We attempted to replicate six top signals for each of the five factors in two independent samples. The first replication sample was from Tecumseh, Michigan, USA. Complete data were obtained for 923 individuals (age: M = 44.3, SD = 15.7; 58% Female), which consists of 110 unrelated individuals and 813 individuals clustering in 424 families. Personality traits were assessed using the NEO-PI, an earlier version of the NEO-PI-R, which assesses the Agreeableness and Conscientiousness factors using 18-item scales instead of the NEO-PI-R's 48-item scales. Twenty five SNPs were successfully genotyped using Taqman® SNP genotyping assays (Applied Biosystems, Foster City, CA). The second replication sample came from the Netherlands and consisted of participants from the Netherlands Twin Register. The analyses for this study were conducted on 1,158 individuals from 418 families (age: M = 45.3, SD = 14.6; 61% Female). Personality traits were assessed using a validated Dutch version of the NEO-FFI, a short version of the NEO-PI-R that assesses each factor using 12 items scale. SNPs were genotyped using Sequenom technology.
