Intelligence Testing: Psychology’s Most
Important Contribution?
• Perhaps Psychology’s Most Familiar Contribution.
•Certainly Not Psychology’s Most Important Scientific
Contribution.
•Boring - Intelligence Is What An Intelligence Test
Measures.
•Piaget - Intelligence Is The Ability To Benefit From
Experience.
Galton’s Laboratory for Measuring Intelligence
(apparatus for testing absolute and differential threshold)
Alfred Binet
Origins of Intelligence Testing
•Galton: Looked for a correlation between acuity of the
senses and intelligence (colloquially defined)
•Alfred Binet and Theodore Simon (1905, 1908 and 1911):
How could they identify young Parisian school children who
could benefits from different levels of instruction?
•Validating procedure was performance at school.
•These schools placed heavy stress on certain traditional areas.
•Still unclear to what extent an intelligence test is measuring
ability to perform in a manner heavily reinforced by certain
segments of society as opposed to true intellectual ability.
Binet’s procedure
•Construct different types of items, e.g., vocabulary,
reading comprehension, reasoning, etc.
•Determine which items can be passed by X% of the
population (Binet: X = 60%; currently, X = 50%). Equivalent
of asking, “what can an average 6, 7, 8, etc. year-old
do?”
•Use novel items so that the test measures aptitude
rather than achievement.
–Example: Mark F if the sentence is foolish, mark S if it
is sensible:
•S F Mrs. Smith has had no children and I understand that
the same was true of her mother.
Mental age
•Concept introduced by Stern.
• Each subtest (arithmetical, memory, vocabulary, spatial relations, etc.)
contains items of graded difficulty.
Examples:
•Year II
–*Place simple blocks properly in 3-hole foam board.
–*Identify models of common objects such as a cup by their use.
–*Identify major part of a doll’s body.
–*Repeat two digits.
•Year III
–*Child is given 48 beads and a shoestring. He must thread beads on the string.
–*Child is given twelve 1-inch blocks. He must make a bridge out of three of them.
•Year VI
–*Child is given a card with mutilated pictures. He must name the parts that are
missing.
–*Child is given twelve 1-inch blocks. He must hand the examiner the number of
blocks he asks for.
•Year VIII
–*Two objects such as baseball and orange are named. The child must say in what way
they are alike and different.
–*A short paragraph is read to the child who must then answer simple questions about
it.
Calculating Mental Age
•Performance on each part of the test is averaged for children of a
particular age to obtain a norm for that age.
•The more subtests a child passes, the higher the child’s mental age.
•Mental age is the age level at which the child gets 50% or fewer items
correct.
•Mental age is obtained independently of chronological age, which is
the child’s actual age in years.
Stern’s measure of IQ: IQ = 100 x MA/CA
•A bright child is one who exceeds the norm for her age level. A dull
child is one who falls below the norm.
Examples of Test Items from Stanford-Binet
Year II
1. Place simple blocks properly in 3-hole foam board.
2. Identify models of common objects such as a cup by their use.
3. Identify major part of a doll’s body.
4. Repeat two digits.
Year III
1. Child is given 48 beads and a shoestring. He must thread beads on
the string.
2. Child is given twelve 1-inch blocks. He must make a bridge out of
three of them.
Examples of Test Items from Stanford-Binet
Year VI
1. Child is given a card with mutilated pictures. He must name the parts that are
missing.
2. Child is given twelve 1-inch blocks. He must hand the examiner the number of
blocks he asks for.
Year VIII
1. Two objects such as baseball and orange are named.
The child must say in what way they are alike and different.
2. A short paragraph is read to the child who must then answer simple questions
about it.
Year X
1. The child is asked to give reasons to questions such as: “Give two reasons
why children should not be too noisy in school.”
2. The child is asked to say as many words as he can in a one-minute period.
Hearings before the Committee on Immigration (cont’d)
This is the most important book that has ever been written on this
subject...Col. Robert M. Yerkes...vouches for this book, and speaks
in the highest terms of Prof. Carl C. Brigham, now assistant
professor of psychology in Princeton University. This comes as
near being official United States Army data as could well be
had...they had two kinds of tests, alpha and beta....They took the
greatest care to eliminate the advantage which native Americans
would otherwise have had....
C. C. Brigham, A Study of American Intelligence.
Princeton: Princeton University Press, 1923.
The Nordics are...rulers, organizers, and aristocrats...
individualistic, self-reliant, and jealous of their personal
freedom...as a result they are usually Protestants....The Alpine race
is always and everywhere a race of peasants...perfect slave(s), the
ideal serf... unstable temperament…and reasoning power so often
found among the Irish...our army sample of immigrants from Russia
is at least one half Jewish....Our figures, then, would rather tend to
disprove the popular belief that the Jew is intelligent...he has the
head form, stature, and color of his Slavic neighbors. He is an
Alpine Slav [pp. 182-3. 185, 189, 190 from Brigham].
Hearing before the Committee on Immigration, United States
Senate, February 20, 1923, (Washington, Government Printing
Office, 1923), pp.80-81.
We have been overrun with a horde of the unfit....we have had no
yardstick....The psychological tests...furnished us with the necessary
yardstick....The Army tests...revealed the intellectual endowment of
the men....The tests are equally applicable to immigrants....All that
is required is a staff of two or three trained psychologists at each
port....
.... See Memoirs of the National Academy of Sciences....We can not be
seriously opposed to immigrants from Great Britain, Holland, Canada,
Germany, Denmark, and Scandinavia....We can, however, strenuously
object to immigration from Italy... Russia ...Poland ...Greece...
Turkey.... The Slavic and Latin countries show a marked contrast in
intelligence with the western and northern European group....One can
not recognize the high-grade imbecile at sight....
Hearings before the Committee on Immigration (cont’d)
They think with the spinal cord rather than with the brain....The
necessity of providing for the future does not stimulate them to
continuous labor....Being constitutionally inferior they are
necessarily socially inadequate....Education can be received only
by those who have intelligence to receive it. It does not create
intelligence. That is what one is born with....The D minus group
can not go beyond the second grade....we shall degenerate to
the level of the Slav and Latin races...pauperism, crime, sex
offenses, and dependency...guided by a mind scarcely superior to
the ox....
...We must protect ourselves against the degenerate horde....We
must view the immigration problem from a new angle....We
must apply ourselves to the task with the new weapons of
science...the perfect weapon formed for us by science....it is
now as easy to calculate one ‘s mental equipment as it is to
measure his height or weight. The examination of over
2,000,000 recruits has tested and verified this standard....this
new method...will enable us to select those who are worthy and
reject those who are worthless.
Hearings before the Committee on Immigration and
Naturalization, House of Representatives, January 3, 4, 5,
22, and 24, 1923, (Washington, Government Printing Office,
1923), pp.589-594.
to further restrict immigration from southern and eastern
Europe...[since] the evidence is abundant...that...it is largely
of a very low degree of intelligence....A large proportion of
this immigration...consists...of the Hebrew
elements...engaged in the garment-making industry....some of
their labor unions are among the most radical in the whole
country....The recent Army tests show...the intelligence of the
Italian immigration...is of a very low grade, as is also that of
the immigration from Poland and Russia. All...rank far below
the average intelligence for the whole country.
Stanford Binet Test Materials
Administering the Stanford-Binet IQ Test
WECHSLER-BELLEVUE INTELLIGENCE TEST
Verbal
Performance
Information
picture arrangement
general comprehension
picture completion
digit
active completion
arithmetic reasoning
block design
similarities
object assembly
vocabulary
digit symbol
Intelligence Test Examples
Intelligence Test Examples
EXAMPLES OF ITEMS FROM WECHSLER-BELLEVUE TEST (VERBAL)
•
Information: (experience and education)
 Easy: How many ears do you have?
 Hard: Why does oil float on water?
 Very hard: What is a lien?
•Comprehension: (Practical knowledge and social judgment)
•What should you do if you cut your finger?
•Why do we elect senators and congressmen?
•Arithmetic: (Concentration and arithmetic reasoning)
•How many pieces result when you cut an apple in half? If a taxi charges 50¢ first 1/5
mile, 15¢ each additional 1/5, how much for a two mile trip?
•Similarities: (Logical and abstract thinking)
•What is similar about a plum and a peach?
•About 49 and 121?
•Digit Span: (Attention and rote memory)
•Repeat 5 4 6 7 4 3 2 6
•Vocabulary: (Word knowledge)
•Define: Diamond, Belfry, Traduce
EXAMPLES OF ITEMS FROM WECHSLER-BELLEVUE TEST
(NON-VERBAL)
Picture completion: (visual alertness and visual memory)
woman with mouth missing, scene with tree without shadow
Picture arrangement:(Interpretation of social situations) cartoons
Block Design: (Analysis and formation of abstract design) match by
synthesis a geometrical form
Object Assembly: (Putting together of concrete forms) jig saw
puzzles
Coding: (Speed of learning and writing symbols) substitute symbols
for letters, e.g. Y = 3, D = 4
Mazes: (Speed of learning and writing symbols) draw path through a
maze
Culture-free tests
Question 1: Pick out one item that does not
belong with the others:
cello hay
drum
violin
guitar
Question 2: Find the three things which are
alike in each list:
store banana basket apple reed plum
IQ and Competence
IQ
COMPTETENCE REPRESENTED
130
Mean of persons receiving Ph. D.
120
Mean of College Graduates
115
Mean of freshmen in typical first year college
Mean of children from white-collar and skilled labor homes
110
Mean of High School graduates
Has a 50 - 50 chance of graduating from college
105
About 50 - 50 chance of passing in academic H. S.
curriculum
100
Average for total population
IQ and Competence (cont’d)
IQ
COMPTETENCE REPRESENTED
90
Mean of children from low income city homes or
rural homes. Adult can perform jobs requiring
some judgment (operate sewing machine, assemble parts)
75
Adult 50 - 50 chance of reaching High School
60
Adult can repair furniture, harvest vegetables,
assist electrician
50
Adult can do simple carpentry, cosmetic work
Adult can mow lawns, do simple laundry
Distribution of IQ Scores
IQ
% of adults
130
120-129
110-119
90-109
80- 89
70- 79
less than 70
2.2
6.7
16.1
50.0
16.1
6.7
7.2
Normal Distribution
Validation of Stanford-Binet
IQ and
IQ and
IQ and
IQ and
IQ and
IQ and
reading comprehension
reading speed
English usage
history
biology
geometry
0.73
0.43
0.59
0.59
0.54
0.48
SAMPLE SUBJECT FROM TERMAN STUDY
A. Successful Subject
Subject A792 graduated from high school at 16, from college at
20, with Phi Beta Kappa honors, and received his Ph. D. in
science at 23. In his undergraduate college years he earned a
quarter of his expenses and in his graduate years supported
himself entirely. He was then awarded a National Research
Fellowship for post-doctoral study, after which he was
appointed to a position in a leading university. By the age of
40, he was nationally eminent and director of a great
scientific laboratory. He is listed in American Men of Science
and Who’s Who.
SAMPLE SUBJECT FROM TERMAN STUDY
B. An Unsuccessful Subject
Subject C49 had almost exactly the same I.Q. rating as A792, also had
a superior record through high school, and in college earned about
the same proportion of his expenses. There the similarity ends,
for C graduated from college well below the average of his class.
After graduation he drifted for several years, then returned to
college and managed to complete his work for a master’s degree.
His occupations since then have ranged from semiskilled labor and
clerical jobs to positions of minor responsibility in business
organizations. His chief handicaps have been inferior social
adjustment, uncertainty with respect to life goals and lack of
drive or persistence. As a result he has accomplished less than
the average college graduate.
Validity of IQ Tests
• Correlates 0.30-0.60 with grades.
• Poor predictor of achievement out of school.
• Best predictor of professional achievement is
socioeconomic status of parent.
Racial Differences in Mean IQ
Is Intelligence Heritable?
In 1923, ETS administered the Binet test to a large
group of immigrants and found the following
percentages of their sample to be feeble minded.
83% Jews
80% Hungarians
79% Italians
87% Russians
MEAN CORRELATION COEFFICIENTS FOR IQ, FOR
VARIOUS CATEGORIES OF PAIRS OF RELATIVES
Type of relationship
# of
separate
studies
# of pairs of
relatives
Mean Correlation
Coefficient
Identical twins raised apart
3
65
0.72
Identical twins raised
together
34
4672
0.86
Same-sex fraternal twins
raised together
29
3670
0.62
Opposite-sex fraternal twins 18
raised together
1592
0.57
Non-twin siblings raised
together
26473
0.47
713
0.30
69
Unrelated (adopted) siblings 11
raised together*
* This category consists of sibling pairs in which either one or both members
were adopted and genetic relationship was zero.
Herrnstein’s syllogism:
•We live in a meritocracy.
•IQ is heritable.
•If e2 decreases, h2 must increase.
(Beware! Improving education,
reduces e2 .)
How to Reduce h2
1.
2.
Interbreed - this reduces 2
Increase 2e.
How to Increase h2
1.
2.
3.
4.
outcrossing - new genes
mutation - new genes
select for rare characteristics
reduce 2e.
Three Classes of Minority Groups
Autonomous minorities- Deliberate separation
from mainstream. Proud of heritage, e.g.,
Amish.
Involuntary minorities- Did not choose their
minority status. Routinely judged as inferior by
dominant majority, e.g., blacks in North America,
Buraku in Japan, Harijans (untouchables) in India.
Immigrant minorities- Hope to better themselves
in accordance with their traditions.
Example of Effect of Membership in an
Involuntary Minority
Ogbu (Japanese minority)
• Have a caste-like status in Japan.
• Culturally, not racially, distinct.
• Average IQ score 10-15 points lower than
dominant majority in Japan.
• No difference in the United States.
time
IQ Scores
IQ Scores
IQ Scores
How does IQ change with time,
say, from 1920-2003?
time
time
Flynn effect
Flynn effect
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