In 1899, Theodore Simon (1873–1961), who worked as an intern at a large institution for children with men- tal retardation, asked Binet to supervise his doctoral research. Binet agreed and viewed this as an oppor- tunity to have access to a large subject pool. Also in 1899, Binet joined the Free Society for the Psy- chological Study of the Child, an organization that sought scientifically valid information about chil- dren, especially about their educational problems. Binet soon became leader of the society. In 1903 Binet and Simon were appointed to the group that the French government commissioned to study the
(Alice and Madeleine), who were 2 1/2 and 4 1/2 years old at the time. The tests he created to inves- tigate his children’s mental operations were very similar to those Jean Piaget later devised. He asked, for example, which of two piles contained more objects and found that the answer was not deter- mined by the number of objects in the piles but by the amount of space the piles took up on the table. Binet also investigated how well his daughters could remember objects that he first showed them and then removed from sight. Binet also employed a number of tests used by Galton and Cattell to measure visual acuity and reaction time. In 1890 he published three papers describing his research on his daughters, and in 1903 he published The Exper-imental Study of Intelligence, which summarized his longitudinal study of the intellectual growth of his children.