Alfred Binet, along with his student Théophile Simon, was tasked by the French Ministry of Education in 1904 to create a method for identifying students who struggled to learn through conventional classroom instruction. This initiative aimed to address overcrowding by placing such students in specialized schools. Binet and Simon developed an intelligence test comprising 30 tasks, ranging from simple commands, like touching one's nose or ear, to more complex tasks, such as drawing designs from memory and defining abstract concepts. This test, which eventually became known as the Stanford-Binet test, remains a widely used tool for measuring intelligence.

Binet introduced the concept of mental age (MA) as a way to assess intelligence. Mental age represents an individual's level of cognitive development compared to what is typical for a particular age group. For instance, a child with low mental ability would perform similarly to a typical younger child. Intelligence can be understood by comparing a person's mental age with their chronological age (CA) or actual age. A child with a mental age significantly higher than their chronological age is considered very bright, while a child with a mental age much lower than their chronological age may be less bright.