INTELLIGENCE QUOTIENT (IQ)
Intelligence Quotient (IQ) is a total score generated from various standardized tests for assessing human intelligence. Such tests are often conducted by a doctoral-level psychiatrist or psychologist or a psychologist with master-level in special IQ testing. The tests can require one to remember numbers and repeat them back to back in the same order, define words, and sorting blocks to match an image or filling problems on the sheet in the quickest possible time. The calculation of IQ compares these results with the age of the person. 100 are the score of average IQ. Evidence form research has shown that the variance IQ is mainly attributable to both the environmental and genetic influences on the etiology of IQ that change from age to age. Skeels and Skoda first noticed this phenomenon in 1949. Several studies since then have been using data from twins as well as adoptive children to study the increased heritability pattern and a decrease in shared effects of the environment with age. This evidence has since been widespread and robust.
The study by Brant et al. (2009) indicates that the magnitude and nature of genetic influences on IQ are the same for average and higher ability levels and that association and linkage studies do not have to focus on a specific ability level when determining the genes that associate with intelligence. The most likely fact is that IQ results from the cumulative impact of several genes. Brant et al. (2009) also suggest that there is the dramatic environmental impact that the children with high intelligent experiences and are more likely to acquire a high cognitive ability as determined by the variability and access to educational materials. The relative impact of environmental influences is reduced after seven years though other factors can lead to such a pattern.
Brant, A, Herberstick B and Corley, R et al. (2009) The Developmental Etiology of High IQ. doi: 10.1007/s10519-009-9268-x