2.  Twin Studies: › Intelligence scores of identical twins raised together are virtually the same (as if the same person took the IQ test twice) › Fraternal twins had less similar scores than identical twins › Identical twins raised separately and identical twins raised together but treated differently also have very similar IQ scores › Brain scans have shown that identical twins have very similar grey matter volume and are virtually the same in areas of verbal and spatial intelligence

3.  Researchers have also compared families with adopted children and families with biological children  In childhood, the IQ scores of adopted children correlate “modestly” with that of their adopted parents  However, over time, the similarities between adopted children and their parents become less and less while similarity with their biological parents increase  This suggests that genetic influence increases over the life span while environmental influence decreases

4.  There is evidence to suggest that environment also has an effect on intelligence.  With regard to genetic make-up, fraternal twins are no more alike than non-twin siblings  However they score more similarly on IQ tests than non-twin siblings  Researchers believe this is because they are treated more the same since they are of the same age

5.  Researchers have done a number of studies in order to determine the effects of environment on intelligence  When studying children who have been moved from orphanages to more stimulating environments, their IQ tends to increase.  This suggests that when children are given more love and attention in a stimulating family environment, their IQ scores will increase

6.  Numerous studies have shown that African- Americans tend to score 15 pts lower on IQ tests. WHY?  In the first half of the 20 th C, some researchers held the controversial view that this was due to genetics.  However, the last 30 yrs of research on IQ differences has shown that it is mainly environmental, not genetic factors that are responsible for this  IQ tests contain questions that reflect the values of white, middle-class western society  As a result, minority groups are automatically disadvantaged when taking these tests