"As Steven Pinker notes in The Blank Slate, studies of identical twins raised apart have demonstrated that only a small portion of personality is due to socialization [and that] the rest is shaped by genetics" (50 Psychology Classics 93).
Discuss the reliability and possible flaws in experimental design of the study mentioned in the above quote in the context of Chapter Four (pg 72-83), The Similarities and Dissimilarities of Twins. Some things to include in your response are environmental factors and (early) development.
Emily Reinherz...ereinherz@aol.com
In Chapter Four, David Shenk highlights some aspects of twin studies that may show astounding results that seem to suggest that genetics truly controls most of the development of a person, while the environment plays a minimal role.
ReplyDeleteThe first is Early Shared Development. As Campbell explains in Chapter 51, animals have something called a critical period. A critical period is a limited developmental phase when certain behaviors are learned (Chapter 51). Especially during parental imprinting, the young learn basic behaviors and skills of the species. For humans, there may not be one specific critical period, but it's inarguable that the very early phases in our lives are a critical factor in our development. These twin studies fail to take account for the complex effects that having early shared development in the womb or very early after birth could have had on the remaining development of the child.
Another are environmental factors, what Shenk describes as "shared cultural circumstances". (81) Twin studies frequently disregard the countless shared cultural traits such as "same age, same sex, same ethnicity....shared (or very similar) social, economic, and cultural experiences." (81) These similarities subject the two twins to possibly very similar interactions with similar types of people. The fact that so many similarities given that they are twins can affect the growth and development of each twin in similar ways is infinite, and also failed to be accounted for in these studies.
Another flaw in the experimental design is the interpretation of the statistical results. As Shenk highlights, the results of these twins studies are often generalized and applied to the larger public. For example, the results on the study of the Jim twins claimed that "60 percent of intelligence comes preset from genes." (78-79) Statistics by definition is the "science of collecting and analyzing numerical data in large quantities." (http://statistics.berkeley.edu/~stark/SticiGui/Text/gloss.htm) Data is collected from a sample of a larger population, and is analyzed to pertain to that group. So these twin studies are specific to that time, place, and situtation. It's statistically inaccurate to apply to the large population when it is specific to identical twins in that particular setting.
Sara Yoojin Lee
(yoojin3795@hotmail.com)