Stephen A. Petrill

Infant Zygosity Can be Assigned by Parental Report Questionnaire Data

A parental report questionnaire posted to a population sample of 18-month-old twins correctly assigned zygosity in 95%of cases when validated against zygosity determined by identity of polymorphic DNA markers. The questionnaire was as accurate when readministered at 3 years of age, with 96% of children being assigned the same zygosity on both occasions. The results validate the use of parental report questionnaire data to determine zygosity in infancy.

The heritability of general cognitive ability increases linearly from childhood to young adulthood

Although common sense suggests that environmental influences increasingly account for individual differences in behavior as experiences accumulate during the course of life, this hypothesis has not previously been tested, in part because of the large sample sizes needed for an adequately powered analysis. Here we show for general cognitive ability that, to the contrary, genetic influence increases with age. The heritability of general cognitive ability increases significantly and linearly from 41% in childhood (9 years) to 55% in adolescence (12 years) and to 66% in young adulthood (17 years) in a sample of 11 000 pairs of twins from four countries, a larger sample than all previous studies combined. In addition to its far-reaching implications for neuroscience and molecular genetics, this finding suggests new ways of thinking about the interface between nature and nurture during the school years. Why, despite lifes ‘slings and arrows of outrageous fortune’, do genetically driven differences increasingly account for differences in general cognitive ability? We suggest that the answer lies with genotype–environment correlation: as children grow up, they increasingly select, modify and even create their own experiences in part based on their genetic propensities.

One-year use and cost of inpatient and outpatient services among female and male patients with an eating disorder: Evidence from a national database of health insurance claims

OBJECTIVE This study examined rates and cost of inpatient and outpatient treatment among 1,932 patients with an eating disorder. METHOD One-year (1995) data were available through MarketScan, a national insurance database containing claims for 1,902,041 male patients and 2,005,760 female patients. RESULTS Female patients (n = 1,756, 0.14% of all females) were significantly more likely to have been treated for an eating disorder than male patients (n = 176, 0.016% of all males), and females received more days of treatment than males. Outpatient treatment was the norm, regardless of gender or type of eating disorder. Average number of days (inpatient or outpatient) was less than the minimum recommended by standards of care. Age-adjusted costs for the treatment of anorexia nervosa and bulimia nervosa were comparable to the cost of treatment for schizophrenia. DISCUSSION The utilization data are discussed in terms of barriers to care and treatment guidelines for eating disorders.

Genetics and Intelligence: What's New?.

Abstract Nature as well as nurture contributes to the development of individual differences in intelligence. Genetic research on intelligence has moved beyond this rudimentary nature-nurture question to make several exciting discoveries about intelligence by investigating developmental change and continuity, multivariate associations among cognitive abilities, and the developmental interface between nature and nurture. Advances in molecular genetics have led to the dawn of a new era for genetic research that makes it possible to identify specific genes responsible for genetic influence on cognitive abilities and disabilities.

Reading Skills in Early Readers Genetic and Shared Environmental Influences

The present study combined parallel data from the Northeast—Northwest Collaborative Adoption Projects (N2CAP) and the Western Reserve Reading Project (WRRP) to examine sibling similarity and quantitative genetic model estimates for measures of reading skills in 272 school-age sibling pairs from three family types (monozygotic twins, dizygotic twins, and unrelated adoptive siblings). The study included measures of letter and word identification, phonological awareness, phonological decoding, rapid automatized naming, and general cognitive ability. Estimates of additive genetic effects and shared environmental effects were moderate and significant. Furthermore, shared environmental effects estimated in twins were generally similar in magnitude to adoptive sibling correlations, suggesting highly replicable estimates across different study designs.

Gender differences in language of AD patients A longitudinal study

Article abstract—We examined gender differences in probable Alzheimers disease (AD) patients on language measures at four data collections (entry, 6, 12, and 18 months) and a normal elderly (NE) comparison group at entry and 18 months. Comparison of gender differences in language abilities of 60 (29 men, 31 women) early (Clinical Dementia Ratings I and 11) AD subjects at entry revealed significant effects for gender on the Boston Naming Test (BNT) and Peabody Picture Vocabulary Test-Revised (PPVT-R) but not on the Word Fluency Test, shortened Token Test, or modified Reporters Test. The 37 subjects (18 men, 19 women) who completed less than four data collection sessions compared with the 23 subjects (11 men, 12 women) who completed all four sessions differed on education and Reporters Test scores. Longitudinal analysis of measures showed that gender differences persisted for the BNT and PPVT-R and that time differences were found on all measures. Gender differences remained after correcting for age, education, duration of illness, and mental status. We found no differences for the NE comparison group for gender or time. All AD subject trends were downward, suggesting that (1) language is affected over time in AD, (2) both men and women decline at similar rates, and (3) language abilities of women are more severely impaired at all time points.

Comorbidity Between Reading Disability and Math Disability: Concurrent Psychopathology, Functional Impairment, and Neuropsychological Functioning

Reading disability (RD) and math disability (MD) frequently co-occur, but the etiology of this comorbidity is not well understood. Groups with RD only (N = 241), MD only (N = 183), and RD + MD (N = 188) and a control group with neither disorder (N = 411) completed a battery of measures of internalizing and externalizing psychopathology, social and academic functioning, and 10 neuropsychological processes. Groups with RD only, MD only, and RD + MD were significantly impaired versus the control group on nearly all measures, and the group with RD + MD was more impaired than the groups with MD and RD alone on measures of internalizing psychopathology, academic functioning, and 7 of 10 neuropsychological constructs. Multiple regression analyses of the neuropsychological measures indicated that deficits in reading and math were associated with shared weaknesses in working memory, processing speed, and verbal comprehension. In contrast, reading difficulties were uniquely associated with weaknesses in phoneme awareness and naming speed, and math deficits were uniquely associated with weaknesses in set shifting. These results support multiple-deficit neuropsychological models of RD and MD and suggest that RD and MD are distinct but related disorders that co-occur because of shared neuropsychological weaknesses in working memory, processing speed, and verbal comprehension.

Genetic and Environmental Contributions to General Cognitive Ability Through the First 16 Years of Life.

The genetic and environmental contributions to the development of general cognitive ability throughout the first 16 years of life were examined using sibling data from the Colorado Adoption Project. Correlations were analyzed along with structural equation models to characterize the genetic and environmental influences on longitudinal stability and instability. Intraclass correlations reflected both considerable genetic influence at each age and modest shared environmental influence within and across ages. Modeling results suggested that genetic factors mediated phenotypic stability throughout this entire period, whereas most age-to-age instability appeared to be due to nonshared environmental influences.

Maternal working memory and reactive negativity in parenting.

We examined the role of working memory in observed reactive parenting in a sample of 216 mothers and their same-sex twin children. The mothers and their children were observed completing two frustrating cooperation tasks during a visit to the home. The mothers worked one-on-one with each child separately. Mothers completed the Vocabulary (verbal), Block Design (spatial), and Digit Span (working memory) subtests of the Wechsler Adult Intelligence Scale—Third Edition. We used a within-family quasi-experimental design to estimate the magnitude of the association between sibling differences in observed challenging behaviors (i.e., opposition and distractibility) and the difference in the mother’s negativity toward each child. As hypothesized, reactive negativity was evident only among mothers with poorer working memory. Verbal and spatial ability did not show this moderating effect. The effect was replicated in a post hoc secondary data analysis of a sample of adoptive mothers and sibling children. Results implicate working memory in the etiology of harsh reactive parenting.

Order in the House!: Associations among Household Chaos, the Home Literacy Environment, Maternal Reading Ability, and Children's Early Reading.

The current study examines whether associations exist between household chaos and children’s early reading skills, after controlling for a comprehensive battery of home literacy environment characteristics. Our sample included 455 kindergarten and first-grade children who are enrolled in the Western Reserve Reading Project. We go on to test whether these associations are moderated by maternal reading ability. Results suggest that the degree of household order is significantly and positively associated with the expressive vocabulary, Woodcock Reading Mastery, and phonological awareness skills of children whose mothers are above-average readers. By contrast, the number of books a child owns or brings home and how often a child amuses self alone with books are significantly associated with the expressive vocabulary, Woodcock Reading Mastery, and phonological awareness skills of children whose mothers are average-ability readers. These results suggest the potential for new approaches to encouraging literacy development in the home beyond those that depend solely on parental literacy.