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Abstract

For centuries, researchers and scientists have been attempting to explain the root of our societal and individual identities, and what triggers our infinite behaviors. At the center of this search for these answers lies the infamous Nature versus Nurture debate, the timeless debate in the field of psychology. This paper will explore how much of an individual’s personality and behavior is a result of nature, and how much is a result of nurture. It will explore whether adoptions studies give a solid illustration of the extent to which nature and nurture affect development. This is an archival study, utilizing sources in the forms of books and journal articles from the Kingsborough Community College Library and several psychological journals. The film documenting the journey of the well-known triplets from the Louise Wise Agency’s twins’ studies will also be reviewed, as the majority of data from this study is redacted or sealed. This paper will not present new experimental or case study research, but instead summarize and analyze existing information, providing a supported conclusion towards the end.
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Nature Versus Nurture: The Timeless Debate
Kyle A. Reese
Kingsborough Community College
Author Note
Honors Contract Project for PSY 1100 with Professor Goodridge
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Nature Versus Nurture: The Timeless Debate
For centuries, researchers and scientists have been attempting to explain the root of our
societal and individual identities, and what triggers our infinite behaviors. At the center of this
search for these answers lies the infamous Nature versus Nurture debate, the timeless debate in
the field of psychology. This paper will explore how much of an individual’s personality and
behavior is a result of nature, and how much is a result of nurture. It will explore whether
adoptions studies give a solid illustration of the extent to which nature and nurture affect
development. This is an archival study, utilizing sources in the forms of books and journal
articles from the Kingsborough Community College Library and several psychological journals.
The film documenting the journey of the well-known triplets from the Louise Wise Agency’s
twins’ studies will also be reviewed, as the majority of data from this study is redacted or sealed.
This paper will not present new experimental or case study research, but instead summarize and
analyze existing information, providing a supported conclusion towards the end.
Literature Review
The majority of works found concluded either that nature and nurture cannot be separated
or were simply inconclusive. Those that conclude that a separation cannot exist argue that
personality and behavior both contain traits that are influenced by both heredity and environment
to differing degrees. The summaries of several of the studies themselves could not come to a
conclusion, similarly, because evidence existed in favor of both heredity and environment.
These authors also seemed to be searching for a polarized answer. It was difficult to locate
sources that were based on real, nonbiased research that argued for solely one or the other.
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The basis of the nature versus nurture debate dates back to 500 B.C., when Hippocrates
and Aristotle were both searching for a way to explain human behavior and animation of the
body. In 1874, Dr. Francis Galton wrote:
“[Nature and nurture] separates under two distinct heads the innumerable elements of
which personality is composed. Nature is all that a man brings with himself into the
world nature is every influence from without that affects him after birth.” (Lock, 2016,
p.14)
Not long after, Erasmus Darwin and his grandson Charles did in depth research on animal
evolution that was applied to human development. Erasmus noted “…that conditions… were not
predestined by nature, but predisposed… Heredity is the result of a malleable admixture of
nature and nurture.” Charles Darwin was the first documented researcher to suggest that the
environment can have an effect on genetics that can last through generations; this study is now
called “epigenetics,” which translates roughly to “around or inside of.”
Nature.
Many studies have been done that involve adopted twins because this seems to be the
most solid way to measure differences. Monozygotic twins exhibit what appear to be mirror-
image traits, and researchers rely on this as a secondary control to their control group. In
Minnesota in the 1970’s, child psychologist Sandra Scarr did a study on the comparative IQ’s
between adopted children and their adoptive parents and siblings using cohesive biological
families as controls. Scarr found a strong correlation between biological predisposal and
quantitative intelligence. (figure 1) Adoptive parent-child pairs had the fewest similarities, with
no genes shared and a twenty two percent correlation. Siblings that were not full blood relatives
had only slightly more similarity in IQ scores, with half-siblings appearing to be the segue to
much more profound similarities. Parent-child pairs and fraternal twins raised together shared
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fifty percent of their genes and had a forty-five to sixty-three percent correlation. Interestingly,
identical twins who were raised apart, sharing one hundred percent of the same genes, had the
highest correlation at seventy-eight percent. Because of this strong correlation, Scarr argued in
favor of heredity, stating that the characteristics of both parent and child determine the child’s
environment. Therefore, a child could never be truly affected by nurture, only nature.
(Goldhaber, 2012)
In her argument, Scarr noted that while development is a product of nature and nurture,
an individual’s experiences are actually driven by their genes. She believes that organisms could
change their surroundings, and that perceptions would cause one to experience the world
differently. She asserted that this predisposal was genetic and the basis of our development. She
set out to learn how nature and nurture works together to produce “variation[s] in development.”
(Scarr, 1983). In her adoption study, despite feeling that our development is genetically driven,
she did acknowledge that adopted children have higher IQ’s than their biological parents, and
that this was likely due to a more nurturing environment provided by the adoptive parents. She
still contradicted this by saying it was written in the adoptive parents’ genes to provide such an
environment. Additionally, Scarr found that twins raised separately still seemed to have the
same hobbies, interests, friend choices, academic achievements, and even food choices.
The strength of genetic predisposition was also illustrated in the extremely unethical and
sweeping study of twins and triplets done by the Louise Wise Agency in New York City. In this
study, researchers utilized this adoption agency to place single-child girls in families with whom
they intended to place separated twins in order to provide a control. In the most well-known
case, they placed each boy from a set of triplets with families of different socioeconomic
backgrounds to see what effect this would have on them. When the triplets were nineteen, they
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found out about the study and it affected them deeply. One of the boys was so affected by this
discovery, as well as their shared mental illnesses, that he ended his own life. It was further
discovered that there were many sets of twins, all with sisters of the same margin of age
difference in varied adoptive circumstances. The researcher who headed the study gave all
records to Yale to be sealed until 2066, long after his death. Because of this, and the study
head’s death, the actual breadth of the Louise Wise Agency’s twins’ study is unknown beyond
those twins that have already come forward.
Because these records are sealed, access to the actual data from researchers is
unobtainable. However, the remaining two triplets did recently make a documentary, featuring
interviews from people who have known them their entire lives, as well as clippings that show
the uncannily similar behaviors that were exhibited whenever they were recorded for interviews
or home videos of them simply being around each other. These clips show similarities between
these individuals who had never met, from their nearly identical face and body composition –
those close to them were taken aback that they all had the same very unique hands. The boys all
moved with the same patterns and displayed the same mannerisms – which is uncanny, since
they were raised separately. It is thought that these types of behavior are learned. In addition,
the boys all suffered through moderate to severe mental health problems from their teenage years
on and did tend to overindulge with drugs and alcohol – this was by no means congruent with
their family lives. (Read, 2018)
Nurture.
Study after study, we appear to be becoming less and less sure of genetics than we were
in 1990, when scientists began the human genome project. It is still easier, however, to define
heredity than it is to define environment: environment can include any factor from events, to
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people in our lives, to illness. Additionally, individuals’ perceptions can potentially make the
same exact factors wildly different between two people. This can cause a single situation
involving two people to be completely separate experiences that mean different things.
(Goldhaber, 2012)
One of the earliest known studies, though not an adoption or twins’ study, is the study of
“Little Albert” by psychologist John Watson in 1920. Watson showed that behavior can be
learned by taking a small child with no previous fears, and instilling fear in him. He did this by
letting Albert play with various animals, to show that he wasn’t afraid of them, and then building
an association between those animals and loud, scary noises. At the end, not only was Albert
afraid of the specific animals, but his fear had generalized to anything resembling them.
(Goldhaber, 2012)
While each of the boys from the Louise Wise triplets struggled with mental health
problems, they also were able to overcome them, at least for some time, due to the environments
in which they were raised. When they were a bit older, they lived together in an apartment and
discovered very quickly the differences between them. Their very different households, while all
very loving, were run in very different ways. Because of this, they all had very different
cleanliness standards – a major problem for anyone living in the same space. They also had very
dissimilar methods of dealing with stress and interacting with the world. Some years later they
opened a restaurant in Manhattan together. Again, their differences showed in clashing
management techniques and levels of commitment which eventually caused one of the triplets to
leave the business. Not long after, the middle twin committed suicide and the restaurant was
shut down.
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Analysis
A great many studies have been done to observe whether behavior and personality are
created by heredity or environment. While the scientists behind this research provide strong
arguments on the specific traits and circumstances they researched, twins’ studies have been
largely inconclusive overall and don’t shed much light on solid answers. Evidence exists in
support of both heredity and environmental factors, and the interplay between them. While
comparing a study in favor of nurture to a one in favor of nature, one will likely find that the
arguments on either side are based on the deficiency of the other, and therefore do not provide
the evidence needed to build their own cases to stand alone. In 1925, biopsychologist Leonard
Carmichael studied fish and amphibians for physical changes caused by environment, and was
able to apply his epigenetic findings to psychology:
“These changes develop as a result of the interplay of heredity and environmental factors,
so in order to have a ‘normal’ individual it is necessary to provide a very specific
environment in which development is to take place… the question of how to separate the
native from the acquired in the responses of man does not seem likely to be answered
because the question itself is unintelligible…. The effort to sever modifications due to
the environment from those which are innately given, is impossible, save at the level of
sterile, verbal abstraction.” (Goldhaber, 2012, 22-27)
Unfortunately, this is not well known because it wasn’t given much attention, but in
short, Dr. Carmichael understood that there is no situation in which an organism can exist
without environmental influence, because environment will always exist. He also felt that the
question of nature versus nurture is “unintelligible” because it was too simplistic; too much goes
into the development of behavior and personality to boil it down that way. Similarly to Dr.
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Carmichael, Neurons to Neighborhoods’ author Jack Shonkoff acknowledges that it is logically
impossible to separate nature from nurture:
“It is impossible to think of an organism that interacts with the environment without
considering the genotypical uniqueness of that individual…. It is time to reconceptualize
nature and nurture in a way that emphasizes their inseparability and complementarity, not
their distinctiveness: it is not nature versus nurture, it is rather nature through nurture.”
(Shonkoff, 2009, pp 40-41)
Despite the fact that the majority of twin’s studies were found to be inconclusive, most of
these researchers working on these projects do acknowledge that any behavioral and personality
trait is influenced by both heredity and environment to some degree. Certainly, each individual
will be predisposed to behaviors and personality traits, but the extent has not been researched.
Revisiting Scarr’s study, in her conclusion she totally disregards events and circumstances that
are out of any individual’s control, such as (but certainly not limited to) illness, large scale
events, and culture. Her study was one dimensional because it fails to take into account the
infinite and uncontrollable variables that occur in any individual’s life that drastically shape how
a person behaves. Shonkoff argues this point as well, saying that it is “potentially misleading to
try to finely distinguish the relative importance of nature and nurture in the course of human
development.” (Shonkoff, 2009, pp 41)
The triplets from the Louise Wise Agency also clearly show that a combination of factors
aid in our development. Though data relating to the study itself is currently unavailable, the
mannerisms and lives of these three individuals can easily be observed in the many different
media platforms on which they were featured. Their documentary also gives very clear
examples of characteristics that are influenced both by their genes, as well as their environment
and upbringing.
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There have also been extensive biological studies of brain development that show a
strong correlation between nature and nurture. Researchers have found that the integration of
nature and nurture is vital for brain growth and development, and thus that our experiences
influence our genetics and our genetics influence our experiences. We are programmed
genetically to expect certain experiences to occur as a catalyst to our development. Researchers
have proven this by depriving infants of patterned light and auditory stimulation and showing
that these can cause deficiencies in how a child behaves for the duration of their lives. In
addition, as individuals experience new things, their brains are stimulated to grow (Shonkoff,
2009, pp. 55).
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Conclusion
The sides of the nature versus nurture debate, if one can look past the argument itself,
complement one another. The biologists arguing in favor of nature fill the gaps where those in
favor of an environmental argument fail. Likewise, those arguing nurture fill gaps where
biologists fail to explain behaviors. Though many adoption studies are inconclusive, they are
only inconclusive in finding nature or nurture to be their answer; they do not sufficiently
consider that both play an equal or varying role in the development of behavior and personality.
Perhaps more compelling are the biological studies of genetics and the human brain in which
scientists have documented since the early twentieth century that genes and biological structure
of the brain as well as body are indeed influenced by the environment in which an organism
lives.
Researchers have also shown that new experiences trigger new brain growth, thus
showing that development may indeed be dependent on our life experiences, and what we see in
the world around us. Many early and modern biological studies also plainly show that the
environment plays a role on the biological, as well as behavioral characteristics of organisms –
which could be considered more profound than the effect of the environment on human behavior.
The twins in both Minnesota and New York City have shown us that there is much variation in
what may play a role in our development. Adoption studies, therefore, would illustrate the
varying degrees of interplay between nature and nurture.
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References
Goldhaber, D. (2012). The nature-nurture debates: Bridging the gap. Cambridge: Cambridge
University Press.
Lock, M.M., & Palsson, G. (2016). Can science resolve the nature-nurture debate? (pp. 13-41).
Cambridge, UH: Polity.
Read, B., Hughes-Hallett, G. (Producers), & Wardle, T. (Director). (2018). Three Identical
Strangers. [Motion Picture]. United States: CNN Films.
Scarr, S., McCartney, K. (1983). How People Make Their Own Environments: A Theory of
Genotype – Environment Effects. Child Development, Volume 54, No 2. Pp 424-435.
Shonkoff, J.P., Phillips, D.A. (2009). From neurons to neighborhoods: The science of early
child development. (pp. 39-51). Washington, D.C.: National Academy Press.
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Figures
Figure 1, Correlation between quantitative intelligence and biological family members
Figure 2, Scale of Psychological Perspectives on Nature versus Nurture
ResearchGate has not been able to resolve any citations for this publication.
Article
How is it possible that in more than one hundred years, the nature-nurture debate has not come to a satisfactory resolution? The problem, Dale Goldhaber argues, lies not with the proposed answers, but with the question itself. In The Nature-Nurture Debates, Goldhaber reviews the four major perspectives on the issue – behavior genetics, environment, evolutionary psychology, and developmental systems theory – and shows that the classic, reductionist strategies (behavior genetics and environmental approaches) are incapable of resolving the issue because they each offer a false perspective on the process of human development. It is only through a synthesis of the two holistic perspectives of evolutionary psychology and developmental systems theory that we will be able to understand the nature of human behavior.
Article
We propose a theory of development in which experience is directed by genotypes. Genotypic differences are proposed to affect phenotypic differences, both directly and through experience, via 3 kinds of genotype leads to environment effects: a passive kind, through environments provided by biologically related parents; an evocative kind, through responses elicited by individuals from others; and an active kind, through the selection of different environments by different people. The theory adapts the 3 kinds of genotype-environment correlations proposed by Plomin, DeFries, and Loehlin in a developmental model that is used to explain results from studies of deprivation, intervention, twins, and families.
Article
We propose a theory of development in which experience is directed by genotypes. Genotypic differences are proposed to affect phenotypic differences, both directly and through experience, via 3 kinds of genotype leads to environment effects: a passive kind, through environments provided by biologically related parents; an evocative kind, through responses elicited by individuals from others; and an active kind, through the selection of different environments by different people. The theory adapts the 3 kinds of genotype-environment correlations proposed by Plomin, DeFries, and Loehlin in a developmental model that is used to explain results from studies of deprivation, intervention, twins, and families.
Can science resolve the nature-nurture debate?
  • M M Lock
  • G Palsson
Lock, M.M., & Palsson, G. (2016). Can science resolve the nature-nurture debate? (pp. 13-41).