Scientists have been evaluating differences in abilities between people for thousands of years. The first recognized systematic attempt to measure intellectual differences was conducted in 1884 by Francis Galton, a cousin of Charles Darwin, and a strong advocate of inherited differences in abilities.
By 1905 the French government asked its leading scientists, Alfred Binet and Theodore Simon to devise a test that could define intelligence. The French government wanted to identify children with learning difficulties so that special educational provision could be made for them. Those tests later became better known as the IQ Tests. Intelligence by those tests was defined as the ability to judge well, comprehend well, and to reason well.
Others suggested that intelligence involved an ability to grasp the essentials of a situation and to act appropriately to those situations. Theorists suggested that intelligence was made up of several different components or abilities. Spearman proposed that intelligence was made up of a general ability ‘g’ and a number of learned aptitudes or specific abilities, which were referred to as ‘s’. Some of the specific or ‘s’ abilities were verbal skills, educational ability, mechanical and spatial abilities.
“Intelligence, as a mental trait, is the capacity to make impulses focal at their early, unfinished stage of formation. Intelligence is therefore the capacity for abstraction, which is an inhibitory process” – L.L. Thurstone