Michael T. Willoughby

Salivary cortisol mediates effects of poverty and parenting on executive functions in early childhood.

In a predominantly low-income population-based longitudinal sample of 1,292 children followed from birth, higher level of salivary cortisol assessed at ages 7, 15, and 24 months was uniquely associated with lower executive function ability and to a lesser extent IQ at age 3 years. Measures of positive and negative aspects of parenting and household risk were also uniquely related to both executive functions and IQ. The effect of positive parenting on executive functions was partially mediated through cortisol. Typical or resting level of cortisol was increased in African American relative to White participants. In combination with positive and negative parenting and household risk, cortisol mediated effects of income-to-need, maternal education, and African American ethnicity on child cognitive ability.

Poverty as a Predictor of 4-Year-Olds' Executive Function: New Perspectives on Models of Differential Susceptibility

In a predominantly low-income, population-based longitudinal sample of 1,259 children followed from birth, results suggest that chronic exposure to poverty and the strains of financial hardship were each uniquely predictive of young childrens performance on measures of executive functioning. Results suggest that temperament-based vulnerability serves as a statistical moderator of the link between poverty-related risk and childrens executive functioning. Implications for models of ecology and biology in shaping the development of childrens self-regulation are discussed.

The measurement of executive function at age 3 years: psychometric properties and criterion validity of a new battery of tasks

In this study, the authors examined the psychometric properties and criterion validity of a newly developed battery of tasks that were designed to assess executive function (EF) abilities in early childhood. The battery was included in the 36-month assessment of the Family Life Project (FLP), a prospective longitudinal study of 1,292 children oversampled from low-income and African American families. Ninety-one percent of children were able to complete 1 or more of the tasks. Psychometric analyses were used to test the dimensionality of each task, evaluate the item and task properties, test the dimensionality of the task battery, and evaluate the criterion validity of the battery with multi-informant measures of attention-deficit/hyperactivity disorder (ADHD) symptomatology and child performance on two subtests of the Wechsler Preschool and Primary Scale of Intelligence. Results indicated that the tasks were successful in measuring interindividual differences in child EF ability, that task scores were most informative about ability level for children in the low to moderate range of ability, that childrens performance across the entire battery was adequately summarized by a single factor, and that individual differences on the EF battery were related to ADHD symptomatology and intelligence in expected ways. Results are discussed with respect to the importance of developing psychometrically sound, scalable instruments that facilitate the measurement of interindividual differences in intraindividual change of EF across the early childhood period.

Maternal and Child Contributions to Cortisol Response to Emotional Arousal in Young Children from Low-Income, Rural Communities.

Relations of maternal and child characteristics to child cortisol reactivity to and recovery from emotional arousal were examined prospectively at approximately 7 months of age (infancy) and then again at approximately 15 months of age (toddlerhood). The sample was diverse and population based (N = 1,292 mother-infant dyads) and included families from predominantly low-income, rural communities. Maternal behavior, family income-to-need ratio and social advantage, and child temperament, attention, and mental development were assessed, and childrens saliva was sampled before and after standardized procedures designed to elicit emotional arousal. Maternal engagement in infancy was associated with greater cortisol reactivity at the infancy assessment and with reduced overall cortisol level at the toddler assessment. Also at the toddler assessment, child attention, mental development, and temperamental distress to novelty were associated with increased cortisol reactivity and regulation, whereas temperamental distress to limitations and African American ethnicity were associated with reduced cortisol reactivity. Findings are consistent with prior work linking early caregiving to the development of the hypothalamic-pituitary-adrenal axis stress response system and with a conceptual model in which developing temperament is characterized by the interplay of emotional reactivity and the emergence of the ability to effortfully regulate this reactivity using attention.

The Efficacy, Safety, and Practicality of Treatments for Adolescents with Attention-Deficit/Hyperactivity Disorder (ADHD)

Studies examining interventions for adolescents diagnosed with attention-deficit/hyperactivity disorder (ADHD) were reviewed to evaluate their efficacy. These efficacy findings were supplemented with a preliminary system for judging safety and practicality. Results suggest that the stimulant drug methylphenidate (MPH) is safe and well-established empirically, but has some problems with inconvenience and noncompliance. Preliminary research supports the efficacy, safety, and practicality of some psychotherapeutic interventions, including behavioral classroom interventions, note-taking training, and family therapy. Treatment with tricyclic antidepressants was judged to have minimal empirical support and debatable safety. Very little is known about long-term effectiveness of treatments, long-term compliance, or multimodal treatments for adolescents such as stimulants plus behavior therapy.

Implications of latent trajectory models for the study of developmental psychopathology

The field of developmental psychopathology is faced with a dual challenge. On the one hand, we must build interdisciplinary theoretical models that adequately reflect the complexity of normal and abnormal human development over time. On the other hand, to remain a viable empirical science, we must rigorously evaluate these theories using statistical methods that fully capture this complexity. The degree to which our statistical models fail to correspond to our theoretical models undermines our ability to validly test developmental theory. The broad class of random coefficient trajectory (or growth curve) models allow us to test our theories in ways not previously possible. Despite these advantages, there remain certain limits with regard to the types of questions these models can currently evaluate. We explore these issues through the pursuit of three goals. First, we provide an overview of a variety of trajectory models that can be used for rigorously testing many hypotheses in developmental psychopathology. Second, we highlight what types of research questions are well tested using these methods and what types of questions currently are not. Third, we describe areas for future statistical development and encourage the ongoing interchange between developmental theory and quantitative methodology.

Contributions of Hot and Cool Self-Regulation to Preschool Disruptive Behavior and Academic Achievement

The construct of self-regulation can be meaningfully distinguished into hot and cool components. The current study investigated self-regulation in a sample of 926 children aged 3–5 years old. Childrens performance on self-regulatory tasks was best described by two latent factors representing hot and cool regulation. When considered alone, hot and cool regulation were both significantly correlated with disruptive behavior and academic achievement. When considered together, cool regulation was uniquely associated with academic achievement, while hot regulation was uniquely associated with inattentive-overactive behaviors. Results are discussed with respect to treatment studies that directly target improvement in childrens self-regulation.

Effects of Methylphenidate and Behavior Modification on the Social and Academic Behavior of Children With Disruptive Behavior Disorders: The Moderating Role of Callous/Unemotional Traits

This study examined whether response to behavior modification with and without methylphenidate differed for children with attention-deficit/hyperactivity disorder (ADHD) and conduct problems (CP) depending on the presence of callous/unemotional (CU) traits. Participants were 37 children ages 7 to 12, including 19 with ADHD/CP-only and 18 with ADHD/CP-CU, referred to a university-based summer treatment program. Results showed that ADHD/CP-CU children had worse behavior in the behavior-therapy-only (BT-only) condition, especially on measures of CP, noncompliance, and rule violations, but these differences largely disappeared when medication was added to BT. Children with ADHD/CP-CU were also less likely to be normalized by treatment than were children with ADHD/CP-only. These findings, though tentative, suggest that children with ADHD/CP-CU may not show a sufficient positive response to BT alone and that the combination of medication and BT may be especially important for them.

The Measurement of Executive Function at Age 5: Psychometric Properties and Relationship to Academic Achievement

This study examined the psychometric properties and criterion validity of a newly developed battery of executive function (EF) tasks for use in early childhood. The battery was included in the Family Life Project (FLP), a prospective longitudinal study of families who were oversampled from low-income and African American families at the birth of a new child (N = 1,292). Ninety-nine percent (N = 1,036) of children who participated in the age 5 home visit completed 1 or more (M = 5.8, Mdn = 6) of the 6 EF tasks. Results indicated that tasks worked equally well for children residing in low-income and not low-income homes, that task scores were most informative about the ability level of children in the low-average range, that performance on EF tasks was best characterized by a single factor, and that individual differences on the EF battery were strongly related to a latent variable measuring overall academic achievement, as well as to individual standardized tests that measured phonological awareness, letter-word identification, and early math skills.

Executive Function in Early Childhood: Longitudinal Measurement Invariance and Developmental Change.

This study tested the longitudinal measurement invariance and developmental changes of a newly developed battery of executive function (EF) tasks for use in early childhood. The battery was administered in the Family Life Project-a prospective longitudinal study (N = 1,292) of families who were oversampled from low-income and African American families at the birth of a new child-at assessments conducted when the child was 3, 4, and 5 years old. All 6 individual EF tasks exhibited strong measurement invariance over time. The EF battery, which was derived from the 6 individual tasks, exhibited partial strong invariance over time. Second-order latent growth curve models revealed individual differences in the levels but not rates of change in latent EF ability. The functional form of change was nonlinear; 60% of the total change in EF ability that was observed between the 3- and 5-year assessments occurred between the Year 3 and Year 4 assessments. Results are discussed with respect to the importance of establishing scalable measures of EF ability prior to investigating experiences that predict or are predicted by changes in EF during early childhood.