Intelligence testing had been the earliest form of psychological tests and has contributed to the popularity of psychology in mainstream culture (Cianciolo & Sternberg, 2004). However, the measurement of intelligence relies heavily on how the test developer or theorist defined intelligence and since the last century, many theories of intelligence have been proposed and in their own time have enjoyed quite a following while it have also led many changes in education and the world of work which are the major consumers of intelligence tests.
The power and authority of intelligence tests are tremendous which is why it is often referred to as high stakes testing. The definition of intelligence has also undergone a process of evolution which we will examine in this essay. The first theory of intelligence was espoused by Francis Galton wherein he said that intelligence can be measured through the identification and testing of behavior that are said to be directly related to intelligence, hence he advocated the use of sensorimotor tasks to measure reaction time and hence intelligence (Cianciolo & Sternberg, 2004).
By the early 1900’s, Alfred Binet developed his own intelligence test as ordered by the French Educational System to identify students who had learning difficulties in order to give them special education classes. Binet followed in the tradition of Galton and believed that intelligence can be measured by assessing cognitive skills; hence he developed the first intelligence test and called this Alfred-Simon Test which contained 30 items of questions regarding everyday problems which were identified as tasks that involved reasoning and logic (Cianciolo & Sternberg, 2004).
The tests was revised a number of times and have been the precursors to most intelligence tests. In America, Lewis Terman and Wilhelm Stern collaborated to modify the Binet-Simon Tests as it was not applicable to their country and culture, hence Terman adapted some of the items to American and established new age norms. Moreover, Terman used Stern’s formula for IQ to categorize the norms of the test and the revised edition now became the Stanford-Binet Test.
After a few years, Terman and a group of psychometricians was tasked with developing intelligence tests designed to be administered to groups specifically for screening volunteers to join the American armed forces (Cianciolo & Sternberg, 2004) since the Stanford-Binet Test was difficult to administer and time-consuming, this became the Alpha and Beta Test which was administered to thousands of recruits. The Beta test was a version of the Alpha test for non-English and illiterate citizens.
The common thread in this period was that intelligence was viewed as a basic trait that was categorized as high or low and which was measured indirectly through the measurement of related processes like reaction time, reasoning and logic. Based on this definition, concepts like intelligence quotient, norms and standardization became prominent and it was apparent that intelligence testing was a viable tool for classifying people and was used in different industries.
With a number of intelligence test in the field, Charles Spearman (1927) observed that if a person did well in an intelligence test he/she also did well in some other task like vocabulary or mathematical ability. He analyzed the existing intelligence tests using factor analysis and found that there is indeed a correlation between intelligence and intellectual tasks that he came out with the two factor theory of intelligence or the most commonly known general “g” ability and specific abilities (Spearman, 1927).
He pointed out that intelligence has a basic component required in the performance of all mental tasks and while there are specific abilities which are required for a specific mental test. However, Spearman was popular for the conceptualization of a general intellectual ability which became the basis of many intelligence tests to come. Tests developed using Spearman’s “g” measured specific abilities like numerical and verbal ability and then the combined scores formed the general ability of the individual which was categorized into poor, below average, average and superior.
Thurstone agreed with the notion of a general intellectual ability but however argued that it is not the most important measure of intelligence but rather is a secondary factor that is a by product of the primary intellectual abilities which he identified to include verbal comprehension, word fluency, number, space, associative memory, perceptual speed and reasoning (Ruzgis, 1994).
Thurstone was the first theorist to adopt the multifactor approach and demonstrated that intelligence can be better defined and measured using primary intellectual skills than a single factor “g” which cannot be identified or explained. Another factor theorist was Raymond Cattell (1941) who proposed that intelligence can be identified as fluid and crystallized. Fluid intelligence refers to the ability of the individual to perceive relationships and is the primary reasoning ability while crystallized intelligence referred to one’s acquired knowledge and skills or factual knowledge.
He also said that fluid intelligence decreases as a person ages and at the same time crystallized intelligence increases with age (Cattell, 1941). Guilford on the other hand proposed that intelligence is not made up of a single factor “g” or of specific abilities but rather it is made up of 180 elementary abilities which can be roughly categorized into operations, contents and products (Francher, 1985). Due to the impracticality of this definition, Guilford’s theory was unpopular and later on was abandoned.
A few years later, Vernon developed a theory that integrated Spearman’s “g” and Thurston’s primary intellectual abilities by proposing that intelligence can be defined in a hierarchical model wherein “g” was at the top, followed by major group factors like verbal-educational ability and practical-mechanical ability, then minor group factors followed which is derived from the major group factors and at the lowest were specific abilities (Francher, 1985).
Vernon’s definition of intelligence has become the framework of many intelligence tests at present due to its applicability and practicality. Later on, another theorist Howard Gardner came out with his theory of multiple intelligences. This theory argues that intelligence cannot be thought of as a single factor and that intelligence can be found in different aspects. He said that there are seven intelligences namely verbal, mathematical, musical, spatial, kinesthetic, interpersonal and intrapersonal (Gardner, 1993).
The basic idea that Gardner proposed was that intelligence is not a trait that either one has or has not but rather people have different intelligences. Gardner’s theory have spurned a controversial issue in education which had relied heavily on intelligence testing that some schools have adopted multiple intelligences as a program of instruction where each child is encouraged to develop the intelligences that he/she has.
Critics however have argued that some of the intelligences Gardner identified are not intelligences but are talents which are not part of intellectual ability. Gardner however has yet to prove the validity of his theory and research into multiple intelligences has not yielded conclusive results. Sternberg early in his career have developed the triarchic model of intelligence which he have revised in the last decade and proposes that there are three intelligences; namely academic, practical and creative (Sternberg, 1996).
Sternberg was not concerned with defining intelligence as a specific ability but rather as how intelligence is used by individuals, thus academic intelligence refer to the abilities like logical reasoning and analytical skills; practical intelligence refers to the ability of the individual to apply knowledge to everyday situations and creative intelligence refer to the ability to use knowledge to generate new ideas or concepts.
The earliest definition of intelligence was attributed as an intellectual trait that is present in all but in varying levels and was thought of as a single entity and was measured based on practical intellectual tasks. From Spearman to Vernon; intelligence has been defined as consisting of multiple factors while Gardner and Sternberg proposed the presence of multiple intelligences.
The difference here is that the earlier theories revolved around the idea of a general ability and specific abilities although they have disagreed on the properties of both factors, they stressed that intelligence is something that a person is born with and can either rage from high to low. Gardner and Sternberg however showed that intelligence can be defined as what a person can do and that intelligence can be enhanced.
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