The ability to perceive approximate numerosity is present in many animal species, and emerges early in human infants. Later in life, it is moderately heritable and associated with mathematical abilities, but the etiology of the Approximate Number System (ANS) and its degree of independence from other cognitive abilities in infancy is unknown.…

Twins regularly score nearly a standard deviation below the population mean on standardized measures of cognitive development in infancy but recover to the population mean by early childhood, making rapid gains through the toddler years. To date, only polynomial growth models have been fit to model cognitive recovery across childhood, limiting the…

Noncognitive factors have gained attention in recent years as potential intervention targets for academic achievement improvement in students. Two notable facets, intelligence mindset and grit, have been of particular interest. Both have been shown to consistently improve educational outcomes, although little work has focused on reading ability.…

Despite growing interest in the potential influence of grandparents on grandchild status attainment, research has not addressed whether the ordinal position or number of grandchildren affects outcomes. We apply sibling- and cousin-fixed effects analyses to Swedish population data to examine how cousin order and cousin group size influence grade…

The aim of the study was to examine associations between life events and self-assessed loneliness in adolescence. We used data from a Norwegian population-based twin sample including seven birth cohorts (N = 2,879, 56% females). The participants completed self-report questionnaires three times throughout adolescence, with 2 years in between (i.e.,…

The current analysis investigates genetic and environmental influences on the bidirectional relationships between temperament and general cognitive ability (GCA). Measures of GCA and three temperament factors (persistence, approach, and reactivity) were collected from 486 children ages 4-9 years (80% white, 50% female) from the Louisville Twin…

Dysregulation of biological stress response, as measured by cortisol output, has been a primary candidate mechanism for how social experiences become biologically embedded. Cortisol is the primary output of the hypothalamic pituitary adrenal (HPA) axis. Cortisol levels vary systematically across the day and change in response to both sudden, acute…

We offer a new analysis of a large-scale trial of an early-childhood education program that targeted premature, low-birthweight children. This targeting heavily oversampled twins, whose outcomes differed significantly from singletons'. Singletons' gains in short-term cognition and age-18 non-cognitive skills were comparable to those of the Perry…

We compared dyad-focused maternal speech (protoconversations and maternal speech describing the dyad) in interactions of mothers with their twin and singleton infants. Nine twins and nine singletons, coming from urban areas of Crete (Greece), were video-recorded at home in spontaneous face-to-face interactions with their mothers, from the 2nd to…

Adaptive behaviour refers to the everyday skills that individuals are expected to have to function independently, based on their age and societal norms. Currently, we know little about the role of genetic and environmental factors in parent-rated adaptive behaviours in early infancy. The aim of this study was to investigate the aetiological…

Children's early vocabulary shows sex differences -- with boys having smaller vocabularies than age-comparable girls -- a pattern that becomes evident in both singletons and twins. Twins also use fewer words than their singleton peers. However, we know relatively less about sex differences in early gesturing in singletons or twins, and also how…

This study explored whether high autistic traits, high attention deficit hyperactivity disorder (ADHD) traits and their interaction were associated with quality of life (QoL) in a sample of 556 of young-adult twins (Mean age 22 years 5 months, 52% Female). Four participant groups were created: high autistic traits, high ADHD traits, high…

Digital Storytelling (DST) employs digital technology to enhance traditional storytelling by incorporating digital elements such as graphics, audio, video, and music. This study, grounded in sociocultural theory (SCT) and constructivism, investigated how DST contributes to and facilitates multi-literacy development and language skills among young…

Reading is a fundamental human capacity that recruits and tunes brain circuitry subserving several neurocognitive skills. Individual differences in reading-related skills are largely influenced by genetic variation. However, the molecular basis of the heritability of reading-related skills remains narrowly replicated. Genome-wide association…

Children's socioemotional and cognitive traits may hinder or support reading comprehension based on models of risk and resilience. Effortful control, attention, and positive affect were examined as promotive factors, and general and test anxiety as risk factors. Participants included 197 twin children (115 girls; M[subscript age] = 13.6 years)…