Attrition in a large-scale habituation task administered at home

Infant research often struggles with selective samples, especially when focusing on behavioural measures, such as those drawn from habituation tasks. However, selectivity may threaten the generalizability and interpretation of results, which is why the current study investigates attrition in a habituation task administered in a household setting in 7-month-old infants. We used a large-scale German dataset, focusing on the children's socioeconomic background, and investigated two aspects of attrition, namely, participation and task completion. The findings suggest significant effects of the children's socioeconomic background on attrition: Maternal education, parental occupation, household income and household language (German vs. other) were positively related to participation and task completion. The analyses indicate that multiple barriers may prevent parents from lower socioeconomic backgrounds from letting their children participate. The study concludes with a critical discussion of possible mechanisms of selectivity in behavioural measures as well as the household setting, in which the data were collected.

Neuroadaptive Bayesian optimisation to study individual differences in infants' engagement with social cues

Infants' motivation to engage with the social world depends on the interplay between individual brain's characteristics and previous exposure to social cues such as the parent's smile or eye contact. Different hypotheses about why specific combinations of emotional expressions and gaze direction engage children have been tested with group-level approaches rather than focusing on individual differences in the social brain development. Here, a novel Artificial Intelligence-enhanced brain-imaging approach, Neuroadaptive Bayesian Optimisation (NBO), was applied to infant electro-encephalography (EEG) to understand how selected neural signals encode social cues in individual infants. EEG data from 42 6- to 9-month-old infants looking at images of their parent's face were analysed in real-time and used by a Bayesian Optimisation algorithm to identify which combination of the parent's gaze/head direction and emotional expression produces the strongest brain activation in the child. This individualised approach supported the theory that the infant's brain is maximally engaged by communicative cues with a negative valence (angry faces with direct gaze). Infants attending preferentially to faces with direct gaze had increased positive affectivity and decreased negative affectivity. This work confirmed that infants' attentional preferences for social cues are heterogeneous and shows the NBO's potential to study diversity in neurodevelopmental trajectories.

Infant formula supplemented with milk fat globule membrane compared with standard infant formula for the cognitive development of healthy term-born formula-fed infants: protocol for a randomised controlled trial

INTRODUCTION

Milk fat globule membrane (MFGM) is a complex lipid-protein structure in mammalian milk and human milk that is largely absent from breastmilk substitutes. The objective of this trial is to investigate whether providing infant formula enriched with MFGM versus standard infant formula improves cognitive development at 12 months of age in exclusively formula-fed full-term infants.

METHODS AND ANALYSIS

This is a randomised, controlled, clinician-blinded, researcher-blinded and participant-blinded trial of two parallel formula-fed groups and a breastfed reference group that were recruited in the suburban Adelaide (Australia) community by a single study centre (a medical research institute). Healthy, exclusively formula-fed, singleton, term-born infants under 8 weeks of age were randomised to either an MFGM-supplemented formula (intervention) or standard infant formula (control) from enrolment until 12 months of age. The reference group was not provided with formula. The primary outcome is the Cognitive Scale of the Bayley Scales of Infant Development, Fourth Edition (Bayley-IV) at 12 months. Secondary outcomes are the Bayley-IV Cognitive Scale at 24 months, other Bayley-IV domains (language, motor, emotional and behavioural development) at 12 and 24 months of age, infant attention at 4 and 9 months of age, parent-rated language at 12 and 24 months of age, parent-rated development at 6 and 18 months of age as well as growth, tolerance and safety of the study formula. To ensure at least 80% power to detect a 5-point difference in the mean Bayley-IV cognitive score, >200 infants were recruited in each group.

ETHICS AND DISSEMINATION

The Women's and Children Health Network Human Research Ethics Committee reviewed and approved the study (HREC/19/WCHN/140). Caregivers gave written informed consent prior to enrolling in the trial. Findings of this study will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

ACTRN12620000552987; Australian and New Zealand Clinical Trial Registry: anzctr.org.au.

Delineating Visual Habituation Profiles in Preschoolers with Neurofibromatosis Type 1 and Autism Spectrum Disorder: A Cross-Syndrome Study

Atypical habituation to repetitive information has been commonly reported in Autism Spectrum Disorder (ASD) but it is not yet clear whether similar abnormalities are present in Neurofibromatosis Type 1 (NF1). We employed a cross-syndrome design using a novel eye tracking paradigm to measure habituation in preschoolers with NF1, children with idiopathic ASD and typically developing (TD) children. Eye movements were recorded to examine fixation duration to simultaneously presented repeating and novel stimuli. Children with NF1 showed a bias for longer look durations to repeating stimuli at the expense of novel stimuli, and slower habituation in NF1 was associated with elevated ASD traits. These findings could indicate aberrant modulation of bottom-up attentional networks that interact with the emergence of ASD phenotypes.

Uncomfortable staring? Gaze to other people in social situations is inhibited in both infants and adults

People attract infants' and adults' gaze when presented on a computer screen. However, in live social situations, adults inhibit their gaze at strangers to avoid sending inappropriate social signals. Such inhibition of gaze has never been directly investigated in infants. The current preregistered study measured gaze and neural responses (EEG alpha power) to a confederate in a live social situation compared to a video of this confederate. Adults looked less at the live confederate than at the video of the confederate, although their neural responses suggest that they were overall equally attentive in both situations. Infants also looked less at the live confederate than at the video of the confederate, with similar neural response patterns. The gaze difference between live social and video situations increased with age. The study shows that young infants are already sensitive to social context and show decreased gaze to strangers in social situations. RESEARCH HIGHLIGHTS: This study shows that infants and adults look more at a video of a stranger than at a stranger that is present live in a social situation. Neural responses suggest that adults are equally attentive in both live and video situations but inhibit their gaze at the stranger in live social situations. Infants show a similar pattern of shorter gaze at a stranger who is present in person than at a video of this stranger. The study shows that gaze in infants and adults may diverge from cognitive processes measured through EEG, highlighting the importance of combining behavioural and neural measures in natural interactions.

OWLET: An automated, open-source method for infant gaze tracking using smartphone and webcam recordings

Groundbreaking insights into the origins of the human mind have been garnered through the study of eye movements in preverbal subjects who are unable to explain their thought processes. Developmental research has largely relied on in-lab testing with trained experimenters. This constraint provides a narrow window into infant cognition and impedes large-scale data collection in families from diverse socioeconomic, geographic, and cultural backgrounds. Here we introduce a new open-source methodology for automatically analyzing infant eye-tracking data collected on personal devices in the home. Using algorithms from computer vision, machine learning, and ecological psychology, we develop an online webcam-linked eye tracker (OWLET) that provides robust estimation of infants' point of gaze from smartphone and webcam recordings of infant assessments in the home. We validate OWLET in a large sample of 7-month-old infants (N = 127) tested remotely, using an established visual attention task. We show that this new method reliably estimates infants' point-of-gaze across a variety of contexts, including testing on both computers and mobile devices, and exhibits excellent external validity with parental-report measures of attention. Our platform fills a significant gap in current tools available for rapid online data collection and large-scale assessments of cognitive processes in infants. Remote assessment addresses the need for greater diversity and accessibility in human studies and may support the ecological validity of behavioral experiments. This constitutes a critical and timely advance in a core domain of developmental research and in psychological science more broadly.

Genetics, molecular control and clinical relevance of habituation learning

Habituation is the most fundamental form of learning. As a firewall that protects our brain from sensory overload, it is indispensable for cognitive processes. Studies in humans and animal models provide increasing evidence that habituation is affected in autism and related monogenic neurodevelopmental disorders (NDDs). An integrated application of habituation assessment in NDDs and their animal models has unexploited potential for neuroscience and medical care. With the aim to gain mechanistic insights, we systematically retrieved genes that have been demonstrated in the literature to underlie habituation. We identified 258 evolutionarily conserved genes across species, describe the biological processes they converge on, and highlight regulatory pathways and drugs that may alleviate habituation deficits. We also summarize current habituation paradigms and extract the most decisive arguments that support the crucial role of habituation for cognition in health and disease. We conclude that habituation is a conserved, quantitative, cognition- and disease-relevant process that can connect preclinical and clinical work, and hence is a powerful tool to advance research, diagnostics, and treatment of NDDs.

Expressive language in infancy and toddlerhood: The roles of child temperament and maternal parenting behaviors

Prompt, appropriate, and contingent maternal behaviors play a role in early language acquisition, as do individual differences in children's temperament. However, little work has investigated the combined influence of maternal psychosocial and child biological factors on expressive language development. The purpose of this study was to evaluate the concurrent and longitudinal contributions of responsive/intrusive parenting and child temperament to multiple expressive language outcomes at 10 and 24 months of age. Participants included 407 mothers and children (209 girls). Mothers completed questionnaires about their infant's temperament and language, and maternal parenting was coded during mother–child interaction tasks. Dependent variables included (1) gestures at 10 months, (2) vocabulary at 24 months, (3) mean length of utterance at 24 months, and (4) sentence complexity at 24 months. After controlling for child sex and maternal education, child temperament was associated with language outcomes at 10 and 24 months, whereas intrusive, but not responsive, parenting related to only 24 month language outcomes. Longitudinally, infant negative affectivity predicted sentence complexity in toddlerhood. These findings elucidate the presence of both psychological and biological predictors as they differentially influence various aspects of expressive language development across the first two postnatal years.

Average fixation duration in infancy: Stability and predictive utility

The current study examined the stability, consistency, and predictive utility of average fixation durations in infancy. In Study 1, infants' (N = 80) average fixation duration when viewing social stimuli was found to show strong relative stability from 3.5 to 9 months of age. In Study 2, strong within-infant consistency was found in 3.5-month-old infants' (N = 73) average fixation durations to social and nonsocial stimuli. In Study 3, 3.5- to 9-month-old infants' (N = 89) average fixation duration was found to systematically vary with parent-reported symptoms of attention deficit hyperactivity disorder (ADHD) at 4-6 years of age. These results suggest that average fixation duration serves as a stable and systematic measure of individual differences in cognitive development beginning early in life.

Numeracy skills in young children as predictors of mathematical competence

As mathematical competence is linked to educational success, professional achievement, and even a country's economic growth, researchers have been interested in early predictors for quite some time. Although there have been numerous studies on domain-specific numerical abilities predicting later mathematical competence in preschool children, research in toddlers is scarce, especially regarding additional influential aspects, such as domain-general cognitive abilities and the children's social background. Using a large-scale dataset, the present study examined predictive effects of numeracy skills in 17-month-olds for later mathematical achievement. We found small, positive effects, even when controlling for child-related variables (i.e., age and sex) and the children's social background (i.e., maternal education and household language). Additionally, we compared results with a domain-general categorization task and found no distinct effect on mathematical competence. The present results are discussed with regard to the specificities of the dataset, as well as implications for future studies on predictors of mathematical competence.

Additive and multiplicative probabilistic models of infant looking times

Additive and multiplicative regression models of habituation were compared regarding the fit to looking times from a habituation experiment with infants aged between 3 and 11 months. In contrast to earlier studies, the current study considered multiple probability distributions, namely Weibull, gamma, lognormal and normal distribution. In the habituation experiment the type of contrast between the habituation and the test trial was varied (luminance, color or orientation contrast), crossed with the number of habituation trials (1, 3, 5, or 7 habituation trials) and crossed with three age cohorts (4, 7, 10 months). The initial mean LT to dark stimuli (around 3.7 s) was considerably shorter than the mean LT to green and gray stimuli (around 5 s). Infants showed the strongest dishabituation to changes from dark to bright (luminance contrast) and weak-to-no dishabituation to a 90-degrees rotation of the gray stimuli (orientation contrast). The dishabituation was stronger after five and seven habituation trials, but the result was not statistically robust. The gamma distribution showed the best fit in terms of log-likelihood and mean absolute error and the best predictive performance. Furthermore, the gamma distribution showed small correlations between parameters relative to other models. The normal additive model showed an inferior fit and medium correlations between the parameters. In particular, the positive correlation between the initial looking time (LT) and the habituation rate was likely responsible for a different interpretation relative to the multiplicative models of the main effect of age on the habituation rate. Otherwise, the additive and multiplicative models provided similar statistical conclusions. The performance of the model versions without pooling and with partial pooling across participants (also called random-effects, multi-level or hierarchical models) were compared. The latter type of models showed worse data fit but more precise predictions and reduced correlations between the parameters. The performance of model variants with auto-regressive time structures were explored but showed considerably worse fit. The performance of quadratic models that allowed non-monotonic changes in LTs were investigated as well. However, when fitted with LT data, these models did not produce non-monotonic change in LTs. The study underscores the utility of partial-pooling models in terms of providing more accurate predictions. Further, it agrees with previous research in that a multiplicative LT model is preferable. Nevertheless, the current results suggest that the impact of the choice of an additive model on the statistical inference is less dramatic then previously assumed.

Infant speech perception and cognitive skills as predictors of later vocabulary

Research has identified bivariate correlations between speech perception and cognitive measures gathered during infancy as well as correlations between these individual measures and later language outcomes. However, these correlations have not all been explored together in prospective longitudinal studies. The goal of the current research was to compare how early speech perception and cognitive skills predict later language outcomes using a within-participant design. To achieve this goal, we tested 97 5- to 7-month-olds on two speech perception tasks (stress pattern preference, native vowel discrimination) and two cognitive tasks (visual recognition memory, A-not-B) and later assessed their vocabulary outcomes at 18 and 24 months. Frequentist statistical analyses showed that only native vowel discrimination significantly predicted vocabulary. However, Bayesian analyses suggested that evidence was ambiguous between null and alternative hypotheses for all infant predictors. These results highlight the importance of recognizing and addressing challenges related to infant data collection, interpretation, and replication in the developmental field, a roadblock in our route to understanding the contribution of domain-specific and domain-general skills for language acquisition. Future methodological development and research along similar lines is encouraged to assess individual differences in infant speech perception and cognitive skills and their predictability for language development.

Look duration at the face as a developmental endophenotype: elucidating pathways to autism and ADHD

Identifying developmental endophenotypes on the pathway between genetics and behavior is critical to uncovering the mechanisms underlying neurodevelopmental conditions. In this proof-of-principle study, we explored whether early disruptions in visual attention are a unique or shared candidate endophenotype of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). We calculated the duration of the longest look (i.e., peak look) to faces in an array-based eye-tracking task for 335 14-month-old infants with and without first-degree relatives with ASD and/or ADHD. We leveraged parent-report and genotype data available for a proportion of these infants to evaluate the relation of looking behavior to familial (n = 285) and genetic liability (using polygenic scores, n = 185) as well as ASD and ADHD-relevant temperament traits at 2 years of age (shyness and inhibitory control, respectively, n = 272) and ASD and ADHD clinical traits at 6 years of age (n = 94).

Results showed that longer peak looks at the face were associated with elevated polygenic scores for ADHD (β = 0.078, p = .023), but not ASD (β = 0.002, p = .944), and with elevated ADHD traits in mid-childhood (F(1,88) = 6.401, p = .013, $\eta _p^2$=0.068; ASD: F (1,88) = 3.218, p = .076), but not in toddlerhood (ps > 0.2). This pattern of results did not emerge when considering mean peak look duration across face and nonface stimuli. Thus, alterations in attention to faces during spontaneous visual exploration may be more consistent with a developmental endophenotype of ADHD than ASD. Our work shows that dissecting paths to neurodevelopmental conditions requires longitudinal data incorporating polygenic contribution, early neurocognitive function, and clinical phenotypic variation.

Infants' Learning of Rule-Based Visual Sequences Predicts Language Outcome at 2 Years

The ability to learn and generalize abstract rules from sensory input - i.e., Rule Learning (RL) - is seen as pivotal to language development, and specifically to the acquisition of the grammatical structure of language. Although many studies have shown that RL in infancy is operating across different perceptual domains, including vision, no studies have directly investigated the link between infants' visual RL and later language acquisition. Here, we conducted a longitudinal study to investigate whether 7-month-olds' ability to detect visual structural regularities predicts linguistic outcome at 2 years of age. At 7 months, infants were tested for their ability to extract and generalize ABB and ABA structures from sequences of visual shapes, and at 24 months their lexical and grammatical skills were assessed using the MacArthur-Bates CDI. Regression analyses showed that infants' visual RL abilities selectively predicted early grammatical abilities, but not lexical abilities. These results may provide the first evidence that RL mechanisms are involved in language acquisition, and suggest that RL abilities may act as an early neurocognitive marker for language impairments.

Early Development of Visual Attention: Change, Stability, and Longitudinal Associations

Visual attention is a basic mechanism of information gathering and environment selection and consequently plays a fundamental role in influencing developmental trajectories. Here, we highlight evidence for predictive associations from early visual attention to emotion regulation, executive function, language and broader cognitive ability, mathematics and literacy skills, and neurodevelopmental conditions. Development of visual attention is also multifaceted and nonlinear. In daily life, core functions such as orienting, selective filtering, and processing of visual inputs are intertwined and influenced by many other cognitive components. Furthermore, the demands of an attention task vary according to the experience, motivation, and cognitive and physical constraints of participants, while the mechanisms underlying performance may change with development. Thus, markers of attention may need to be interpreted differently across development and between populations. We summarize research that has combined multiple measurements and techniques to further our understanding of visual attention development and highlight possibilities for the future.

Iodine supplementation of lactating women and assessment of infant visual information processing and maternal and infant thyroid function: A randomized trial

Iodine deficiency is one of the major causes of brain damage in childhood. However, iodine supplementation during early pregnancy and lactation can prevent the ill effects of iodine deficiency. This study evaluated maternal and infant thyroid function and infant visual information processing (VIP) in the context of maternal iodine supplementation. A community-based, randomized, supplementation trial was conducted. Mother infant dyads (n = 106) were enrolled within the first 10 days after delivery to participate in this study. Mothers were randomly assigned either to receive a potassium iodide capsule (225 μg iodine) daily for 26 weeks or iodized salt weekly for 26 weeks. Maternal thyroxine (T4), triiodothyronine (T3), thyroid stimulating hormone (TSH), thyroglobulin (Tg), urinary iodine concentration (UIC), breast milk iodine concentration (BMIC) and infant T4, TSH, UIC and VIP were measured as outcome variables. At baseline, neither mothers nor infants in the two groups were significantly different in any of the biomarkers or anthropometric measurements. Maternal TSH and goiter prevalence significantly decreased following iodine supplementation. The percentage of infants who preferentially remembered the familiar face was 26% in the capsule and 51% in the I-salt groups. Infant sex, length for age Z score, BMIC, maternal education and household food security were strong predictors of novelty quotient. In conclusion supplementation daily for six months with an iodine capsule or the use of appropriately iodized salt for an equivalent time was sufficient to reduce goiter and TSH in lactating women. Higher BMIC and LAZ as well as better household food security, maternal education, and male sex predicted higher novelty quotient scores in the VIP paradigm.

Beyond the Bayley: Neurocognitive Assessments of Development During Infancy and Toddlerhood

The use of global, standardized instruments is conventional among clinicians and researchers interested in assessing neurocognitive development. Exclusively relying on these tests for evaluating effects may underestimate or miss specific effects on early cognition. The goal of this review is to identify alternative measures for possible inclusion in future clinical trials and interventions evaluating early neurocognitive development. The domains included for consideration are attention, memory, executive function, language, and socioemotional development. Although domain-based tests are limited, as psychometric properties have not yet been well-established, this review includes tasks and paradigms that have been reliably used across various developmental psychology laboratories.

Antibacterial Activity of Semenovia suffruticosa (Essential Oil) Against Pathogenic Bacteria and Determination of Chemical Composition of Essential Oils by Gas Chromatography-Mass Spectrometry Analysis in Four Regions of Kerman

The use of medicinal plants has been considered due to increasing bacterial resistance to antibiotics. Semenovia suffruticosa is a plant with high potential in medicine. The aim of this study was to evaluate the antibacterial activities and gas chromatography-mass spectrometry (GC-MS) analyses of the essential oil of S. suffruticosa from four regions in Kerman: Hezar Mountain, Laleh Zar, Bidkhan, and Rabor. The essential oil of this plant was extracted by Clevenger. The antibacterial activities were evaluated against three Gram-negative bacteria (P. aeruginosa, K. pneumonia, Acinetobacter) and three Gram-positive bactria (B. subtilis, S. aureus, S. pneumoniae). By disk diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were determined. The composition of essential oil was identified by GC-MS analysis. In our study, most yield of essential oil of S. suffruticosa was 1.2% from the Laleh Zar region and the main components were Z-β-ocimene (25.4%) in Laleh Zar, linalool (17.7%) in Hezar, Z-β-ocimene (18.5%) in Bidkhan, and β-pinene (10.5%) in the Rabor region. Maximum inhibition zone by the essential oil from region Bidkhan was observed against K. pneumoniae (30 mm). The MIC value for S. suffruticosa collected from Laleh Zar was 1.25 mg/ml against S. aureus and S. pneumonia. The results of this study confirm that the significant antibacterial effects of S. suffruticosa and make it a valuable compound in essential oils for pharmaceutical use and a good replacement for chemical antibiotics. Environmental conditions can result in a difference in yields and components; this can be considered significant potential for this plant.

Developing Hierarchical Schemas and Building Schema Chains Through Practice Play Behavior

Examining the different stages of learning through play in humans during early life has been a topic of interest for various scholars. Play evolves from practice to symbolic and then later to play with rules. During practice play, infants go through a process of developing knowledge while they interact with the surrounding objects, facilitating the creation of new knowledge about objects and object related behaviors. Such knowledge is used to form schemas in which the manifestation of sensorimotor experiences is captured. Through subsequent play, certain schemas are further combined to generate chains able to achieve behaviors that require multiple steps. The chains of schemas demonstrate the formation of higher level actions in a hierarchical structure. In this work we present a schema-based play generator for artificial agents, termed Dev-PSchema. With the help of experiments in a simulated environment and with the iCub robot, we demonstrate the ability of our system to create schemas of sensorimotor experiences from playful interaction with the environment. We show the creation of schema chains consisting of a sequence of actions that allow an agent to autonomously perform complex tasks. In addition to demonstrating the ability to learn through playful behavior, we demonstrate the capability of Dev-PSchema to simulate different infants with different preferences toward novel vs. familiar objects.

The Efficiency of Infants' Exploratory Play Is Related to Longer-Term Cognitive Development

In this longitudinal study we examined the stability of exploratory play in infancy and its relation to cognitive development in early childhood. We assessed infants' (N = 130, mean age at enrollment = 12.02 months, SD = 3.5 months; range: 5-19 months) exploratory play four times over 9 months. Exploratory play was indexed by infants' attention to novelty, inductive generalizations, efficiency of exploration, face preferences, and imitative learning. We assessed cognitive development at the fourth visit for the full sample, and again at age three for a subset of the sample (n = 38). The only measure that was stable over infancy was the efficiency of exploration. Additionally, infants' efficiency score predicted vocabulary size and distinguished at-risk infants recruited from early intervention sites from those not at risk. Follow-up analyses at age three provided additional evidence for the importance of the efficiency measure: more efficient exploration was correlated with higher IQ scores. These results suggest that the efficiency of infants' exploratory play can be informative about longer-term cognitive development.

Developmental change in look durations predicts later effortful control in toddlers at familial risk for ASD

BACKGROUND

Difficulties with executive functioning (EF) are common in individuals with a range of developmental disorders, including autism spectrum disorder (ASD). Interventions that target underlying mechanisms of EF early in development could be broadly beneficial, but require infant markers of such mechanisms in order to be feasible. Prospective studies of infants at high familial risk (HR) for ASD have revealed a surprising tendency for HR toddlers to show longer epochs of attention to faces than low-risk (LR) controls. In typical development, decreases in look durations towards the end of the first year of life are driven by the development of executive attention-a foundational component of EF. Here, we test the hypothesis that prolonged attention to visual stimuli (including faces) in HR toddlers reflects early differences in the development of executive attention.

METHODS

In a longitudinal prospective study, we used eye-tracking to record HR and LR infants' looking behaviour to social and non-social visual stimuli at ages 9 and 15 months. At age 3 years, we assessed children with a battery of clinical research measures and collected parental report of effortful control (EC)-a temperament trait closely associated with EF and similarly contingent on executive attention.

RESULTS

Consistent with previous studies, we found an attenuated reduction in peak look durations to faces between 9 and 15 months for the HR group compared with the LR group, and lower EC amongst the HR-ASD group. In line with our hypothesis, change in peak look duration to faces between 9 and 15 months was negatively associated with EC at age 3.

CONCLUSIONS

We suggest that for HR toddlers, disruption to the early development of executive attention results in an attenuated reduction in looking time to faces. Effects may be more apparent for faces due to early biases to orient towards them; further, attention difficulties may interact with earlier emerging differences in social information processing. Our finding that prolonged attention to faces may be an early indicator of disruption to the executive attention system is of potential value in screening for infants at risk for later EF difficulties and for evaluation of intervention outcomes.

Intergenerational associations of the approximate number system in toddlers and their parents

From birth, humans are able to discriminate quantities using the approximate number system (ANS). However, previous methods have only been suitable to examine ANS functioning in infancy and older children. The goals of this study were twofold: first, to modify an existing method of assessing ANS functioning for toddlerhood; and second, to investigate individual differences in toddlers' ANS performance by examining correlations with their parents' ANS acuity. Using a preferential looking paradigm, we found that 1- to 3-year-olds (N = 46) looked significantly longer to numerically changing images compared to numerically constant ones suggesting that the paradigm is a suitable measure of ANS functioning in toddlerhood. Furthermore, we found a positive relation between toddlers' ANS performance and that of their parents (assessed using a non-symbolic number comparison task) independent of children's vocabulary or parents' perceived math ability or preference for math. These findings are consistent with a specific intergenerational transmission of the ANS. Statement of contribution What is already known on this subject? Past methods used to examine ANS functioning were only suitable for infants and older children. Little research has examined sources underlying individual difference in ANS acuity. What does this study add? We developed a preferential looking task to assess ANS functioning in toddlerhood. Individual differences in toddlers' ANS functioning are correlated with their parents' ANS acuity.

Precursors to language development in typically and atypically developing infants and toddlers: the importance of embracing complexity

In order to understand how language abilities emerge in typically and atypically developing infants and toddlers, it is important to embrace complexity in development. In this paper, we describe evidence that early language development is an experience-dependent process, shaped by diverse, interconnected, interdependent developmental mechanisms, processes, and abilities (e.g. statistical learning, sampling, functional specialization, visual attention, social interaction, motor ability). We also present evidence from our studies on neurodevelopmental disorders (e.g. Down syndrome, fragile X syndrome, Williams syndrome) that variations in these factors significantly contribute to language delay. Finally, we discuss how embracing complexity, which involves integrating data from different domains and levels of description across developmental time, may lead to a better understanding of language development and, critically, lead to more effective interventions for cases when language develops atypically.

The effects of stimulus symmetry on hierarchical processing in infancy

The current study investigated the effects of stimulus symmetry on the processing of global and local stimulus properties by 6-month-old short- and long-looking infants through the use of event-related potentials (ERPs). Previous research has shown that individual differences in infant visual attention are related to hierarchical stimulus processing, such that short lookers show a global processing bias, while long lookers demonstrate a local processing bias (Guy, Reynolds, & Zhang, 2013). Additional research has shown that in comparison with asymmetry, symmetry is associated with more efficient stimulus processing and more accurate memory for stimulus configuration (Attneave, 1955; Perkins, 1932). In the current study, we utilized symmetric and asymmetric hierarchical stimuli and predicted that the presence of asymmetry would direct infant attention to the local features of stimuli, leading short lookers to regress to a local processing strategy. Results of the ERP analysis showed that infants familiarized with a symmetric stimulus showed evidence of global processing, while infants familiarized with an asymmetric stimulus did not demonstrate evidence of processing at the global or local level. These findings indicate that short- and long-looking infants, who might otherwise fail to process global stimulus properties due to limited visual scanning, may succeed at global processing when exposed to symmetric stimuli. Furthermore, stimulus symmetry may recruit selective attention toward global properties of visual stimuli, facilitating higher-level cognitive processing in infancy.

The Development of Implicit Memory From Infancy to Childhood: On Average Performance Levels and Interindividual Differences

The present multimethod longitudinal study aimed at investigating development and stability of implicit memory during infancy and early childhood. A total of 134 children were followed longitudinally from 3 months to 3 years of life assessing different age-appropriate measures of implicit memory. Results from structural equation modeling give further evidence that implicit memory is stable from 9 months of life on, with earlier performance predicting later performance. Second, it was found that implicit memory is present from early on, and no age-related improvements are found from 3 months on. Results are discussed with respect to the basic brain structures implicit memory builds on, as well as methodological issues.

Reduced engagement with social stimuli in 6-month-old infants with later autism spectrum disorder: a longitudinal prospective study of infants at high familial risk

Background

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects more than 1 % of the population and close to 20 % of prospectively studied infants with an older sibling with ASD. Although significant progress has been made in characterizing the emergence of behavioral symptoms of ASD, far less is known about the underlying disruptions to early learning. Recent models suggest that core aspects of the causal path to ASD may only be apparent in early infancy. Here, we investigated social attention in 6- and 12-month-old infants who did and did not meet criteria for ASD at 24 months using both cognitive and electrophysiological methods. We hypothesized that a reduction in attention engagement to faces would be associated with later ASD.

Methods

In a prospective longitudinal design, we used measures of both visual attention (habituation) and brain function (event-related potentials to faces and objects) at 6 and 12 months and investigated the relationship to ASD outcome at 24 months.

Results

High-risk infants who met criteria for ASD at 24 months showed shorter epochs of visual attention, faster but less prolonged neural activation to faces, and delayed sensitization responses (increases in looking) to faces at 6 months; these differences were less apparent at 12 months. These findings are consistent with disrupted engagement of sustained attention to social stimuli.

Conclusions

These findings suggest that there may be fundamental early disruptions to attention engagement that may have cascading consequences for later social functioning.

Electronic supplementary material

The online version of this article (doi:10.1186/s11689-016-9139-8) contains supplementary material, which is available to authorized users.

Pathways From Toddler Information Processing to Adolescent Lexical Proficiency

This study examined the relation of 3-year core information-processing abilities to lexical growth and development. The core abilities covered four domains-memory, representational competence (cross-modal transfer), processing speed, and attention. Lexical proficiency was assessed at 3 and 13 years with the Peabody Picture Vocabulary Test (PPVT) and verbal fluency. The sample (N = 128) consisted of 43 preterms (< 1750 g) and 85 full-terms. Structural equation modeling indicated concurrent relations of toddler information processing and language proficiency and, independent of stability in language, direct predictive links between (a) 3-year cross-modal ability and 13-year PPVT and (b) 3-year processing speed and both 13-year measures, PPVT and verbal fluency. Thus, toddler information processing was related to growth in lexical proficiency from 3 to 13 years.

Splenium development and early spoken language in human infants

The association between developmental trajectories of language-related white matter fiber pathways from 6 to 24 months of age and individual differences in language production at 24 months of age was investigated. The splenium of the corpus callosum, a fiber pathway projecting through the posterior hub of the default mode network to occipital visual areas, was examined as well as pathways implicated in language function in the mature brain, including the arcuate fasciculi, uncinate fasciculi, and inferior longitudinal fasciculi. The hypothesis that the development of neural circuitry supporting domain-general orienting skills would relate to later language performance was tested in a large sample of typically developing infants. The present study included 77 infants with diffusion weighted MRI scans at 6, 12 and 24 months and language assessment at 24 months. The rate of change in splenium development varied significantly as a function of language production, such that children with greater change in fractional anisotropy (FA) from 6 to 24 months produced more words at 24 months. Contrary to findings from older children and adults, significant associations between language production and FA in the arcuate, uncinate, or left inferior longitudinal fasciculi were not observed. The current study highlights the importance of tracing brain development trajectories from infancy to fully elucidate emerging brain-behavior associations while also emphasizing the role of the splenium as a key node in the structural network that supports the acquisition of spoken language.

Infant feeding effects on early neurocognitive development in Asian children

BACKGROUND

Breastfeeding has been shown to enhance global measures of intelligence in children. However, few studies have examined associations between breastfeeding and specific cognitive task performance in the first 2 y of life, particularly in an Asian population.

OBJECTIVE

We assessed associations between early infant feeding and detailed measures of cognitive development in the first 2 y of life in healthy Asian children born at term.

DESIGN

In a prospective cohort study, neurocognitive testing was performed in 408 healthy children (aged 6, 18, and 24 mo) from uncomplicated pregnancies (i.e., birth weight >2500 and <4000 g, gestational age ≥37 wk, and 5-min Apgar score ≥9). Tests included memory (deferred imitation, relational binding, habituation) and attention tasks (visual expectation, auditory oddball) as well as the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Children were stratified into 3 groups (low, intermediate, and high) on the basis of breastfeeding duration and exclusivity.

RESULTS

After potential confounding variables were controlled for, significant associations and dose-response relations were observed for 4 of the 15 tests. Higher breastfeeding exposure was associated with better memory at 6 mo, demonstrated by greater preferential looking toward correctly matched items during early portions of a relational memory task (i.e., relational binding task: P-trend = 0.015 and 0.050 for the first two 1000-ms time bins, respectively). No effects of breastfeeding were observed at 18 mo. At 24 mo, breastfed children were more likely to display sequential memory during a deferred imitation memory task (P-trend = 0.048), and toddlers with more exposure to breastfeeding scored higher in receptive language [+0.93 (0.23, 1.63) and +1.08 (0.10, 2.07) for intermediate- and high-breastfeeding groups, respectively, compared with the low-breastfeeding group], as well as expressive language [+0.58 (-0.06, 1.23) and +1.22 (0.32, 2.12) for intermediate- and high-breastfeeding groups, respectively] assessed via the BSID-III.

CONCLUSIONS

Our findings suggest small but significant benefits of breastfeeding for some aspects of memory and language development in the first 2 y of life, with significant improvements in only 4 of 15 indicators. Whether the implicated processes confer developmental advantages is unknown and represents an important area for future research. This trial was registered at www.clinicaltrials.gov as NCT01174875.

Looking in the eyes to discriminate

Studies showed that individual differences in encoding speed as well as looking behaviour during the encoding of facial stimuli can relate to differences in subsequent face discrimination. Nevertheless, a direct linkage between encoding speed and looking behaviour during the encoding of facial stimuli and the role of these encoding characteristics for subsequent discrimination has not been investigated yet. In the present habituation study, an eye-tracker was used to investigate how individual differences in encoding speed (number of habituation trials) relate to individual differences in looking behaviour on faces and the internal facial features (eyes, nose, and mouth) during encoding as well as discrimination. Forty infants habituated to a photograph of a female face. In a subsequent dishabituation phase, a new face was followed by the familiar one. As expected, the results showed that most of the infants were able to habituate to the face and that they managed to discriminate between the new and the familiar face. Furthermore, correlations and analyses of variance showed that individual differences in encoding during habituation related to differences in looking behaviour during habituation as well as dishabituation. Slower-habituating infants could better discriminate between the new and the familiar face and showed a higher interest in the eyes during habituation as well as dishabituation than faster-habituating infants. These data underline that individual differences in encoding speed relate to individual differences in looking behaviour and that increased looking behaviour to important social cues might help subsequent discrimination.

Does bilingual experience affect early visual perceptual development?

Visual attention and perception develop rapidly during the first few months after birth, and these behaviors are critical components in the development of language and cognitive abilities. Here we ask how early bilingual experiences might lead to differences in visual attention and perception. Experiments 1–3 investigated the looking behavior of monolingual and bilingual infants when presented with social (Experiment 1), mixed (Experiment 2), or non-social (Experiment 3) stimuli. In each of these experiments, infants' dwell times (DT) and number of fixations to areas of interest (AOIs) were analyzed, giving a sense of where the infants looked. To examine how the infants looked at the stimuli in a more global sense, Experiment 4 combined and analyzed the saccade data collected in Experiments 1–3. There were no significant differences between monolingual and bilingual infants' DTs, AOI fixations, or saccade characteristics (specifically, frequency, and amplitude) in any of the experiments. These results suggest that monolingual and bilingual infants process their visual environments similarly, supporting the idea that the substantial cognitive differences between monolinguals and bilinguals in early childhood are more related to active vocabulary production than perception of the environment.

Behavioral assessment of language brain processing in the first year of life

An up-to-date review of the behavioral assessments of language development in the first year of life is reported. After recalling the anatomical bases of the early development of the auditory system, the different stages of language development during the first year of life are considered: discrimination, transition and perception. The different kinds of behavioral assessment during the course of the first year are then described by stressing their indications and limitations.

Zinc supplementation sustained normative neurodevelopment in a randomized, controlled trial of Peruvian infants aged 6-18 months

A double-blind, randomized clinical trial was conducted to determine the effects of prevention of zinc deficiency on cognitive and sensorimotor development during infancy. At 6 mo of age, infants were randomly assigned to be administered a daily liquid supplement containing 10 mg/d of zinc (zinc sulfate), 10 mg/d of iron (ferrous sulfate), and 0.5 mg/d of copper (copper oxide), or an identical daily liquid supplement containing only 10 mg/d of iron and 0.5 mg/d of copper. Various controls were implemented to ensure adherence to the supplement protocol. A battery of developmental assessments was administered from 6 to 18 mo of age that included a visual habituation/recognition memory task augmented with heart rate at 6, 9, and 12 mo of age; the Bayley Scales of Infant Development, 2nd edition (BSID2) at 6, 12, and 18 mo; the A-not-B error task at 9 and 12 mo; and free-play attention tasks at 12 and 18 mo. Only infants supplemented with zinc had the normative decline in look duration from 6 to 12 mo during habituation and a normative decline in shifting between objects on free-play multiple-object attention tasks from 12 to 18 mo of age. The 2 groups did not differ on any of the psychophysiologic indices, the BSID2, or the A-not-B error task. The findings are consistent with zinc supplementation supporting a profile of normative information processing and active attentional profiles during the first 2 y of life. This trial was registered at clinicaltrials.gov as NCT00589264.

Individual Differences in Infant Oculomotor Behavior During the Viewing of Complex Naturalistic Scenes

Little research hitherto has examined how individual differences in attention, as assessed using standard experimental paradigms, relate to individual differences in how attention is spontaneously allocated in more naturalistic contexts. Here, we analyzed the time intervals between refoveating eye movements (fixation durations) while typically developing 11-month-old infants viewed a 90-min battery ranging from complex dynamic to noncomplex static materials. The same infants also completed experimental assessments of cognitive control, psychomotor reaction times (RT), processing speed (indexed via peak look during habituation), and arousal (indexed via tonic pupil size). High test-retest reliability was found for fixation duration, across testing sessions and across types of viewing material. Increased cognitive control and increased arousal were associated with reduced variability in fixation duration. For fixations to dynamic stimuli, in which a large proportion of saccades may be exogenously cued, we found that psychomotor RT measures were most predictive of mean fixation duration; for fixations to static stimuli, in contrast, in which there is less exogenous attentional capture, we found that psychomotor RT did not predict performance, but that measures of cognitive control and arousal did. The implications of these findings for understanding the development of attentional control in naturalistic settings are discussed.

Infants' selective attention to reliable visual cues in the presence of salient distractors

With many features competing for attention in their visual environment, infants must learn to deploy attention toward informative cues while ignoring distractions. Three eye tracking experiments were conducted to investigate whether 6- and 8-month-olds (total N = 102) would shift attention away from a distractor stimulus to learn a cue-reward relation. While 8-month-olds showed evidence of increasingly selective attention toward the predictive cues, even when the distractors were highly salient, 6-month-olds shifted attention toward the predictive cues only when the distractors were equally (not more) engaging. These experiments suggest that attention in infancy is highly dependent on the relative weightings of predictiveness and visual salience, which may differ across development and context.

Human infancy…and the rest of the lifespan

Human infancy has been studied as a platform for hypothesis and theory testing, as a major physiological and psychological adjustment, as an object of adults' effects as well as a source of effects on adults, for its comparative value, as a stage of life, and as a setting point for the life course. Following an orientation to infancy studies, including previous reviews and a discussion of the special challenges infants pose to research, this article focuses on infancy as a foundation and catalyst of human development in the balance of the life course. Studies of stability and prediction from infancy illustrate the depth and complexity of modern research on infants and provide a long-awaited reply to key philosophical and practical questions about the meaningfulness and significance of infancy.

Long-term effects of LCPUFA supplementation on childhood cognitive outcomes

BACKGROUND

The effect of long-chain polyunsaturated fatty acid (LCPUFA) intake on cognitive development is controversial. Most randomized trials have assessed cognition at 18 mo, although significant development of cognitive abilities (early executive function) emerge later.

OBJECTIVE

The objective was to evaluate cognition beyond 18 mo and longitudinal cognitive change from 18 mo to 6 y in children who were fed variable amounts of docosahexaenoic acid (0.32%, 0.64%, and 0.96% of total fatty acids) and arachidonic acid (ARA; 0.64%) compared with children who were not fed LCPUFA as infants.

DESIGN

Eighty-one children (19 placebo, 62 LCPUFA) who participated in a double-blind, randomized trial of LCPUFA supplementation as infants were re-enrolled at 18 mo and tested every 6 mo until 6 y on age-appropriate standardized and specific cognitive tests.

RESULTS

LCPUFA supplementation did not influence performance on standardized tests of language and performance at 18 mo; however, significant positive effects were observed from 3 to 5 y on rule-learning and inhibition tasks, the Peabody Picture Vocabulary Test at 5 y, and the Weschler Primary Preschool Scales of Intelligence at 6 y. Effects of LCPUFAs were not found on tasks of spatial memory, simple inhibition, or advanced problem solving.

CONCLUSIONS

The data from this relatively small trial suggest that, although the effects of LCPUFAs may not always be evident on standardized developmental tasks at 18 mo, significant effects may emerge later on more specific or fine-grained tasks. The results imply that studies of nutrition and cognitive development should be powered to continue through early childhood. This parent trial was registered at clinicaltrials.gov as NCT00266825.

Separable Attentional Predictors of Language Outcome

The aim of this study was to examine the combined influences of infants attention and use of social cues in the prediction of their language outcomes. This longitudinal study measured infants' visual attention on a distractibility task (11 months), joint attention (14 months), and language outcomes (word -object association, 14 months; MBCDI vocabulary size and multi-word productions at 18 months of age). Path analyses were conducted for two different language outcomes. The analysis for vocabulary revealed unique direct prediction from infants' visual attention on a distractibility task (i.e., maintaining attention to a target event in the presence of competing events) and joint attention (i.e., more frequent response to tester's bids for attention) for larger vocabulary size at outcome; this model accounted for 48% of variance in vocabulary, after controlling for baseline communication status (assessed at 11 months). The analysis for multi-word productions yielded direct effects for infants' distractibility, but not joint attention; this model accounted for 45% of variance in multi-word productions, again after controlling for baseline communication status. Indirect effects were not significant in either model. Results are discussed in light of the unique predictive role of attentional factors and social/attention cues for emerging language.

Infant attention and early childhood executive function

Individual differences in infant attention are theorized to reflect the speed of information processing and are related to later cognitive abilities (i.e., memory, language, and intelligence). This study provides the first systematic longitudinal analysis of infant attention and early childhood executive function (EF; e.g., working memory, inhibitory control, cognitive flexibility). A group of 5-month-olds (n = 201) were classified as short or long lookers. At 24, 36, and 48 months of age, children completed age-appropriate EF tasks. Infant short lookers (i.e., more efficient information processors) exhibited higher EF throughout early childhood as compared to infant long lookers, even after controlling for verbal ability (a potential indicator of intelligence). These findings are discussed in relation to the emergence of executive attention.

Origins of Effortful Control: Infant and Parent Contributions

Effortful control (EC) refers to the ability to inhibit a dominant response to perform a subdominant one and has been shown as protective against a myriad of difficulties. Research examining precursors of EC has been limited to date, and in this study, infancy contributors to toddler EC were examined. Specifically, parent/family background variables (e.g., education, income), maternal temperament, perceived stress, and internalizing symptoms were addressed, along with infant temperament: positive affectivity/surgency (PAS), negative emotionality (NE), and regulatory capacity/orienting (RCO); and laboratory observation-based indicators of attention. Infant attention indexed by the latency to look away after initially orienting to the presented stimuli emerged as an important predictor of later EC, after accounting for other child and parent/family attributes, with shorter latencies predicting higher levels of EC. Mothers' extraversion and parenting stress were the only parent/family attributes to significantly contribute to the prediction of toddler EC, with the former promoting and the latter undermining the development of EC. Infant temperament factors were also examined as a moderator of parent/family influences, with results indicating a significant interaction between mothers' EC and infant RCO, so that children with greater RCO and mothers high in EC exhibited the highest EC scores in toddlerhood.

Systems and cascades in cognitive development and academic achievement

A large-scale (N = 552) controlled multivariate prospective 14-year longitudinal study of a developmental cascade embedded in a developmental system showed that information-processing efficiency in infancy (4 months), general mental development in toddlerhood (18 months), behavior difficulties in early childhood (36 months), psychometric intelligence in middle childhood (8 years), and maternal education either directly or indirectly (or both) contribute to academic achievement in adolescence (14 years).