Psychologists have debated for many years over whether nature or nurture plays a more important role in determining or causing individual differences in personality and behavior. Historically, most have supported the idea that nature is the larger factor in determining personality. Some psychologists even supported the idea of tabula rasa, or the blank slate, which states that humans acquire all or almost all of their behavioral traits from nurture (1).
Most modern psychological researchers now believe that both biological and environmental factors interact to form a child’s personality. To further examine the roles of nature and nurture scientists perform adoption and twin studies. Many psychological researchers have become convinced that at birth infants already have some personality characteristics, which they call temperament (1).
Temperament is defined as the part of the personality, which is genetically based. Temperament refers to stable, early appearing individual differences in behavioral tendencies that have a constitutional basis. For example, some children cry easily while others seem more relaxed; some babies are more active while others are more sedentary (2).
Temperament can be modified by environmental factors and maturation, which alter the ways a child’s personality is expressed (2). While this seems like a plausible explanation for how personality develops, there are still many unanswered questions. The first questions is, how is temperament created? Where do these personality characteristics come from?
The two designs used most frequently by geneticists to unravel genetic and environmental influences in infant and child temperament are twin studies and studies of adopted children. When studying twins, researchers compare monozygotic twins, who are genetically identical, with dizygotic twins who only share fifty percent of their genes. If temperament is based on genetics, these studies should show that the monozygotic twins are more similar than the dizygotic twins. They also examine differences between monozygotic twins, which can only be due to environmental factors (3).
Many twin studies have provided evidence that there is a strong genetic influence on infant personality. Studies have shown that monozygotic twins are more similar than dizygotic twins across many different temperament dimensions including emotionality, activity, shyness and sociability. Adoption studies have also found genetic influences across temperament (3).
The problem with these studies is that they are quantitative in nature, which means that they provide strong evidence that shows how important genes are in creating a child’s personality, but they do not identify specific genes responsible. Recent advances in molecular genetic techniques may mean that we will soon be able to identify some genes associated with personality. These traits are unlikely to be major genes, which segregate in a simple way. Most likely they are influenced by many genes, of small and varying effect size, which all make a small contribution to variability in a particular personality trait. These traits are referred to by molecular geneticists as quantitative trait loci or QTLs. Genes associated with attention deficit hyperactivity disorder, neuroticism, motor organization and negative emotionality have already been discovered (3).
Now that we have some idea where these traits come from, it is logical to wonder how malleable they are. How much influence do our genes have on the person we become? How much control do we have over our behavior? Steven Pinker talked about the difference between environmental, interactional and genetic traits, “Concrete behavioral traits that patently depend on content provided by the home or culture —which language one speaks, which religion one practices, which political party one supports— are not heritable at all. But traits that reflect the underlying talents and temperaments —how proficient with language a person is, how religious, how liberal or conservative— are partially heritable.” In other words, there is no way to predict your future from examining your genes. While you may be more likely to be interested in something, or exhibit a specific kind of behavior because of your genes, the actual path your life takes depends a lot on the environment and what options are available to you (1).
While it is true that our environment does play a large role in creating our personality, our underlying temperament is always a part of us. A study by Lahey et al., 2008 attempted to predict conduct problems in children aged 4-13 from measures of infant temperament and parenting in the first year of life. They surveyed 1863 families from 1986-2004 and had the caregiver’s complete measures of infant temperament and ratings of conduct problems later in childhood. They found that maternal rating of infant fussiness, activity level, predictability, and positive affect each predicted conduct problems during ages 4-13 years. The more difficult the child was in infancy, the more difficult the child was at ages 4-13 (4).
However, mothers who were rated as responsive to their child in the first year of life by the interviewer conducting the survey reported fewer conduct problems later in life. This was only true for children who were deemed “low fear”. “High fear” infants, who showed greater anxiety, did not show any change in temperament even with responsive mothers. This study shows that basic temperament may be malleable, with the influence of responsive care giving during a time when the brain is still developing (4).
There is support for this theory from the standpoint of molecular geneticists, who believe that it is a mistake to view genetic factors as unchangeable. Genes are dynamic in nature, and change over time in the quantity and quality of their effects. As much as it may go against mainstream belief, genes can change and develop over time. We do not know how consistent or inconsistent genetic traits are, and whether environmental influence could be the cause of this change (3).
The study by Lahey et al., and the evidence that genes are not immutable shows just how important and influential parenting can be. Temperament may set children on a dangerous path, but if these children are cared for by responsive parents who are attuned to their child’s needs, at risk children may be saved. Unfortunately, parenting can also influence children in the opposite way. If children are born with a temperament that shows no risk for precarious behavior, neglectful parents who create an insecure attachment may be responsible for that child developing atypical behavior such as a conduct disorder later in life (5).
Attachment theory provides a framework for understanding emotional reactions in infants by linking infant and caregiver in a paired set of complementary control systems. Attachment is an instinctual need to connect with other human beings. If the theories about temperament discussed in this paper are true, attachment may function as a regulator between infant temperament and outside environmental influences.
Attachment is a property of the dyadic relationship between infant and caregiver, which means that attachment security is not a reflection of the caregivers parenting skills or whether the child has an easygoing temperament. Attachment is a reflection of the goodness of fit between the parent’s temperament and the infant’s temperament. For example, a cautious infant who takes time to warm up to people could pose a challenge to caregivers who need immediate feedback in order to feel successful in their interaction with their baby (6).
If it is possible that good parenting can change a child’s basic temperament by helping them to regulate their emotion and behavioral urges in a positive way we need to work on educating parents about temperament and attachment. Maybe with more education parents can learn to help children who are exhibiting signs of a disordered temperament.
- Saudino, K. (2005). Behavioral Genetics and Child Temperament. Journal of Developmental Behavioral Pediatrics, 26, 214-223.