who was responsible for the initial work on measuring intelligence
Alfred Binet Alfred Binet (French: [binɛ]; July 8, 1857 – October 18, 1911) was a French psychologist who invented the first practical IQ test, the Binet–Simon test.[2] In 1904, the French Ministry of Education asked psychologist Alfred Binet to devise a method that would determine which students did not learn effectively from regular classroom instruction so they could be given remedial work. Along with his collaborator Théodore Simon, Binet published revisions of his test in 1908 and 1911, the last of which appeared just before his death.
Heritability of IQ The relative influence of genetics and environment for a trait can be calculated by measuring how strongly traits covary in people of a given genetic (unrelated, siblings, fraternal twins, or identical twins) and environmental (reared in the same family or not) relationship. One method is to consider identical twins reared apart, with any similarities which exists between such twin pairs attributed to genotype. In terms of correlation statistics, this means that theoretically the correlation of tests scores between monozygotic twins would be 1.00 if genetics alone accounted for variation in IQ scores; likewise, siblings and dizygotic twins share on average half of their alleles and the correlation of their scores would be 0.50 if IQ were affected by genes alone (or greater if, as is undoubtedly the case, there is a positive correlation between the IQs of spouses in the parental generation). Practically, however, the upper bound of these correlations are given by the reliability of the test, which is 0.90 to 0.95 for typical IQ tests[69]