The Role of Nature and Nurture in Prenatal Development
The role of heredity and environment in the human development (the ‘nature versus nurture debate’) has been a subject of serious scientific discussion. Scientists used to consider either genetics (nature) or environment (nurture) as a determiner of individual differences. Currently, developmental psychologists recognize that they both interact to shape human development. Several empirical studies provide convincing evidence for the support of this position. Firstly, a number of studies of twins shows a relationship between genes and environmental factors in the development of schizophrenia. Additionally, there are some studies that provide evidence for the impact of prenatal experiences on baby’s preferences after birth. Finally, there also exists proof that improper environmental stimuli affect physical, cognitive and emotional well-being of the fetus.
To begin with, nature-nurture interaction in human development becomes evident based on the number of studies of schizophrenia. On one hand, genes influence not only physical, but also cognitive and emotional development. For instance, many diseases including schizophrenia are thought to be genetically transmitted. On the other hand, the study by Gottesman & Hanson (2005) supports that the development of hereditary disorder results from the interaction between a genetically determined predisposition and various environmental factors. The study tested monozygotic twins with inherited risk of schizophrenia. It showed clear absence of 100% concordance between twins despite having initially identical genomes. Thus, it has been proven that schizophrenia is not an inherited disorder. It is rather based on the person’s proneness to it. Gottesman & Hanson (2005) drew the conclusion that a genotype determines a range of possible responses to different types of environmental stimuli. Therefore, this study proves that genes produce a mere predisposition to developing a disease, while the type and strength of environmental factors determine the outcome.
Similarly, intelligence and personality are influenced by the interaction between multiple genes and the environment. Developmental psychologists agree that environmental factors play a critical role in realizing human hereditary potential. Additionally, there is proof in favor of the existence of ‘immediate early genes’ responsible for learning and memory. They are activated only by certain kinds of environmental stimuli. There are certain sensitive periods when fetus is particularly susceptible to these stimuli. For example, research shows that at age of 28 weeks the fetus is already capable of learning. In the study, thirty-three women read aloud a passage from Dr. Seuss’s story The Cat in the Hat daily during the last 1,5 months of pregnancy (DeCasper &Spence, 1987). The newborns were later tested to determine which passage was more reinforcing: the previously recited or a new one. As a result, infants preferred the sound of that particular story after their birth. The study suggests that prenatal auditory experiences have impact on postnatal preferences. Likewise, it has been proven that the mother’s diet during pregnancy has effect on the child’s flavor preferences (Mennella et al. 2001). These studies reinforce the opinion that environment plays a great role in the prenatal development.
Finally, there has been extensive empirical research on the effects of negative prenatal experiences on the person’s later development. Negative environmental stimuli ( eratogens) such as malnutrition, mother’s illness, emotional stress, virus, and abuse of drugs, chemicals, alcohol, and nicotine have been proven to hinder proper development. For instance, Gluckman & Hanson (2005) examined the correlation between maternal stress and postnatal outcomes. The study shows that the mother’s emotional state affects the baby. Thus, women who are anxious and tense during the last months of pregnancy are more likely to have irritable infants who sleep and eat poorly. The reason lies in adaptation of the fetus’s autonomic nervous system to the chemical changes produced by the mother’s emotional state. According to the study, the fetus receives biological signals (such as high concentration of hormone cortisol, which is released during stress) via placenta and ‘predicts’ the future environment. As a result, people who received improper biological signals in prenatal period tend to have emotional and behavioral struggles after birth. Additionally, they are disposed to the greater risk of various chronic diseases later in life. Furthermore, heavy drinking and use of drugs during pregnancy is associated with negative fetal outcomes such as facial disproportions, mental retardation, behavior and emotional problems, slow reaction, and low birth weight. These results provide evidence that baby’s health is determined not only by heredity, but by prenatal experiences as well.
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Currently scientist agree that genetics and environment are greatly intertwined. Genetic inheritance determines the person’s development potential. However, its realization depends on the interactions between genes and environment which takes place long before birth. Initially, the fetus’ environment is limited to the mother’s womb. Therefore, there is little opportunity to discover all the influences of external factors in the pre-birth period. Although, several studies prove the existence of interaction between nature and nurture. One study focuses on the influence of environment on the development of schizophrenia in monozygotic twins. Other research shows connections between prenatal experiences and postnatal preferences. The third one has exhibited a deep understanding of effects of developmental teratogenes (mother’s stress and anxiety levels) on prenatal development and postnatal health of the fetus. Thus, interaction between genetic and environmental factors becomes undisputable in shaping human development.