General Cognitive Development Research Articles

Individual differences in theory of mind and children’s advanced scientific reasoning in elementary school

Recently, there has been an increased interest in the associations between theory of mind (ToM), the ability to infer others’ mental states, and academic functioning in middle childhood including scientific reasoning. This study follows this trend and addresses two gaps in the literature. First, it examines whether individual differences in ToM primarily relate to children’s acquisition of advanced scientific reasoning or also help them overcome less-sophisticated conceptions. Second, it investigates the associations between scientific reasoning and distinct aspects of the multidimensional construct of ToM (here we assessed recursive ToM, interpretive ToM, and social awareness ToM). Participants were 84 8-, 9-, and 10-year-olds (41 F, 43 M) attending elementary school in northern Italy. Children were assessed for their ToM, scientific reasoning, inhibitory control, and verbal and non-verbal ability. Results showed that ToM was uniquely correlated with children’s acquisition of advanced conceptions of scientific reasoning but not with the overcoming of naïve and intermediate levels of understanding. Hierarchical regression analyses showed that this finding applies to all three ToM components and that the association between ToM and advanced scientific reasoning was independent of children’s general cognitive development (inhibitory control, and verbal and non-verbal ability). Overall, our findings suggest that ToM paves the way for more sophisticated reasoning in the science domain and that several distinct mechanisms may underlie this effect.

Improvements in executive functions by domain-specific cognitive training in youth elite soccer players

This study examined the impact of sport-specific cognitive training (CT) on executive functions (EFs) in youth soccer players. Thirty-one athletes (13–15 years) participated, 13 in the intervention group (IG) and 18 in the control group (CG). The IG underwent an 8-week soccer-focused CT program, while the CG maintained regular training. The assessments included working memory, inhibition, and cognitive flexibility tasks. The results revealed no significant improvements in EFs in the IG compared to those in the CG. Both groups showed enhanced cognitive flexibility, possibly due to general cognitive development or learning effects. The study suggested that an 8-week sport-specific CT may not enhance EFs in young soccer players, potentially due to a ceiling effect in highly skilled athletes. These findings should be considered when designing cognitive training programs for athletes, and future research could explore the optimal duration of such programs.

Cognitive control in infancy: Attentional predictors using a tablet-based measure.

Cognitive control is a predictor of later-life outcomes and may underpin higher order executive processes. The present study examines the development of early cognitive control during the first 24-month. We evaluated a tablet-based assessment of cognitive control among infants aged 18- and 24-month. We also examined concurrent and longitudinal associations between attentional disengagement, general cognitive skills and cognitive control. Participants (N=60, 30 female) completed the tablet-task at 18- and 24-month of age. Attentional disengagement and general cognitive development were assessed at 5-, 8-, 12-, 18- and 24-month using an eye-tracking measure and the Mullen Scales of Early Learning (MSEL), respectively. The cognitive control task demonstrated good internal consistency, sensitivity to age-related change in performance and stable individual differences. No associations were found between infant cognitive control and MSEL scores longitudinally or concurrently. The eye-tracking task revealed that slower attentional disengagement at 8-month, but faster disengagement at 18-month, predicted higher cognitive control scores at 24-month. This task may represent a useful tool for measuring emergent cognitive control. The multifaceted relationship between attention and infant cognitive control suggests that the rapid development of the attentional system in infancy results in distinct attentional skills, at different ages, being relevant for cognitive control development.

The development of desire language: A corpus study of ‘want’

Children’s usage of mental state verbs can reveal evidence of their theory of mind and general cognitive development. Children produce a certain class of mental state verbs, namely desire verbs such as want, like, and love, early in development. Among these desire verbs, they produce want the most frequently. We report on a corpus study of 450 + instances of want as gathered from children’s dialogues with caretakers in the CHILDES database. We developed a novel coding scheme to measure children’s use and understanding of want utterances: i.e., we analyzed the kinds of things that children described wanting for themselves or others, as well as the agents to whom they ascribed desires. We report on the frequencies of these features across the ages of 24 to 59 months (2–4 years of age), and highlight noteworthy trends in the way children used want. Children appear to talk about their own desires most often; they primarily use questions to talk about second person desires; and they describe more complex desires as they mature. We describe how these patterns of linguistic competency may serve as an index for the development of mechanisms that underlie mental state reasoning.

Особенности развития и психическое здоровье близнецов раннего возраста: обзор отечественных и зарубежных исследований

<p style="text-align: justify;"><strong>Objectives. </strong>Due to the increasing birth rate of twins and the high risk of delayed physical, cognitive, and psychosocial development in twins at an early age, there is a need to identify factors that contribute to the mental health and developmental trajectory of children.</p> <p style="text-align: justify;"><strong>Methods. </strong>We conducted a review and analysis of recent domestic and international research from 183 articles published between 2009 and 2024, and available in the Scopus, Semantic Scholar, PubMed, Bielefeld Academic Search Engine, Russian Science Citation Index (RSCI) and Crossref databases. The search used the keywords “infant twins”, “twins at early age”, “twins early development”, “twins interaction”.</p> <p style="text-align: justify;"><strong>Results. </strong>The interest of researchers in different aspects of the mental health and development of children born from monozygotic and dizygotic twin pregnancies is shown. The main factors affecting the health and development of twins are genetic factors, congenital defects, gestational age and birth weight, the presence of trauma during birth, as well as the somatic health of children in the first months of life. The early development of twins is closely related to the features of the care organization and parenting, interaction with the mother, as with a caring adult, a set of environmental factors and conditions for the education. At an early age, twins are at high risk of lagging in general physical, cognitive and speech impairment development compared with singleton, which should be taken into account in monitoring the need for early help for children.</p> <p style="text-align: justify;"><strong>Conclusions. </strong>There is a need for relevant domestic research on the features of the development of twins at an early age. The study of the individual trajectory of early development of each child from twins should be carried out taking into account the factor of discordance in a twin pair.</p>

The development and diversity of religious cognition and behavior: Protocol for Wave 1 data collection with children and parents by the Developing Belief Network.

The Developing Belief Network is a consortium of researchers studying human development in diverse social-cultural settings, with a focus on the interplay between general cognitive development and culturally specific processes of socialization and cultural transmission in early and middle childhood. The current manuscript describes the study protocol for the network's first wave of data collection, which aims to explore the development and diversity of religious cognition and behavior. This work is guided by three key research questions: (1) How do children represent and reason about religious and supernatural agents? (2) How do children represent and reason about religion as an aspect of social identity? (3) How are religious and supernatural beliefs transmitted within and between generations? The protocol is designed to address these questions via a set of nine tasks for children between the ages of 4 and 10 years, a comprehensive survey completed by their parents/caregivers, and a task designed to elicit conversations between children and caregivers. This study is being conducted in 39 distinct cultural-religious groups (to date), spanning 17 countries and 13 languages. In this manuscript, we provide detailed descriptions of all elements of this study protocol, give a brief overview of the ways in which this protocol has been adapted for use in diverse religious communities, and present the final, English-language study materials for 6 of the 39 cultural-religious groups who are currently being recruited for this study: Protestant Americans, Catholic Americans, American members of the Church of Jesus Christ of Latter-day Saints, Jewish Americans, Muslim Americans, and religiously unaffiliated Americans.

Simplification principles and child language development in Armenian

At certain stages of their general cognitive development and language acquisition, children apparently employ their innately growing (cognitive) knowledge and skills to meet the challenges they face in L1 acquisition. Among other things, children use different sets of simplification strategies, such as cropping words, replacing or displacing syllables or syllabic constituents, omitting suffixes, and using simpler syntax. We catalog processes like fortition, reduplication, and the various stages of acquisition. This paper presents some language development data in Armenian children. Empirically, our study is one of the few (if only) known studies on the language acquisition of Armenian. The data provides valuable theoretical insight into the strategies that children pursue in communication, as well as in cognitive processing of speech.

The Use of an Open-Ended Learning Approach on The Ability To Recognize The Concept of Numbers: Its Effectiveness for Children 4-5 Years Old

The formation of numerical concepts is a critical stage in early childhood development. Understandingnumbers lays the groundwork for future mathematical abilities and academic success. This study aimsto investigate the effect of an open-ended learning strategy on the capacity of 4-5-year-old childrento recognize number concepts. To reach the research goal, a quantitative approach was used, alongwith experimental methodologies. The study participants were children aged 4-5 years old, and datawas collected via total sampling. The experimental group was taught using an open-ended learningtechnique, while the control group followed a traditional structured teaching method. Pre-and post-testswere used to examine the children’s ability to recognize number concepts. Statistical analysis, includingt-tests, was used to compare the performance of the experimental and control groups. The results of thisstudy show that using an open-ended learning strategy improves the capacity of 4-5-year-old children torecognize number concepts. In comparison to traditional structured teaching method, the open-endedapproach stimulates active inquiry, independent thinking, and problem-solving, which improves children’scognitive development with regard to numerical concepts. This study suggests that open-ended learningtechniques are excellent educational strategies for developing number concept identification in youngchildren. This study’s findings have ramifications for early childhood educators and curriculum makers.This study stresses the necessity of implementing such tactics in educational settings by demonstratingthe benefits of an open-ended learning strategy in developing number concept awareness. Open-endedlearning techniques can improve children’s mathematics ability while also contributing to their generalcognitive development. Furthermore, these findings may motivate additional study and inquiry into theuse of open-ended learning approaches in various domains of early childhood education, increasing ourunderstanding of successful teaching strategies for young children.

Associations of screen use with cognitive development in early childhood: the ELFE birth cohort.

The associations of screen use with children's cognition are not well evidenced and recent, large, longitudinal studies are needed. We aimed to assess the associations between screen use and cognitive development in the French nationwide birth cohort. Time and context of screen use were reported by parents at ages 2, 3.5 and 5.5. Vocabulary, non-verbal reasoning and general cognitive development were assessed with the MacArthur-Bates Communicative Development Inventory (MB) at age 2, the Picture Similarities subtest from the British Ability Scales (PS) at age 3.5 and the Child Development Inventory (CDI) at ages 3.5 and 5.5. Outcome variables were age-adjusted and standardized (mean = 100, SD = 15). Multiple imputations were performed among children (N = 13,763) with ≥1 screen use information and ≥1 cognitive measures. Cross-sectional and longitudinal associations between screen use and cognitive development were assessed by linear regression models adjusted for sociodemographic and birth factors related to the family and children, and children's lifestyle factors competing with screen use. Baseline cognitive scores were further considered in longitudinal analysis. TV-on during family meals at age 2, not screen time, was associated with lower MB scores at age 2 (β [95% CI] = -1.67 [-2.21, -1.13]) and CDI scores at age 3.5 (-0.82 [-1.31, -0.33]). In cross-sectional analysis, screen time was negatively associated with CDI scores at ages 3.5 (-0.67 [-0.94, -0.40]) and 5.5 (-0.47 [-0.77, -0.16]), and, in contrast, was positively associated with PS scores (0.39 [0.07, 0.71]) at age 3.5. Screen time at age 3.5 years was not associated with CDI scores at age 5.5 years. Our study found weak associations of screen use with cognition after controlling for sociodemographic and children's birth factors and lifestyle confounders, and suggests that the context of screen use matters, not solely screen time, in children's cognitive development.

A brain structural connectivity biomarker for autism spectrum disorder diagnosis in early childhood.

Autism spectrum disorder (ASD) is associated with altered brain development, but it is unclear which specific structural changes may serve as potential diagnostic markers, particularly in young children at the age when symptoms become fully established. Furthermore, such brain markers need to meet the requirements of precision medicine and be accurate in aiding diagnosis at an individual rather than only a group level. This study aimed to identify and model brain-wide differences in structural connectivity using diffusion tensor imaging (DTI) in young ASD and typically developing (TD) children. A discovery cohort including 93 ASD and 26 TD children and two independent validation cohorts including 12 ASD and 9 TD children from three different cities in China were included. Brain-wide (294 regions) structural connectivity was measured using DTI (fractional anisotropy, FA) together with symptom severity and cognitive development. A connection matrix was constructed for each child for comparisons between ASD and TD groups. Pattern classification was performed on the discovery dataset and the resulting model was tested on the two independent validation datasets. Thirty-three structural connections showed increased FA in ASD compared to TD children and associated with both autistic symptom severity and impaired general cognitive development. The majority (29/33) involved the frontal lobe and comprised five different networks with functional relevance to default mode, motor control, social recognition, language and reward. Overall, classification achieved very high accuracy of 96.77% in the discovery dataset, and 91.67% and 88.89% in the two independent validation datasets. Identified structural connectivity differences primarily involving the frontal cortex can very accurately distinguish novel individual ASD from TD children and may therefore represent a robust early brain biomarker which can address the requirements of precision medicine.

Links between Daytime Napping, Night-Time Sleep Quality and Infant Attention: An Eye-Tracking, Actigraphy and Parent-Report Study.

The current study explored the potential influence of infant sleep, measured by parental report and actigraphy, and family functioning on attention development using eye tracking. The use of actigraphy in parallel with parental report, has the advantage of measuring participant's sleep throughout the night without parental observation and the ability to objectively assess sleep quality. An eye-tracking version of the Gap-Overlap task was used to measure visual attention. Questionnaires and behavioural assessment were used to assess family function, and general cognitive development. Fifty infants (Mean age = 13.44 months, SD = 3.10) participated in the study, 23 of which had full final datasets. Results show that daytime sleep duration, as measured by parental report, and proportion of light sleep at night, as measured by actigraphy, are linked to visual attention. A higher proportion of light sleep, a marker of poorer sleep quality, and less daytime sleep were negatively linked with facilitation and disengagement on the Gap-Overlap task. Family functioning was not associated with attention. The results provide initial evidence that in addition to the amount of daytime sleep; quality of night-time sleep as measured by proportion of light sleep, is a potentially useful sleep variable which requires further focus in the study of attention development.

VECA: A New Benchmark and Toolkit for General Cognitive Development

The developmental approach, simulating a cognitive development of a human, arises as a way to nurture a human-level commonsense and overcome the limitations of data-driven approaches. However, neither a virtual environment nor an evaluation platform exists for the overall development of core cognitive skills. We present the VECA(Virtual Environment for Cognitive Assessment), which consists of two main components: (i) a first benchmark to assess the overall cognitive development of an AI agent, and (ii) a novel toolkit to generate diverse and distinct cognitive tasks. VECA benchmark virtually implements the cognitive scale of Bayley Scales of Infant and Toddler Development-IV(Bayley-4), the gold-standard developmental assessment for human infants and toddlers. Our VECA toolkit provides a human toddler-like embodied agent with various human-like perceptual features crucial to human cognitive development, e.g., binocular vision, 3D-spatial audio, and tactile receptors. We compare several modern RL algorithms on our VECA benchmark and seek their limitations in modeling human-like cognitive development. We further analyze the validity of the VECA benchmark, as well as the effect of human-like sensory characteristics on cognitive skills.

Клініко-діагностичні паралелі між станом плаценти та несприятливими наслідками глибоко недоношених дітей

Premature newborns are a special category of children with their inherent morpho-functional immaturity and specific pathological conditions that cause significant differences in the survival, morbidity and their baby care consequences in comparison with children of other weight categories. The problems of premature babies are at the forefront of neonatal research and perinatal care. Purpose - to establish a link between the formation of adverse consequences in preschool children born prematurely, with a body weight of less than 1500 g, and placental changes. Materials and methods. The study involved 220 preschool children born prematurely. The results of a pathomorphological study of the placentae of mothers of 220 children were analyzed. Its results enabled to distinguish 5 groups of mothers according to the classification of changes in the placentae. In the course of the study, this category of children was under observation of the doctors the Prematurity and Hight-Risk Neonates Post-discharge Follow-ups Department in order to regular assess their health. Clinical indicators such as body weight, height, head circumference, neurological, general cognitive development and low severity dysfunction, the post-discharge history including respiratory diseases, skeletal system problems, hematological and metabolic disorders, were analyzed. Ophthalmological and audiological examinations were performed prospectively to assess vision and hearing. Depending on the severity of disabling pathology, children with severe disabling consequences (n=54) were isolated - 24.5%. Further analysis concerned the state of health of these children, divided into 5 groups according to the identified changes in the placentas of their mothers. Results. All the children involved in the study had a disease combination in the neonatal period that caused severe conditions. Pathological changes of the placenta significantly affected the course of the neonatal period. Thus, newborns with signs of inflammatory changes and immaturity were 10 times more likely to suffer generalized intrauterine infections and neonatal sepsis, they also significantly more frequently have intraventricular hemorrhages, periventricular leukomalacia, and bronchopulmonary dysplasia. The course of the neonatal period in groups of children with signs of premature aging of placenta and blood flow disorders was characterized by a low frequency of infections, but periventricular leukomalacia was diagnosed 5 times more often. Conclusions. It was found out that transplacental infection and pathological placenta immaturity had a negative impact on the health of children of groups III and IV, causing their birth 3 weeks prematurely, unlike the children in the comparison group. Newborns of groups III and IV needed resuscitation care in the delivery room 9 times more often, and the need for respiratory support was 10 times higher than in the comparison group, which predetermined a significantly longer duration of hospital stay for children of groups III and IV - on average 30-45 days longer compared to newborns of Group V. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the author. Key words: premature babies, Neonates Post-discharge Follow-ups Department, disability, long-term consequences.

Cognitive flexibility in 12-month-old preterm and term infants is associated with neurobehavioural development in 18-month-olds

There is growing evidence that preterm children are at an increased risk of poor executive functioning, which underlies behavioural and attention problems. Previous studies have suggested that early cognitive flexibility is a possible predictor of later executive function; however, how it develops in infancy and relates to the later neurobehavioural outcomes is still unclear in the preterm population. Here, we conducted a longitudinal study to investigate oculomotor response shifting in 27 preterm and 25 term infants at 12 months and its relationship with general cognitive development and effortful control, which is a temperamental aspect closely associated with executive function, at 18 months. We found that moderate to late preterm and term infants significantly inhibited previously rewarded look responses, while very preterm infants did not show significant inhibition of perseverative looking at 12 months. Moreover, lower inhibition of perseverative looking was significantly associated with lower general cognitive development and attentional shifting at 18 months. These findings suggest that the early atypical patterns of oculomotor response shifting may be a behavioural marker for predicting a higher risk of negative neurobehavioural outcomes, including attention-related problems in preterm children.

Neuromuscular Diseases Affect Number Representation and Processing: An Exploratory Study.

Spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD) both are rare genetic neuromuscular diseases with progressive loss of motor ability. The neuromotor developmental course of those diseases is well documented. In contrast, there is only little evidence about characteristics of general and specific cognitive development. In both conditions the final motor outcome is characterized by an inability to move autonomously: children with SMA never accomplish independent motoric exploration of their environment, while children with DMD do but later lose this ability again. These profound differences in developmental pathways might affect cognitive development of SMA vs. DMD children, as cognition is shaped by individual motor experiences. DMD patients show impaired executive functions, working memory, and verbal IQ, whereas only motor ability seems to be impaired in SMA. Advanced cognitive capacity in SMA may serve as a compensatory mechanism for achieving in education, career progression, and social satisfaction. This study aimed to relate differences in basic numerical concepts and arithmetic achievement in SMA and DMD patients to differences in their motor development and resulting sensorimotor and environmental experiences. Horizontal and vertical spatial-numerical associations were explored in SMA/DMD children ranging between 6 and 12 years through the random number generation task. Furthermore, arithmetic skills as well as general cognitive ability were assessed. Groups differed in spatial number processing as well as in arithmetic and domain-general cognitive functions. Children with SMA showed no horizontal and even reversed vertical spatial-numerical associations. Children with DMD on the other hand revealed patterns in spatial numerical associations comparable to healthy developing children. From the embodied Cognition perspective, early sensorimotor experience does play a role in development of mental number representations. However, it remains open whether and how this becomes relevant for the acquisition of higher order cognitive and arithmetic skills.

Body Composition, Psychological, Cardiovascular, and Physical Activity Factors Related with Academic School Performance

The aim of the present study was to analyse body composition, anxiety, cardiovascular, and physical activity factors related with academic performance of school students as well as to analyse differences, by age, in these factors. We analysed in 266 primary school students’ (8.81 ± 1.62 years, range: 5–13 years) heart rate, anthropometric variables to calculate body mass index, physical activity performance, anxiety levels and academic results by the average of marks. Students were divided in two different groups, firstly by their lower or higher academic performance, and secondly by age. Results showed a negative correlation between academic performance and age, weight, body mass index and trait anxiety variables. Additionally, significant differences were found by age, presenting older students higher scores in body mass index and lower physical activity, trait anxiety, heart rate and academic performance values than younger students. Overweight and obesity may have a great impact in academic performance in children and we pointed out the necessity to establish programs related with healthy habits which include improvements in physical activity and nutrition behaviours with the objective to enhance children’s health general status, psychological profile, cognitive and motor development, and academic performance.

Cognitive functioning in Deaf children using Cochlear implants

BackgroundCognitive abilities like language, memory, reasoning, visualization, and perceptual functioning shape human action and are considered critical to the successful interaction with the environment. Alternatively, hearing loss can disrupt a child’s ability to communicate, and negatively impact cognitive development. Cochlear implants (CI) restore auditory input thereby supporting communication and may enhance cognitive performance. This study compares general cognitive development after cochlear implantation (2017–2019) in two groups of Jordanian children implanted earlier (age:4–6 years, N = 22) and later (7–9 years, N = 16) to the development of randomly selected normal hearing peers (N = 48).DesignVisualization, reasoning, memory, and attention were assessed using the Leiter-R scale at baseline (before implantation), 8 months and 16 months post implantation for children with hearing loss. Same times of testing (baseline, 8 months and 16 months) were used for normal hearing peers.ResultsOver the 16-month period, the cognitive improvement of 4–6-year-old deaf children was greater than that of their normal hearing peers on the scales of visualization (5.62 vs. 4.40), reasoning (2.53 vs. 2.38) and memory (17.19 vs. 11.67). while the improvement of 7–9-year-old was less major than that of their normal hearing peers on all scales.ConclusionsThese results suggest that CI not only enhances communication skills but may improve cognitive functioning in deaf children. However, the extent of this improvement was dependent on age at intervention; current results demonstrated that the children received CI at young ages had better cognitive improvements.

Prenatal perfluoroalkyl substance exposure and neuropsychological development throughout childhood: The INMA Project

BackgroundPerfluoroalkyl substances (PFASs) have been related to neurodevelopmental toxicity in animals. However, human studies are inconclusive. ObjectivesTo evaluate the association between prenatal PFAS exposure and neuropsychological development during childhood. Methods1240 mother–child pairs from the Spanish INMA Project were analyzed. Perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorononanoic acid (PFNA) were measured in first-trimester maternal plasma. Neuropsychological development was assessed at 14 months, 4–5 and 7 years covering four domains: general cognitive, general motor, attention, and working memory. Associations were studied by means of multivariable regression analyses. ResultsPFHxS, PFOA, PFOS, and PFNA medians were: 0.6, 2.4, 6.1, and 0.7 ng/mL. Higher PFAS prenatal exposure was associated with worse motor development at 14 months, especially in the case of PFHxS (β[95%CI]: −1.49[−2.73, −0.24]) and to a lesser extent PFOS (−1.25[−2.62, 0.12]). There was also a marginal positive association between general cognitive development at 4–5 years and PFOS (1.17[−0.10, 2.43]) and PFNA (0.99[−0.13, 2.12]). No clear associations for other neuropsychological outcomes or any sex differences were found. DiscussionThis study shows no clear-cut evidence of an association between prenatal PFAS exposure and adverse neuropsychological development in children up to the age of 7 years.

General Cognitive Abilities and Psychosocial Development in Children and Adolescents Having a Co-Twin with Down Syndrome

To examine the general cognitive and psychosocial development in children and adolescents having a co-twin with Down syndrome. A case control study with an individually matched control group was conducted. Participants included families with twins discordant for Down syndrome as well as with typically developing twins. The group of unaffected co-twins aged 4-16years was compared with a control group of typically developing twins in terms of general cognitive abilities, behavioral problems, and prosocial behavior. The age and sex and the sex composition of the twins were individually matched. The Sijnders-Oomen nonverbal intelligence test was applied to assess children's IQ, and parents completed the Strength and Difficulties Questionnaire. The unaffected co-twins did not differ from typically developing twins with respect to their IQ. Concerning the psychosocial development, significantly heightened values in unaffected co-twins twins were only obtained for the conduct problems scale (P=.01; r=0.45), neither for the total difficulties score nor for the other behavioral problemscales significant differences were found. The general cognitive development of the unaffected co-twin of children with Down syndrome is not affected by the presence of their Down syndrome twin. Unaffected co-twins showed increased conduct problems, which is most pronounced in the younger children.

The Predictive Value of Children's Understanding of Indeterminacy and Confounding for Later Mastery of the Control-of-Variables Strategy.

Prior research has identified age 9–11 as a critical period for the development of the control-of-variables strategy (CVS). We examine the stability of interindividual differences in children's CVS skills with regard to their precursor skills during this critical developmental period. To this end, we relate two precursor skills of CVS at age 9 to four skills constituting fully developed CVS more than 2 years later, controlling for children's more general cognitive development. Note that N = 170 second- to fourth-graders worked on multiple choice-assessments of their understanding of indeterminacy of evidence and of confounding. We find relations between these two precursor skills and children's CVS skills 2 years later at age 11 in planning, identifying, and interpreting controlled experiments, and in recognizing the inconclusiveness of confounded comparisons (understanding). In accordance with the perspective that both indeterminacy and confounding constitute critical, related yet distinct elements of CVS, both precursor skills contribute to the prediction of later CVS. Together, the two precursor skills can explain 39% of students' later CVS mastery. Overall, the understanding of indeterminacy is a stronger predictor of fully developed CVS than that of confounding. The understanding of confounding, however, is a better predictor of the more difficult CVS sub-skills of understanding the inconclusiveness of confounded comparisons, and of planning a correctly controlled experiment. Importantly, both precursor skills maintain interactive predictive strength when controlling for children's general cognitive abilities and reading comprehension, showing that the developmental dynamics of CVS and its precursor skills cannot be fully ascribed to general cognitive development. We discuss implications of these findings for theories about the development of CVS and broader scientific reasoning.