An ambiguity exists in how psychological scientists use the word “interaction.” This word can refer to physical interactions between components that form the mechanisms in complex systems, but it can also refer to statistical interactions revealed by General Linear Statistical Models (e.g., Analyses of Variance). Statistical interactions indicate that the nature of the relationship between two variables depends on a third variable, but the discovery of such interactions does not constitute evidence of physical interactions between components in a system. Studies conducted using traditional behavioral genetics methods sometimes reveal statistical interactions between genes and environments, but the presence or absence of such interactions tell us surprisingly little about actual, physical interactions between genes and their contexts. This is important, because it is only the latter kinds of interactions that cause the development of behavioral phenotypes, including developmental disabilities. Therefore, when behavioral scientists discover (or fail to discover) Genotype × Environment interactions, it is important to exercise care in interpreting their meaning and in assessing the utility of such findings.