Variation in the "FMR1" gene may affect aspects of cognition, such as executive function and memory. Environmental factors, such as stress, may also negatively impact cognitive functioning. Participants included 1,053 mothers of children with and without developmental disabilities. Participants completed self-report measures of executive…

The association between physical fitness and age-related differences in cognition and brain structure has been studied fairly extensively during development and aging, yet comparatively less in young adulthood. The current study examined 1,195 young adults aged 22 to 36 (54% female; 67% Caucasian) to better understand associations between physical…

Epigenetic modifications of chromatin structure provide a mechanistic interface for gene-environment interactions that impact the individualization of health trajectories across the lifespan. A growing body of research indicates that dysfunctional epigenetic regulation contributes to poor cognitive outcomes among aged populations. Here we review…

The present study explored the environmental and genetic etiologies of the longitudinal relations between prereading skills and reading and spelling. Twin pairs (n = 489) were assessed before kindergarten (M = 4.9 years), post-first grade (M = 7.4 years), and post-fourth grade (M = 10.4 years). Genetic influences on five prereading skills (print…

Aging-related declines occur in many different domains of cognitive function during middle and late adulthood. However, whether a global dimension underlies individual differences in changes in different domains of cognition and whether global genetic influences on cognitive changes exist is less clear. We addressed these issues by applying…

This twin study examined the relative contributions of genes and environment on 2nd language reading acquisition of Chinese-speaking children learning English. We examined whether specific skills-visual word recognition, receptive vocabulary, phonological awareness, phonological memory, and speech discrimination-in the 1st and 2nd languages have…

In previous papers [Johnson, W., & Bouchard Jr., T. J. (2005a). Constructive Replication of the Visual-Perceptual-Image Rotation (VPR) Model in Thurstone's (1941) Battery of 60 Tests of Mental Ability. Intelligence, 33, 417-430.] [Johnson, W., & Bouchard Jr., T. J. (2005b). The Structure of Human Intelligence: It's Verbal, perceptual, and image…

In the last decade there has been an exponential increase in studies on neurobiological measures in childhood-onset schizophrenia (COS). There seems to be a consensus that structural changes in COS are more marked than in adolescence-onset (AdOS) or adult-onset schizophrenia (AOS). Atrophy of total brain volume is progressive throughout the course…

Dramatic developments in brain research and imaging technology are rapidly advancing our understanding of the human brain. The new biologically based brain theories suggest that "nature" dominates "nurture" and that many current beliefs about instruction, learning, and memory are wrong. This article explains neural Darwinism…

Grade 1 literacy skills of twin children in Australia (New South Wales) and the United States (Colorado) were explored in a genetically sensitive design (N = 319 pairs). Analyses indicated strong genetic influence on word and nonword identification, reading comprehension, and spelling. Rapid naming showed more modest, though reliable, genetic…

Though many cognitive abilities exhibit marked decline over the adult years, individual differences in rates of change have been observed. In the current study, biometrical latent growth models were used to examine sources of variability for ability level (intercept) and change (linear and quadratic effects) for verbal, fluid, memory, and…

Multivariate genetic analysis was used to examine the genetic and environmental aetiology of the interrelationships of diverse linguistic skills. This study used data from a large sample of 4 1/2-year-old twins who were tested on measures assessing articulation, phonology, grammar, vocabulary, and verbal memory. Phenotypic analysis suggested two…

We use a genetically sensitive design to examine the relationship between language and nonverbal ability at 4 and a half and reading skills at 7 years of age in a sample of more than 1,000 children participating in the Twins Early Development Study. We find that nonphonological as well as phonological measures of early language make significant…

The contribution of heredity to scores on a digit span intelligence test, Jensen's Memory for Numbers, was estimated with a standard heritability formula. The test measures level I mental ability--the capacity to store and recall, but not ability to elaborate or manipulate stimuli. Subjects were 35 monozygotic (MZ) twins and 35 same-sex dizygotic…

A multivariate hierarchical model of specific cognitive abilities was fitted to data from 196 adopted and 213 nonadopted children from the Colorado Adoption Project and 120 of their siblings to assess genetic influence on specific mental abilities. Genetic effects occur in middle childhood that differentially influence mental ability scores.…