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


In 1938 Louis Thurstone disagreed with what he termed, ‘Spearman’s limited premise’ and instead examined the performance of students on a battery of 56 tests and from the data obtained claimed to have identified seven factors which underlie human intelligence:

  1. Verbal comprehension: advanced ability to understand language, e.g. measured with a vocabulary test
  2. Verbal fluency: how quickly you can solve anagrams or word puzzles
  3. Number: the ability to use arithmetic operations
  4. Spatial visualization: the ability to recognize objects from different viewpoints
  5. Memory: as measured with a simple recall test
  6. Reasoning: solving problems such as how much paint is needed to decorate a room
  7. Perceptual speed: a simple example would be the ‘spot the difference’ type quiz


Raymond Cattell further suggested that the structure of intelligence should be considered in terms of two factors, ‘fluid’ and ‘crystallized’ intelligence. Those aspects of intelligence that could be improved through education or training, the learned aptitudes described above, he called ‘fluid’ intelligence to indicate their more dynamic nature. ‘Crystallized’ intelligence is that component of intelligence that was more rigid and less likely to be changed by education or experience.


“Intelligence is how well an individual deals with environmental changes throughout their lifespan.” – Sternberg


Robert Sternberg’s 1985 model took a more cognitive approach to intelligence attempts to integrate aspects of previous multi-component theories into a coherent whole. Sternberg suggests that intelligent behavior results from three distinct aspects of human intelligence:

  1. Contextual Intelligence
  2. Componential Intelligence
  3. Experiential Intelligence


Sternberg thought that while the basic information processing components were the same, different contexts and different tasks require different kind of intelligence.


Finally, Howard Gardner’s theory of multiple intelligence is based on a neuropsychological analysis of an individual’s ability and their brain function. By examining the sorts of impairments that can arise from brain dysfunction or damage, Gardner claimed to have identified seven distinct types of intelligence:

  1. Logical/Mathematical Intelligence
  2. Verbal Intelligence
  3. Spatial Intelligence
  4. Bodily/Kinesthetic Intelligence
  5. Personal intelligence includes two subtypes:
    1. Intrapersonal intelligence
    2. Interpersonal intelligence
  6. Musical intelligence
  7. Naturalistic