Recent results of international assessment programs (e.g., PISA) have shown a large difference in high school students' performance between northern and southern Italy. On this basis, it has been argued that the discrepancy reflects differences in average intelligence of the inhabitants of regions and is associated with genetic factors ( and ).…

We studied the age-related differences in inspection time and multiple cognitive domains in a group of monozygotic (MZ) and dizygotic (DZ) twins aged 7 to 17 years. Data from 111 twin pairs and 19 singleton siblings were included. We found clear age-related trends towards more efficient visual information processing in older participants. There…

The relation between intelligence and birth order was shown in a recent publication [Bjerkedal, T., Kristensen, P., Skjeret, G. A. & Brevik, J. I. (2007). Intelligence test scores and birth order among young Norwegian men (conscripts) analyzed within and between families. "Intelligence," 35, 503-514] to be negative. Subjects in this…

Examines the influence of apolipoprotein E gene states on three cognitive outcomes in 173 people at age 11 and in the same people at age 77 and examined the change in IQ between these ages. There was no significant main effect of gene status on IQ in youth or old age, nor in cognitive change across the lifespan. (SLD)

IQ scores from five kinship categories of 7- to 12-year-olds were analyzed into genetic and environmental components. The common environmental effects were larger for older children than younger children. Overall, the Genetic and Common Environment Sources each accounted for approximately 40% of the IQ variability in the data. (Author/LMO)

Etiology of high and low cognitive ability in adulthood was explored through multiple regression analysis of data from 302 pairs of Swedish twins (median age=65.6 years). Both high and low cognitive ability groups demonstrate significant group heritability, with shared rearing environment of relatively low importance. (SLD)