The Twin Design

Having been a part of twin testing since I was a small child, I have always found the different tests we have participated in interesting. Lately I have spent more time trying to see where their research has gone. There are many groups that use this type of testing nationally and internationally.



The testing models for twins have found that twins can be used as representative of the general population. Twins have been found to be comparable on temperament and personality measures. Another main assumption of the design is our equality of environments. It is not only identical twins that they use for their studies, but fraternal twins as well.


There is evidence to show that a high maternal age can influence the rate of fraternal twins. Maternal age can also affect the parenting style and congenital anomalies. I have always believed that it is also more likely to have fraternal twins when the mother takes different fertility treatments.


It is therefore necessary for the investigators to control these differences when they conduct their studies. Environmental similarities found with identical twins have been found to not cause the twins to have their behavioral similarities.


These assumptions are tested by comparing the findings of multiple studies using different methods. They can then compare the results to other findings from family and adoption studies.


The types of testing that Aspenn and I participated were the tests for the behavior genetic program. They study the genetic influences on individual differences in behavior. They also tested our parents as part of a biological relative test to see how likely they were to also have the same behavior. If they do, they can determine if it is more of a hereditary type of behavior. The twin studies in the behavior genetic designs have been found to be powerful approaches for studying development.


I am proud to have participated in the twin studies. Though as we get older there are less things we can participate in, it has been an experience that I would never want to miss out on. I will continue to try to research the information they have found from the types of testing that we participated in.


I have used some information from a Twin Studies article online while writing this blog post: http://social.jrank.org/pages/666/Twin-Studies.html