Twin Study

1. Methods and results In this study, Thomas Bouchard and David Lykken, along with their associates at the University of Minnesota, were attempting to prove if nature is the determining factor in a person’s personality or if it really is the nurturing environment. They wanted to see if twins who were separated at birth and raised in different environments would still have similar personalities, which support the theory that a person’s genes has more impact on a person’s character than the environment. In order to study their hypothesis, Bouchard and Lykken located identical twins that were separated by birth due to adoption and spent a week conducting various tests; four personality trait scales, three aptitude and occupational interest inventories as well as two intelligence tests. Through these examples and other tests, Bouchard and Lykken complied copious amounts of data on the twins. The results of the study favored the nature theory in that an overwhelming percentage of the twins had similar results and personalities despite having never grown up together.

2. Analysis It does appear that this study’s results proved whether nature or nurture is important in the development of a person’s personality. At least this seems to have been proven in the instance of identical twins. However, there was no mention of research done involving twins raised in the same household to compare to this study’s results. I do believe that the experiment was done properly in coordination with the scientific method but that various psychologists should have replicated the experiment numerous times over time.

3. Criticisms As with all published findings, there were those who argued against the claims made by Bouchard and Lykken. Some members of the psychological community believed that what was published was incomplete and therefore cannot be regarded as true unless all the results are made available. In addition, some critics claim that Bouchard and Lykken are guilty of the “equal environment assumption” which is that identical and fraternal twins are treated equally and raised in identical environments. This assumption is untrue as parents treat fraternal twins, two separately fertilized eggs versus one that split, as complete different individuals like any other siblings born at separate times. Other psychologists agreed with Bouchard and Lykken and even completed their own studies about genetic influence on people’s personalities as well as choices, and many of these studies had similar results, thus further supporting Bouchard and Lykken.
4. Conclusion The overall meaning of this study is that the debate of nature versus nurture continues in the field of psychology and it is more a matter of interpretation of data and personal belief rather than something set in stone. Psychologists continue to follow the study’s example by investigating the impact of genetics on a person’s choices and actions such as whom they fall in love with and other complexities of human behavior. This study changed psychology in that there was a new element, genes, for psychologists to analyze for explanations about the human psyche.