Many leading molecular genetic researchers in behavioral genetics and psychiatric genetics have adopted the position of 'missing heritability' as an explanation for their failure to discover genes. Given the widespread acceptance of behavioral genetic and psychiatric genetic positions, coupled with tremendous technological advances, several decades of molecular genetic research should by now have uncovered the genes that are believed to underlie behavioral differences and psychiatric disorders. Four major problems with the missing heritability concept as it is used in the evaluation of molecular genetic studies of behavioral characteristics are listed. A large group of genetic researchers headed by Teri Manolio of the National Human Genome Research Institute, which included Francis Collins and other prominent investigators, published a 2009 article in Nature entitled, 'Finding the Missing Heritability'. Although, molecular genetic research is the ultimate test of genetic interpretations of twin studies, which include twin method MZT-DZT comparisons and TRA studies.