In the history of science, instruments have vied with theories in producing revolutionary breakthroughs in particular disciplines. The construction of the telescope in astronomy and the microscope in biology are examples of instrumental innovations of revolutionary significance. It is really not farfetched to say that the intelligence scale, introduced by Alfred Binet and Theodore Simon, has become psychology's microscope. Like the microscope, the intelligence test is both a clinical tool of great diagnostic value and a research instrument of considerable precision and depth. And, like the microscope, the intelligence scale has been parent to a wide range of like instruments from achievement tests to personality scales. As a discipline, psychology is still most closely identified, in the popular mind, with one or another sort of testing.
Despite the value of their contributions, the inventors of instruments are much less well known than their inventions. How many people can recall offhand