Estimates of shared environmental influence on educational attainment (EA) using the Classical Twin Design (CTD) have been enlisted as genetically sensitive measures of unequal opportunity. However, key assumptions of the CTD appear violated for EA. In this study we compared CTD estimates of shared environmental influence on EA with estimates from…

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…

Future orientation tends to prevent engagement in risk behaviours and results in good academic performance among adolescents. Our study aimed to establish whether genetic factors contributed to future orientation among Chinese adolescents. We recruited 988 pairs of twins from Beijing. By constructing a high-order A (additive genetic variance) C…

Background: Educational attainment is connected to many important life outcomes, and the previous research has already focused on identifying its genetic and environmental components. However, most of these studies used twin data only and did not incorporate information from other family members. Twin studies typically decompose the phenotypic…

Behavior genetic methods are useful for examining mechanisms underlying the interaction between genetic and family environmental factors of internalizing problem behavior (INT). Previous twin studies, however, have shown little consistency in interaction patterns, depending on type and operationalization of measured environments. The aim of the…

Early life stress, daily life experiences, and the stress responsive hypothalamic-pituitary-adrenal (HPA) axis have each been examined as predictors of the development of psychopathology. Rarely have researchers attempted to understand the covariation or interaction among these stress domains using a longitudinal design in the prediction of…

Behavioral and molecular genetic research has established that child cognitive ability and academic performance are substantially heritable, but genetic variation does not account for all of the stratification of cognitive and academic outcomes across families. Which specific contexts and experiences contribute to these "shared…

Vocabulary knowledge was tested in a native (Cantonese-Chinese) and foreign (English) language in 150 twins and 150 singletons aged 6-11 years, matched on age, gender, grade level, nonverbal intelligence, parents' education, family income, and number of siblings and household members. The singletons clearly outperformed the twins on the native…

Both genes and the environment are important for individual differences in expertise, but little is known about gene-environment interactions underlying domain-specific achievement. Here we explored this issue in a large Swedish twin cohort (N = 6,610), using moderator modeling with musical expertise as a model domain. Specifically, we tested…

Despite cross-cultural universality of core human values, individuals differ substantially in value priorities, whereas family members show similar priorities to some degree. The latter has often been attributed to intrafamilial socialization. The analysis of self-ratings on eight core values from 399 twin pairs (ages 7-11) and their biological…

Twin studies have documented that parenting behavior is partly heritable, but it is unclear how parents' genetics shape their caregiving. Using tools of molecular genetics, the present study investigated this process by testing hypotheses about associations between a genome-wide polygenic score for educational attainment and parental caregiving in…

The Theory of Optimal Stimulation (Zentall & Zentall, "Psychological Bulletin," 94, 1983, 446) posits that the relation between activity level (AL) and cognitive performance follows an inverted U shape where midrange AL predicts better cognitive performance than AL at the extremes. We explored this by fitting linear and quadratic…

Purpose: Variability in the timing of infant developmental milestones is poorly understood. We used a twin analysis to estimate genetic and environmental influences on motor development and activity levels in infancy. Method: Data were from the Gemini Study, a twin birth cohort of 2,402 families with twins born in the United Kingdom in 2007.…

The author states that raising her twins the Montessori way has made her life easy. Imagine two 1-year-olds eating entire meals on their own, setting their own tables by 20 months, and becoming potty-trained before 2. These are not statistics found in just one household. Children raised the Montessori way can take care of themselves and their…

Background: "Food fussiness" (FF) is the tendency to be highly selective about which foods one is willing to eat, and emerges in early childhood; "food neophobia" (FN) is a closely related characteristic but specifically refers to rejection of unfamiliar food. These behaviors are associated, but the extent to which their…