A prominent contention before the beginning of this century was that because intelIigence
could not be measured in physical terms, it could not be measured at all. Like politics,
religion, and sexuality, it was not considered quantifiable. Mental ability was too abstract to
be measured.
However, Sir Francis Galton, a highly versatile Englishman with no financial worries, felt
otherwise. He entertained himself by making scientific inquiries in various fields. Then he
founded the Anthropometric Laboratory in South Kensington, London, where a person could
be measured for hearing, strength, sensitivity to visual movement, and several mental
reactions, all for a three-penny fee. On this basis Galton is considered to have inaugurated
the mental-testing movement.
Galton devised a graded series of weights to be presented in random order to a blindfolded
subject who would indicate whether any given weight was heavier or lighter than the one
preceding it. He tested people known to be of exceptionally high or very low mental ability
and discovered that they were also high or low respectively in sensory discrimination.
A common set of tests to evaluate intellectual abilities also came from China, in which
applicants for government jobs were given examinations of their knowledge of Confucian
philosophy and poetry. During the Industrial Revolution, large numbers of individuals needed
to be tested for their ability to do clerical work. Today, many industrialized societies rely
heavily on tests in schools and the workplace. Although tests of abilities are used worldwide
and can have significant consequences for individuals' lives, they rely on having a valid
theory of what kind of abilities are important for a given context and on knowing how to
measure those abilities.
The first tests resembling modern intelligence tests were devised by the French psychologist
Alfred Binet in the late nineteenth century. In 1881, the French government passed a law
which made school attendance compulsory for all children. Because of this, teachers had to
cope with a wide range of individual differences. As a result, the government asked Binet to
create a test that would detect children who were too slow intellectually to benefit from a
regular school curriculum.
A number of intelligence tests and assessments have prevailed over the years.
Binet’s Early Scales :
The fundamental idea in Binet's approach was to arrange a series of questions in order of
increasing difficulty. At the lowest level, the child simply followed with his or her head and
eyes a lighted candle moved about the room. In later tests, the child was asked to imitate
gestures and obey brief orders. At a still higher level, the child was required to define words,
remember numbers, think abstractly, and discriminate among a series of weights, as Galton
had suggested. Binet and his
collaborator, Theophile Simon, tested normal schoolchildren and then in 1905 published
this collection of items. Popularly known as the Binet-Simon Test, it was the first
scientifically devised test of intelligence (Binet & Simon, 1905). This test however, became a
target of criticism as many defects were found and pointed out.
The Stanford-Binet Intelligence Scale :
In 1916, Lewis Terman published the Stanford revision of the Binet tests which referred to
The Stanford-Binet Intelligence Scale. Here, Terman standardized the administration of the
Binet’s test and developed age-level norms by giving the test to thousands of children of
various ages. It was revised in 1937, 1960, 1972, 1986 and most recently in 2003. Despite its
age, the Stanford-Binet is still one of the most used intelligence tests.
Terman retained Binet’s concept of mental age and adopted a convenient index of
intelligence suggested by the German psychologist William Stern. This index is the
lntelligence quotient (IQ), which expresses
intelligence as a ratio of mental age to chronological age:
IQ = MA/CA x 100
The number 100 is used as a multiplier so that the IQ will have a value of 100 when MA is
equal to CA. If MA is lower than CA the IQ will be less than 100; if MA is higher than CA the IQ
will be more than 100. The most recent revision of the Stanford-Binet uses standard age
scores instead of IQ scores. These can be interpreted in terms of percentiles, which show the
percentage of individuals in the standardization group falling above or below a given score.
The Wechsler Intelligence Scales :
In 1939, David Wechsler developed a new test because he thought the Stanford-Binet
depended too heavily on language ability and was not appropriate for adults. The
Wechsler Adult Intelligence Scale, or WAIS (1939, 1955, 1981 ) is divided into two parts - a
verbal scale and a performance scale that yield separate scores as well as a full-scale IQ.
Items on the performance scale of the Wechsler test require the manipulation
or arrangement of blocks, pictures, or other materials. The Wechsler scales also provide
scores for each subtest. so the examiner has a clearer picture of the individual's intellectual
strengths and weaknesses. For example, a discrepancy between verbal and performance
scores prompts the examiner to look for specific learning problems such as reading
disabilities or language handicaps.
Both the Stanford- Binet and the Wechsler scales are fairly valid predictors of achievement in
school. Intelligence test
scores also predict adult incomes, because school achievement leads to better work
opportunities (Ceci & Williams, 1997).
Validity of Intelligence Tests : The concept of validity concerns with the extent to which a
test measures what it claims to measure. To demonstrate validity, a well-constructed test
requires a statistical evaluation against a criterion, such as school achievement or some
other evidence pf intellectual competence. Furthermore, an individual test which is
administered to one person at a time, is much more likely to yield a valid result than a group
test which, is administered to large groups and therefore restricted to written answers,
usually verbal or numerical. The skill of the
test user is also an important concern.
An intelligence test can be useful for predicting school performance and certain other
goal-directed activities, especially in various professions. But it is only one of many factors
to be considered. Motivation, creativity, and social skills are also important, as well as
special ability in art, music, athletics, and other areas.
Sources :
Norman Leslie Munn’s Introduction To Psychology.
Atkinson and Hilgard’s Introduction To Psychology.