of the total aggregate genetic effect, and how that total genetic effect may differ across different environments, but it tells us nothing about the specific genes involved or the underlying biology. It has been suggested that now that we have the capability to measure specific genes, the utility of twin studies is limited, and they should be resigned as a thing of the past. However, until we have identified all of the specific genes that make up the predisposition to any given trait (a goal that we are not yet close to achieving for any psychological outcome), twin studies will continue to provide the only method of studying overall genetic influence for any given trait.
