Developmental Psychology

Revisiting Jerome Kagan and his research legacy: An introduction to a special issue of Developmental Psychology.
This special issue of Developmental Psychology is dedicated to the legacy of Jerome Kagan, whose pioneering work profoundly shaped the field of developmental psychology. Kagan’s groundbreaking research on temperament, emotional development, and the role of biology in shaping human behavior provided a foundation for understanding individual differences across the lifespan. The 20 articles featured in this issue reflect the breadth and depth of Kagan’s influence, spanning topics such as the biological underpinnings of temperament, the interplay between genetics and environment, and the implications of early temperament for later emotional and social outcomes. These contributions come from leading scholars who build on, critique, and reframe Kagan’s work. Each article offers a unique perspective, using diverse methodologies and theoretical approaches. This special issue not only pays tribute to a luminary in the field but also seeks to contribute new insights into the fundamental processes of development. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
How he saw: Jerome Kagan’s contexts of discovery.
Jerome Kagan was a psychologist and pioneer of developmental psychology, but he was intrigued by the natural sciences and read widely across history, biography, poetry, philosophy, cross-cultural anthropology, and the humanities. Drawing on unpublished archival and other primary source material, this essay describes two of Kagan’s seminal studies in child development to demonstrate how their “contexts” facilitated scientific discovery and Kagan’s own development as a researcher. A subset of Kagan’s archival papers—including grant materials, correspondence, personal notes, and clipped articles—are also discussed to showcase the personal and scholastic material that Kagan read, wrote, and annotated, and which further advanced his scientific thinking. Collectively, these materials reveal the multiple contexts, both applied and private, in which Kagan “saw,” thereby guiding his interdisciplinary approach to the scientific study of child development. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
The developmental context of culture: Reflections on the contributions and legacy of Jerome Kagan.
Although the path of Kagan’s career led him inexorably toward biology, in the few years between his first benchmark publication on infancy and his later focus on temperament, he turned to other cultures in order to evaluate emerging insights about early development, namely, that major developmental transitions in behavior are maturational products. These forays contributed profoundly to our current understanding of culture and human development and inspired several of his students to focus their own careers on human development in culture, or, turned around, what we might call the developmental context of culture. Drawing largely on Kagan’s own writings, this essay attempts to understand what the cross-cultural work meant to him and its lasting influence on his students. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Schema formation and stimulus–schema discrepancy: A basic unit and its properties.
Research with 2-day-old neonates shows that they create mental representations—schemata—for their experiences and that this cognitive ability is hardwired and functional at birth. This research and studies with older infants indicate that both the formation and the expansion of schemata occur through moderate discrepancies, a concept that Jerome Kagan promoted conceptually and through his research. Discrepancy, as distinct from novelty, is insufficiently acknowledged in the literature on schema theory. The schema is both cognitive and affective and develops in unison in a curvilinear pattern with a gradual onset and exponential expansion. Optimal attentiveness and positive affect occur at the peak of formation and to moderate discrepancies. Redundancy beyond the optimal level produces decreasing interest and positive affect and increasing negative affect resulting in boredom and avoidance. These characteristics of schema development are difficult to study with older children and adults. Rumelhart (1980) regarded the schema as the “building block of cognition” and Kagan (2002) called its expansion through moderate discrepancies an “engine of change” implying widespread application for cognition and behavior throughout life. Kagan urged the search for structure (form) as opposed to function in cognition, and the curvilinear pattern of schema development and its characteristics, it is argued, is the structure he sought. Implications and select applications of schema development and expansion are presented. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Reexamining developmental continuity and discontinuity in the 21st century: Better aligning behaviors, functions, and mechanisms.
Developmental science aims to explain development across the lifespan. Jerome Kagan observed that the same behavior can occur for different reasons, and differing behaviors can occur for the same reason. To help account for persistence, desistence, and transformation of behavior across development, Kagan introduced various types of continuity and discontinuity of forms and functions of behavior. This framework provides opportunities for identifying explanatory mechanisms in behavior development. However, misconceptions remain in applying the concepts that Kagan introduced. Much of the literature assumes developmental continuity in constructs without examining whether assumptions are supported, leading to faulty developmental inferences. For instance, the use of the same measure across time to assess development assumes that the behavior occurs for the same reason across time (homotypic continuity). In addition, just because one behavior predicts a different behavior at a later time does not necessarily indicate that age-differing behaviors occur for the same reason (heterotypic continuity). This review aims to advance conceptualizations of continuity and discontinuity from a contemporary perspective with aims to improve mechanistic understanding of behavior development across the lifespan. To better align behaviors, functions, and mechanisms, research should (a) examine (dis)continuity of individual behaviors rather than merely syndromes, (b) identify the function(s) of the given behavior(s), and (c) identify the cognitive and biological processes that underlie the behavior–function pairs. Incorporating examples from research on development of humans and nonhuman animals, I discuss challenges from work that has followed Kagan’s ideas and ways to advance understanding of continuity and discontinuity across development. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Response bias is genetically biased: Another argument for Kagan’s philippic against questionnaires in developmental psychology.
One of the concerns of Jerome Kagan (2007) in his article “A Trio of Concerns” was the frequent use of questionnaires in developmental psychology and related disciplines. His main reasons were the minimal overlap between (self-)reported and observed phenotypes, the ambiguity of items, and systematic socioeconomic status (SES) disparities in responding. We wondered whether genetic differences would also influence response bias in cases of ambiguous or even absurd items triggering an acquiescence bias to agree with even impossible question content. We examined the genetic predisposition for the acquiescence response bias in 257 families with twins. Both parents and twins completed a modified Wildman Symptoms Questionnaire and provided salivary DNA samples. From published genome-wide association studies (GWAS), we derived polygenic score (PGS) algorithms for indicators of SES (educational attainment [EA] and income) and for general intelligence (IQ), which were applied to the GWAS results of our participants’ DNA. The twins (N = 514 children, 55% monozygotic pairs) were on average 7.92 years old (SD = 0.66), and 51.6% were female. The primary parents were on average 40.48 years old (SD = 4.66), and 91% were female. In 90% of the families, both parents were born in the Netherlands and 91% were from a middle or higher socioeconomic background. Higher PGSs for EA and income but not for IQ predicted less acquiescence response bias in parents and children. In addition to Kagan’s reasons for his concerns about questionnaires, we found a genetic predisposition to response bias triggered by the ambiguous form of questions and answers. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Advancing differential susceptibility research: Development and validation of the temperamental sensitivity Q-scale.
Temperamental sensitivity (TS), which is a correlated suite of traits reflecting a lower threshold of environmental stimulation and heightened responsivity to a range of environmental contexts, is an empirically documented susceptibility factor that increases children’s plasticity to supportive and harsh family environments. To expand the limited options for assessing TS, this article tested the psychometric properties of a new Q-set measure (i.e., TS Q-scale) derived from the California Child Q-Set (CCQ-Set) and completed by experimenters. Participants in Study 1 consisted of 243 mothers, their partners, and their preschool children (Mage = 4.60 years; 56% girls; 54% Black or multiracial; 16% Latinx). For Study 2, participants included 201 mothers and their young children (Mage = 2.25 years; 44% girls; 63% Black or multiracial; 11% Latinx). Both longitudinal studies utilized multimethod, multiinformant measurement batteries. The TS Q-scale evidenced satisfactory internal consistencies across both studies. Support for the convergent and discriminant validity in Study 1 was evident in its large, unique, and significantly stronger association with a standard, more extensive, observational assessment of TS when compared with conventional dimensions of temperament. In each study, the TS Q-scale significantly moderated the association between family functioning and latent change analyses of children’s functioning for most of the forms of child adjustment. Supporting its predictive validity as a differential susceptibility attribute, children with higher scores on the TS Q-scale exhibited substantially better functioning than their peers in supportive socialization contexts and considerably worse functioning in harsh rearing conditions. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Behavioral inhibition in a translational nonhuman primate model: A pilot study of Kagan’s behavioral inhibition paradigm modified for use in infant rhesus macaques (Macaca mulatta).
Behavioral inhibition (BI), a temperamental trait first described by Jerome Kagan, is characterized by wariness to unfamiliar persons and novel situations. BI is a moderately stable trait, with biological and genetic underpinnings. Kagan’s methodology for assessing BI is widely used in humans. Although this paradigm could be readily translated for use in nonhuman primates, thereby increasing generalizability from nonhuman primates to humans and fortifying evidence that BI is evolutionarily conserved, researchers have not done so. To address this, this study utilized a modified version of Kagan’s paradigm to assess behaviors and biological markers of BI in nonhuman primates. Over the first 5 weeks of life, nursery-reared rhesus monkeys (Macaca mulatta; N = 12) were rated using the standardized Infant Behavior Assessment Scale for nonhuman primates on measures related to BI (consolability, irritability, struggle, and predominant state). Three months later, behavioral assessments were made in relation to a novel playroom, an unfamiliar peer, and a variety of attention-grabbing, unfamiliar stimuli, followed by the introduction of a human stranger. Behaviors from Kagan’s studies of BI in toddlers (freezing, exploration, and latency to approach) and physiological measures related to BI (heart rate) were assessed. Random effects models showed that subjects rated high in temperamental BI spent less time exploring the environment and socializing with peers and more time freezing (an indication of anxiety in rhesus monkeys). These findings suggest that Kagan’s paradigm is readily adapted for use in nonhuman primates and support the utility of rhesus monkeys as translational models for assessing the causes and consequences of human BI. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Prenatal maternal immune activation predicts observed fearfulness in infancy.
Fear reactivity is an early emerging temperament trait that predicts longer term behavioral and health outcomes. The current analysis tests the hypothesis, an extension of prior research on maternal immune activation (MIA), that the prenatal maternal immune system is a reliable predictor of observed fear reactivity in infancy. The analysis is based on a prospective longitudinal cohort study that collected data from the first trimester and conducted observational assessments of temperament at approximately 12 months of age (n = 281 infants). MIA was assessed from immune biomarkers measured in maternal blood at each trimester; infant temperament was assessed using the Laboratory Temperament Assessment Battery assessment at 12 months; covariates included family and sociodemographic factors. Patterns of inflammatory markers across gestation reliably predicted observed temperament: elevated prenatal MIA was associated with high fear reactivity to novel stimuli. The findings provide novel evidence of prenatal origins of fear reactivity and suggest developmental mechanisms that may underlie early emerging individual differences in child temperament. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Neonatal neural responses to novelty related to behavioral inhibition at 1 year.
Behavioral inhibition (BI), an early-life temperament characterized by vigilant responses to novelty, is a risk factor for anxiety disorders. In this study, we investigated whether differences in neonatal brain responses to infrequent auditory stimuli relate to children’s BI at 1 year of age. Using functional magnetic resonance imaging (fMRI), we collected blood-oxygen-level-dependent (BOLD) data from N = 45 full-term, sleeping neonates during an adapted auditory oddball paradigm and measured BI from n = 27 of these children 1 year later using an observational assessment. Whole-brain analyses corrected for multiple comparisons identified 46 neonatal brain regions producing novelty-evoked BOLD responses associated with children’s BI scores at 1 year of age. More than half of these regions (n = 24, 52%) were in prefrontal cortex, falling primarily within regions of the default mode or frontoparietal networks or in ventromedial/orbitofrontal regions without network assignments. Hierarchical clustering of the regions based on their patterns of association with BI resulted in two groups with distinct anatomical, network, and response-timing profiles. The first group, located primarily in subcortical and temporal regions, tended to produce larger early oddball responses among infants with lower subsequent BI. The second group, located primarily in prefrontal cortex, produced larger early oddball responses among infants with higher subsequent BI. These results provide preliminary insights into brain regions engaged by novelty in infants that may relate to later BI. The findings may inform understanding of anxiety disorders and guide future research. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Categorical and latent profile approaches to temperamental infant reactivity and early trajectories of socioemotional adjustment.
This article examines the patterns, and consequences, of infant temperamental reactivity to novel sensory input in a large (N = 357; 271 in current analysis) and diverse longitudinal sample through two approaches. First, we examined profiles of reactivity in 4-month-old infants using the traditional theory-driven analytic approach laid out by Jerome Kagan and colleagues, and derived groups characterized by extreme patterns of negative reactivity and positive reactivity. We then used a theory-neutral, data-driven approach to create latent profiles of reactivity from the same infants. Despite differences in sample characteristics and recruitment strategy, we noted similar reactivity groups relative to prior cohorts. The current data-driven approach found four profiles: high positive, high negative, high motor, and low reactive. Follow-up analyses found differential predictions of internalizing, externalizing, dysregulation, and competence trajectories across 12, 18, and 24 months of life based on 4-month reactivity profiles. Findings are discussed in light of the initial formulation of early reactivity by Kagan and the four decades of research that has followed to refine, bolster, and expand on this approach to child-centered individual differences. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
The structure, development, and etiology of observed temperament during middle childhood.
Investigating the structure and etiology of temperament is key to understanding how children interact with the world (Kagan, 1994). Although these topics have yielded an abundance of research, fewer studies have employed observational data during middle childhood, when unique environmental challenges could influence temperament development. To address this gap, Israeli twin children were observed at Age 6.5 (N = 1,083, 564 families; 50.6% females) and again at Age 8–9 (N = 768, 388 families; 52.0% females; 611 children from 322 families had data from both ages). Temperament was assessed globally by trained coders and, at Age 8–9, also by the experimenter who interacted with the child. We examined whether Rothbart et al.’s (2000) three-factor model, according to which temperament includes the domains negative affect, positive affect/surgency, and effortful control, emerges from the data. In addition, we considered a bifactor model, where a fourth global factor accounts for all behaviors’ commonality. Across the two ages and rating methods, confirmatory factor analyses supported the bifactor model. The global factor’s loadings suggested that it reflects children’s expressiveness. Adding this factor changed the associations between the other factors and enabled differentiation between surgency and positive affect. This suggests that in observational settings that capture temperament impressions holistically, children’s expressiveness affects other traits’ behavioral displays. Twin models revealed genetic influences for most traits. Importantly, twin models revealed shared-environmental influences for negative affect and expressiveness, which modestly contributed to temperament consistency across ages. These findings shed light on temperament traits’ interrelatedness and stress the importance of the shared environment to temperament development during middle childhood. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Self-regulation in elementary school: Do teacher-reported effortful control and directly assessed executive function codevelop?
Self-regulation (SR) is a central developmental task of early childhood and is considered essential for children’s success during elementary school. It has typically been conceptualized as effortful control (EC) or executive function (EF), drawing respectively on research traditions in temperament and cognitive development. These aspects of SR are theorized to emerge from an intertwined developmental process, but the nature of their relation throughout elementary school has not been established. In particular, it is not known whether ratings given by teachers based on behavioral observations align with those directly assessed via novel performance tasks. This article addresses this gap in the knowledge by examining the codevelopment of EC and EF with regard to intraindividual trajectories of change. Drawing on a national sample (N = 8,742) from the Early Childhood Longitudinal Study-Kindergarten Cohort of 2010–2011, two longitudinal modeling approaches (parallel-process latent growth curves with structured residuals, Curran et al., 2014; multidimensional growth mixture models, Wickrama et al., 2021) were applied to examine children’s SR between second and fifth grade. Overall, results do not reveal a systematic codevelopmental relation between EC and EF when accounting for intraindividual processes. Findings are discussed with regard to developmental theory and application. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Behavioral inhibition and social maladjustment: The moderation role of social behaviors during cooperative and competitive peer interactions.
Behavioral inhibition (BI) is a temperamental characterized in early childhood by intense wariness and negative affect toward novelty, and is linked to children’s emotional symptoms and peer problems. How children behave or respond toward diverse social contexts can influence the relation between BI and social adjustment. This study investigated the effect of children’s affiliative and antagonistic behavior in cooperative and competitive contexts on the relation between early BI and social adjustment using a longitudinal design. Children’s BI (at age 2) was assessed via laboratory observations. Affiliative and antagonistic behaviors (at age 4) were coded during a dyadic truck game in the cooperative and competitive contexts. Children’s emotional symptoms and peer problems (at age 4) were assessed using parental reports. These results suggest that high affiliative behavior in the cooperative context was linked to a reduced level of peer problems in inhibited children. Interestingly, highly antagonistic behavior in the competitive context was linked to a reduced level of emotional symptoms in inhibited children. These findings extend our understanding of the role social behavior plays in the social adjustment of behaviorally inhibited children by highlighting the contribution of socially appropriate behaviors in social contexts. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Predicting pointing from early socioemotional communication with mothers, fathers, and strangers through the lens of temperamental reactivity.
Socioemotional and referential communication are primary expressions of interpersonal engagement in infancy and beyond. Early socioemotional communication in dyadic interactions may form a foundation for triadic referential communication and gesture production, yet the role of temperament in moderating their association has not been examined. We investigated whether early socioemotional communication behaviors, and infant temperamental reactivity, were associated with later pointing production. Participants were 51 infants (45% girls) and both their parents (86.5% Dutch). Early infant socioemotional communication (production of smile, vocalizations, and gaze) was observed during separate home-based face-to-face interactions with mothers, fathers, and strangers at 4 and 8 months. At both ages, mothers and fathers reported on infant temperamental surgency and negative affectivity, and overall means were calculated. Referential communication (declarative pointing) was measured during structured lab-based observations at 12 and 15 months. Socioemotional and referential communication behaviors were microanalytically coded second by second. Poisson multilevel regression analyses indicated interaction effects between temperament and smile, vocalizations, and gazes to the adult’s face with each partner in predicting pointing. High levels of infant temperamental surgency tended to enhance positive associations between early socioemotional communication behaviors with mothers and fathers and pointing. By contrast, high levels of negative affectivity tended to dampen associations between early communication behaviors with strangers and pointing. Results highlight the importance of infant socioemotional communication with diverse partners and the moderating role of temperamental reactivity in predicting referential communication. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Attachment relationship quality with mothers and fathers and child temperament: An individual participant data meta-analysis.
A growing body of research suggests that, compared with single parent–child attachment relationships, child developmental outcomes may be better understood by examining the configurations of child–mother and child–father attachment relationships (i.e., attachment networks). Moreover, some studies have demonstrated an above-chance level chance of concordance between the quality of child–mother and child–father attachment relationships, and child temperament has been offered as a plausible explanation for such concordance. To assess whether temperament plays a role in the development of different attachment network configurations, in this preregistered individual participant data meta-analysis we tested the degree to which the temperament dimension of negative emotionality predicts the number of secure, insecure-avoidant, insecure-resistant, and disorganized attachment relationships a child has with mother and father. Data included in the linear mixed effects analyses were collected from seven studies sampling 872 children (49% female; 83% White). Negative emotionality significantly predicted the number of secure (d = −0.12) and insecure-resistant (d = 0.11), but not insecure-avoidant (d = 0.04) or disorganized (d = 0.08) attachment relationships. Nonpreregistered exploratory analyses indicated higher negative emotionality in children with insecure-resistant attachment relationships with both parents compared to those with one or none (d = 0.19), suggesting that temperament plays a small yet significant role in child–mother/child–father insecure-resistant attachment relationships concordance. Taken together, results from this study prompt a more in-depth examination of the mechanism underlying the small yet significantly higher chance that children with increased negative emotionality have for developing multiple insecure-resistant attachment relationships. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Maternal contingent responsiveness moderates temperamental risk to support adaptive infant brain and socioemotional development across the first year of life.
In the first few months of life, infants display intriguing individual differences in how they react to novel stimuli in their environment. Infant “negative reactive” tendencies have been robustly linked to resting brain activity profiles that confer risk for maladaptive socioemotional outcomes. The present study examines whether and how caregiver behavior in early infancy may interact with infant negative reactivity to alter the extent to which such tendencies predict risk-related brain activity profiles. In the present study, 51 mothers (all White; age M = 32 years, SD = 3; 70.8% monthly household income > 3,400 U.S. dollars) and their infants (39.2% female at birth) participated. We measured infant negative reactivity and maternal contingent responsiveness to infant’s gaze during mother–infant interactions at age 4 months. At 10–11 months, we assessed infants’ resting electroencephalographic (EEG) 6–9 Hz frontal asymmetry (a marker of risk for maladaptive regulatory behaviors and withdrawal), infant fearful withdrawal, and infant empathic behavior. We found that maternal contingent responsiveness to 4-month-old infant’s gaze in naturalistic interactions moderated the relation between 4-month infant negative reactivity and 11-month resting EEG asymmetry. Results suggest that maternal contingent responsiveness alters the extent to which early reactive tendencies end up “embedded” in infant brain activity profiles. Exploratory analyses revealed that the interaction between maternal contingent responsiveness and infant reactivity predicting infant resting EEG asymmetry, in turn predicted infants’ fearful withdrawal and empathic behaviors also assessed at 10–11 months. Findings demonstrate the critical buffering role of maternal contingent responsive behaviors in reducing potential maladaptive neural and socioemotional outcomes. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
How biology shapes the development of shyness within specific contexts: A longitudinal, cross-lagged investigation.
Shyness is a temperamental trait that refers to fear and wariness in the face of social novelty and is known to have a biological basis. One proposed physiological correlate of shyness has been the change in respiratory sinus arrhythmia (RSA) from baseline to a stressor. However, past research linking shyness and RSA change has been mixed, which may be, in part, due to a failure to carefully consider the context under which RSA change is measured and the directionality of relations. Using a longitudinal design and cross-lagged analysis (N = 103, 52 girls), we examined parent-reported shyness and RSA change during a stranger approach task (social stressor) and a locked box task (nonsocial stressor) at ages 3 (Mage at Time 1 = 3.50 years, SDage = 0.19 years) and 4 (Mage at Time 2 = 4.76 years, SDage = 0.38). Cardiac vagal withdrawal during the stranger approach task, but not during the frustration task, at age 3 positively predicted shyness at age 4. Shyness at age 3 did not predict cardiac vagal change in either context at age 4. We also found that changes in RSA measured during the frustration task were stable across time, but changes in RSA measured during the stranger approach task were not stable across time, suggesting a developmental change in physiological regulatory systems to social threat. These results suggest that, although biology may come first in shaping children’s behavior, this relation depends critically on the context and the incentives in the child’s environment. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Biological basis of temperament: Respiratory sinus arrhythmia and inhibitory control across childhood.
Temperamental inhibitory control is a foundational capacity for children’s social, emotional, and behavioral development. Even though temperament is suggested to have a biological basis, the physiological indicators of inhibitory control remain unclear amid mixed empirical results. In this study, we leveraged a multicohort longitudinal design to examine resting respiratory sinus arrhythmia (RSA) as a physiological correlate of inhibitory control across the early and middle childhood years. Data were collected annually across four time points from cohorts of 4- (n = 150, Mage = 4.53; SD = 0.30; 49.7% female) and 8- (n = 150; Mage = 8.53; SD = 0.29; 49.7% female) year-old children and their caregivers. There were weak, albeit significant, associations between resting RSA and caregiver-reported inhibitory control in middle childhood but not in early childhood. A stronger association was found for older children when latent trait assessments of RSA and inhibitory control were derived from commonalities across the four annual assessments. We conclude that using repeated measures to extract latent trait scores increases power to detect potential physiological indicators of temperament. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Development of temperament types from infancy to adolescence: Genetic and environmental influences with an economically and racially/ethnically diverse sample.
Kagan theorized biologically based temperament types that are present in infancy, stable across development, and essential for understanding individual differences. Despite evidence, temperament research remains focused on a few prominent dimensions of temperament, without adequately addressing covariance among dimensions and temperament types. Using longitudinal twin data, we took a person-centered statistical approach to identify temperament types and examined continuity and change across five developmental periods (Ninfancy = 602; Ntoddlerhood = 522; Nearly childhood = 390; Nlate childhood = 718; Nearly adolescence = 700). We then examined the genetic and environmental etiology of temperament types. Twins were boys and girls (51–53% female), primarily Hispanic/Latinx (23–30%) and non-Hispanic/Latinx White (56–63%), and from socioeconomically diverse families (28–38% near-or-below the poverty line). Using latent profile analysis, we identified three temperament types at each age characterized by negative reactivity and dysregulation, positive reactivity and strong self-regulation, and moderate reactivity and regulation. Latent transition analyses revealed considerable continuity in membership type for “negative dysregulated” beginning in infancy, log odds = 1.58 (SE = .65) to 3.16 (SE = .77), p <.01, of remaining relative to transitioning to “typical expressive”, and “positive well-regulated” beginning in early childhood, log odds = 1.41 (SE = .56) to 2.25 (SE = .47), p <.05. Twin analyses revealed moderate heritability and a consistent role of the shared environment on positive well-regulated, with negative dysregulated and typical expressive also moderately heritable with the shared environment being important at some ages. Findings support the presence of theorized biologically based temperament types that develop rapidly in infancy and toddlerhood and provide a foundation for the study of individual differences and risk and resilience processes across the lifespan. (PsycInfo Database Record (c) 2024 APA, all rights reserved)
Associations among temperament characteristics and telomere length and attrition rate in early childhood.
There is growing interest in telomere length as an indicator of current and future health. Although early childhood is a period of rapid telomere attrition, little is known about the factors that influence telomere biology during this time. Adult research suggests that telomere length is influenced by psychological characteristics. This study’s goal was to test associations among repeated measures of temperament and telomere length in a community sample of children (N = 602; 52% male, 73% non-Hispanic White, middle-to-high socioeconomic status) from infancy to age 3 years. Relative telomere length was assessed from DNA in saliva samples collected at infancy (M = 8.4 months), 2 years (M = 24.9 months), and 3 years (M = 37.8 months). Temperament was assessed via maternal report questionnaires administered at infancy (Infant Behavior Report Questionnaire–Revised) and ages 2 and 3 years (Early Childhood Behavior Questionnaire). Temperament was operationalized in two ways: using the established domains of negative affectivity, surgency/extraversion, and regulation/effortful control and using person-centered scores that identified three groups of children with similar profiles across domains (emotionally and behaviorally regulated; emotionally and behaviorally dysregulated; introverted and overcontrolled). Analyses revealed that greater regulation/effortful control was associated with longer telomere length across time points. Additionally, higher surgency/extraversion, beginning in infancy, was associated with decreased rate of telomere attrition. There were no sex differences in the relations between temperament and telomere measures. These findings suggest that, as early as infancy, temperament may influence telomere biology, with a potential protective effect of positive temperament characteristics on telomere erosion. (PsycInfo Database Record (c) 2024 APA, all rights reserved)

Developmental Psychology - Vol 60, Iss 11