Final answer:
Lewis Terman used the original Binet-Simon test to assess the genetic contribution of intelligence, later developing the Stanford-Binet Intelligence Scales. The IQ test most widely used today was developed by David Wechsler.
Step-by-step explanation:
The individual who used the original Binet-Simon test to assess the genetic contribution of intelligence was Lewis Terman. He revised the Binet-Simon Intelligence Scale and adapted it for use in the United States, leading to the development of the Stanford-Binet Intelligence Scales. This adaptation included norming and standardizing the test, which allowed for a consistent method of administration and the establishment of average scores for each age, creating a bell curve of intelligence scores.
In terms of the IQ test that is most widely used today, David Wechsler developed the Wechsler Adult Intelligence Scale (WAIS) and the Wechsler Intelligence Scale for Children (WISC), which are still in use.
Regarding the foundational debate on intelligence, it is important to note that research into the nature of intelligence includes assessments of genetic factors, environmental influences, and their interactions.