[1] During much of his early life, he was fascinated by Alfred Binet's work and constantly read his books.

In 1899, Simon was appointed as a PhD student at the asylum at Perray-Vaucluse where he began his famous work on abnormal children that led to his thesis on the topic in 1900.

[2] This drew Binet's attention, who was at the time studying the correlation between physical growth and intellectual development.

[3] This sparked Binet and Simon's work on establishing a scale to identify abnormal children.

Simon was critical of the immoderate and improper use of the Binet-Simon Intelligence Scale by other psychologists and professionals due to his belief that the scale was being over-used, which may have been inappropriate, preventing psychologists from achieving Binet's ultimate goal of understanding human beings, their nature, and their development.

After 1905 until 1920, Simon worked as the head psychiatrist at Saint-Yon hospital in Essonne department in Île-de-France (northern France).