“Intelligence is whatever intelligence tests measure.” (Boring, 1923) Although people have been evaluating differences in abilities between people for thousands of years, probably the first systematic attempt to measure intellectual differences was that of Galton (1884). Galton, who was a cousin of Charles Darwin, was a strong advocate of inherited differences in abilities.

One of the first approaches to defining intelligence was that of Binet and Simon (1905) who were asked by the French government to devise a test that could identify children with learning difficulties so that special educational provision could be made for them. For Binet and Simon intelligence was the ability judge well, comprehend well and to reason well, so their theory was quite general in approach.

Other generalist theories have also been developed. Heim (1970) suggested that intelligence involved an ability to grasp the essentials of a situation and to act appropriately to them.

However other theorists have suggested that intelligence may be made up of several different components or abilities. Spearman (1904) proposed that intelligence was made up of a general ability ‘g’ and a number of learned aptitudes or specific abilities which he referred to as ‘s’.

Other researchers have adopted similar approaches. Burt (1955) and Vernon (1971) suggested that verbal skills, educational ability, mechanical and spatial abilities, might all be examples of ‘s’.

Thurstone (1938) 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:

  • verbal comprehension: advanced ability to understand language, e.g. measured with a vocabulary test
  • verbal fluency: how quickly you can solve anagrams or word puzzles
  • number: the ability to use arithmetic operations
  • spatial visualization: the ability to recognize objects from different viewpoints
  • memory: as measured with a simple recall test
  • reasoning: solving problems such as how much paint is needed to decorate a room
  • perceptual speed: a simple example would be the ‘spot the difference’ type quiz

Cattell (1971) further examined the data of Thurstone (1938) and came to the conclusion that second order factors could be identified which would simplify the seven factor model of Thurstone. Cattell (1971) 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.

Sternberg (1985) model 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, contextual intelligence, componential intelligence and experiential intelligence.

Contextual Intelligence is said to reflect evolutionary change brought about by natural selection. Within this framework, adaptation is concerned with how well a person fits into their environment. The second part of contextual intelligence, selection, deals with our ability to choose a career or identify activities that we enjoy and that we know we can do well.

Componential Intelligence consists of three elements. Metacomponents are strategic features of intelligence concerned with the identification of a problem and the planning required to solve it. Once this has been achieved then performance components can be used to actually execute the tasks required for a solution. The third facet of this type of intelligence is known as the knowledge acquisition component, and is concerned with the acquisition of new knowledge and the integration of that knowledge into what is already known.

Experiential Intelligence deals with a person’s ability to solve problems that are similar to those they have already had to face, i.e. the ability to benefit by experience. The person with good experiential intelligence will, when faced with a novel problem, be able to make use of previous experience with similar problems to more effectively find solutions to the new problem.

Gardner (1983) has based his theory of intelligence on a neuropsychological analysis of ability and brain function. By examining the sorts of impairments that can arise from brain dysfunction or damage, Gardner claims to have identified seven distinct types of intelligence: logical/mathematical intelligence, verbal intelligence, spatial intelligence, bodily/kinesthetic intelligence, personal intelligence includes two subtypes, firstly an awareness of ones own feelings (intrapersonal intelligence) and secondly the ability to recognize and respond to the feelings of others (interpersonal intelligence). Finally there is musical intelligence, the ability to produce or appreciate music. (Gardner Learning Approaches)

Gardner argues that these different types of intelligence can be clearly mapped onto the brain and reveal themselves often by their absence when the brain is damaged. For example people with damage to the frontal lobes have difficulty evaluating the significance of social situations, and people with injury to the left parietal lobe often show apraxia, an inability to perform sequences of skilled actions, like those of a typists or a dancer.