measure derived from several self-report assessments, with the relationship being mediated by genetic factors (Smit et al., 2007b). Finally, a recent study using a large sample of 9-10-year-old twins yielded low (11-28%) but significant heritability estimates for FA (Gao et al., 2009). More recently, studies implicating specific genetic variants in FA began to emerge. An association between FA and serotonin receptor-1a gene polymorphism (HTR1a) has been reported, although effect sizes were small, with d ranging from .03 to .06. (Bismark et al., 2010). Another study found that a variant of the dopamine receptor D4 gene (DRD4) moderated the relation between the pattern of resting frontal EEG asymmetry at 9 months and regulation and attention at 48 months in a sample of typically developing children (Schmidt et al., 2009).
