Discuss the role of genetics and cultural differences in the development of measured intelligence.
Intelligence is mental activity directed towards purposive adaptation to, and selection and shaping of, real-world environments relevant to one's life. There tends to be a gap between definitions of intelligence and tests of intelligence. The key question is, is measured intelligence related more to hereditary or social and cultural influences. The most common measure of intelligence is the intelligence quotient or IQ.
The most popular method of assessing the relative importance of hereditary and environment in determining individual differences in intelligence is to conduct a twin study. There are two different types of twins monozygotic (MZ) and dizygotic (DZ). Monozygots have an identical genotype from one egg whereas dizygots come from two separate eggs. If heredity is very important then we would expect MZ twins to be considerably similar than tic twins. But if environmental factors are all important, then MZ twins should be no more alike then DZ twins. Bouchard and McGue (81) reviewed 111 studies on twins. They reported that the mean correlation for identical twins or MZ's was +86 which is quite high, and +0.60 for fraternal twins or DZ's. These findings would lead you to believe that genetic factors play an important role in determining intelligence, although they may do for twins it is not so true for relations. For example, siblings reared together had a correlation of +0.47. The fact that MZ twins were much more similar in intelligence than DZ twins suggests that heredity is of major significance in determining intelligence. However, that is on the assumption that the degree of environmental similarity experienced by MZ twins is the same as that to DZ twins. Evidence has shown that identical twins have similar IQ's because due to the similar treatment they received such as, parental treatment and playing together.