The nature versus nurture controversy has been a long-standing debate between scientists, behavioral analysts, psychologists and psychiatrists. The controversy essentially boils down to the question of which influences or shapes us most: is it the genes that we inherited from our parents or the environment in which we grow up in? This question can be further expanded to “For a particular trait, which has the most impact; hereditary predisposition or environmental effects on development?”
Scientists have long held that we are only as good as our genes allow us to be. The traits we inherit from our parents define what traits we exhibit during our life. Others however argue that although genes give us the predisposition for a trait, without the environment with which that trait can express itself, that trait would have reduced chances of expression. The questions in this debate however must always be framed not as a general nature versus nurture clause but a specific query regarding the effects of both on a specific trait. Another aspect worth considering is that although nature is generally defined as the set of alleles an individual obtains from its parents, nurture or environment is much harder to define. Nurture or environment may contain several facets: the physical environment, the developmental one (rearing, academics, etc.), and the social environment. Thus, the debate itself cannot be resolved in one broad sweep but can only be tackled using specific cases for particular traits and situations.
Several studies have been framed to provide an answer to questions under the framework of this controversy. Most often cited are twin studies. Twin studies follow the development and expression of traits in identical and fraternal twins that have been reared in different environments. Since identical twins (or mozygotic twins) essentially come from the same fertilized egg, they have identical genomes (unless mutations arose during development), thus negating “nature” differences and allowing scientists to focus on the “nurture” aspects of the study. Advances in molecular genetics have also enhanced studies done under the auspices of the nature versus nurture debate, being able not just to ascertain the presence of a gene but to notice activation and changes throughout development.
Language aptitude, I.Q., attitude, mental illness and emotional predisposition have all been delved into using twin studies. It was found that there was no significant difference in language aptitude between twins raised in different families. Another study focused on the correlation of verbal ability of parents who had both birth and adoptive children when compared to each; and adopted children when compared to their birth and adoptive parents. It was determined that correlation of verbal activity was lowest between adopted children and adoptive parents. An unrelated anatomical study by Paul Thompson on identical and fraternal twins showed that I.Q. was determined to be more inherited than influenced by environmental factors. Studies on schizophrenia have shown a higher effect of nature over nurture. Nurture on the other hand plays a larger role in emotional development and attitude. In particular, substance use has been shown to be influenced largely by nurture aspects.
These studies are in essence simply structured glimpses on the real relationship of nature and nurture in aspects of human development. Most of these aspects are triggered by an amalgam of factors, with no 1:1 or even 1:10 correlation is observed between them. In addition, the measures for these aspects (intelligence, emotions and adaptability) are tenuous at best, they are highly amorphous and are defined more or less by the statistics used. It is also important to note that studies on nature and nurture are often also influenced by prevailing opinion, both public and academic. Thus, interpretations as well as studies conducted may yield different results.
The debate between nature versus nurture can best be resolved with the following maxim. Nature outlines the maximum potential of an individual and the environment determines how much of, or the degree that that potential may be realized. A frog cannot flap wings that it does not have.