Genetic factors contribute more than environmental factors in determining intelligence. For the sake of clarity, I would like to define a few key terms. Genes- a specific segment on the strand of DNA that contains instructions for making proteins, the chemical building blocks from which all the parts of the brain and body are constructed Environment- a : the complex of physical, chemical, and biotic factors (as climate, soil, and living things) that act upon an organism or an ecological community and ultimately determine its form and survival b : the aggregate of social and cultural conditions that influence the life of an individual or community Intelligence- is defined in different ways. Some psychologists believe that intelligence is best defined by measuring cognitive abilities. Others argue that a definition of intelligence based entirely on cognitive abilities is much too narrow. Instead they believe that there are many kinds of intelligence, such as musical, motor, creative, or practical intelligence. There have been many experiments that have been performed to test the nature-nurture question, which is whether genetic factors contributed to intelligence more than environmental factors. In most of these cases, it has been the case that genetics do contribute more than the environment does. The team found that the amount of gray matter in the frontal parts of the brain is determines by the genetic make-up of an individual s parents, and strongly correlates with the individuals cognitive ability, as measured by intelligence test scores (UCLA). There have been many studies that have been performed on twins, both fraternal, and identical. Identical Twins: twins developed from a single fertilized ovum and therefore identical in genetic make-up at the time of conception, meaning they have 100% of their genes in common. Fraternal Twins: twins developed from two separate fertilized ova and therefore different in genetic makeup, meaning the have 50% of their genes in common.

Experiments have been done testing the IQ of both identical and fraternal twin who were raised together, as well as those that were raised separately. Tests prove that the correlation between twins that grow up with each other is very high, and even twins that did not grow up together still have very similar IQ s. For identical twins that were reared together the median correlation was .85, which for those reared apart was .72, which is still very high. For fraternal twins that were reared together it was .60, which is still high.(Introduction to Psychology). This goes to prove that even when the twins are not together, they still have very close IQ s. We were stunned to see that the amount of gray matter in frontal brain regions was strongly inherited, and also predicted an individual s IQ score, said Paul Thompson, the study s chief investigator and an assistant professor of neurology at UCLA Laboratory of Neuro Imaging (UCLA). The twins that were being selected for experiments in this department were twins that either lived together, or were adopted by different families, and had no relation to each other. The case for heredity seems to be ironclad: Identical twins have very similar IQ scored even when they have not been raised together (Understanding Psychology).