Binet was working at the Sorbonne when he first became involved in measuring human intelligence. He began by using Broca's technique of measuring skulls and went to various schools measuring the heads of children and seeing if they conformed to the teacher's designation of smart of dumb. He found that there was not always a correlation and his work basically ended the popularity of the theory of craniometry. He devised a test consisting of a series of tasks that had age levels assigned to them. From this, he was able to identify school children who required special training. He had three rules that he followed for using his tests. Those who came after him did not always follow the rules which is why they abused so many people with the results.