February 9th, 1979 gave the world of psychology a breakthrough when a set of identical twins reunited for the first time in thirty-nine years. James Arthur and James Springer were identical twins separated at three weeks old and adopted by two different families. Despite being raised in different environments for nearly four decades, both gentlemen shared stunning similarities including marrying and divorcing a woman named Linda; and remarrying another named Betty. They both named their sons the same (James Alan and James Allen). They named their childhood dog Toy, worked in law enforcement, enjoyed carpentry and vacationed at the same resort. Their favorite color is blue. Both loved Pepsi and light beer and smoked the same brand of cigars and drove similar cars (Bouchard, et al., 1990).
This remarkable coincidence spurred on further research to bridge the nature-nurture divide. This ongoing debate has tried over the years to determine which variable determines an individual’s personality and behavior. Although, each side believes one variable has a greater influence than the other, contemporary psychologists are finding common ground on the contributions of both variables. I’m in favor of the view that both are useful. However, the question is, to which extent does this happen?
The nature-nurture debate has plagued researchers and psychologists for decades. I believe the reason for this debate is because, knowledge of which theory exerts greater influence will make it possible to treat a problem rightly. For instance, if genetics plays a greater role, a person’s behavior or personality may be modified through some biological means; likewise, if it is the environment, then the environment will be modified effectively. But in the instance that this divide cannot be bridged due to the equally important roles that both play, Psychologists may experience complications in treating their patients and may have to do due diligence in providing the right combinations of treatment centered on both theories.
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Deciphering these two theories has a wider application across diverse areas of life. For instance, in criminology, the question arises as to which variable is to blame for an individual’s action. A child born to a criminal parent grows up to become one; who is to blame, heredity or environment? Did the child learn the criminal behavior from witnessing a parent’s behavior, did unexpected circumstances occur during the child’s life that triggered a reaction of survival or is the child predisposed to the behavior by means of aggressive traits inherited from a parent? In the medical field, it helps to explain whether a patient’s genetic predisposition has a greater likelihood to cause a chronic illness than the environment. Intelligence, academics, talents, sports, skills and abilities are some of the areas that could gain insight from nature-nurture theories.
On the nature side, proponents have supported claims with studies that show heredity or genetics greatly influencing Intelligence. Bouchard, et al (1990), conducted a study to examine the similarities in Intelligence Quotient (IQ) of monozygotic (identical) and dizygotic (fraternal) twins. James Lewis and James Springer together with over 100 subjects were studied. The study revealed that similarities were about 70%. The study further showed that monozygotic twins reared together shared a lot of similarities which was no different from dizygotic twins reared apart indicating that genetics played a greater role in spite of their environments. Several recent studies also support this claim…
On the nurture divide, proponents argue that the environment contributes significantly to IQ. Turkheimer et al (2003) reported significant variations between genetics and environment in a study that analyzed the IQ of 7 year old twins using the Wechsler Intelligence Scale for Children (WISC). The study reported that a substantial proportion of the subjects were raised in families with low socio-economic status (close or below poverty line). Results showed that the two variables varied nonlinearly with socioeconomic status (SES). Analysis indicated that 60% of the variance in IQ was the result of the environment, and that the contribution of genes was nearly nonexistent.
Conversely, the opposite was revealed for subjects raised in affluent families. Several prior and recent studies have supported this claims. In a study by Kendler, et al (2015) of 436 Swedish male-male sibships, one member was either reared by biological or adoptive parent(s). their IQs was measured between ages 18-20 and compared against Parental (both biological and adoptive) educational level. Results were further replicated in an independent sample of male-male half sibships (n = 2,341). Analysis showed that subjects placed in highly educated adoptive families performed better than their siblings reared in the original families. Likewise, those adopted to less educated families than the biological family performed worse than their counterparts reared by biological parents; indicating that rearing environment affects cognitive abilities or IQ in late adolescence.
Additionally, results between subjects who shared environment and genes with biological parents with average IQ were about the same as those adopted by average IQ families who only shared an environment with the subjects; indicating that genes did not play any major role in the cognitive abilities of the adopted siblings. Analysts explain that several factors within an environment affects the cognitive abilities of children. For instance, in high SES families, parents are likely to engage children in intellectual discussions, provide learning materials (audio and visuals), take children on trips and vacation to educational sites and afford quality education that increase the knowledge of their children as compared to those who are biologically intelligent yet lack these opportunities.
Nature-nature theories have contributed immensely in explaining behavior on each side, and both are equally important. In my observation and analysis, I conclude that behavior is a result of both genetic and environmental factors. An individual never exists independent of genes thus a person’s personality cannot be solely determined by the environment. Similarly, the same is true about the environment; it is the cradle that holds an individual’s experiences. Larmack () proposed a term known as genetic nurture which postulates a combination of genes and environment.
Snibbe (2004) published a paper titled “Taking the ‘vs.’ out of nature vs. nurture”. He reported the outcome of a conference (which is first formal meeting) between cultural and evolutionary psychologists who exchanged findings and philosophies on this subject. He described the conference as “white flags of truce flew over the nature vs. nurture wars” (Snibbe, 2004). To answer the question; I assert that the extent to which one has a greater influence may depend on other intervening variables which make human personalities unique. Hence, a thorough analysis of behavior, personality or intelligence should utilize a case-by-case approach.
In conclusion, the remarkable coincidence of identical twins James Arthur and James Springer has shed light on the nature-nurture debate. The ongoing debate has been about which variable plays a significant role in behavior or intelligence. Prior and recent studies on both sides have presented support to each proponent. Contemporary psychologists advocate a middle ground to bridge the sides. In my opinion, both genes and environment contribute to behavior or intelligence. None is independent of the other hence, the extent to which one significantly influences the other is based on other intervening variables. A case-by-case approach should be utilized in a thorough analysis of behavior.
