What is a twin study?


There are two main types of twin studies.

The first type focuses on the twins themselves, their development and mutual relations. Studies of this sort ask questions such as the following: How do twins develop as opposed to non-twins? Are there dissimilarities between different kinds of twins (identical and non-identical; boy and girl as compared to same sex) in terms of certain abilities or the quality of relations between them? Which processes can parents do, or are already doing, in order to facilitate the twins' proper development, while taking the unique connection between them into account?

Although many twin studies have been conducted over the years, only a few of them have researched the twins themselves and the nature of their mutual relations. Most twin studies are intended to assist the research on development of behavior and different traits by providing answers to one of the most important questions in Psychology: nature or nurture? In other words, what is the extent of the genetic influence as opposed to the environmental impact on human development? The nature-nurture question is investigated through performing comparisons between identical twins (who share 100% of their DNA) and non-identical twins (who share an average of 50% of their DNA). Since the impact of the environment is similar for both identical and non-identical twins, whereas the DNA is identical only in identical twins, these comparisons enable us to learn more about children's development/

One of the unique features of the Israeli Twin Study is that it deals with both kinds of questions, investigating the nature of the twins themselves but also the influence of nature or nurture on development.

Additional fascinating studies are being conducted on identical twins who have been separated at birth and given to adoption. These cases are especially interesting because any differences found between the twins later on in lifecan be attributed solely to the different environments they grew up in (their DNA is 100% identical and thus cannot account for any of the differences). Statistical analysis of these differences enables researches to determine the influence of the genetic and environmental factorson the specific traits that are being investigated.