The original intelligence test developed by Binet and Simon set out to measure performance in , which refers to the chronological age that typically corresponds to a given level of performance.

Mental age

Explanation:

According to the theory created by Binet and Simon ,intelligence was measured through test.They worked upon age related intellectual ability of children through testing it by creating particular intelligence baseline.

They focus their first step towards children with special requirement for assessing their mental age in respect with chronological age through test to know their performance.  This test helped to know about children's mind and support them for their need as per mental requirements.