1857: Born on July 8 in Nice, France.
1878: Receives a license in law, a career he chose not to pursue.
1879 or 1880: Began reading about psychology in a Paris library.
1880: Publishes his first article, "On the Fusion of Similar Sensations."
1884: Marries Laure Balbiani, daughter of biologist E. G. Balbiani.
1885: Birth of his daughter, Madeleine.
1886: Publishes his first book, The Psychology of Reasoning.
1887: Birth of his daughter, Alice.
1894: Receives a doctoral degree in natural science from the Sorbonne.
1895: Helps found the first French psychological journal.
1896: Publishes a paper outlining "individual psychology" with Victor Henri.
1899: Began working with Théodore Simon.
1900: Helps organize the Free Society for the Psychological Study of the Child.
1905: Along with Simon, introduces the first version of the Binet-Simon Scale.
1911: Makes the last revision of the Binet-Simon Scale. Dies on October 18.
Nevertheless, twin studies are one of the best tools psychologists have for separating the effects of nature and nurture.
The Minnesota study showed that identical twins who had been raised apart grew up to be almost as similar in intelligence as identical twins who had been raised together. The degree of similarity was impressive. For example, one test the twins took was the Wechsler Adult Intelligence Scale, currently the most widely used IQ test for adults. The scores of identical twins reared apart correlated at 0.69, a high correlation that was not much different from the 0.88 correlation in the scores of identical twins reared together.
On some other tests of mental ability, the correlations were even closer. For example, on a test called Raven's Progressive Matrices, the correlation for the reared apart identical twins was 0.78. For the reared-together identical twins, it was 0.76.
Overall, the Minnesota study and others like it have found that about half of the differences in intelligence within a group of people may be due to differences in genes. Of course, this also means that half of the differences are due to other things. In addition, what is true for a group of people is not always true for a particular individual. In the Minnesota study, for example, one pair of twins scored almost 30 points apart in IQ.
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