?

Feasibility of a syndrome-informed micro-intervention for infants with Down syndrome

BACKGROUND

Infants with Down syndrome (DS) are at risk for a range of phenotypic outcomes, including delays in the onset of reaching behaviour, a critical skill that facilitates early learning. This parallel-group feasibility and pilot study presents findings from a parent-mediated micro-intervention that aimed to support the development of reaching behaviour in a sample of infants with DS.

METHODS

Participants were 73 infants with DS and their caregivers. Infants who qualified for the home-based intervention (based on manual skill performance on Bayley Scales of Infant and Toddler Development, Third Edition items) were randomly assigned individually or by geographical region to a treatment or an alternative treatment condition that involved toy-based interactions with caregivers. Infants in the treatment condition experienced facilitated reaching during the toy-based interactions through the use of Velcro-affixed mittens and toys.

RESULTS

Forty-two infants met criteria to participate in the intervention, and 37 participated in both baseline and post-treatment visits. At post-treatment, infants in the treatment condition demonstrated shorter latencies to make contact with objects and showed higher frequencies of reach attempts and swats at objects than infants in the alternative treatment group. These findings were more pronounced when examining a chronological age-restricted subgroup of infants 5 to 10 months.

CONCLUSIONS

Findings suggest that a syndrome-informed approach to targeted intervention may be a promising application of phenotyping science in DS and other neurogenetic conditions associated with intellectual disability.

Relations between fine motor skills and intelligence in typically developing children and children with attention deficit hyperactivity disorder

BACKGROUND

The embodied cognition hypothesis implies a close connection between motor and cognitive development. Evidence for these associations is accumulating, with some studies indicating stronger relations in clinical than typically developing samples.

AIMS

The present study extends previous research and investigates relations between fine motor skills and intelligence in typically developing children (n = 139, 7-13 years) and same-aged children with attention deficit hyperactivity disorder (ADHD, n = 46). In line with previous findings, we hypothesized stronger relations in children with ADHD than in typically developing children.

METHODS AND PROCEDURE

Fine motor skills were assessed using the standardized Movement Assessment Battery for Children. Intelligence was measured with the standardized Wechsler Intelligence Scale for Children.

OUTCOMES AND RESULTS

Regression analyses indicated significant relations between fine motor skills and full-scale IQ, perceptual reasoning, working memory, and processing speed. Moderation analyses identified stronger relations between fine motor skills and full-scale IQ, perceptual reasoning, and verbal comprehension in children with ADHD compared to typically developing children.

CONCLUSIONS AND IMPLICATIONS

Results suggest a close relation between fine motor skills and intelligence in children with and without ADHD, with children diagnosed with ADHD showing stronger relations. Findings support combined motor-cognitive interventions in treating children with ADHD.

Scaffolded reaching can encourage motor development: Commentary on van den Berg & gredebäck (2020)

Recent findings regarding the effectiveness of sticky mittens training as a motor intervention have been mixed. This commentary argues that despite inconsistent results, overall patterns suggest that sticky mittens may facilitate reaching behavior. More research on this topic is needed.

The sticky mittens paradigm: A critical appraisal of current results and explanations

Almost two decades ago, the sticky mittens paradigm was demonstrated as a way to train reaching and grasping behaviors in pre‐reaching infants, and consequently improve visual attentional abilities. In that first study, Needham and colleagues fitted 3‐month‐old infants with Velcro loop‐covered mittens and allowed them to interact with Velcro hook‐covered toys over the course of 2 weeks. In this review, we scrutinize the 17 studies that have followed those first sticky mittens results in regards to the motor, social perception, and visual attentional domains. Furthermore, we discuss the proposed mechanisms of the sticky mittens training. Current evidence strongly suggests that sticky mittens training facilitates social perception, which is consistent with prior correlational work showing links between action production and action perception. However, studies targeting motor and visual attentional abilities have too diverse results to warrant firm conclusions. We conclude that future research should focus on uncovering if there is a connection between sticky mittens training and motor behavior.

Object exploration during the transition to sitting: A study of infants at heightened risk for autism spectrum disorder

Learning to sit promotes infants' object exploration because it offers increased access to objects and an improved position for exploration (e.g., ). Infants at heightened risk (HR) for autism spectrum disorder (ASD) exhibit delays in sitting and differences in object exploration. However, little is known about the association between sitting and object exploration among HR infants. We examined changes in object exploration as HR infants (N = 19) and comparison infants with no family history of ASD (Low Risk; LR; N = 23) gained experience sitting independently. Infants were observed monthly from 2.5 months until 1 month after the onset of independent sitting. At 12, 18, 24, and 36 months, infants completed standardized developmental assessments, and HR infants were assessed for ASD symptoms at 36 months. Although HR infants began sitting later than LR infants, both groups increased time spent grasping, shaking, banging, and mouthing objects as they gained sitting experience. Groups only differed in time spent actively mouthing objects, with LR infants showing a greater increase in active mouthing than HR infants. Findings suggest that HR infants experience a similar progression of object exploration across sitting development, but on a delayed time scale.

Predictors of longer-term development of expressive language in two independent longitudinal cohorts of language-delayed preschoolers with Autism Spectrum Disorder

BACKGROUND

Studies estimate that 30% of individuals with autism are minimally verbal. Understanding what factors predict longer-term expressive development in children with language delays is critical to inform identification and treatment of those at-risk for persistent language impairments. The present study examined predictors of expressive language development in language-delayed preschoolers followed through later school-age and young adulthood.

METHODS

Children using single words or less on the Autism Diagnostic Observation Schedule (ADOS) at approximately 3 years old were drawn from the Early Diagnosis (EDX) and Pathways in ASD longitudinal cohorts. Age-3 predictors of Age-19 ADOS language level were identified using Classification and Regression Trees (CART) in the EDX sample. Linear mixed models examined the effects of CART-identified predictors on Vineland expressive communication (VExp) trajectories from Age-3 to Age-19. The same linear mixed models were examined in the Pathways sample, identifying predictors of VExp from ages 3 to 10.5 years.

RESULTS

Significantly delayed fine motor skills (T-score < 20) was the strongest CART predictor of Age-19 language. In the linear mixed models, time, Age-3 fine motor skills and initiation of joint attention (IJA) predicted VExp trajectories in the EDX sample, even when controlling for Age-3 visual receptive abilities. In the Pathways sample, time and Age-3 fine motor skills were significant predictors of VExp trajectories; IJA and cognitive skills were not significant predictors.

CONCLUSIONS

Marked deficits in fine motor skills may be a salient proxy marker for identifying language-delayed children with ASD who are at risk for persistent language impairments. This finding adds to the literature demonstrating a relation between motor and language development in ASD. Investigating individual skill areas (e.g., fine motor and nonverbal problem-solving skills), rather than broader indices of developmental level (e.g., nonverbal IQ) may provide important cues to understanding longer-term language outcomes that can be targeted in early intervention.

The teleological stance: Past, present, and future

We review the support for, and criticisms of, the teleological stance theory, often described as a foundation for goal-directed action understanding early in life. A major point of contention in the literature has been how teleological processes and assumptions of rationality are represented and understood in infancy, and this debate has been largely centered on three paradigms. Visual habituation studies assess infant's abilities to retrospectively assess teleological processes; the presence of such processes is supported by the literature. Rational imitation is a phenomenon that has been questioned both theoretically and empirically, and there is currently little support for this concept in the literature. The involvement of teleological processes in action prediction is unclear. To date, the ontology of teleological processes remains unspecified. To remedy this, we present a new action-based theory of teleological processes (here referred to as the embodied account of teleological processes), based on the development of goal-directed reaching with its origin during the fetal period and continuous development over the first few months of life.

Motor atypicalities in infancy are associated with general developmental level at 2 years, but not autistic symptoms

LAY ABSTRACT

Atypicalities in motor functioning are often observed in later born infant siblings of children with autism spectrum disorder. The goal of our study was to investigate motor functioning in infants with and without familial history of autism spectrum disorder. Specifically, we investigated how infants catch a ball that is rolling toward them following a non-straight path, a task that requires both efficient planning and execution. Their performance was measured using detailed three-dimensional motion capture technology. We found that several early motor functioning measures were different in infants with an older autistic sibling compared to controls. However, these early motor measures were not related to autistic symptoms at the age of 2 years. Instead, we found that some of the early motor measures were related to their subsequent non-social, general development. The findings of our study help us understand motor functioning early in life and how motor functioning is related to other aspects of development.

Play enhances visual form perception in infancy-an active training study

Motor experiences and active exploration during early childhood may affect individual differences in a wide range of perceptual and cognitive abilities. In the current study, we suggest that active exploration of objects facilitates the ability to process object forms and magnitudes, which in turn impacts the development of numerosity perception. We tested our hypothesis by conducting a preregistered active exploration intervention with 59 8-month-old infants. The minimal intervention consisted of actively playing with and exploring blocks once a day for 8 weeks. In order to control for possible training effects on attention, we used book reading as a control condition. Pre- and post-test assessments using eye-tracking showed that block play improved visual form perception, where infants became better at detecting a deviant shape. Furthermore, using three control tasks, we showed that the intervention specifically improved infants' ability to process visual forms and the effect could not be explained by a domain general improvement in attention or visual perception. We found that the intervention did not improve numerosity perception and suggest that because of the sequential nature of our hypothesis, a longer time frame might be needed to see improvements in this ability. Our findings indicate that if infants are given more opportunities for play and exploration, it will have positive effects on their visual form perception, which in turn could help their understanding of geometrical concepts.

Stabilities of Infant Behaviors and Maternal Responses to Them

Consistency in the order of individuals in a group across substantial lengths of time-stability-is a central concept in developmental science for several reasons. Stability underscores the meaningfulness of individual differences in psychological phenomena; stability informs about the origins, nature, and overall developmental course of psychological phenomena; stability signals individual status and so affects the environment, experience, and development; stability has both theoretical and clinical implications for individual functioning; and stability helps to establish that a measure constitutes a consequential individual-differences metric. In this three-wave prospective longitudinal study (Ns = 40 infants and mothers), we examined stabilities of individual variation in multiple infant behaviors and maternal responses to them across infant ages 10, 14, and 21 months. Medium to large effect size stabilities in infant behaviors and maternal responses emerged, but both betray substantial amounts of unshared variance. Documenting the ontogenetic trajectories of infant behaviors and maternal responses helps to elucidate the nature and structure of early human development.

Neural correlates of infant action processing relate to theory of mind in early childhood

The mechanisms that support infant action processing are thought to be involved in the development of later social cognition. While a growing body of research demonstrates longitudinal links between action processing and explicit theory of mind (TOM), it remains unclear why this link emerges in some measures of action encoding and not others. In this paper, we recruit neural measures as a unique lens into which aspects of human infant action processing (i.e., action encoding and action execution; age 7 months) are related to preschool TOM (age 3 years; n = 31). We test whether individual differences in recruiting the sensorimotor system or attention processes during action encoding predict individual differences in TOM. Results indicate that reduced occipital alpha during action encoding predicts TOM at age 3. This finding converges with behavioral work and suggests that attentional processes involved in action encoding may support TOM. We also test whether neural processing during action execution draws on the proto-substrates of effortful control (EC). Results indicate that frontal alpha oscillatory activity during action execution predicted EC at age 3-providing strong novel evidence that infant brain activity is longitudinally linked to EC. Further, we demonstrate that EC mediates the link between the frontal alpha response and TOM. This indirect effect is specific in terms of direction, neural response, and behavior. Together, these findings converge with behavioral research and demonstrate that domain general processes show strong links to early infant action processing and TOM.

Training of 7-month-old infants' manual object exploration skills: Effects of active and observational experience

In the present study, a fine motor training was developed and evaluated in which infants were trained to manually explore objects in an advanced manner. Fifty 7-month-old infants were randomly assigned to three different training conditions: (1) to an active manual exploration training, in which they learned to explore objects efficiently, (2) to an observational manual exploration training, in which they observed how an adult performed sophisticated actions on objects, or (3) to a control group receiving no training. The results impressively indicate that infants with a low level of object exploration skill prior to the training showed the most training effects as compared to infants with proficient object exploratory actions. Interestingly, this differential training effect was true for both the active and observational training, highlighting the role of social learning in infancy. Importantly, our study shows for the first time the impact of normal individual variation in infants' manual object exploration skills on the effects of a fine motor training.

Feasibility and Effectiveness of Intervention With the Playskin Lift Exoskeletal Garment for Infants at Risk

BACKGROUND

Infants born preterm and/or with brain injury often exhibit delays in the development of reaching and object exploration, increasing their risk of associated delays in cognitive development.

OBJECTIVE

The objective of this study was to longitudinally evaluate feasibility of use of the novel Playskin Lift exoskeletal garment (Playskin; developed and trademarked by Dr. Lobo's Super Suits FUNctional Fashion and Wearable Technology Program at the University of Delaware, Newark, DE, USA), the assistive and rehabilitative effects of intervention with the garment on reaching and object exploration ability, and to relate changes in reaching and object exploration to changes in cognition during intervention for infants at risk for developmental delays.

DESIGN

A multiple baseline single-case design with 1- to 2-month Baseline, 4-month Intervention, and 1-month Postintervention phases was implemented.

METHODS

Ten infants born preterm and/or with brain injury, mean [SD] age 2.2 [1.3] months at the beginning of the study, were assessed biweekly throughout the study both with and without the Playskin Lift. Assessments included a Reaching Assessment and the cognitive subscale of the Bayley Scales of Infant and Toddler Development. Reaching and object exploration behaviors were coded from videos of the Reaching Assessment. Results were analyzed using multilevel modeling in SAS.

RESULTS

The Playskin Lift improved infants' reaching ability, hand orientation for grasp and object exploration, and multimodal object exploration when worn within sessions, especially during the Intervention phase. The garment also improved independent reaching and object exploration across time during the Intervention phase, with retention of gains in the Postintervention phase. Improvement in reaching ability was positively related to changes in cognitive outcomes during the Intervention phase.

LIMITATIONS

Limitations included modest sample size and the potential confounds of development and experience with time.

CONCLUSIONS

The Playskin Lift can serve as a feasible, effective, and accessible assistive and rehabilitative device to advance reaching, object exploration, and cognition for infants at risk for future delays.

Play for Success: An intervention to boost object exploration in infants from low-income households

Infants from low-income households typically spend less time exploring objects and use less mature strategies when they do explore compared to their higher-income peers (e.g., Clearfield et al., 2014). The current study tested a novel intervention designed to boost early object exploration in infants from low-income households. The intervention, called Play for Success, was administered through the Early Head Start home visiting program, and asked all infants to explore a toy with a caregiver for 10 min a day every day for two weeks. Forty-two 6- to 10-month-old infants were randomly assigned to one of three intervention groups: Social (unstructured direction), Teach Two (simple structured direction), or Teach Many (complex structured direction). Infants' exploratory behaviors were tested three times: before the intervention, immediately following, and again four weeks later. The results demonstrated that only infants in Teach 2 maintained their level of exploration at both the post-test and 4 weeks later while infants in the other groups showed significant decreases in exploration over time. These results suggest that Play for Success is a promising new intervention, but only in the condition that included repeated simple structured direction.

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.

Object exploration facilitates 4-month-olds' mental rotation performance

How do infants learn to mentally rotate objects, to imagine them rotating through different viewpoints? One possibility is that development of infants' mental rotation (MR) is facilitated by visual and manual experience with complex objects. To evaluate this possibility, eighty 4-month-olds (40 females, 40 males) participated in an object exploration task with Velcro "sticky mittens" that allow infants too young to grasp objects themselves to nonetheless explore those objects manually as well as visually. These eighty infants also participated in a visual habituation task designed to test MR. Half the infants (Mittens First group) explored the object prior to the MR task, and the other half afterwards (Mittens Second group), to examine the role of immediate prior object experience on MR performance. We compared performance of male and female infants, but found little evidence for sex differences. However, we found an important effect of object exploration: The infants in the Mittens First group who exhibited the highest levels of spontaneous object engagement showed the strongest evidence of MR, but there were no consistent correlations between these measures for infants in the Mittens Second group. These findings suggest an important contribution from object experience to development of MR.

Relationships between full-day arm movement characteristics and developmental status in infants with typical development as they learn to reach: An observational study

Background: Advances in wearable sensor technology now allow us to quantify the number, type and kinematic characteristics of bouts of infant arm movement made across a full day in the natural environment. Our aim here was to determine whether the amount and kinematic characteristics of arm movements made across the day in the natural environment were related to developmental status in infants with typical development as they learned to reach for objects using their arms.

Methods: We used wearable sensors to measure arm movement across days and months as infants developed arm reaching skills. In total, 22 infants with typical development participated, aged between 38 and 203 days. Of the participants, 2 infants were measured once and the other 20 infants were measured once per month for 3 to 6 visits. The Bayley Scales of Infant Development was used to measure developmental level.

Results: Our main findings were: 1) infant arm movement characteristics as measured by full-day wearable sensor data were related to Bayley motor, cognitive and language scores, indicating a relationship between daily movement characteristics and developmental status; 2) infants who moved more had larger increases in language and cognitive scores across visits; and 3) larger changes in movement characteristics across visits were related to higher motor scores.

Conclusions: This was a preliminary, exploratory, small study of the potential importance of infant arm movement characteristics as measured by full-day wearable sensor data. Our results support full-day arm movement activity as an area of interest for future study as a biomarker of neurodevelopmental status and as a target for early intervention.

Relationships between full-day arm movement characteristics and developmental status in infants with typical development as they learn to reach: An observational study

Background: Advances in wearable sensor technology now allow us to quantify the number, type and kinematic characteristics of bouts of infant arm movement made across a full day in the natural environment. Our aim here was to determine whether the amount and kinematic characteristics of arm movements made across the day in the natural environment were related to developmental status in infants with typical development as they learned to reach for objects using their arms. Methods: We used wearable sensors to measure arm movement across days and months as infants developed arm reaching skills. In total, 22 infants with typical development participated, aged between 38 and 203 days. Of the participants, 2 infants were measured once and the other 20 infants were measured once per month for 3 to 6 visits. The Bayley Scales of Infant Development was used to measure developmental level. Results: Our main findings were: 1) infant arm movement characteristics as measured by full-day wearable sensor data were related to Bayley motor, cognitive and language scores, indicating a relationship between daily movement characteristics and developmental status; 2) infants who moved more had larger increases in language and cognitive scores across visits; and 3) larger changes in movement characteristics across visits were related to higher motor scores. Conclusions: This was a preliminary, exploratory, small study of the potential importance of infant arm movement characteristics as measured by full-day wearable sensor data. Our results support full-day arm movement activity as an area of interest for future study as a biomarker of neurodevelopmental status and as a target for early intervention.

Development of fine motor skills is associated with expressive language outcomes in infants at high and low risk for autism spectrum disorder

Background

A growing body of research suggests that fine motor abilities are associated with skills in a variety of domains in both typical and atypical development. In this study, we investigated developmental trajectories of fine motor skills between 6 and 24 months in relation to expressive language outcomes at 36 months in infants at high and low familial risk for autism spectrum disorder (ASD).

Methods

Participants included 71 high-risk infants without ASD diagnoses, 30 high-risk infants later diagnosed with ASD, and 69 low-risk infants without ASD diagnoses. As part of a prospective, longitudinal study, fine motor skills were assessed at 6, 12, 18, and 24 months of age and expressive language outcomes at 36 months using the Mullen Scales of Early Learning. Diagnosis of ASD was determined at the infant’s last visit to the lab (18, 24, or 36 months) using the Autism Diagnostic Observation Schedule.

Results

Hierarchical linear modeling revealed that high-risk infants who later developed ASD showed significantly slower growth in fine motor skills between 6 and 24 months, compared to their typically developing peers. In contrast to group differences in growth from age 6 months, cross-sectional group differences emerged only in the second year of life. Also, fine motor skills at 6 months predicted expressive language outcomes at 3 years of age.

Conclusions

These results highlight the importance of utilizing longitudinal approaches in measuring early fine motor skills to reveal subtle group differences in infancy between ASD high-risk and low-risk infant populations and to predict their subsequent language outcomes.

Electronic supplementary material

The online version of this article (10.1186/s11689-018-9231-3) contains supplementary material, which is available to authorized users.

Characteristics of brief sticky mittens training that lead to increases in object exploration

The onset of independent prehension marks the beginning of infants' direct interaction with the physical world. The success infants have in contacting objects with their hands and arms can have both visual and auditory consequences; objects may move and collide with other objects or fall onto table surfaces. Seeing and hearing these events could have important consequences for infants' learning about objects and their subsequent behavior toward objects. The current research assessed the effects of brief object manipulation experiences and how a specific characteristic of training, auditory feedback produced by hard plastic toys colliding with a tabletop surface, affects pre-reaching infants' subsequent object exploration. In Experiment 1, infants participated in either active "sticky" mittens training or passive "nonsticky" mittens training with a set of toys; before and after this experience, infants explored a teether. Results showed that infants participating in active training increased looking toward and sustained touching of the teether from pre- to post-training, whereas infants receiving passive training decreased their looking toward and touching of the teether following training. To investigate whether infants' exploration behaviors were related to the amount of auditory feedback produced by the objects during training, in Experiment 2 data were collected from infants who received active sticky mittens training that had either more or less auditory feedback potential. Results showed more robust increases in infants' exploratory activity from pre- to post-training in the more auditory feedback condition compared with infants' exploratory activity in the less auditory feedback condition. These findings support the idea that active control of objects, including experiencing contingent feedback through multiple sensory modalities, promotes the development of object exploration during early infancy.

Plasticity may change inputs as well as processes, structures, and responses

Significant work has documented neuroplasticity in development, demonstrating that developmental pathways are shaped by experience. Plasticity is often discussed in terms of the results of differences in input; differences in brain structures, processes, or responses reflect differences in experience. In this paper, I discuss how developmental plasticity also effectively changes input into the system. That is, structures and processes change in response to input, and those changed structures and processes influence future inputs. For example, plasticity may change the pattern of eye movements to a stimulus, thereby changing which part of the scene becomes the input. Thus, plasticity is not only seen in the structures and processes that result from differences in experience, but also is seen in the changes in the input as those structures and processes adapt. The systematic study of the nature of experience, and how differences in experience shape learning, can contribute to our understanding of neuroplasticity in general.

The development of motor behavior

This article reviews research on the development of motor behavior from a developmental systems perspective. We focus on infancy when basic action systems are acquired. Posture provides a stable base for locomotion, manual actions, and facial actions. Experience facilitates improvements in motor behavior and infants accumulate immense amounts of experience with all of their basic action systems. At every point in development, perception guides motor behavior by providing feedback about the results of just prior movements and information about what to do next. Reciprocally, the development of motor behavior provides fodder for perception. More generally, motor development brings about new opportunities for acquiring knowledge about the world, and burgeoning motor skills can instigate cascades of developmental changes in perceptual, cognitive, and social domains. WIREs Cogn Sci 2017, 8:e1430. doi: 10.1002/wcs.1430 For further resources related to this article, please visit the WIREs website.