Evidence for the genetic contribution to individual intelligence is (1) family studies indicate that intelligence occurs in families, (2) studies of twins illustrate a greater connection between identical twins in terms of IQ than between non-identical or fraternal twins. This is true even when identical twins raised apart are contrasted with fraternal twins raised together. (3) Adoption studies suggest that adopted children are marginally comparable to their biological parents in terms of intelligence. The emphasis here is on differences and similarities and the extent to which they are created by genetic effects, as opposed to environmental influences. Since the components of a family are genetically similar, the traits found within that family can be reasonably designated as having a genetic basis or reasonably significant genetic influence. Although there are no known genes that have been conclusively linked to intelligence, and it is likely that a combination of genetic factors are at work here, it is widely accepted that "g » (or general intelligence) is hereditary. It's not the same thing as intelligence quotient, but it's roughly comparable. Many studies have discovered this, and observations also support it. Identical twins have exactly the same genes, while non-identical twins share about half of their genes, just like siblings as a whole. Another aspect of twins that makes them an ideal choice for research is that they are raised in nearly the same environment. If a certain element is the same in identical twins, but not in fraternal twins, then there is a good chance that these are the genes that work on that characteristic. Twin studies show the following: First-degree relatives are likely to have a "g" correlation. of approximately 0.4 ...... middle of paper ...... networks of synaptic connections in certain areas of the brain than rats in sterile environments. Early enrichment programs, such as Head Start, should promote mental growth. Works CitedBernstein, Douglas A. et al (2010) PsychologyMyers, David G. (2010) PsychologyPyle, William Henry. (2010) The Science of Human Nature Kindle edition Straub, Richard O., (2007) Study guide to accompany the psychology of David G. Myers Sternber, Richard J. (2010) Encyclopedia Britannica article “Human Intelligence” White, J. Nolan and Ciccarelli, Sandra (2009) Introduction to PsychologyHeredity versus Environment - The Nature-Nurture Controversy, Exploring Heredity and Environment: Research Methods, Beyond Heredityhttp:// www.pbs.org/wgbh/pages/frontline/video/flv/generic.html?s= frol02p66&continu=1