Heredity plays a big role in differences between individuals but not in differences among groups. Environmental factors play important roles in creating differences between individuals and groups." Zimbardo (1997, p446)

In recent years the issue of the origin of intelligence has caused much debate from those studying intelligence. As Zimbardo states, "both heredity and environment affect intelligence." While the influences of heredity and the environment on individuals and groups must be acknowledged, the question that remains is: are humans intelligent in different degrees because of their heredity, their environment or an interaction between the two"

There have been many studies conducted to show that heredity is a significant factor in determining intelligence. While studies conducted by early psychologists, such as Sir Francis Galton, show that intelligence runs in families, these studies to not necessarily prove this because of genetic reasons. While family members share similar genetic material, they also...