Preschoolers: not just very young children

Pediatric neuropsychologists are keenly aware through their didactic education and experiential background that principles and procedures related to adult onset brain disease and disorder are often misapplied to children. The adage ‘children are not just small adults’ captures this sentiment succinctly. Also increasing is recognition that procedures, interpretive rules, and algorithms applied to the evaluation of brain function in school-aged children do not translate optimally to preschoolers who have an even more immature brain (Baron & Anderson, 2012). Thus, another tenet deserving of instantiation is ‘preschoolers are not just very young children.’

This special issue was conceived as a broad-based forum for the dissemination of current and original research and commentary to highlight the range of advances being made regarding brain development and preschooler neuropsychological functioning. The only thematic directive to authors was that there should be an emphasis on children aged between 2 and 6 years. This is a maturational period that encompasses dynamic gains in brain growth and connectivity, and when subtle to profoundly adverse medical and psychological outcomes result when circumstances alter the typical trajectory. Communication was encouraged through a review of the literature, case presentation, critique of theory or methods, novel experimental paradigms, or report of application of rehabilitative intervention.

The preschool years are highly instructive about early brain development and the maturation of emergent intellectual, neuropsychological, and behavioral functions. Yet, the effects of adverse health circumstances were long understudied by pediatric neuropsychologists who mostly investigated and evaluated children of school age or older, rarely preschoolers (Baron & Leonberger, 2012). This omission was fostered by a limited exposure to preschoolers in training and practice settings, a tendency for referral sources to rely on non-neuropsychologists for neurodevelopmental evaluation, few neuropsychological publications that informed about brain-behavioral function in preschoolers, and scarce age-appropriate tests and normative data. Consequently, neuropsychological knowledge about these formative years and the early neuropsychological trajectory associated with either normal or atypical brain development lagged. Challenges that further contributed to the gap in understanding developmental course included that present and future biophysiological, medical, epigenetic, psychological, social-emotional, cultural, and socioenvironmental influences will interplay in complex ways to affect neurocognition, personality, and adaptive function over a child’s extended maturational course.

Thus, it was intended that the contributions to this special issue would further promote greater understanding of the high relevance of furthering our scientific and clinical knowledge about brain–behavior relationships during these formative preschool years, lessening a wide gap that only began to be rectified with rigor around the late 1990s to early 2000s. The richness of data able to be acquired by study of this under-investigated age group is vital for critical lifespan study. It also is a natural extension of the fetal origins hypothesis of adult disease that links fetal and perinatal circumstances to adult medical outcomes (Barker, 1992; Barker, Andrade, Morton, Romanowski, & Bowles, 2010; Barker, Gluckman, & Robinson, 1995). This conceptualization intersects well with the seminal teachings of proponents of the ecology of human (child) development, which incorporates family, economic, and political structures with the aim to understand an individual’s developmental course from childhood to adulthood (Bronfenbrenner, 1981; Bronfenbrenner & Ceci, 1994).

‘Neuropsychology of Preschoolers’ commences with ‘Measurement of Neurodevelopmental Changes in Children Treated with Radiation for Brain Tumors: What is a True “Baseline?”’ by Ris, Grosch, Fletcher, Mehta, and Kahalley (2017). How to estimate baseline is a crucial methodological decision in longitudinal research. This paper, written with a context of measurement effects related to pediatric brain tumor pathology and its therapy, has relevance for every professional engaged in quantitative measurement of a developmental trajectory. Ris and colleagues first describe options for how one might construct, or reconstruct, baseline in order to evaluate cognitive change while also commenting on the advantages and disadvantages of each method. They then proceed to review the methods utilized in their review of studies of pediatric brain tumor. They highlight confounds and endorse an explicit study design that will maximize one’s research objective, irrespective of the clinical population and age of the children studied.

Raghubar and Barnes’s (2017) following review, ‘Early Numeracy Skills in Preschool-aged Children: A Review of Cognitive and Neurobiological Findings,’ brings together a disparate literature and coalesces a substantial base of current knowledge for the reader regarding the development of skills that are foundational components of numeracy, linking these to their neurobiological substrate. The discussion acknowledges the importance of early detection at preschool age in order to provide timely and appropriate intervention for both typically developing children and those with clinical conditions. The reader will find a valuable summation of a complex area of cognitive development that has long received insufficient attention even though numeracy has strong predictive ability for outcomes over one’s lifespan.

In Antonini, Miloh, Dreyer, and Caudle’s (2017) paper, ‘Neuropsychological Functioning in Preschool Aged Children Undergoing Evaluation for Organ Transplant,’ the authors first review the substantial clinical advances in solid organ disease that are increasingly beneficial to preschoolers. Disease, surgical treatment, and anesthetic exposures make these children a highly vulnerable population. Yet, they have long been atypical referrals to pediatric neuropsychologists who have much to contribute to their ongoing care. The authors help fill a gap in the literature by comparing pre-transplant neurocognitive, adaptive, and emotional–behavioral data obtained from children aged 2 to 6 years and diagnosed with heart or lung disease. Their data reveal adverse neurocognitive and adaptive effects but unimpaired emotional-behavioral regulation. Organ transplantation alters the young child’s prognosis for health and survival, and neuropsychological evaluation informs about the effects during a time of dynamic brain maturation. These data will further impress the reader with the obvious need for serial evaluation to better appreciate which developing brain regions are most susceptible to such powerful medical interventions.

Anderson and Burnett’s (2017) paper, ‘Assessing Developmental Delay in Early Childhood – Concerns with the Bayley-III Scales,’ addresses a serious flaw in one of the most widely used infant development scales. The Bayley-III under-identifies developmental delay and therefore over-estimates a child’s developmental performance, a situation with profound implications for clinicians and researchers alike. The authors highlight how essential it is to question and not blindly accept revised test editions as acceptable updates that will perform as anticipated. Diagnostic decisions are made daily for infants and young children based on the results of this instrument yet many practitioners may be unaware of the particularly relevant discrepancy between Bayley-II and Bayley-III results when serial testing results are the basis for continued care and treatment decisions. The authors suggest a mixed sampling procedure used for Bayley-III standardization explains this critical problem. They not only identify the inherent problem but suggest strategies to offset this weakness, recommending either new normative data after exclusion of the high-risk children, or a re-standardization of the test, or development of a completely new version with new normative data. An immediate solution could be an application of available regional norms, but they advise against applying any algorithm of transformation except when a direct comparison with the former version is intended. Finally, data are reported on the predictive validity of the Bayley scales, considering specificity and sensitivity, and correlational data.

‘Preschool Predictors of School-Age Academic Achievement in Autism Spectrum Disorder’ by Miller, Burke, Troyb, Knoch, Herlihy, and Fein (2017) reports the results of a study conducted in children at ages 2, 4, and 10 years that succeeded in identifying predictors of school-age academic achievement. Their study provides a roadmap for how to maximize the benefits of longitudinal research originating in the preschool years. Knowing which academic readiness or skill proficiencies directly bear on school age achievement is essential for appropriate early intervention not delayed until later age. Such data hold the promise of real and lasting benefit when there is early diagnosis, early discrimination of neuropsychological component functions, knowledge of the range of preschool-age predictors of future functioning, and the provision of proactive and precisely calibrated interventions to further contribute to the more favorable outcomes of children who are diagnosed with autism spectrum disorder.

Woodward, Lu, Morris, and Healey (2017) conducted a prospective longitudinal study in which they concluded that ‘Preschool Self Regulation Predicts Later Mental Health and Educational Achievement in Very Preterm and Typically Developing Children’. They utilized direct observation, questionnaires, and third-party report initially at ages 2–4 years, and follow-up measures of mental health and educational achievement at age 9 years. These data further reinforce that a broader range of psychological effects than might typically be examined in a research protocol should be included in any evaluation or study of those whose gestational course is interrupted early. Prospective longitudinal data in preterm research are often the most illuminating about late effects of insult to the immature brain. This study adds to a growing literature that has begun to suggest it is reasonable to expect direct, albeit variable, adverse implications in self-regulatory skills that will underlie functional and adaptive abilities over the individual’s life span.

‘Associations Among Parent-Child Relationships and Cognitive and Language Outcomes in a Clinical Sample of Preschool Children’ by Leiser, Heffelfinger, and Kaugars (2017) reminds the reader that the quality of caregiver–child reciprocal interactions can be expected to have a critical and long-lasting impact on a child’s development. By specifically addressing positive and negative characteristics of parent–child interactions and language and cognitive functioning in preschoolers who sustained a neurological insult, the authors highlight that a full understanding of a child is not achieved if one’s evaluation is limited to only traditional measurement methods. Awareness and evaluation of non-disease-specific characteristics will result in a more nuanced understanding of how a very young child’s neuropsychological capacities mature and shape future adaptive functioning, and lead to timely family-based interventions.

Sheehan, Kerns, and Müller’s (2017) contribution, ‘The Effect of Task Complexity on Planning in Preterm-Born Children,’ illustrates how essential it is to consider novel ways to assess a young child’s performance, to remain grounded by developmental principles in test development, and to supplement typically reported scores with novel measures that are sensitive to finer neuropsychological component functions within the broader task (in this case, to examine the impact of the cognitive workload). The authors report results of their comparison of performances by children born with extremely low birth weight, at late preterm, and at term gestational age using measures of planning that have inherently different cognitive workload demands. Their cross-sectional data at ages 3, 6, and 9 years showed that their novel task and analytic methods could indeed distinguish the subtle difficulties of an at-risk population that would likely be missed had there only been reliance on standard neuropsychological measurements.

Miranda and Malloy-Diniz (2017) continue an example set by colleagues in the pediatric neuropsychological community, albeit too rarely. As described in ‘Development of a Version of the Self-ordered pointing Task: A Working Memory Task for Brazilian Preschoolers,’ the authors lacking a test with appropriate methods, validity, or normative data for their preschool population in Brazil took the initiative to develop a measure of working memory known to facilitate examination of frontostriatal circuit function. Consequently, they have a measure that meets clinical practice standards for assessment of young children in Brazil, one that they can rely on to continue to contribute to the scientific literature.

Finally, one of the greatest conundrums in preterm research concerns why one exceptionally early-born extremely preterm (EEEP) infant will have a favorable neurodevelopmental course while another EEEP with a similar medical history and comparable sociodemographic characteristics will demonstrate neuropsychological and behavioral/adaptive impairment. Such as yet unexplained discrepancies serve to limit accurate prognostication about eventual outcome based solely on medical variables and complications, and indicate that gestational age and birth weight, while relevant, are not entirely determinant of long-term outcome. ‘Birth at 22 Gestational Weeks: Case Report of Cognitive Resilience’ by Hopp and Baron (2017) provides case data, using both chronological age and adjusted-for-prematurity age, that show a remarkable outcome for a three-year-old born at the absolute lowest limit of viability, 22 weeks’ gestation. While prediction based on the extant literature would understandably be of profound neurodevelopmental and neuropsychological impairment, this preschooler unexpectedly demonstrated only subtle deficits and a profile that could easily be considered that of a typically developing child born at term gestational age. The reasons that likely contributed are discussed within the context of factors that suggest.

A debt of deep gratitude is due to each contributing author whose combined expertise has enabled communication of a valuable message about how pediatric neuropsychological practice and research enhances outcomes for both typically developing and neuropsychologically compromised preschoolers. Equal gratitude is due TCN’s Editor-in-Chief, Yana Suchy, for her openness to the special issue proposal of a series of papers intended to bring attention to the richness of what can be accomplished when pediatric neuropsychologists focus on the youngest children. Preschoolers have distinctive attributes and developmental dynamics that must be more thoroughly investigated and understood.

Disclosure statement

No potential conflict of interest was reported by the author.

Ida Sue Baron
Pediatrics and Neurology, University of Virginia School of Medicine, Charlottesville, VA, USA
The George Washington University, Washington, DC, USA; Independent Private Practice, Potomac, MD, USA