Intelligence refers to the ability to understand complex ideas, learn from experiences, reason, and adapt to new situations. There are several theories of intelligence, including Spearman's two factors of general and specific intelligence, Gardner's theory of multiple intelligences consisting of nine types, and Sternberg's triarchic theory of analytical, creative, and practical intelligence. Intelligence is commonly measured using tests such as Binet's mental ability test, the Stanford-Binet test, and the Wechsler tests for children and adults. Individual differences in intelligence include mental retardation, with mild to profound classifications based on IQ ranges below 70, and giftedness, referring to those with IQs above 130.

1. INTELLIGENCE
DEFINITION:
Intelligence is the capacity to understand the world, think
rationally and use resources effectively when found with
challenges.
Intelligence is the ability to learn from one’s experience,
acquire knowledge and use resources effectively in
adopting to new situations of solving problems.
THEORIES OF INTELLIGENCE-
1. Spearman’s Two Factors: According to him there are
two abilities in intelligence :-
a) General intelligence
b) Specific intelligence
a) G-factor: The ability to reason and solve problems.
b) S-factor: The ability to excel in certain areas or specific
intelligence. e.g. music, art etc.

2. 2. Gardner’s Multiple intelligences :
Gardner(1993,1999)said overall intelligence comprises nine
different types. They are-
1) Verbal, 2) Musical, 3) Mathematical or logical
4) Visual, 5) Movement, 6) Interpersonal and Intrapersonal,
8) Naturalist, 9) Existentialist
3. Sternberg’s Triarchic Theory : There are three aspects of
intelligence-
a) Analytical intelligence :The ability to break problems down
into component parts or analysis for problem solving.
b) Creative intelligence :The ability to deal with new and
different concepts and to come up with new ways of
solving problems.
c) Practical intelligence : The ability to use information to get
along in life and become successful.

3. MEASURING INTELLIGENCE:
Intelligence test means a battery of measures used
to determine a person’s level of intelligence.
1) Binet's Mental Ability Test: Alfred Binet a French
psychologist, was asked by the French Ministry of
Education to design a formal test of intelligence
that would help identify children who were
reasonable to learn as quickly or well as others so
that they could be given remedial education. Binet
and his colleague, Simon(1916) came up with a
test that not only distinguished between fast and
slow learners but also between children of
different age groups as well.

4. How to measure:
Children were assigned a score that corresponded
to their mental age, the average age of children
taking the test who achieved the same score.
For example: If a nine year old boy received a
score of 45 on the test and this was the average
score received by the 8 years old boy, his
mental age would be considered to be 8 years.
Mental age concept was given by Alfred Binet.

5. 2. STANFORD-BINET TEST :
Terman (1916) a researcher at Stanford
University, adopted William Stern’s method
IQ.
Stern’s formula of IQ (Intelligence Quotient):
MA/CA×100
For example: If a child who is 10 years old
takes the test and scores mental age of 15,
the IQ would be : 15/10×100=150
This test is generally used for children.

6. 3. THE WECHSLER TEST :
David Wechsler (1981,1990,1991) developed an IQ
test for adults. He later designed test for older
school age children and pre-school age children
also. He introduced three version of test. They are:
• WAIS: Wechsler Adult Intelligence Scale.
• WISC: Wechsler Intelligence scale for children.
• WPPSI: Wechsler Pre-school and Primary Scale of
intelligence.
It measures Verbal Ability and Performance Ability of
individual.

7. • Verbal ability : It includes: Information,
Comprehension, Arithmetic, Similarities, Vocabulary.
• Performance ability: Picture arrangement, Picture
completion, Block design, Object assembly, Digit
symbol.
On the Wechsler’s IQ test, the percentages under each
section of the normal curve are like this-

8. INDIVIDUAL DIFFFERENCES IN INTELLIGENCE:
1) Mental Retardation(Developmental Delay)
2) Giftedness
1. Mental Retardation(Developmental Delay): When a
person’s behavioral and cognitive skills exists at an
earlier developmental stage is known as developmental
delay. It affects intelligence but not on affection, love
etc.
Criteria:
a) The person’s IQ must fall below 70.
b) A person’s adoptive behavior is severely below a level
appropriate for the person’s age.
c) This limitation must be present before the age of 18
years.

9. Classification:
Causes:
a. Environmental: Lead & Mercury poisoning
b. Biological : Down Syndrome ,Fetal alcohol syndrome
and Fragile X syndrome.
c. Other causes are: lack of oxygen at the time of birth,
damage to the Fetus due to diseases, infection, drugs or
accident.
Mental Retardation Level IQ Range
1. Mild Retardation 50-70
2. Moderate Retardation 40-55
3. Severe Retardation 25-40
4. Profound Retardation Below 25

10. 2. Giftedness: 2% of the population falling on the upper
end of the normal curve and possesses IQ of 130 and
above are called gifted person. Gifted persons become
successful in life than intelligence and high academic
achievement.
Criteria:
a) IQ > 130
b) IQ>140-They are called genius.
Characteristic:
a. typically grow up to the well adjusted adults except
when pushed to achieve at younger ages.
b. Extreme geniuses may experience social and behavioral
adjustment issues at childhood.