Complex phenotypes result from multiple inputs from genetic and environmental sources, with intricate subsystems mediating the influence of both sources on the phenotype. Experiments that attempt to describe the influence of a particular gene involve partial isolation of the sub-system in which that gene is an element from other components of the total system influencing the phenotype. Any interactions that exist between the controlled variables and the processes downstream of the gene in the normally operating total system become undetectable; therefore, the results of the experiment can be restricted to the particular configuration of the controlled variables. The inescapable price of the precision of knowledge generated by experiment is a reduction in the generalizability of the results beyond the constrained circumstances of the particular experimental situation. Integrative research, permitting the influence of related subsystems, is required to provide a comprehensive assessment of the influence of a gene.