Limitations of Studying Twins

http://www.apa.org/monitor/apr04/second.aspx

Twins have long been a fascinating topic for psycologists. They offer a potential chance to study the effects of the environment on the mind independent of differences in genetics. Of course while identical twins share DNA, fraternal twins only share about 50%, making them less ideal for dependent experiments. These experiments rely on a few mainstay assumptions about twins that include:

-Research into twins assumes that they are just as likely to pick a partner that is unlike them as they would a partner similar to them. If it is indeed true that similarities are more attractive, then fraternal twins would share more than 50% DNA because their mother and father would be more similar.
-It's assumed that identical twins growing up in the same home experience a very similar environment
-Genes are effected by their environment. This phenomenon is often left out of these experiments despite the fact they alter the basis for the study
-Dominant and recessive genes fight behind the scenes, changing genetic structures without possibly altering the visual appearance of the twins.

The trait being studied has a large effect on the usefulness of studying twins. For instance, it is believed that mates are chosen more frequently based on similar intelligence than they are similarities in other, more negative qualities or quirks. Therefore, "a scientist studying intelligence may have to worry more about nonrandom mating than researchers who study personality." Studying twins' extended family can remedy alot of these issues, as there becomes much more data available to study the impact of twin's lifestyle choices beyond the immediate behaviors. Lastly, genetic research plays a huge role in studying twins today. Differences in the DNA offers insights that traditional analysis methods can't match and combining the two is offering a continuously more complete picture of the subject.

Being a twin, I think the concept of studying twins for psychological purposes is fascinating. They offer a unique opportunity to isolate the environment as the variable, keeping genetics constant for posterity. The differences that arises in twins has always fascinated me, and I can personally attest to being extremely different from my brother both physically and personality wise. Despite our variable lifestyles, we retain a commonality that is hard to pinpoint, but concrete. Psychologists are determining what this link is whether its purely genetic or something more, and I'm looking forward to their ever-evolving hypothesizes.