The Nature versus Nurture debate concerns the relative importance of an individual's innate qualities versus personal experiences in determining or causing differences in physical and behavioral traits. (Ridley, Matt. "What Makes You Who You Are." Time Magazine. 25 May 2003).
Almost everyone in any related field has an opinion as to which is truly more important, nature or nurture. The director of a group called the Minnesota Study of Twins Reared Apart, Thomas Bouchard, believes that 70 percent of a person's personality is genetic and 30 percent is due to environment. The director of the Lewisville Twin Study, Adam Matheny, however, says it is 50-50.
In my opinion, both nature and nurture are very important. Nature and nurture are both influential to language development and emotions. A lot of physical development is pre-programmed to coincide with brain development and is brought about through nature. Nurture, such as stimulation, is also essential for the brain to develop. Even the cases of identical twins are not a perfect example of nature being superior to nurture. If some of the ties happen to be a coincidence and some happen to be based on vague knowledge of their past, the entire idea is less credible. For example, the fact that the Jim twins both named their sons James Allen or James Alan could be simply naming the child after themselves. Allen/Alan might be because they were told that their birth father was named Alan. The only way to know for sure is to know more about the context of all the things that are similar between the two. Since we don't know any of it, we can only take it as vague information. Based on all this information, I believe nurture is more important than nature, at a balance of 70 percent of early childhood development being influenced by a person's environment and 30 percent being influenced by genetics. The two are so tied together that you cannot fully separate one from the other.
Nurture has been historically referred to as the care given to children by their parents, in particular the mother. It is now widely regarded as any environmental (not genetic) factor. This includes the influences of development arising from prenatal, parental, extended family and peer experiences. It also extends to such influences as media, marketing, and socio-economic status (SES). Additionally, although childhood experience is often regarded as more influential in who one becomes, a broader interpretation might count all life experiences as "nurture."
Identical twins, particularly those raised separately, are a natural way to view nature versus nurture because they are exactly the same genetically (nature). This means that a large part of the differences between the two have something to do with nurture and the environment they grew up in. It is often thought that a pair of identical twins raised together may be more different than a pair raised apart. The problem is that there have only been about 100 pairs of twins like these that have ever been studied. This creates a fairly small amount of data to study. There is a reason that the twins may be more similar if they are raised separately. It is thought that twins raised together may "divide up the territory" and also compete to be different because they are seen as a single unit instead of individuals. When raised separately, they do not feel the need to make themselves different and do not act unnaturally just to be so. (Malmstrom, Poland. "The Art of Parenting Twins." 2007.)
There are several problems with this type of data on twins. If there are birth defects, the twins may be different physically or even mentally. This would change the nature and possibly even nurture of the children, making them more different than regular siblings, which means that even if they are raised apart, they may not be useful to these kinds of studies. Also, some of the similarities may be more based on...