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Steinberg, Douglas (2006). Determining Nature vs. Nurture. Scientific American Mind,
October/November 2006, 12 – 14.
Summary by Zach Schlesinger and Alex Kagawa
For Dr. Mill’s Psychology 100 class, Fall, 2008
Douglas Steinberg’s article, “Determining Nature vs. Nurture,” describes how molecular
evidence is emerging to better explain the intersection of the environment and genes and the
impact on human behavior. Behavior once thought determined just by genes may actually be
influenced by the environment. As a result, drugs, psychotherapy and other environmental
interventions may help with some disorders, such as depression and schizophrenia. Much of the
article is focused on epigenetics, the study of how tiny molecules stick to particular genes that
generate proteins which can then influence human behavior. Moreover, he adds that epigenetic
changes can occur in mature cells and not just primitive cells, which adds fuel to fire of how the
environment can influence genetic chemistry and human behavior.
Schizophrenia and depression may be better explained with epigenetics. Schizophrenia
is usually discovered in teens and young adults in their early twenties. According to Professor
Dennis R. Grayson of the University of Illinois: “’Something happens during puberty that causes
changes in gene expression’” (Steinberg, 14). Schizophrenia cannot be defined by a mutant
gene, but perhaps by the influence of “’something’” (Steinberg, 14) on that gene. Grayson and
his colleagues have conducted postmortem research on brains of schizophrenics looking at genes
and their molecular activity.
Professor Eric J. Nestler from the University of Texas Southwestern has done research on
mice which shows how the environment and epigenetic changes are linked to depression. By
putting a small mouse with a large aggressive mouse in his experiments, Nestler altered the
protein generation in the brain of the small mouse and made it depressed. “The researchers
discovered that such treatment also caused methyl groups to stick to histones (the DNA-spooling
proteins) in the hippocampus. This action suppressed a gene that, as a result, failed to generate a
protein suspected of helping the brain adapt to stress” (Steinberg, 14). Moreover, when the small
mouse received anti-depressants, its gene activity was restored and it was more socially active.
There is another reason for why the mouse may be scared or determine why it becomes
who it is as adult, which is maternal influence. For example, Professor Michael Meaney at
McGill observed if a rat pup is licked less and groomed less by its mother, then it will be more
fearful as it matures. The team of scientist working on this discovered, “that a hippocampal gene
sheds methyl-group molecules during the first week of a pup’s life if its mother is a ‘high
licker’” (Steinberg, 14). In other words, the environmental influence of the licking by the mother
changed the molecular make-up of the gene. Moreover, these result showed that epigenetic
changes could happen not only in primitive or fetal cells but also in the mature cell as well.
These findings created many skeptics because it meant a mother’s parenting style could affect a
child’s genes.
As new technologies improve to understand molecular changes, this advances the
understanding of epigenetics and behavior. This may better explain the relationship between
genes and the environment, the relationship between nature and nurture. Alleviating human
disorders, like schizophrenia and depression, however, it is still a long time in the future.
Outline
A. Nature vs. Nurture
1. Molecular evidence emerging on debate: Nature vs. Nurture
2. Drugs, psychotherapy and other environmental interventions may help some
disorders
3. Epigenetics: the study of how tiny molecules stick to genes that generate proteins
which affect human behavior.
4. Epigenetic changes in mature cells and not just primitive cells
5. How the environment influences genetic chemistry and behavior
B. Schizophrenia and Depression
1. Occur in teens and young adults
2. During puberty, “something” causes a gene to change its expression
3. Schizophrenia is not cause by mutant gene
4. Scientists Grayson, Guidotti, and Costa found the brains of schizophrenias have
sharp reduction in a specific gene’s activity and an increase in a gene that promotes
attachments of methyl groups to DNA
5. Professor Nestler created an experiment to see if a how the environment and
epigenetic changes are linked to depression in mice
a. Larger more aggressive mouse in a cage with a smaller mouse
b. Big mouse attacked the smaller mouse and it became scared
c. Small mouse’s DNA molecules were changed, and its brain could no
longer adapt to stress
d. When given an anti-depressant, the small mouse improved
C. Maternal Influence and Epigenetics
1. Psychiatrist Michael Meaney found that a rat pup that receives less licking and
grooming from its mother will be more fearful
2. Licking affects a hippocampal gene which sheds the methyl group molecules in
the first week of a pup’s life.
3. Environmental impact of licking changes gene
4. Change in mature cells and not only primitive and fetal cells
D. Epigenetics and Behavior
1. Just at the beginning with new technologies
2. May help explain the relationship with genes and the environment
3. Cures may not be speedy
Critical Review
In the review of this article, we found some points very interesting.
Part A
1. We have never heard of epigenetics before and believe this field may be able to explain a
lot of the affects of the environment on genes.
2. We found it amazing that giving antidepressants to rats worked.
3. We also were surprised to learn that mother rats licking their young changed the
molecules in genes.
Part B
1. On the other hand, we had a hard time understanding the research on the schizophrenic
brains.
2. We still aren’t sure how all of the rat experiments will apply to humans.
3. Finally, we felt that there must be more research in this area and wondered if the article
wasn’t complete enough.
Test Questions
1. Can drugs or psychotherapy or other environmental interventions alleviate human
disorders that are largely caused by genes?
a. No
b. Yes
c. Epigenetics is beginning to address these issues.
2. Scientists believe that molecular changes that determine the proteins that influence
behavior:
a. Only happen in primitive cells in embryonic or fetal development
b. Only happen in the mature cells of children or adults
c. Now believe they happen in both primitive and mature cells
3. Epigenetics:
a. Is the study of how tiny molecules may or may not stick to genes that generate
proteins that help humans cope
b. Is the basis for some studies of rats and depression
c. May explain some of how the environment impacts the chemistry of genes
d. All of the above
4. Schizophrenia and Depression may be influenced by the environment. (T/F)
5. Proteins help a rat’s brain adapt to stress or hostile environments. (T/F)
6. This article proves that a mother’s parenting style does not affect the activity of a
child’s genes that create proteins which impact human behavior. (T/F)
Answers:
1. C
2. C
3. D
4. T
5. T
6. F