Multivariate analyses can also be used to determine whether similar genetic or environmental factors may be contributing to a brain structure and a cognitive or behavioral phenotype. Previous studies in adults had found that shared genetic influences contributed to both brain volume and IQ (Hulshoff Pol et al. 2006; Posthuma et al. 2002). We carried out a multivariate analysis of brain structures with verbal and non-verbal IQ measures in the CPB pediatric twin sample to determine what kind of relationship might exist during this period of rapid cognitive development. Interestingly, a common environmental factor affected variation in both verbal IQ and gray matter volume. Nonverbal IQ, on the other hand, shared a common genetic factor with regional variation in both gray and white matter volumes. These results suggested that different mechanisms underlie the relationship of specific subcomponents of intelligence to brain structure, at least in this younger cohort (Raznahan et al. 2010; Wallace et al. 2010)
