One of the core concepts of psychology is understanding how and why we became who we are. There are two main stances on this topic, nature and nurture. Nature is the idea that we receive our features from our biology and we have little control over physical and behavioral traits. Nurture is the idea that we are molded by our environment such as parenting and schooling and have a larger degree of control over our traits.
Some of the strongest support for nature is the examination of monozygotic (fraternal) twins reared in separate environments. Due to their circumstances, their genetic makeup is the same while their environments are vastly different. Thomas Bouchard, David Lykken and their colleagues analyzed such a study in Minnesota. The study involved finding sets of twins raised together and apart and administering a range of physiological, personality, intelligence, social attitude and psychological tests.
What they found was an extremely strong correlation between the twins; scores regardless of whether they were raised together or apart.The correlation of the similarity of the two scores were also very strong. The scores were extremely strong for physiological and intelligence tests at .5 to .8 while the personality and psychological were moderately strong at around .5 and the social attitude score were relatively weak at .3 to .5. Also, the similarity of the various scores between twins reared together and apart is extremely strong ranging from .8 to 1.2.
However, opponents of this research claim that this ignores the differences of environment in twins raised together thus skewing the comparisons correlations score higher. Also, some feel that the findings are invalid due to only some of the findings being published. They claim that the researchers only published the scores that supported their claim.
Another proponent of the nature argument is Gazzaniga’s analysis on split brain cases. He claimed that parts of the brain are naturally better at certain tasks due to their structure and biology. He tested patients who had the connection between their left and right brain cut, their corpus callosum, on various tactile, vocal, auditory and visual tasks. Due to the left side of the brain controlling the right and the right controlling the left he was able to isolate tasks to one side of the body and identify which performed better. He found that vocal and tactile skills were accomplished better with the left side of the brain while the right side performed auditory and visual task better.
This predisposition for tasks to one hemisphere of the brain has been presented as an argument for genetic disposition to these various tasks. Opponents of these ideas argue that Gazzaniga’s treatment of the hemispheres as separate entities is highly flawed. They claim that the brain is meant to work with both sides on all tasks and each side merely contributes different information to the problem at hand. This would mean that the sides of the brain are not necessarily separate in development and genetic disposition.
Behaviorist provide many of the arguments for the nurture side of the debate as they spend much of their time analyzing learning in humans. Pavlov’s research on classical conditioning is often cited as an example of changes in natural behavior. He found that if he took a stimuli a dog would not normally respond to, such as a bell, and rang it when feeding the dogs he would like the increase in salivation from the food with the sound of bell. After sufficient repetitions, he could ring the bell and cause the dogs to salivate, notably an involuntary response.
These findings have been transferred over to humans with high levels of success. One such instance is linking the involuntary action of pupil dilation to the ringing of a bell causing an individual to dilate their pupils when the bell is rung even in a well lit room. The significance of this is that one is ne would be able to override their natural biology with conditioning.
Another important figure in the behaviorist front is B. F. Skinner. His research on various aspects of human behavior gave a new explanation for traits previously thought to be genetic. One such study was his examination of superstitions and transference to pigeons. He placed a timer on a food dispenser that fed a hungry pigeon. The pigeons random behavior was reinforced and all of them developed separate superstitions as to how to make more food arrive. Many humanists argue that his ideas fail to touch upon the greater concepts that lie behind the simplicity of everyday behavior.
These experiments are in no way a complete list however they sum up some of the main arguments for and against nature and nurture. Hopefully however, future studies will open doors to new possibilities, perspectives and support for each side.
Works Cited
Bouchard, T., Lykken, D., McGue, M., Segal, N., & Tellegen, A. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250, 223-229.
Gazzaniga, M. S. (1967). The split brain in man. Scientific American, 217(2), 24-29.
Pavlov, I. P. (1927). Conditioned reflexes. London: Oxford University Press
Skinner, B. F. (1948). Superstition in the pigeon. Journal of Experimental Psychology, 38, 168-172.