Nature Versus Nurture: Really?

Dec 31, 2010

As I read Steven Pinker’s book The Blank Slate: Modern Denial of Human Nature I was, for lack of a better word, flabbergasted, about the extent of acrimony that seemingly persists regarding the nature versus nurture debate.  This parley, from my naive perspective, was over long ago.  Yet Pinker detailed the extensive history to which some intellectuals, even today, attack the notion of any genetic contribution to traits such as IQ, behavior, political views, religious views, and personality.

 

For me there is very little question about the impact of genes.  It is clear as day in my family.  My daughter for example is very much like me.  And I see the influence of genes nearly every day in my practice.  As a psychologist with a specialty in evaluating and treating difficult to manage children (i.e., Autism Spectrum Disorder, Oppositional Defiant Disorder, and ADHD), I often work with families who have an exceptionally strong willed and self directed child.  The children that have these latter traits, without Autistic like symptoms, are often classified as Oppositional Defiant.  Along with such independent mindedness, typically comes an explosive temperament and a highly sensitive and precocious level of personal dignity.   It is important to note that a vast majority of the time, the child is a proverbial chip off the ole-block: usually, the father was similarly quite difficult to manage as a youngster.

 

One with a nurture bias might suggest that my daughter and those oppositional children I see are simply products of their environment.  But here is what is interesting.  Often in the families I serve, there are other well behaved, well adjusted, and polite children.  To suggest that the environment uniquely and exclusively shaped the behavior and affect of the troubled child would suggest that there was a substantial level of differential parenting going on in the home.  This scenario is far too common to be a product of differentiated parenting style.  And thorough behavioral analysis almost always rules out this variable.  Socially, the parents are blamed for their bad kid, not because of their gene contribution, but because their alleged poor parenting practices.  Well, most often, poor parenting is not the cause of the problem!  And my daughter’s similarity to me unfolded despite my attempts to foster in her, her own unique identity and insufficient environmental influence.

 

The argument really is moot.  Genes do matter!  The evidence is substantial and it transcends the anecdotes I just shared.  Only those with an ideological position inconvenienced by this reality argue otherwise.  I actually prefer the idea that genes don’t matter.  It would give me greater capacity to affect change in homes given my behavior analytic skills.  It would also give me more hope that my daughter will not develop the same geeky interests that I have.  Too late!  She is a geology major.  Like me, she loves rocks.  It would also give me hope that she wont develop the same G/I ailments that have incapacitated me, my mother, and my grandfather. Again too late.  Sadly, the other day she had to buy some Tums.

 

People are uncomfortable with the idea that issues such as personality and IQ, for example, would have any genetic determinism.  It seems too limiting, too materialistic, and too deterministic.  People, I think, are more comfortable with the idea that they can affect change – that they can arrange outcomes, that the power is in our hands.  But the real power, it seems, is spread out – residing both in our hands and in our genes.  Environmental determinism, in fact, is more consistent with my political and social views, but no matter how inconvenient, I am compelled by evidence to soften my stance regarding this romantic notion.  How I wish that DNA did not enter the picture with regard to such issues.  Or do I?  Had it not, we wouldn’t be here to write/read such musings.  You’ve heard of the whole evolution by means of natural selection thing, haven’t you?

 

As it turns out, we are products of our genes and our environment.  No duh!  Debate over!  Right?  Nope!   I had assumed that it was commonly accepted that genes matter.  I had no idea that acknowledging this reality was in a sense sacrilegious to some.  Although Pinker made clear the debate, I suspected that perhaps this was an esoteric intellectual war of words limited to philosophical types with high brow notions about macro economic models and so on.  But, I became more aware of the lingering embers of environmental determinism as a result of a firestorm that erupted last week regarding an essay written by an environmental advocacy group spread about on Twitter and a subsequent article posted in the Huffington Post.  These articles essentially minimized genetic determinism in major health issues due to the failure of the Human Genome Project to isolate specific genes responsible for specific illnesses.  Out with the genes – in with the environment the proponents celebrated.   Environmental determinists pounced on the absence of evidence as if it were evidence of absence (Carmichael, 2010).  As it turns out, genes are really complex and diseases are influenced, it seems, by gene cohorts rather than any one specific gene.  I am less familiar with the research regarding genetic influence on disease but the tone of the banter reminded me of the debate about human nature detailed by Pinker.

 

I have discussed in several recent posts the impact of genes on important issues such as personality, adaptive functioning, and even political perspectives.  The psychologist Eric Turkheimer pulled together the unusually robust evidence from extensive studies of twins (fraternal and identical) reared together and apart as well as studies of adopted children relative to biological children and concluded that there are three important laws that help explain the development of personality characteristics and intelligence.   The three laws are as follows:

 

  1. All Human traits are heritable;
  2. The effect of being raised in the same family is smaller than the effect of the genes; and
  3. A substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families.

 

These laws are best summarized based on current research from behavioral genetics as follows:

 

  1. Heredity accounts for about 50% of the variance in the adaptive functioning outcomes of children.
  2. The home environment, as it is influenced by parents, accounts for 0 to 10%, and
  3. The child’s peer group accounts for the remainder (40-50%)  (Pinker, 2002).

 

Corresponding laws regarding the variants affecting diseases are perhaps unclear at this time.  But denial of genetic influence is much like the denial of the heliocentric theory of the solar system or the arguments put forth by Creationists and anti vaccine advocates.  They are guided by ideological notions that hang by a thin thread.  Something near and dear to the hearts of the proponents of exclusive environmental determinism is threatened by evidence.  The only recourse is denial.  Its an old and tired song and dance.  Genes matter – but not exclusively.  Environment matters – but not exclusively.  Get used to it.

 

References:

 

Carmichael, M. (2010). DNA, Denial, and the Rise of “Environmental Determinism”. Wild Type. http://marycarmichael.wordpress.com/2010/12/22/dna-denial-and-the-rise-of-environmental-determinism/#comments

 

Katz, D. (2010).  Is There a Genie in the Genome? The Huffington Post. http://www.huffingtonpost.com/david-katz-md/is-there-a-genie-in-the-g_b_792844.html

 

Latham, J., & Wilson, A. (2010). The Great DNA Data Deficit: Are Genes for Disease a Mirage? The Bioscience Resource Project Commentaries.  http://www.bioscienceresource.org/commentaries/article.php?id=46

 

Pinker, S. (2002). The Blank Slate: Modern Denial of Human Nature. New York: Penguin Books.

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3 Responses so far | Have Your Say!

  1. Tweets that mention Essay has afterlife: expands on it + comment from actual env determinist (they do exist!) -- Topsy.com
    December 31st, 2010 at 4:17 pm #

    […] This post was mentioned on Twitter by BetterBio. BetterBio said: RT @mary_carmichael: Essay has afterlife: @gtguild expands on it http://bit.ly/gerchc + comment from actual env determinist (they do exi … […]

  2. 2010 – A Year in Review: How Do You Think? « How Do You Think?
    January 8th, 2011 at 9:00 pm #

    […] The evolution of understanding regarding the power and importance of Intuitive relative to Rational Thinking was humbling at times and Daniel Simons' and Christopher Chabris' book, The Invisible Gorilla, certainly provided a mind opening experience.  Hey, our intuitive capabilities are incredible (as illustrated by Gladwell in Blink & Lehrer in How We Decide) but the downfalls are amazingly humbling.  I've covered other topics such as  happiness, superstition, placebos, and the debate over human nature. […]

  3. Gerald Guild
    January 30th, 2011 at 9:28 am #

    See http://bit.ly/gPMUiZ for an updated discussion of this topic.

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