Sunday, February 6, 2011

Behavior Genetics and the 21st Century Parent : How Genes, Parenting and Environment Shape the Psychological Development of Your Child

The question of nature versus nurture has long been the object of debate in developmental psychology. Are the behavior and the character of a child mostly created by parenting, schooling and other environmental factors or are they the result of inheritance and genetic predisposition? Are children born as blank slates molded by the interactions with the people and experiences they encounter as they grow up (nurture) or do they come in the world with a set of pre-existing biological and psychological traits, characteristics and behaviors (nature)?

Behavior genetics and the study of twins

The question of genetic influences on personality and behavior is one that many researchers of the past century and of today have been attempting to answer. The nature /nurture debate is a very ancient one, but modern advances in genetics have brought this issue to the attention of the scientific community and psychologists with a renewed thrust. There is even a specific branch of psychology, called behavior genetics, devoted to the study of the development of personality in terms of genetic factors. One of the ways in which research in this field has been carried out has been by studying population samples with the potential to reveal possible hereditary behavioral traits, such as, for example, the study of the traits of identical twins, fraternal twins and adopted children, raised in the same environment or raised apart.

At the Minnesota Center for Twin and Adoption Research, founded by Thomas Bouchard in 1976, hundreds of twins have been tested and studied over the years in a series of longitudinal studies, revealing that, indeed, there seems to be many character and personality traits that could be substantially explained by genetic factors. The Minnesota Study of Twins Raised Apart (MISTRA) has been particular useful for observing the similarities and differences in personality and behavior in adults that have identical or very similar DNA, but were separated at birth or soon after birth. For several of the traits measured and tested throughout the years at the center, a substantial amount of the variation was found to be due to heredity, leaving just over a half determined by the influence of parents, home environment and other experiences in life combined. These results would seem to suggest that many personality traits are indeed genetic in origin and that in some instances genes are at least as influential as parenting in the determination of many a child’s character and behavioral traits, seemingly contradicting the most widely held ideas in modern psychology, where it is believed that it is the quality of parenting that is predominant in shaping a child’s psyche. Twin studies not only show personality traits such as intelligence, openness , agreeableness, conscientiousness and extraversion to be strongly genetically determined, but also qualities such as sense of well-being and zest for life, alienation, vulnerability, resistance to stress, fearfulness and risk-seeking. Even social attitudes such as religiousness and work ethics seemed to be strongly determined by genetic factors and not just by parental upbringing, as may have been previously through.

Behavior genetics and molecular gene research

If the emphasis of the 20th century was on traditional psychological research, comparing the lives of twins through the use of life histories and questionnaires, in the new millennium we are seeing the study of behavior genetics looking directly at the DNA itself. With new and exciting advances in genetics, researchers are now busy trying to isolate the genes that are responsible for various personality traits , attempting to create a human genome relative to personality. This research, which is in many ways still in its infancy, seems to show that it is not one gene but combinations of genes that may be responsible for various aspects of an individual’s psychological makeup.

The directly genetic approach has been most successful to date in identifying potential locations for genes associated with major mental illnesses such as schizophrenia and bipolar disorder. But the search for genes associated with characteristics such as sexual preference and basic personality traits has not been very fruitful as yet. Molecular geneticists have found some significant links between genes and behaviors associated with inherited conditions, such as the mental retardation associated with Down's syndrome, which is a genetic disorder caused by the presence of an extra chromosome. We also know the effects for a number of single-gene disorders that result in mental retardation, including phenylketonuria (PKU), a treatable metabolic disorder for which all newborns in the United States are tested. But the specific gene and gene cluster contribution to most aspects of behavior and personality, if present, still remain undiscovered. In a nutshell, this research is still in its early days , the genetic mapping of personality traits is still far away, aside from instances where the behaviors are directly linked to disorders that have a definite biological cause, such as most bipolar disorders, schizophrenia and Down syndrome.

But is it all about the genes?

However, while research in behavior genetics seems to explain at least in part many traits of personality and behavior, with molecular genetics beginning the job of finding the exact genes and gene clusters responsible for those inherited traits and behaviors, it is important to note that genetics only shows a propensity towards those traits. A genetic propensity towards schizophrenia or alcoholism does not, in and by itself, automatically predetermine a child or an individual to develop those traits in later life: environmental factors still play a major role. That is, a child who has a genetic propensity to developing mental illness, but is raised in a caring and supportive environment may never experience the activation of a mental disorder. But a child with that hereditary predisposition, raised in a hostile environment, may develop mental illness more easily than a child without that propensity. Interestingly research shows that while standard parenting does not seem to be more determining than genes in the development of certain aspect of a child’s psyche, an abusive childhood has negative consequences that far out way any hereditary factors. Providing a child with an optimal environment for growth is still of pivotal importance regardless of any discoveries in genetics. It could be argued that this is just common sense, but its nice to see science confirm these intuitive facts.

On the other hand a child that is genetically predisposed to being introverted, may become more or less shy depending on the kind of nurturing he or she receives, but will probably never become a full on extrovert : it’s just not in his or her genetic makeup. So behavior genetics, assuming that we will eventually manage to understanding exactly which parts of our personalities are mostly hereditary and which are not, could definitely be seen as helpful in showing us the potential both positive and negative displayed by our children. It could be that at some point in the not too distant future, that it may be possible to prevent the manifestation of undesirable hereditary factors such as mental illness or addictions early in a child’s life, and to support the development of the innate characteristics, talents and gifts, by creating an optimal environment, matched to the child’s genetic needs.

Research also shows that the environment beyond the quality of parental care, such as the influence of school, education and peers, counts quite considerably in the development of personality and behavior. That is research supports the idea that the school your child goes to, the education and opportunities he or she receives and the friends and people he or she spends time with, are important components in the determining who your little one will grow up to be. Again, common sense, but useful to see these facts confirmed.

The fact that parenting and other environmental factors are still significant regardless of genetic predisposition in creating the developing personality and mental health of our children, is in many ways a relief. A purely genetic view of personality development could be worryingly problematic. If it were found for example that intelligence was purely hereditary and the genes responsible for intelligence were all found, would a DNA test discourage us from educating our child? Selective breeding, eugenics and genetically based discrimination are just some of the issues that we could encounter in a world where all gene influences are mapped and their effects explained in 100% deterministic terms. But fortunately all studies in this field still show that the environment is just as important as genes in creating who we are. And a more recent branch in genetic research confirms the importance of environment in an even more fundamental way.

Epigenetics and the biology of belief

Contemporary discoveries show that the DNA is not set in stone. A branch of genetic research called epigenetics shows that a person’s genetic makeup is not as fixed as it was once thought, with the genes themselves being influenced and shaped by environment. The active gene components of the DNA can be modified by lifestyle choices and experiences. Although the composition of the DNA itself is not fundamentally altered by experience, the genes, the building blocks of the DNA, can be switched on or off by environmental factors i.e. by the parenting, education and the circumstances and experiences encountered in life. So, for example, it is possible for identical twins that start in life with identical DNA, to end up with different active genes in their later years, due to having lived very different lives. So even if certain traits may be determined by genes, those genes can be switched on or off by non-biological factors. Interestingly enough, it also seems that the experiences that cause the genes to switch on or off, can cause alterations in active DNA that can be passed down to ones offspring. That is, if our grandparents had experiences that caused certain genes to switch off, we can inherit that switched-off gene and, as a result display similar traits that we would have displayed if we had gone through those experiences ourselves. This gives the concepts of ancestral karma and taking responsibility for the world we are leaving to the children of our children to a whole different level! Genes and the environment are not only not mutually exclusive, but inextricably intertwined, affecting one another beyond just an individual’s lifetime, with effects that stretch across generations and time.
And if things were not complicated enough, other discoveries in cellular biology seem to point to the fact that life is not controlled by the genes but that the DNA is controlled by signals outside the cell membrane.

Internationally recognized cellular biologist Bruce Lipton, in his book The Biology of Belief, goes as far as saying that these signals from outside the membrane which can modify the genetic structure include also the energetic messages emanating from our positive and negative thoughts, suggesting the idea that we can change our bodies by retraining our thinking. Observations of this kind certainly would seem to also point even further away from genetic determinism, leaving much room to the idea that we can determine our own lives and the lives of our children, beyond our genetic heritage.


So, is nature or nurture more influential in generating the personality, character and behavior of your children? The answer is obviously that children are a bit of both: a unique blend of their parents’ genes, born into this world with an innate set of personality traits as well as the product of the caring and stimulation they receive (or don’t receive) in their developing years. The question is therefore not really whether genes or parenting are responsible for the psychological health of your child, but which of these aspects contributes the most and in what way. It has always been known that a good seed is a good start, but that even a good seed can’t do much without fertile soil. Our children have within them the unique signatures of greatness as well as their own little bundle of genetic challenges passed onto them by their parents (and as it turns out, by their ancestors too). But this does not mean in any way that they will automatically actualize that greatness, nor that they are doomed by a curse of bad genes. Every area of research we have looked at seems to show that with appropriate care and attention, we can maximize our children’s potential for greatness and minimize the negative aspects of inherited traits. As usual, good parenting, aimed at nurturing the true essence of the child, education that is supportive of a child’s unique spirit, and a positive and healthy environment of both school and peers, go a long way in creating the soil in which our most precious seed, our children, can thrive.

©2008 Katie Gallanti. All rights reserved. This article was first published in Inspired Parenting Magazine in the fall of 2008.

References and further reading

Bouchard T.J. et al. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250, 223-228.
Bouchard T.J. (1994). Genes, environment and personality. Science, 264, 1700-01.
Engler, B. (1999). Personality Theories. Hougton Mifflin.
Hobert, O. (2003). Introduction: Behavior Genetics- The third century. Journal of Neurobiology, 54, 1-3
Lang K.L. & Livesley (1996). Hereditability of the big five personality traits and their facets: A twin study. Journal of Personality, 64, 577-597.
Bruce H. Lipton, Ph.D. (1995). The Biology of Belief: Unleashing the Power of Consciousness, Matter and Miracles. Hay House.
Horizon. BBC Documentary. The Ghost in the Genes.
The Human Genome Project: Behavior Genetics
Plomin R. at Al. (2001) Behavior Genetics. New York: Worths Publishers.

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