COMMONLY USED INTELLIGENCE TESTS
The three most commonly used intelligence tests are:
Stanford-Binet Intelligence Scales
Wechsler-Adult Intelligence Scale
Wechsler Intelligence Scale for Children
CONCEPTS OF IQ & DEVIATION IQ
Before we go into the details of the three tests, let us first understand the two basic concepts that are
employed in the tests. These are the concepts of IQ & Deviation IQ
THE INTELLIGENCE QUOTIENT (IQ or RATIO IQ)
Binet regarded the mental age (MA) as an index of mental performance. Each item successfully passed
on a Binet test signified a certain number of months' credit. At the conclusion of the test, the items
passed were added up and the MA emerged. Thus, there was nothing magical about an MA: all it meant
was the X numbers of items has been passed.
Subsequently, Stern (1938) developed the concept of intelligence quotient (1Q) to circumvent several
problems that had arisen in using the difference between the chronological age (CA) and the MA to
express deviance. At first glance, two children, one with an MA of 4 years and a CA of 5 years and
another with an MA of 14 years and a CA of 15 years, would seem to be equally deficient. However,
this is not the case, because intellectual growth is much more rapid at younger age levels. Therefore,
even though there is only a one-year discrepancy between the MA and the CA of both children, the
younger child is actually more deviant than the older one. The IQ notion enables us to perform the
following computation:
IQ=MA/CA x 100
As a result, we find that our 15-year-old has an IQ of 93, whereas the 5-year-old has an IQ of 80.These
differing scores better reflect the reality of more rapid intellectual growth at younger ages.
It should be noted that in measuring intelligence, we cannot be sure that we are dealing with equalinterval
measurement. We cannot be sure that an IQ of 50 is really twice as much as an IQ of 25 or that
our scale has an absolute zero point. We cannot add and subtract IQs. All we can do is state that a
person with an IQ of 50 is brighter than a person with an IQ of 25. All of this should serve to remind us
that IQs and MAs are merely scores.
DEVIATION IQ: Although initially appealing, the ratio IQ is significantly limited in its application to
older age groups. The reason is that a consistent (even if very high) mental age (MA) score
accompanied by an increasing chronological age (CA) score will result in a lower IQ. Thus, it may
appear that IQ has decreased over time when, in fact, one's intellectual ability has been maintained.
To deal with this problem, Wechsler introduced the concept of deviation IQ. The assumption is made
that intelligence is normally distributed throughout the population. A deviation IQ then involves a
comparison of an individual's performance on an IQ test with that of his or her age peers. Thus, the
same IQ score has a similar meaning, even if two individuals are markedly different in age (for
example, a 22-year-old versus an 80-year-old). In both cases, an IQ of 100 indicates an average level of
intellectual ability for that age group.
THE CLINICAL ASSESSMENT OF INTELLIGENCE
In this section, we will briefly describe several of the most frequently used intelligence tests for children
and adults.
THE STANDFORD-BINET SCALE
The Stanford-Binet Intelligence Scale: Fourth Edition (SB: FE) is a standardized test that measures
intelligence and cognitive abilities in children and adults, from age two through mature adulthood.
The Stanford-Binet Intelligence Scale has a rich history.
It is a descendant of the Binet-Simon scale which was developed in 1905 and became the first
intelligence test.
The Stanford-Binet Intelligence Scale was developed in 1916 and was revised in 1937, 1960, and
1986. The present edition was published in 1986, and is called the Stanford-Binet Fourth Edition, or
SB-4.
PURPOSE
The Stanford-Binet Intelligence Scale was originally developed to help place children in appropriate
educational settings. It can help determine the level of intellectual and cognitive functioning in
preschoolers, children, adolescents and adults, and assist in the diagnosis of a learning disability,
developmental delay, mental retardation, or giftedness.
It is used to provide educational planning and placement, neuropsychological assessment, and research.
The Stanford-Binet Intelligence Scale is generally administered in a school or clinical setting.
DESCRIPTION
The Stanford-Binet Intelligence Scale is comprised of four cognitive area scores which together
determine the composite score and factor scores. The test consists of 15 subtests, which are grouped into
the four area scores.
These area scores include: Verbal Reasoning, Abstract/Visual Reasoning, Quantitative Reasoning,
and Short-Term Memory.
The composite score is considered to be what the authors call the best estimate of "g" or "general
reasoning ability" and is the sum of all of subtest scores. General reasoning ability or "g" is considered
to represent a person's ability to solve novel problems. The composite score is a global estimate of a
person's intellectual functioning.
The following is a review of the specific cognitive abilities that the four area scores measure.
1. The Verbal Reasoning area score measures verbal knowledge and understanding obtained from the
school and home learning environment and reflects the ability to apply verbal skills to new situations.
Examples of subtests comprising this factor measure skills which include: word knowledge, social
judgment and awareness, ability to isolate the inappropriate feature in visual material and social
intelligence, and the ability to differentiate essential from non-essential detail.
2. The Abstract/Visual Reasoning area score examines the ability to interpret and perform mathematic
operations, the ability to visualize patterns, visual/motor skills, and problem-solving skills through the
use of reasoning. An example of a subtest which determines the Abstract/Visual Reasoning score is atimed test that involves tasks such as completing a basic puzzle and replicating black and white cube
designs.
3. The Quantitative Reasoning area score measures: numerical reasoning, concentration, and knowledge
and application of numerical concepts. The Quantitative Reasoning area is combined with the
Abstract/Visual Reasoning area score to create an Abstract/Visual Reasoning Factor Score.
4. The Short-Term Memory score measures concentration skills, short-term memory, and sequencing
skills. Subtests comprising this area score measure visual short-term memory and auditory short term
memory involving both sentences and number sequences. In one subtest that measures visual short-term
memory, the participant is presented with pictures of a bead design, and asked to replicate it from
memory.
Each subtest is composed of items at varying levels of difficulty, from age 2 to adulthood. SB-4 uses an
adaptive testing procedure called multistage testing.
The examiner first gives the Vocabulary Test to determine the entry point (that is, which item to start
with) for each remaining subtest. This initial estimate of ability provides a more appropriate entry or
starting point on subsequent subtests, and is likely to result in more efficient testing, than relying
exclusively on chronological age as a guide for a starting point. Thus, not all examinees of the same age
are given the same items.
THE WECHSLER SCALES
David Wechsler used a deviation IQ concept. This approach, as we have seen, assumes that intelligence
is normally distributed and compares individuals with their age peers. In effect, it compares the
performance of a 15-year-old with that of other 15-year-olds. This method statistically establishes an IQ
of 100 as the mean for each age group. As a result, an IQ of 100 means the same thing for any person,
regardless of the person's age.
BACKGROUND OF WAIS
Earlier versions of the Stanford-Binet had a number of disadvantages that led David Wechsler in 1939
to develop the Wechsler-Bellevue Intelligence Scale. This was a test designed for adults – one that
would offer items whose content was more appropriate for and more motivating to adults than the
school-oriented Binet.
In contrast to the Stanford-Binet, whose items were arranged in age levels, the Wechsler-Bellevue
Intelligence Scale grouped its items into subtests. For example, all arithmetic items were put into one
subtest and arranged in order of increasing difficulty. In addition, there was a Performance Scale and a
Verbal Scale (consisting of five and six subtests, respectively). A separate IQ for each scale could be
calculated, along with a Full Scale IQ. The systematic inclusion of performance items helped remedy
the overemphasis on verbal skills that limited the utility of the earlier Stanford-Binet with special
populations
THE WAIS-III
DESCRIPTION
A new version of the Wechsler Bellevue, known as the Wechsler Adult Intelligent Scale (WAIS), first
appeared in 1955. A revised edition (WAIS-R) was published in 1981. The most recent version, the
Wechsler Adult Intelligent Scale-Third Edition (WAIS-III), was introduced in 1997. It is an
individually administered measure of intelligence, intended for adults aged 16–89.
PURPOSE
The WAIS-III is intended to measure human intelligence reflected in both verbal and performance
abilities. Besides being utilized as an intelligence assessment, the WAIS-III is used in
neuropsychological evaluation, specifically with regard to brain dysfunction. Large differences in
verbal and nonverbal intelligence may indicate specific types of brain damage.
The WAIS-III is also administered for diagnostic purposes. Intelligence quotient (IQ) scores reported by
the WAIS-III can be used as part of the diagnostic criteria for mental retardation, specific learning
disabilities, and attention-deficit/hyperactivity disorder (ADHD).
The WAIS elicits three intelligence quotient scores, based on an average of 100, as well as subtest and
index scores. WAIS subtests measure specific verbal abilities and specific performance abilities. The
WAIS elicits an overall intelligence quotient, called the full-scale IQ, as well as a verbal IQ and a
performance IQ. The three IQ scores are standardized in such a way that the scores have a mean of 100
and a standard deviation of 15.
The WAIS also elicits four indices, each based on a different set of subtests: verbal comprehension,
perceptual organization, working memory, and processing speed.
The verbal and performance IQ scores are based on scores on the 14 subtests. The full-scale IQ is based
on scores on all of the subtests and is a reflection of both verbal IQ and performance IQ. It is considered
the single most reliable and valid score elicited by the WAIS. However, when an examinee's verbal and
performance IQ scores differ significantly, the full-scale IQ should be interpreted cautiously.
Following are 14 WAIS-Ill subtests. Seven are the verbal subsets and 7 are the performance tests:
THE VERBAL IQ is derived from scores on seven of the subtests: information, digit span,
vocabulary, arithmetic, comprehension, similarities, and letter-number sequencing. Letter-number
sequencing is a new subtest added to the most recent edition of the WAIS (WAIS-III).
The information subtest is a test of general knowledge, including questions about geography and
literature. The digit span subtest requires test takers to repeat strings of digits. The vocabulary and
arithmetic subtests are general measures of a person's vocabulary and arithmetic skills. The
comprehension subtest requires test takers to solve practical problems and explain the meaning of
proverbs. The similarities subtest requires test takers to indicate the similarities between pairs of things.
The letter-number sequencing subtest involves ordering numbers and letters presented in an unordered
sequence. Scores on the verbal subtests are based primarily on correct answers.
THE PERFORMANCE IQ is derived from scores on the remaining seven subtests: picture
completion, picture arrangement, block design, object assembly, digit symbol, matrix reasoning,
and symbol search. Matrix reasoning and symbol search are new subtests and were added to the most
recent edition of the WAIS (WAIS-III).
In the picture completion subtest, the test taker is required to complete pictures with missing elements.
The picture arrangement subtest entails arranging pictures in order to tell a story. The block design
subtest requires test takers to use blocks to make specific designs. The object assembly subtest requires
people to assemble pieces in such a way that a whole object is built. In the digit symbol subtest, digits
and symbols are presented as pairs and test takers then must pair additional digits and symbols. The
matrix reasoning subtest requires test takers to identify geometric shapes. The symbol search subtest
requires examinees to match symbols appearing in different groups. Scores on the performance subtests
are based on both response speed and correct answers.
VERBAL SUBTESTS PERFORMANCE SUBTESTS
Vocabulary Picture completion
Similarities Digital Symbol-Coding
Arithmetic Block Design
Digit Span Picture Arrangement
Information Matrix Reasoning
Comprehension Symbol Search
Letter-Number Sequencing Object Assembly
PRECAUTIONS
The WAIS III is not considered adequate measure of extremely high and low intelligence (IQ scores
below 40 and above 160). The nature of the scoring process does not allow for scores outside of this
range for test takers at particular ages. Wechsler himself was even more conservative, stressing that his
scales were not appropriate for people with an IQ below 70 or above 130. Also, when administering the
WAIS to people at extreme ends of the age range (below 20 years of age or above 70), caution should
be used when interpreting scores.
The age range for the WAIS III overlaps with that of the Wechsler Intelligence Scale for Children
(WISC) for people between 16 and 17 years of age, and it is suggested that the WISC provides a better
measure for this age range.
Administration and scoring of the WAIS require an active test administrator who must interact with the
test taker and must know test protocol and specifications. WAIS administrators must receive proper
training and be aware of all test guidelines.
THE WISC-III
The Wechsler Intelligence Scale for Children (WISC) was first developed in 1949 and revised in 1974
(WISC-R) The latest version, the Wechsler Intelligence Scale for Children-Third Edition WISC-III),
was published in 1991.
It is an individually administered measure of intelligence intended for children aged six years to 16
years and 11 months.
PURPOSES
The WISC is designed to measure human intelligence as reflected in both verbal and nonverbal
(performance) abilities. The WISC is used in schools as part of placement evaluations for programs for
gifted children and for children who are developmentally disabled.
In addition to its uses in intelligence assessment, the WISC is used in neuropsychological evaluation,
specifically with regard to brain dysfunction. Large differences in verbal and nonverbal intelligence
may indicate specific types of brain damage.
The WISC is also used for other diagnostic purposes. IQ scores reported by the WISC can be used as
part of the diagnostic criteria for mental retardation and specific learning disabilities. The test may
also serve to better evaluate children with attention-deficit/hyperactivity disorder (ADHD) and other
behavior disorders.
WISC III scores yield an overall intelligence quotient, called the full scale IQ, as well as a verbal IQ
and a performance IQ. The three IQ scores are standardized in such a way that a score of 100 is
considered average and serves as a benchmark for higher and lower scores. Verbal and performance IQ
scores are based on scores on the 13 subtests.
The full scale IQ is derived from the child's scores on all of the subtests. It reflects both verbal IQ and
performance IQ and is considered the single most reliable and valid score obtained by the WISC. When
a child's verbal and performance IQ scores are far apart, however, the full scale IQ should be interpreted
cautiously.
VERBAL IQ
The child's verbal IQ score is derived from scores on six of the subtests: information, digit span,
vocabulary, arithmetic, comprehension, and similarities.
The information subtest is a test of general knowledge, including questions about geography and
literature. The digit span subtest requires the child to repeat strings of digits recited by the examiner.
The vocabulary and arithmetic subtests are general measures of the child's vocabulary and arithmetic
skills. The comprehension subtest asks the child to solve practical problems and explain the meaning of
simple proverbs. The similarities subtest asks the child to describe the similarities between pairs of
items, for example that apples and oranges are both fruits.
PERFORMANCE IQ
The child's performance IQ is derived from scores on the remaining seven subtests: picture completion,
picture arrangement, block design, object assembly, coding, mazes, and symbol search.
In the picture completion subtest, the child is asked to complete pictures with missing elements. The
picture arrangement subtest entails arranging pictures in order to tell a story. The block design subtest
requires the child to use blocks to make specific designs. The object assembly subtest asks the child to
put together pieces in such a way as to construct an entire object. In the coding subtest, the child makes
pairs from a series of shapes or numbers. The mazes subtest asks the child to solve maze puzzles of
increasing difficulty. The symbol search subtest requires the child to match symbols that appear in
different groups. Scores on the performance subtests are based on both the speed of response and the
number of correct answers.

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