Background: Children's numerical and arithmetic skills differ greatly already at an early age. Although research focusing on accounting for these large individual differences clearly demonstrates that mathematical performance draws upon several cognitive abilities, our knowledge concerning key abilities underlying mathematical skill development is…

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…

We investigated time-related patterns in levels of cognitive performance during the period from 1970 to 1993 based on data from Swedish draft boards. The conscripts, including more than a million 18-19-year old men, had taken one of two versions of the Swedish enlistment battery (SEB67; 1970-1979 or SEB80; 1980-1993), each composed of four…

Irrespective of the grading system, grades are the most valid instrument for predicting educational success. Previous studies have shown that criterion-referenced compulsory school grades are multidimensional, reflecting subject-specific dimensions and a common grade dimension, both of which contribute to the predictive validity of grades. This…

Previous analyses have identified a genetic contribution to the correlation between declines with age in processing speed and higher cognitive abilities. The goal of the current analysis was to apply the biometric dual change score model to consider the possibility of temporal dynamics underlying the genetic covariance between aging trajectories…

Using data from the Swedish Individual Statistics Project, changes in intelligence among 13-year olds are documented over a 25-year period. The average spatial and reasoning intelligence has risen successively. A clear increase is found for verbal intelligence in the 1960s, with more irregular growth since then. (SLD)

Collected data on twins' performance on 13 cognitive variables measured three times at three-year intervals. Twins were monozygotic or dizygotic pairs reared together or apart and were in six cohorts ranging in age from 41 through 84 years. Found stable mean cognitive performance across time on eight measures for the younger cohorts, and…

Changes in intelligence among Swedish 13-year-olds during a 20-year period was studied. Results show: (1) the average of spatial and reasoning intelligence has risen; (2) verbal intelligence increased during the 1960s, but declined thereafter; and (3) by the 1980s girls surpassed in verbal ability and equalled in spatial ability. (Author/LMO)

Changes in verbal, spatial, and reasoning intelligence among Swedish 13-year olds were studied from 1960 to 1990. Rising verbal scores until 1980 have been followed by a decline to essentially the 1960 level. Spatial and reasoning results have risen continuously. Gender and social class differences are discussed. (SLD)

As part of a continuing evaluation of the Swedish school system, changes in intelligence test scores from 1960 to 1995 were studied in relation to cohort, gender, and socioeconomic background. Changes in verbal, spatial, and reasoning ability were studied by comparing results on identical tests given to representative samples of Swedish…

This study investigated possible changes in verbal, spatial, and reasoning intelligence in Swedish 13-year-olds over a 20-year period. The first sample included about 12,000 students born in 1948. Data consisted of (1) information from school records, (2) information on personal background, (3) scores on three intelligence tests and three…