Enviromental Effects on Behavior

Enviromental Effects on Behavior
The level of genetic influences on a person?s behavior is called the heritability of the behavior. Based on previous research intelligence as measured by IQ scores is thought to be attributed mostly to genetic influences. However it has been suggested by several researchers that genetic influences are moderated by the environment a person grows up in. There have been several studies that have explored the effects of environmental effects on heritability. However these studies have been methodologically limited because they did not have a large enough sample size or they did not measure the zygosity of the twins they use. Other studies measured change in heritability across different birth cohorts. However these studies might have been influenced by the different circumstances that might have been present during the different time periods these people lived in.
Some general reasons why there is a lack of evidence for the moderating effects of the environment is that the studies conducted so far did not use measures environmental variables to detect differences in the environment, Another possibility is that the environment of different subjects tested may not have been the same since those with higher intelligence might have altered their environments so they would have been more conducive to developing intelligence.

In this study a total of 20,745 high school students were assessed on their intelligence and on environmental influences. Included in this sample were 3139 sibling pairs which consisted of twins, siblings, half siblings or unrelated but raised together. The twins where then grouped into monozygotic and dizygotic based on their appearance and genetic testing. Of these students only those included in the largest group of Blacks and Whites where included in this study. The students where then asked to complete a questionnaire about the educational level of their parents. They were ranked on a numerical scale of 0 for the least education and 6 for the most. The students then took a test of their verbal IQ.

The results of this experiment indicate that the correlation of intelligence increases as the pairs are more closely related. As for the effects of the environment on genetics it has been found that the environment moderating the heritability of the students intelligence decreased as the education level of the parents decreased. Students that came from a background where their parents had less of an education felt the negative effects of their environment more then students whose parents were more educated. The heritability of IQ increased from 25% in homes where parents had low education to 75% in homes where the parents? level of education was higher.

This study while more detailed then most other studies did have some limitations. The IQ measured in this study was only the verbal IQ but the nonverbal IQ was not measured so this study might not make completely accurate conclusions about g. This study was also restricted to white and black ethnic groups so it is not conclusive about these effects on other groups. However this study is still judged to show the effects of genetics and environment quite accurately.

Enviromental Effects on Behavior 7.8 of 10 on the basis of 3366 Review.