Multitudes of research have been done to answer this seemingly simple question. The question is really quite basic; which has the most profound affect on a child's behavior and personality, nature or nurture (heredity vs. environment)? Behaviorists argue that the parents' actions and methods of child rearing have a direct bearing on the outcome. Environment definitely makes a difference. Some geneticists, however, strongly disagree. According to them, once the parent has donated his or her gene pool, their contributing influence on the development of an individual is complete (King). In fact, Sandra Scarr "asserts that genes are the primary determinant of developmental outcomes. Thus, once parents have passed on their genes to their children, the most important work is done" (King). Judith Harris continued in this vein with her book, The Nurture Assumption: Why Children turn Out the Way They Do. Then, there are those who insist that both heredity and environment have a direct bearing on the individual's development. In other words, it remains a hotly debated issue in the practice of psychology.
In reality, the question is simply a theoretical one. Complete separation of these two factors can only be made analytically; in practice, it is impossible; a child cannot be raised without a genetic influence to see the impact of nurture alone or without a parental influence to see the impact of nature alone. In fact, being raised without parents is an impact of nurture. More recently, extensive research has been done to, examining the idea that multiple sources influence the development of the individual. Realistically, it is hard to imagine that there are only two variables which ultimately effect development (either heredity or environment). More likely, there are a multitude of variables that affect development which are now being identified and, therefore being researched and addressed. As they arise, the understanding of individual behavior will continue to grow.
Though there are many, perhaps the most famous proponent of the nurture theory was Freud. Freud's works contained no real discussion of genetics, a science that was really in its infancy during Freud's time. Instead, he focused on external influences and how they impacted the individual. It is no secret that he blamed the parents for the problems of the child (Lehrer, 2009). The mother, in particular, took the brunt of the blame in his view (Lehrer, 2009). However, there are more contemporary behaviorists who have conducted much more in depth studies regarding the effect of the parents on the development of the child. Many of them have come to similar conclusions, if not blaming parents for children's problems, at least acknowledging that how a parent raises a child has a significant influence on that person.
Diana Baumrind was one of the first researchers to do extensive research on the manner in which parenting styles affect children's behavior. In her model, children are capable of learning from their parents that "they are competent individuals who can do things successfully for themselves. This fosters high self-esteem, cognitive development, and emotional maturity" (Grobman, 2008). Obviously, she is in support of the view that parents' behavior impacts children's development. While nurture may not be able to obliterate the impact of nature, it appears clear that nurture is an important part of personality development.
Baumrind's research has found consistent support in later studies. For example, "a longitudinal study by W. Andrew Collins and his colleagues (2000) supported Baumrind's claims: it showed that even with genetic influences taken into account, parenting practices made a difference in children's lives" (King). Currently, he is "studying alternative developmental pathways leading to competencies traditionally associated with adolescent development" (Collins et al., 2000). In fact he states that he has, "shown that a history of supportive social relationships with parents and with friends is associated with constructive patterns of identity exploration in middle adolescence and in early adulthood" (Collins et al., 2000) He too, is obviously of the mindset that parenting affects development, at least that supportive parenting helps shape functioning people, though his research does not uncover the impact of how negative parenting impacts the individual.
Judith Harris, Sandra Scarr, and David Rowe, are all of the opinion that the most significant factor in determining an individual's development is heredity. In fact, they would all argue that "Good Enough" parents do the child rearing job just as well as superparents" (Psychology Today Staff, 1993). Scarr goes as far to state that, "Parents should be given less credit for kids who turn out great and blamed less for kids who don't" (Psychology Today Staff, 1993). If one is to accept their theory, it does not mean that anything then anything done as parents (other than severe and sustained physical or emotional abuse) has absolutely no bearing on a child's development; it simply means that, beyond a certain threshold, things done as parents do not really impact behavioral development.
What is clear is that nature remains a very strong force. "Consider the results of twin adoption studies. When adoptees grow up in the homes of folks like lawyers and academics, they have a 50 -- 50 chance of above average performance in life. The biological kids of those educated parents have an 80% chance of being above average" (Psychology Today Staff, 1993). However, behavioral development and IQ are two separate parameters. Equating IQ with behavioral performance is not sufficient. How would those children have performed had they been in a house that did not stress academic performance? Furthermore, why would one make the assumption that lawyers and academics would engage in better parenting practices? It seems equally likely that those are the same types of people who would overly emphasis academic performance. That is not to suggest that nature has no real influence. "Several studies have uncovered uncanny similarities between identical twins separated at birth and reared in completely different families. One such study found a set of twins obsessively compulsive about neatness even after one twin grew up with slobs, the other with neatniks. Nature's thumbprint, again" (Psychology Today Staff, 1993). That "thumbprint" is a recurrent theme in numerous studies which support the fact that our genes play a significant role in our development. These studies, on the whole, however, do not refute the fact that our development is also strongly impacted by our parents.
Currently, the behaviorists (as well as the geneticists) are moving away from the black and white view that development is either nature or nurture. A common method today relies on "short-term longitudinal designs to better distinguish parenting effects from the characteristics of the child" (Collins et al., 2000). Short-term longitudinal designs measure aspects of child functioning and development at more than a single point in time (Collins et al., 2000). "In the absence of randomized experimental design, this strategy provides indirect evidence that parenting conceivably affects- rather than is simply accompanying or following from- child adjustment. Such indirect evidence is important because one cannot randomly assign children to different home environments" (Collins et al., 2000).
"Significant longitudinal relations between parenting and child adjustment after taking into account their concurrent relation also help to rule out a number of third variable explanations, including the possibility that the observed association is due to factors that parents and their children share, such as genes or socioeconomic status" (Collins et al., 2000). Thus, providing indirect evidence that children's behavior is not solely determined by genetics. Though, admittedly, there may be (and probably are) other contributing factors besides the nurturing of the parents. Additionally, there is now a relatively new development called Evolutionary Psychology. According to Oliver James, the basic argument is that "almost anything in modern life is understandable as being a consequence of how we adapted to life in the primordial swamp" (Arena Magazine, 2008).
Evolutionary Psychology, by its very nature, is on the heredity side of the debate. By this view, natural selection is simply running its course (Arena Magazine, 2008). Oliver James, however, asserts that "the problem with this is that it confuses the argument about evolution. The argument about evolution -- that nobody much would dispute -- says that natural selection resulted in us acquiring basic potentialities, such as the capacity for language, for humor or aggression and the like" (Arena Magazine, 2008). However, basic potentialities should not be confused with personality, a point that James makes exceedingly clear. He further states:
the key point I'm making is that when you are talking about individual differences between siblings from the same family or whether you're talking about people from different social classes -- these things, I would argue, in evolutionary terms, should be very plastic. For example, in order for me to be successful as a boy in a family of three girls, I need to be flexible about how to attract my parents' resources -- if you want to look at it in that evolutionary model. Of course, there are lots of other models that you can look at this from, but even within the evolutionary…