An Independent Evaluation of the Psychometric Properties of the Russian Version of the Pediatric Daytime Sleepiness Scale (PDSS).

Background: The quality of sleep significantly impacts children's day-to-day performance, with at least 20% reporting issues with sleepiness. Valid tools for assessing the quality of sleep are needed.

Objective: In this study, we assessed the psychometric properties of the Russian version of the Pediatric Daytime Sleepiness Scale (PDSS).

Cross-cultural Analysis of Models of the Relationship between the Cognitive Abilities and Academic Achievement in Primary School Education.

Background: The cognitive predictors of academic achievement are associated both with basic cognitive abilities such as the information processing speed, number sense and visuospatial working memory, as well as with general ability including nonverbal intelligence. However, the ratio between cognitive development and school achievement can depend on sociocultural conditions.

Objective: The results of a cross-cultural analysis of the relationship between cognitive development and academic achievement during primary education are presented.

Twin classroom dilemma: To study together or separately?

There is little research to date on the academic implications of teaching twins in the same or different classroom. Consequently, it is not clear whether twin classroom separation is associated with positive or negative educational outcomes. As a result, parents and teachers have insufficient evidence to make a well-informed decision when twins start school.

THE CORRELATION BETWEEN g LOADINGS AND HERITABILITY IN RUSSIA.

The study focused on the extent to which the general factor of intelligence g and heritability coefficients of the subtests of an IQ battery correlate. Modest to strong positive correlations were found in five studies from Western countries and six studies from a Japanese meta-analysis. The results for Russian twins were compared with those of the Western and Japanese studies.

Why children differ in motivation to learn: Insights from over 13,000 twins from 6 countries.

Little is known about why people differ in their levels of academic motivation. This study explored the etiology of individual differences in enjoyment and self-perceived ability for several school subjects in nearly 13,000 twins aged 9-16 from 6 countries. The results showed a striking consistency across ages, school subjects, and cultures.

Literacy and numeracy are more heritable than intelligence in primary school.

Because literacy and numeracy are the focus of teaching in schools, whereas general cognitive ability (g, intelligence) is not, it would be reasonable to expect that literacy and numeracy are less heritable than g. Here, we directly compare heritabilities of multiple measures of literacy, numeracy, and g in a United Kingdom sample of 7,500 pairs of twins assessed longitudinally at ages 7, 9, and 12. We show that differences between children are significantly and substantially more heritable for literacy and numeracy than for g at ages 7 and 9, but not 12.

Polymorphisms of the serotonin transporter gene (5-HTTLPR, A/G SNP in 5-HTTLPR, and STin2 VNTR) and their relation to personality traits in healthy individuals from Russia.

Objective: Numerous studies have reported association of the serotonin transporter gene (5-HTT) polymorphisms and neuroticism and traits characterizing sociability and activity. This study aimed to define a single genotype effect of three polymorphic markers in the 5-HTT gene (5-HTTLPR, A/G SNP in 5-HTTLPR and STin2 VNTR) and to check possible association of the 5-HTT haplotypes and personality traits [assessed with Eysenck Personality Inventory (EPI) and Temperament and Character Inventory (TCI) questionnaires] in 301 healthy young individuals.

Methods: To investigate single genotype and haplotype effects of all polymorphic markers, multivariate analysis of variance and haplotype trend regression analyses were conducted correspondingly.

Heritability and "environmentability" of electroencephalogram in infants: the twin study.

We estimated relative contribution of genetic and environmental factors to electroencephalogram (EEG) frequency and amplitude parameters in infants. EEG was registered in 49 pairs of monozygotic and 45 pairs of dizygotic twins aged 7-12 months during (1) visual attention and (2) darkness. The variability of occipital alpha frequency depended mainly on genetic, probably nonadditive factors.

Longitudinal genetic analysis of childhood IQ in 6- and 7-year-old Russian twins.

Using a longitudinal twin study of Moscow children, we have studied the development of psychometric intelligence during the transition from preschool (age 6) to school (age 7). Children were tested using the Wechsler Intelligence Scale for Children (WISC). Simplex models were applied to explore the relationship of different sources of phenotypic variance.