The concept of Intelligence has long been part of any consideration of brain and mind. All humans are more intelligent than the brightest chimpanzees. And real differences seem to exist in human abilities.
Some people seem much better at certain tasks.
The modern approach to intelligence began with the work of Alfred Binet who was hired by the Paris school system to develop tests which would identify those students not likely to benefit from further schooling. The mind is a machine. 1890s Alfred Binet in Paris develops tests to identify poor achievers. Chronological age is a standard by which we can compare behavioral accomplishments of individuals and thereby determine their natural ability. The reality of any psychological construct is dependent upon the method of measurement.