1. Human Mental Abilities
Lecture 5
Leonardo Gabales

2. Introduction to Major ‘IQ’ Tests
There are a more than 10,000 different standardized tests of cognitive abilities available - they differ with respect to the domain of mental abilities that are assessed
(For various reasons) some tests are used more often than others – here, we review:
The Stanford-Binet Test
The Wechsler Intelligence Tests

3. Linking Theory & Practice…
Early test-development & interpretation was influenced by the prevalent theory of the time - ‘g’ theory (the 1st Wave of Test Interpretation)
Assessment of ‘general intellectual functioning’ - e.g., the SB provided a single composite intelligence score – ‘IQ’
Developments in theories of intelligence (e.g., Gf-Gc theory) led to the construction of new tests & post hoc interpretations of existing tests in a more differentiated manner (the 2nd & 3rd Waves of Test Interpretation)
Profile analyses become more prevalent - e.g., the WAIS-R provided Verbal, Performance, & Full-Scale IQ scores
More recently, theory-based test development & interpretation has become more prevalent
E.g., The Woodcock-Johnson Psycho-educational Battery-III (WJ-III) is based explicitly on CHC theory

4. The Stanford-Binet
Binet & Simon developed their first test battery in 1905 (the test was revised in 1908 & 1911)
They were particularly concerned with the development of a test that would "objectively" assess performance of school children in order to identify “dull” children
They considered many different types of problems but kept only those that had high predictive validity for school achievement
As a result, their scale contained items of a more abstract & complex nature than had been previously employed in tests of mental ability

5. “The scale, properly speaking, does not permit the measure of the intelligence, because intellectual qualities are not superposable, and therefore cannot be measured as linear surfaces are measured.”
(Alfred Binet)

6. “There is nothing about an individual as important as his IQ.”
(Lewis Terman)

7. Development of the Stanford-Binet
During WWI it was translated into English & was standardized at Stanford University in the most recent revision (the 5th) was carried out in 2003
Many aspects of test development were repeated with subsequent tests & many new intelligence tests used scores on the Stanford‑Binet as a criterion in validation studies
Hence, it is important to consider the principles involved in the construction of this test

8. Development of the Stanford-Binet
Items were assigned mental age levels on the basis of typical performance of children at a particular age information gathered in the process of test standardization
“A millimeter is short; a kilometer is ” was assigned to age 7 because about 50% of the children at that age provided a correct answer
“What do we mean by (Constant, Courage, Skill, Juggler)?” is assigned to age 12 because, again, about 50% of children at that age provide correct answers to these questions

9. Development of the Stanford-Binet
Children were given not only items that corresponded to their own age but also items assigned to different ages
If a child whose chronological age was, say, 8 years managed to solve items that were assigned to the age of 10, he/she was said to have mental age of 10

10. Development of the Stanford-Binet
In early versions of the Stanford-Binet, IQ was calculated by a very simple formula:
IQ = (Mental Age/Chronological Age)*100
if Mental Age>Chronological Age, IQ is above average
if Mental Age<Chronological Age, IQ is below average
Thus, an 8 year old who performs at the level of an average 10 year old would have an IQ of 125: (10/8) x 100 = 125
This is referred to as Ratio IQ

11. Ratio IQ
Allows comparison of intellectual performance across age levels
E.g., 2/4 * 100 = 50 vs 10/12 * 100 = 83
BUT: It only works if mental age increases parallel with age
What would be an “age-level-typical” task for a 43year old?
What does it mean if a 50 year old has a mental age of 25?
time
age
intellectual ability

12. The Stanford-Binet IV
The 1986 revision of the Stanford-Binet (SB-IV) has a very high reliability coefficient (r=.90 for total test score; SEM is about 5)
Test manual provides several types of evidence for its validity:
e.g., Assessment by teachers
Gifted group: an average IQ of 121
Learning disabled group: an average IQ of 75
Mentally retarded children: an IQ of  50

13. The Stanford-Binet IV
Earlier versions of the SB had a large number of verbal items
The 1986 version is based on Gf/Gc theory & has a more balanced composition of verbal (i.e., largely Gc) & non‑verbal (i.e., largely Gf) items
The test consists of 15 scales, chosen to represent 4 major cognitive areas:
Verbal reasoning
Abstract/visual
Quantitative reasoning
Short-term memory

14. SB-IV Tests

15. E.g., The word is charlatan. What does charlatan mean?
SB-IV Tests
Vocabulary: Given to all participants (since routing test)
Naming pictured items (1-14);
Defining spoken words (15-46)
E.g., The word is charlatan. What does charlatan mean?
Pass: fake, quack, impostor, con artist
Query: bad person, a cheat, two-timer, acts cunning or sly
Fail: joker, romantic, noble, imaginary or make-believe

16. SB-IV Tests Bead Memory Quantitative
Locating beads in a pictorial array (1-10)
Arranging beads on a stick to match a pattern presented for 5 seconds (11-42)
Quantitative
Counting or arranging dice (1-12)
Solve verbally presented numerical problems (13-40)
E.g., A piece of furniture is priced at $600. If it is paid for in 24 monthly instalments, the payments are $30 each month. How much more does it cost to pay for piece of furniture in monthly payments than to pay the full price at the time of purchase?

17. SB-IV Tests Memory for Sentences Pattern Analysis
Repeating sentences of successively greater length
E.g., it was raining this morning, so the children carried umbrellas to school
Pattern Analysis
Fitting shapes to form boards (1-6)
Arranging black-and-white blocks to match a given 2-D pattern

18. e.g., why should doctors be licensed?
SB-IV Tests
Comprehension
Identifying body parts (1-6)
Answering questions on practical and social matters (7-42)
e.g., why should doctors be licensed?
Pass: to make sure he/she knows what he/she is doing; so people know they are qualified
Query: for safety of patient; patient will feel secure.
Fail: so won’t hurt; would be lawsuits, etc.
Absurdities
Indicating an unusual or impossible aspect of a picture

19. SB-IV Tests Memory for Digits Copying
Repeating a sequence of digits forwards and backwards
e.g., ………
Copying
Constructing a pattern with blocks (1-12)
Drawing copies of simple geometric designs (13-28)

20. SB-IV Tests Memory for Objects Matrices
Recalling pictured items presented briefly (1 sec) e.g.,
Matrices
Completing a matrix by selecting an item from an array

21. SB-IV Tests Number Series Paper Folding & Cutting
Completing a series of numbers by determining the rule
3, 5, 7, 9, 11, __, __
(13, 15)
2, 6, 4, 12, 10, 30, 28, __, __
(84, 82)
Paper Folding & Cutting
Determining how a folded piece of paper would appear when unfolded

22. SB-IV Tests

23. e.g., gold, silver, platinum, NOT iron
SB-IV Tests
Verbal Relations
Explaining similarity between items
e.g., gold, silver, platinum, NOT iron
Pass: expensive; precious/rare metal
Query: value; beautiful; heavier; decorative metals
Fail: shiny; metals; minerals; etc

24. SB-IV Tests Equation Building
Arranging numerals and arithmetic signs to form an equation
= ?
(2 + 3 = 5)
x = ?
(2 x 4 – = 9)

25. SB-IV: Concluding Remarks
The SB-IV:
Combined “old tasks & new theory” (Thorndike & Lohman, 1990, p. 126)
Offers a total score as well as profile scores
Has an easy, flexible & versatile administration format, & good psychometric properties (validity & reliabilities)
Major weaknesses of the SB-IV:
The (un-)representative normative sample
Disputed factor structure

26. Wechsler Adult Intelligence Scale WAIS-III
David Wechsler
( )

27. Historical Trajectory
1939 Wechsler Bellevue Adult Intelligence Scale
1955 Wechsler Adult Intelligence Scale (WAIS)
1981 WAIS-R
1997 WAIS-III
2008 WAIS-IV

28. Wechsler’s Definition of Intelligence
“Intelligence is the aggregate or global capacity of the individual to act purposefully, to think rationally and to deal effectively with his environment.”
Global because it characterizes individual’s behavior as a whole
Aggregate because it is composed of elements or abilities that are qualitatively differentiable
Wechsler, 1939

29. Proclamation of incompleteness
Measure what can be measured
Analysing measures
Factor analysis
Taxonomy of measures --> “theories” of intelligence
Difficulties in measuring creativity, wisdom, learning agility …
Ergo: Our account of intelligence is limited

30. Basic Description of the WAIS–III
Individual Administration
Duration: 60 to 80 minutes
Depending on subsets, goal, and … examinee
Assessment of Cognitive Functioning in Adults, Aged 16 – 89 Years
Scale Composition
14 Subtests

31. The WAIS Tests
In all Wechsler's tests, items that have the same format are grouped together to form what is called a ‘subscale’
Sometimes, tests that do not have items grouped are called the "omnibus" tests of intelligence - the early versions of the Stanford‑Binet test were omnibus tests of intelligence
The WAIS differs from the Stanford‑Binet test in that subscales contain items that are identical across the age groups
Thus, a person at the age of 20 will do the same items as the person at the age 70

32. Picture Completion
What important part is missing?

33. Vocabulary “I want you to tell me the meaning of some words …
Tell me what … means
1. Bed …
3. Penny
17. Sanctuary
18. Designate
31. Encumber
32. Tirade

34. Digit Symbol-Coding
“Look at these boxes. Notice that each has a number in the upper part and special mark in the lower part. Each number has its own mark.“

35. Digit Symbol-Coding
“Now look down here where the squares have numbers in the top part but the squares at the bottom are empty …
… In each of the empty squares, put the mark that should go there. Like this … (Test presenter puts in the first 4 symbols)

36. Similarities
“In this section, I am going to read two words to you, and I want you to tell me how they are alike.”
1. Piano – Drum …
11. Work – Play
13. Egg – Seed
19. Enemy – Friend

37. Block Design Material: 4 to 9 identical blocks
Task: to replicate models or pictures of two-colour designs. 8 2 9

38. Arithmetic 3. “How much is $4 plus $5?“ (time limit 15 sec) …
14. “What is the average of these numbers: 10, 5, 15?” (time limit 60 sec)

39. Matrix Reasoning
“… for each picture there is a part missing. Look at the aspects of each picture carefully and choose the missing part from the five choices.”

40. Digit Span Forward
“I am going to say some numbers. Listen carefully, and when I am through, I want you to say them right after me. Just say what I say.”
2. “five-eight-two” (ISI: 1 sec., lower voice at the end) …
8. “ ”

41. Digit Span Backwards
“Now I am going to say some more numbers. But this time when I stop, I want you to say them backward.”
List length varies from 2 to 9 digits

42. Information 5. “What is a thermometer?” …
10. “Who was Martin Luther King, Jr.?”
24. “What was Marie Curie famous for?”
28. “Who wrote Faust“

43. Picture Arrangement
“These pictures tell a story about a worker building a house, but the are in the wrong order. Put them in the right order so they will tell a story that makes sense.”

44. Picture Arrangements
Presentation
Solution

45. Comprehension
“Now I‘m going to ask you to tell me some solutions to everyday problems or social concerns”:
“Why do people wash their clothes?” …
“Tell me some reasons that we have a parole system.”
“What does this saying mean? ‘Shallow brooks are noisy.”

46. Symbol Search
… check whether either of the two symbols on the right matches any of the symbols on the left
120 seconds,
60 items

47. Letter-Number Sequencing
Numbers and letters are presented aurally
Reproduction of
numbers first in ascending order
then letters in alphabetical order

48. Object Assembly

49. Proclamation of incompleteness
Wechsler: test does not claim to measure all what constitutes general intelligence (intelligence in general?)
What we can expect from an intelligence scale is that it measures essential aspects of intelligence so that it can be used as a more or less reliable index for the global ability of a given examinee

50. Wide Variety of Intelligences?
Education-based knowledge
Language, numbers, shapes
Concrete, abstract
Speeded, un-speeded
Memory
Abstract reasoning, rule inference
Practical knowledge …

51. One or many Intelligence(s)? What should we expect?
Reasonable assumptions:
Being good in one task may carry a price in being poor at others
seeing spatial patterns vs. verbal skills
focus on details vs. speed
speed vs. memory
Not true
All tests correlate positively
( )
Positive manifold
Is it just “g” after all?!

52. Just Spearman’s g? … not quite
tests
“All animals are equal, but some animals are more equal than others”
All tests are positively related…
But there are groups of tests that display especially high relationships to each other:
Vocabulary, Information, Similarities, Comprehension
Arithmetic, Digit Span, Letter-Number Sequencing …

53. Mental abilities measured in the WAIS III
Verbal Comprehension
Perceptual Organization
Working Memory
Processing Speed
Vocabulary
Similarities
Information
Comprehension
Picture Completion
Block Design
Matrix Reasoning
Picture arrangement
Arithmetic
Digit Span
Letter-Number Sequencing
Digit Symbol-Coding
Symbol Search

54. WAIS–III Subtests for IQ Scores
Verbal Performance
Vocabulary
Similarities
Arithmetic
Digit Span
Information
Comprehension
Picture Completion
Digit Symbol-Coding
Block Design
Matrix Reasoning
Picture Arrangement

55. WAIS Psychometric Properties
This test has a very good reliability & a small standard error of measurement:
Reliability
SEM
Verbal IQ
.97
2.74
Performance IQ
.90
4.14
Full Scale IQ
.96
2.53

56. Factorial structure of the WAIS-III
(Deary, 2001, p. 128)

57. IQ Scores
In all recently developed tests of intelligence, the concept of 'mental age' has been abandoned
The IQ score now represents a measure of the difference between a person’s ability & the average performance level of all people of that age
Thus, an IQ of 100 means that a persons performs at the same level as the average person of his own age, & IQ of 115 means that the person is one standard deviation above the average

58. The WAIS & Other Measures
WAIS Full Scale IQ score correlates about .50 with school marks & has a high correlation (~.85) with the SB
The WAIS has been employed in some research at the University of Sydney:
Results suggest that average Full Scale IQ for the 1st Year students is 115
This is about one standard deviation higher than the average IQ of the population
The lowest score obtained by a university student was 99 & there were many cases of IQ higher than 130

59. The WAIS & Other Measures
Interestingly, the average IQ scores for Performance & Verbal scales differ from Full Scale average
The average Performance IQ is about 110 ‑ closer to the average of the population
The average Verbal IQ score, on the other hand is  122.
Thus, our University students tend to be considerably better than the population at large in verbal ability
Uni students seem to be selected mainly on the basis of their verbal achievement in school & on exams

60. Summary The link between theory & practice
Major tests of intelligence – the SB & the WAIS
The proclamation of incompleteness
IQ scores & the concept of mental age