This article laid out the specifics of twin studies. The purpose of twin studies is to "shed light on human behavioral genetics", by analyzing how much genetics and/or the environment plays in our behaviors and traits. The article begins with a overall look at views on the studies, stating that it is controversial. While behavioral geneticists seem to favor the studies, some psychologists question the "assumptions". The article than goes on to outline the methods and theories behind twin studies. Many of the twin studies rely on studying twins that were raised in the same environments. It also talks about the differences of identical twins and fraternal twins, and how they can be used to as a comparison stool. Some of the assumptions of Twins studies, are that the parents randomly mated to create the twins. But some of the argument against twin studies, are that people generally mate with people who are similar to themselves, causing there children to have similar traits. Other assumptions include: equal environments, gene environment interaction ("researchers think that interactions between genes and environments, rather than genes and environment separately"), and genetic mechanisms. Lastly the article looked at the value of twin studies. While limitations, exists many psychologists argue that twin studies are evolving and are a really great tool for looking at human behavior.