Monday, October 12, 2009

Evidence Supporting Nurture

Now that you have been exposed to both sides of the debate, I would like to shed light on the evidence supporting the nurture theory.

Darwin’s theory of evolution led William Hamilton, George Williams and many others to the idea of personality evolution. They proposed that like physical organs, your personality is the result of natural selection for survival of the fittest. You do as your genes dictate. They suggest that fear of death, fear of injury, fear of snakes, shyness, addiction, criminality and sexual orientation are main examples of inheritable behaviors. However, there is strong criticism on this approach:

1- There is no single universal behavior which can be proved evolutionary. Even fear of death, that seems natural, is overridden in crusades, suicides and suicide bombings.

2- Humans are made of 25,000 to 30,000 genes. Chimpanzees share 95% of your genetic characteristics. However, they do not even share 10% of your behaviors.

3- People do not differ in behaviors as they do differ in skin pigments. Extroverts, introverts, optimists, pessimists, criminals, liberals, etc. are found in all societies and cultures. Even identical twins, with the exact same genes, and fraternal twins, with half of the same genes, behave differently in most cases.

4- No genome scientist has related genes or a set of genes with any kind of behaviors.

5- There are a good number of living organisms and fossils which suggest intermediary stages to the physical evolution. However, no such intermediary stages are available for personality evolution.

Study: Supportive Parenting Can Prevent Substance Abuse
A study published in the Journal of Consulting and Clinical Psychology says that supportive parenting can counteract the effects of a genetic risk factor that increases the likelihood of substance use among youth. The research focused on the 5HTT gene that transports serotonin in the brain. According to many studies, most people possess two copies of a long version of this gene, but a few that possess one or two copies of a short version are more likely to consume alcohol or other substances and partake in impulsive and risky behavior. Youth with the short version of the gene that received minimal supportive parenting used three times more than youth who had high levels of parental support. The effect of the genetic risk was essentially zero with strong relationships between children and parents.

This study provides evidence for the nurture theory. Even though a child is predisposed for substance abuse with the presence of a particular gene, parental support can override that predisposition, and the child can live a normal life. This goes to show that our body predisposes us to certain risks and diseases, but our mind and experiences have the final outcome.


  1. I watch a lot of Law and Order SVU. On the show a lot of rapists were sexually abused as a child. The environment we grow up in influences much of our behavior. I have a lot of trust issues because so many people broke promises to me. I think nature and nurture are closely related.

  2. Yes, nature and nurture are both closely related, but there are those who argue heavily for one side or the other.

    The brain is also malleable. If you have trust issues because lots of people broke promises, then do you think your issues will be relieved somewhat if people began keeping their promises?

  3. Interesting point. I don't know. That makes sense. I cannot wait to read more.

  4. The line between what people consider Nature and what people consider Nurture, is in a Grey Area. It would be difficult to say yes this trait is solely attributed Nature or Nurture. In the Nature vs. Nurture debate, many people bring up serial killers and people try to discover which influence makes a person behave in such a manor, which do you believe cause a person to become a killing machine?

  5. The line between the two is something extremely difficult to figure out, and this is what people have been debating for a long time. I have no idea when this line will be drawn...

    Criminal behavior is an interesting topic to consider. I have found connections between brain abnormalities and aggression level. The amount of serotonin also affects aggression. These links between nature and aggression appear to be strong. However, there are those who also believe that the people you congregate with may change your level of aggressiveness.
    I must say that I have been around hot-tempered people who release their anger furiously despite being around kind, warm-hearted individuals.

  6. I think that people are born with certain characteristics, tendencies and proclivities (nature). Whether or not these are immutable (characteristics) or mutable (tendencies and proclivities) traits is also a function of nature which I think we are only now discovering. If they are mutable, then the circumstances in which they exist and they way they interact with unchanging traits determines outcome.

  7. Lots of research is still in progress to determine exactly what traits are changeable or unchangeable and how they interact.

    You say our predispositions are mutable. So...what about a predisposition to diabetes? Is it changeable if the person eats less sugar? More sugar?

    Nice choice of words, by the way :)

  8. Indeed, I do think so to some extent. I think mutability and immutabilty exist on a continuum much like the Kinsey scale (on sexuality). Immutability is on one end of the scale and mutability on the other end. What is always immutable is very limited and what is always mutable is very limited. Every other trait falls on the continuum. To make matters more complicated each person has his/her own continuum and while it may have quite a lot of similarity to every other human it is still absolutely unique to that person.

    Thanks. You did say it was for English class right? ;-)

  9. So the person with a predisposition to diabetes could avert the outcome of diabetes by their lifestyle. If they are particularly athletic and if they eat an appropriate diet they may avert the outcome of diabetes (avoiding a predisposition).

  10. I like your continuum example in relation to this. It reminded me of the political spectrum with conservative on one side and liberal on the other with lots of in-between space. There are people on the far right and far left, but there are also lots of them in the middle. The average American is "moderate."

    It does get complicated when each individual also has their own continuum in addition to the overall continuum. It reminds me of a fractal...a neverending geometric pattern repeating itself.

    Yes, the person with a predisposition to diabetes MAY avert the disease, but there are healthy people who can get it as well.

    I greatly appreciate your comments. Thanks :)
    (Yes, it is for English. You have no idea how curious I am to find out who you are, mystery person :p)

  11. Im doing this as a psychology paper at college and we have to choose a side, i chose nurture as there is just far more evidence from skinners experiment all the way to modern publications in scientific journals. Everytime somebody finds the "bad" gene its proven its dormant untill triggered by environment and can be suppressed in a loving environment. Im not saying there is no nature in our behaviour but from speaking to psychologists and social workers that convinced me with massive doses of evidence nature has far more influence

    1. Can someone tell me the evidence that refutes the nature perspective of attachment. thank you

  12. Fantastic help, but if you could post credentials and qualifications, that would be great. Thanks!