The first intelligence test was developed by psychologist Alfred
Binet, in 1905, in Paris, France. He was hired by the public
school system to develop a test which would identify students
who were in need of special education classes. He came up
with measures of many mental abilities, and gave these tests
to the children in the school system. He assigned scores to the
test results, based on the ages of the children who took the
test. He called the scores “mental ages”, based on the
typical score earned by children of a specific age. A Mental
Age of 8 was the average score achieved by the eight years
olds. So a child who scored a Mental Age of 8 on the test
scored the same as the average 8 year old. If a seven year
old scores a Mental Age of 8, is he smart or stupid?
Alfred Binet
In 1916, psychologist Lewis Terman, of Stanford University, brought
Binet’s test to the United States, standardized it on American children,
and named the American version the Stanford-Binet Intelligence
Scale. Terman introduced the concept of the Intelligence Quotient
(I.Q.), which he calculated by dividing a child’s Chronological Age
(actual age in years, months, and days) by his Mental Age score on
the test, and multiplying the result by 100. So the formula was
I.Q. = MA/CA x 100.
So a 10 year old child with a Mental Age score of 12 years would have
an I.Q. of what?
The child’s I.Q. is 120
Lewis Terman

Two versions
› WAIS-III and WISC-III

Each has two subscales
› Verbal skills subscale
› Performance skills subscale

Produces verbal, performance, and
overall scores
Verbal Items – Items that require the use of language.
Performance Items – Non-language items
The Wechsler Scales are the major individual
intelligence tests used in the USA today.
Administered by one examiner to many people at a time
Advantages:
Less bias
Objective scoring
Disadvantages:
Examiner may miss problems
Some are not used to taking group tests
Learning disabilities do better on individual tests

Heredity
› IQs of identical twins
› adoption studies

Environment
› nutrition
› human interaction
› socioeconomic status
(SES) of parents
What is your I.Q.?
What is the I.Q. of the average graduating college senior In the
United States?
What can a person with an I.Q. of 65 do?
What is a “genius?”
Classification
IQ Score
Percent Included
Very Superior
130 and above
2.2
Superior
120-129
6.7
High Average
110-119
16.1
Average
90-109
50.00
Low Average
80-89
16.1
Borderline
70-79
6.7
Mental Retardation
69 and below
2.2
Mental Retardation
Mild Mental Retardation
IQ 50-55 to 70
Moderate Mental Retardation
I.Q. 35-40 to 50-55
Severe Mental Retardation
I.Q. 20-25 to 35-40
Profound Mental Retardation
I.Q. below 20 or 25
Psychologists today no longer use Terman’s formula to calculate IQ test scores.
Instead, modern intelligence tests apply statistical methods to produce a score
reflecting one's performance as compared to the average performance of his
peers . The normal IQ score is still 100, meaning that the average score people
get is 100. That happens because IQ test scores have a so-called “normal”
distribution. In a normal distribution, most of the values cluster around the
average with few values that differ significantly from it. That creates a bell
shaped curve, known as the IQ bell curve, which is illustrated below.
 Genetic Conditions - Down Syndrome, Fragile X, PKU, Overexposure to X-Rays
Problems During Pregnancy - Use of alcohol or drugs by the pregnant mother can cause
mental retardation. Malnutrition, rubella, glandular disorders and diabetes, cytomegalovirus,
and many other illnesses of the mother during pregnancy may result in a child being born with
mental retardation. Physical malformations of the brain and HIV infection originating in prenatal
life may also result in mental retardation.
 Problems at Birth - Although any birth condition of unusual stress may injure the infant’s brain,
prematurity and low birth weight predict serious problems more often than any other conditions.
 Problems after birth - Childhood diseases such as whooping cough, chicken pox, measles,
and diseases which may lead to meningitis and encephalitis can damage the brain, as can
accidents such as a blow to the head or near drowning. Substances such as lead and mercury
can cause irreparable damage to the brain and nervous system.
 Poverty and cultural deprivation - Children in poor families may become mentally retarded
because of malnutrition, disease-producing conditions, inadequate medical care and
environmental health hazards. Also, children in disadvantaged areas may be deprived of many
common cultural and day- to-day experiences provided to other youngsters. Research suggests
that such under-stimulation can result in irreversible damage and can serve as a cause of
mental retardation.
 Mild Mental Retardation - Approximately 85% of the mentally retarded population is
in the mildly retarded category. Their IQ score ranges from 50-75, and they can often
acquire academic skills up to the 6th grade level. They can become fairly selfsufficient and in some cases live independently, with community and social support.
 Moderate Mental Retardation - About 10% of the mentally retarded population is
considered moderately retarded. Moderately retarded individuals have IQ scores
ranging from 35-55. They can carry out work and self-care tasks with moderate
supervision. They typically acquire communication skills in childhood and are able to
live and function successfully within the community in a supervised environment such
as a group home.
 Severe Mental Retardation - About 3-4% of the mentally retarded population is
severely retarded. Severely retarded individuals have IQ scores of 20-40. They may
master very basic self-care skills and some communication skills. Many severely
retarded individuals are able to live in a group home.
 Profound Mental Retardation - Only 1-2% of the mentally retarded population is
classified as profoundly retarded. Profoundly retarded individuals have IQ scores
under 20-25. They may be able to develop basic self-care and communication skills
with appropriate support and training. Their retardation is often caused by an
accompanying neurological disorder. The profoundly retarded need a high level of
structure and supervision.
 The term “gifted” has no precise definition. Many schools or programs for the
gifted require an I.Q. of 130 or above.
 Gifted children are far above average in at least one ability, but may be much
closer to average in other abilities. That being said, people who are far above
average in one ability are usually above average in other abilities.
 The term “genius” has no technical definition, but it implies an extreme degree of
ability in at least one area. The brightest of children, to whom this term may be
fairly applied, often teach themselves to read at a very early age. For example a
three year old child may be reading at the second grade level, without any
training, other than being read to while sitting in an adult’s lap. These children
develop very large vocabularies and use their words correctly (and with correct
grammar.) They may go to college at age 10 or 12, and be in graduate school a
couple of years later.
 Most gifted children are well adjusted socially.
Here is an eight year old college student.

I.Q. Tests Do Measure:

I.Q. Tests Do Not Measure:

Analytical Intelligence Ability to learn
how to do things, acquire new
knowledge, solve problems, carry out
tasks effectively. (Sternberg)

Creativity (Sternberg)

Musical Intelligence Gardner)
Logical-Mathematical Intelligence
(Gardner)

Bodily-Kinesthetic Intelligence (Gardner)

Interpersonal Intelligence (Gardner)

Intrapersonal Intelligence (Gardner)

Naturalistic Intelligence Gardner)

Emotional Intelligence – Knowing one’s
own emotions, managing one’s
emotions, recognizing the emotions of
other people, and managing
relationships. (Goleman)


Linguistic Intelligence (Gardner)

Spatial Intelligence (Gardner)
All good tests must be valid and reliable.
Validity means that the test measures what it claims to measure.
If I make up a test and call it an I.Q. test but the test consists of
measuring your shoe size, is my new test valid?
If I make up a test of knowledge of American History, and it has only one
question on it, that being “Which explorer discovered the Pacific
Ocean”, is this a valid test? Why or why not?
Reliability means that the test produces consistent results. If I give you
an I.Q. test on January 5, and then test you again on July 7, the results of
the two tests should be very similar to each other. If the results are not
consistent, the test is not reliable.
By the way, the explorer who is credited with discovering
the Pacific Ocean is Vasco Núñez de Balboa.
Balboa was a Spanish conquistador and explorer. He was
the first European to see (and stand in the waters of) the
eastern shore of the Pacific Ocean, on September 13,
1513.
King Ferdinand of Spain appointed Balboa to serve under
Dévila as governor of Panama. Unfortunately for Balboa, Dávila
was a jealous man who did not like seeing the growing
popularity and influence which Balboa was developing. In
1518, Governor Pedro Arias Dávila falsely accused Balboa of
treason, had him arrested, ordered a speedy trial and
sentenced Balboa to death. In January 1519, Balboa and four
friends were beheaded.