Based on previous association studies of the DRD2 TaqI A polymorphism, individuals with at least one A1 allele were designated as A1+ and those who were homozygous for the A2 allele were designated A1-. Similarly, DRD4 48 bp VNTR genotypes were separated into long allele (7 repeats or longer) present (L+) and long allele absent (L−) groups. The principal data analyses used a tiered analysis. First, since several past studies have found that SOB effects vary by gender, factorial 2 (Male/Female)×2 (Winter-Born/Not-Winter-Born) ANOVAs were conducted. Then to see if genotype interacted with SOB to effect the traits in question, DRD2 and DRD4 genotypes were added to each factorial model (2 [Male/Female]×2 [Winter-Born/No-Winter-Born]×2 [A1+/A1−]×2 [L+/L−], although four-way interactions were considered uninterpretable and are not discussed). Similarly, categorical dependent variables were first analyzed with forward conditional factorial binary logistic regression models with dichotomized SOB and gender and then secondarily include DRD2 and DRD4. Direct SOB effects and SOB interactions with genotypes are the main focus of the study. Since this study is only concerned with sexual dimorphism in so far as it
