Citation
Ellen, L.; Horn, E.; & Turkheimer, E. (2014). Understanding the mechanism of the Wilson effect. Behavior Genetics Association 44th Annual Meeting.Abstract
Heritability of intelligence increases with age, starting at about 20–25 % in early childhood and asymptoting at approximately 80 % by early adulthood (Bouchard 2013; Tucker-Drob et al. 2013). This effect, known as The Wilson Effect, is robust and has been replicated by many researchers using a wide range of samples drawn from across the Western world. Although useful for determining the genetic and environmental factors contributing to the development of intelligence across the lifespan, heritability studies inherently lose information through the process of standardization. That is, demonstrating that the proportion of variance in intelligence explained by genetic factors increases with age does not yield information about the mechanisms by which this phenomenon occurs. In the present study, we seek to understand these mechanisms using cognitive ability scores of ado- lescent and adult twin and sibling pairs. We will evaluate the role of age in this developmental process both descriptively (examining howintraclass correlations and within-pair variances vary with age) and using structural equation modeling (in which age is used to moderate the genetic and environmental variance components of IQ). Preliminary results using 177 MZ and 266 DZ pairs from the Midlife in the United States (MIDUS) Sample (age range=34–82, Median=54) show that regardless of changes in the total variance in intelligence, raw additive genetic variance increases consistently with age. Similar results using 262 MZ and 411 DZ twin pairs from the National Longitudinal Study of Adolescent Health (Add Health; age range 11–20, Median=16) were observed. In terms of absolute pair
differences, adolescent DZ twins showed increasing differences with age, whereas no systematic differences in absolute pair differences were evident in the adult sample. Results will be discussed in terms of phenotype-environment correlation (rPE).
URL
http://dx.doi.org/10.1007%2Fs10519-014-9678-2Reference Type
Conference proceedingBook Title
Behavior Genetics Association 44th Annual MeetingAuthor(s)
Ellen, L.Horn, E.
Turkheimer, E.