Heritability of Educational Achievement in 12-year-olds and the Overlap with Cognitive Ability

Meike Bartels, Marjolein J. H. Rietveld, G. Caroline M. Van Baal, Dorret I. Boomsma
2002 Twin research  
I n order to determine high school entrance level in the Netherlands, nowadays, much value is attached to the results of a national test of educational achievement (CITO), administered around age 12. Surprisingly, up until now, no attention has been paid to the etiology of individual differences in the results of this national test of educational achievement. No attempt has been made to address the question about the nature of a possible association between the results of the CITO and cognitive
more » ... CITO and cognitive abilities, as measured by psychometric IQ. The aim of this study is to explore to what extent psychometric IQ and scholastic achievement, as assessed by the CITO high school entrance test, are correlated. In addition, it was investigated whether this expected correlation was due to a common genetic background, shared or nonshared environmental influences common to CITO and intelligence or a combination of these influences. To this end multivariate behavior genetic analyses with CITO and IQ at ages 5, 7, 10 and 12 years have been conducted. The correlations were .41, .50, .60, and .63 between CITO and IQ assessed at age 5, 7, 10, and 12 respectively. The results of the analyses pointed to genetic effects as the main source of variance in CITO and an important source of covariance between CITO and IQ. Additive genetic effects accounted for 60% of the individual differences found in CITO scores in a large sample of Dutch 12-year-olds. This high heritability indicated that the CITO might be a valuable instrument to assess individual differences in cognitive abilities in children but might not be the right instrument to put the effect of education to the test. In the Netherlands, nowadays, much value is attached to the results of a national test of educational achievement (CITO), administered around age 12, in order to determine high school entrance level. The results of the test are often used as an independent judgment, besides the teachers' opinion, in advising the parents on the future educational level of their child. So the CITO is used as an aid in choosing the most appropriate type of high school (e.g., academic versus technical). From a historical perspective, this attention for "independent" testing has to do with the possibilities for selection. The establisher of the CITO (Eindtoets Basisonderwijs, 2002) emphasized that this national test of educational achievement has put the effect of education in a particular school to the test besides measuring possible learning potential or cognitive abilities in children (Geldermans, 2001) . It was hypothesized that success in scholastic achievement depended on the quality of the elementary school. A large number of articles in Dutch daily newspapers were dedicated to the influences of the school population and school neighborhood on the test results of the pupils. In these articles the influences of socioeconomic status (SES) and ethnic background of the majority of the children at a certain school were considered important factors to classify the school and the future success of the pupils. Several studies agreed on the claim that family variables (e.g., family size, SES, parental involvement, cultural level) influenced the development and educational achievement of children (Christenson et al., 1992; Garcia & Rosel, 2001; Marjoribanks, 1994). If this were true, influences of shared environmental factors on CITO would show up as significant in the classical twin design. Alternatively, parental SES might reflect the parents' cognitive abilities. Heritable influences on cognition would predict CITO scores to be genetically mediated. Intelligence has been found to explain a significant amount of the variance in educational achievement (Eaves & Darch, 1990; Jensen, 1972) . In the Netherlands no attempt has been made to address the question about the nature of a possible association between the results of the CITO and cognitive abilities, as measured by psychometric IQ. Even more striking, no attention has been paid to possible genetic influences on the results of the national test of educational achievement. In emphasizing that the CITO was a test for the level of the school and the classification of children, the CITO-group might have underestimated the true content and value of the results of this test. It could be interesting to establish whether the possible association between intelligence and results of the CITO was based either on overlapping genetic influences, overlapping environmental influences (SES, school population), or both. Numerous behavior genetic studies have been conducted in which cognition and educational achievement were examined separately. Studies on cognition have yielded the largely consistent result that genetic differences accounted for at least 50% of the observed variability
doi:10.1375/136905202762342017 pmid:12573186 fatcat:6bhinrf4pndu5lwzmwrglzgq2a