Twin Studies

"Twins have a special claim upon our attention; it is, that their history affords means of distinguishing between the effects of tendencies received at birth, and those that were imposed by the special circumstances of their after lives." - Sir Francis Galton

Twins are fundamental in the study of genetics. For years, twin studies have been conducted to answer the questions arise from nature vs. nurture. In fact, the first concept that appears when you search behavior, personality or genetics is the twin study. In essence the twin study is can be explained through the following graphic:

Basically, twins, who have mostly the same genetic makeup, are impacted by the environment they are in. However, these studies made many assumptions which possibly skew the results. Assumptions are commonly made on the concepts of random mating (researchers assume that people choose partners who are different from themselves), equal environments (assumed that twins raised in the same home are in the same environment), gene-environment interactions (thought that interactions between genes and environment, instead of thinking as both concepts separately, may influence traits) and genetic mechanisms (inheritance of traits through different gene mechanisms).

These assumptions, or limitations, don’t make the studies useless because there is an extent to which limitations matter. However, that doesn’t mean that twin studies aren’t going to change. Modern genetic research is focusing on studying not only twins but their extended families, longitudinal studies and other variations in attempts to address limitations.