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Human Mental Abilities

Lecture 5

Leonardo Gabales

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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

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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

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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

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“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)

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“There is nothing about an individual as important as his IQ.”

(Lewis Terman)

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Development of the Stanford-Binet

During WWI it was translated into English & was standardized at Stanford University in 1937 - 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

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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

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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

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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

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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

age

intellectual ability

time

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?

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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

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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

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SB-IV Tests

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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

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SB-IV Tests Bead Memory

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?

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SB-IV Tests Memory for Sentences

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

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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 qualifiedQuery: 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

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SB-IV Tests

Memory for Digits Repeating a sequence of digits forwards and

backwards

e.g., 5-7-8 ……….8-1-7-4-9-3-2-6-5

Copying Constructing a pattern with blocks (1-12) Drawing copies of simple geometric designs (13-28)

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SB-IV Tests Memory for Objects

Recalling pictured items presented briefly (1 sec) e.g.,

 

Matrices

Completing a matrix by selecting an item from an array

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SB-IV Tests Number Series

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

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SB-IV Tests

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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

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SB-IV Tests Equation Building

Arranging numerals and arithmetic signs to form an equation

2 3 5 + = ? (2 + 3 = 5)

2 4 5 6 9 + - x = ? (2 x 4 – 5 + 6 = 9)

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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

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Wechsler Adult Intelligence Scale WAIS-III

David Wechsler(1896-1981)

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Historical Trajectory 1939 Wechsler Bellevue Adult Intelligence

Scale

1955 Wechsler Adult Intelligence Scale (WAIS)

1981 WAIS-R

1997 WAIS-III

2008 WAIS-IV

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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

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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

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Basic Description of the WAIS–IIIBasic 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

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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

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What important part is missing?

Picture Completion

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Vocabulary

“I want you to tell me the meaning of some words …Tell me what … means

1. Bed…

3. Penny…

17. Sanctuary18. Designate

…

31. Encumber32. Tirade

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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.“

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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)

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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

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Block DesignMaterial: 4 to 9 identical

blocksTask: to replicate models or pictures of two-colour designs.

2 8

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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)

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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.”

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Digit SpanForward

“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. “7-1-3-9-4-2-5-6-8”

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Digit SpanBackwards

“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

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Information• 5. “What is a thermometer?”

• …

• 10. “Who was Martin Luther King, Jr.?”

• …

• 24. “What was Marie Curie famous for?”

• …

• 28. “Who wrote Faust“

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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.”

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Picture ArrangementsPresentation

Solution

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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.”

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Symbol Search … check whether either of the two symbols

on the right matches any of the symbols on the left

120 seconds, 60 items

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Letter-Number Sequencing Numbers and letters are

presented aurally

Reproduction of

numbers first in ascending order

then letters in alphabetical order

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Object Assembly

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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

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

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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

(.30 - .80) Positive manifold

Is it just “g” after all?!

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Just Spearman’s g? … not quite

“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 …

teststests

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Mental abilities measured in the WAIS III

• Vocabulary• Similarities • Information• Comprehension

• Arithmetic

• Digit Span

• Letter-Number Sequencing

• Picture Completion

• Block Design

• Matrix Reasoning

• Picture arrangement

• DigitSymbol-Coding

• Symbol Search

Verbal Verbal ComprehensionComprehension

Perceptual Perceptual OrganizationOrganization

WorkingWorkingMemoryMemory

ProcessingProcessingSpeedSpeed

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WAIS–III Subtests for IQ Scores

• Vocabulary• Similarities• Arithmetic• Digit Span• Information• Comprehension

• Picture Completion• Digit Symbol-Coding• Block Design• Matrix Reasoning• Picture Arrangement

VerbalVerbal PerformancePerformance

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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

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

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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

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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

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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

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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