Intelligence Dr Verity Leeson Imperial College. Learning Objectives What is Intelligence? What is...

IntelligenceIntelligence

Dr Verity LeesonDr Verity Leeson

Imperial CollegeImperial College

Learning ObjectivesLearning Objectives

What is Intelligence?What is Intelligence? How is intelligence measured?How is intelligence measured? Understanding the use and application of Understanding the use and application of

the WAIS the WAIS Evaluating the strengths and limitations of Evaluating the strengths and limitations of

IQ tests IQ tests Understanding psychometric approaches to Understanding psychometric approaches to

intelligenceintelligence How do heredity and environment influence How do heredity and environment influence

intelligenceintelligence

What is Intelligence?What is Intelligence?

AA property of mind that encompasses property of mind that encompasses many related mental abilities, such as many related mental abilities, such as the capacity tothe capacity to reasonreason planplan solve problemssolve problems think abstractlythink abstractly comprehend ideas and languagecomprehend ideas and language learnlearn

What is Intelligence?What is Intelligence?

When two dozen prominent theorists When two dozen prominent theorists were asked to define intelligence, were asked to define intelligence, they gave two dozen somewhat they gave two dozen somewhat different definitionsdifferent definitions (Sternberg & (Sternberg & Detterman, 1986)Detterman, 1986)

To some extent it is To some extent it is culturally culturally shapedshaped and defined, since cultural and defined, since cultural practices tend to recognise socially practices tend to recognise socially useful intellectual qualitiesuseful intellectual qualities

Measurement of Measurement of IntelligenceIntelligence

Sir Francis Galton (1822-1911) Sir Francis Galton (1822-1911) At London’s 1884 International At London’s 1884 International

Exposition 10,000 people paid 3P to Exposition 10,000 people paid 3P to undergo tests of reaction time, undergo tests of reaction time, memory, sensory ability, etc.memory, sensory ability, etc.

To his surprise the tests correlated To his surprise the tests correlated very little together, nor did they very little together, nor did they correlate with social class; the first correlate with social class; the first application of application of correlationcorrelation to the to the problem.problem.

Binet – Mental AgeBinet – Mental Age

France. Napolean Bonaparte recognised France. Napolean Bonaparte recognised the national importance of education and the national importance of education and required a method of identifying slow required a method of identifying slow learners for remediationlearners for remediation

Alfred Binet (1904) was commissioned to Alfred Binet (1904) was commissioned to develop tests.develop tests.

Tests were developed for each age group Tests were developed for each age group and a child’s ability was expressed as and a child’s ability was expressed as Mental Age (MA) corresponding to the Mental Age (MA) corresponding to the level of ability of a particular level of ability of a particular chronological age (CA) that they matched. chronological age (CA) that they matched.

Intelligence Quotient - Intelligence Quotient - IQIQ

USA. Lewis Terman of Stanford USA. Lewis Terman of Stanford University, adapted the test (Stanford-University, adapted the test (Stanford-Binet, 1916) and developed an IQ formula Binet, 1916) and developed an IQ formula to allow comparisons between individuals. to allow comparisons between individuals. IQ = (MA/CA x 100).IQ = (MA/CA x 100). (MA peaks at 15 yrs). (MA peaks at 15 yrs).

A person of average intelligence has an IQ A person of average intelligence has an IQ of 100.of 100.

Terman also devised the test so that the Terman also devised the test so that the IQ had a normal IQ had a normal bell-shaped distributionbell-shaped distribution with each standard deviation representing with each standard deviation representing 15 IQ points.15 IQ points.

IQ DistributionIQ Distribution

IQ TestsIQ Tests Tests are used for many purposes, such as Tests are used for many purposes, such as

selection, diagnosis, and evaluationselection, diagnosis, and evaluation Single type of item or questionSingle type of item or question

Peabody Picture Vocabulary Test (a Peabody Picture Vocabulary Test (a measure of children's verbal intelligence) measure of children's verbal intelligence)

Raven's Progressive Matrices (a Raven's Progressive Matrices (a nonverbal, untimed test that requires nonverbal, untimed test that requires inductive reasoning about perceptual inductive reasoning about perceptual patterns)patterns)

Many different types of items, both verbal Many different types of items, both verbal and nonverbaland nonverbal Wechsler tests Wechsler tests Stanford-BinetStanford-Binet

Raven’s Progressive Raven’s Progressive MatricesMatrices

Wechsler Intelligence Wechsler Intelligence ScalesScales

Wechsler’s (1939) tests are widely used Wechsler’s (1939) tests are widely used today (revised).today (revised).

To avoid literacy biases IQ was divided into To avoid literacy biases IQ was divided into Verbal IQ Verbal IQ - facility for symbolic thought - facility for symbolic thought

and language - & and language - & Performance IQPerformance IQ - symbolic nonverbal - symbolic nonverbal

thought and processing speed.thought and processing speed. Total IQ -Total IQ - 11 subtests, 6 verbal and 5 11 subtests, 6 verbal and 5

nonverbal.nonverbal. The equivalent test for children (7-16) is The equivalent test for children (7-16) is

the the Weschler Intelligence Scale for Weschler Intelligence Scale for Children (WISC/WISC-III)Children (WISC/WISC-III)

Verbal subtestsVerbal subtests

InformationInformation Examines general knowledgeExamines general knowledge

What day comes after Saturday?What day comes after Saturday? Who painted the Sistine Chapel?Who painted the Sistine Chapel? What is the speed of light? (between What is the speed of light? (between

238,000-320,000 km/sec)238,000-320,000 km/sec) 1 point for each correct answer1 point for each correct answer Discontinued after 6 consecutive Discontinued after 6 consecutive

incorrect responsesincorrect responses

Verbal subtestsVerbal subtests ComprehensionComprehension

What do people use money for?What do people use money for? Why should people pay taxes?Why should people pay taxes?

2 points – recognition that taxes financially 2 points – recognition that taxes financially support the government support the government

1 point – specifically mention of two or more 1 point – specifically mention of two or more institutions supported by the governmentinstitutions supported by the government

0 points – reference to one specific 0 points – reference to one specific institution, “it is illegal not to”institution, “it is illegal not to”

What does this saying mean? “still What does this saying mean? “still waters run deep.”waters run deep.”

Discontinued after 4 consecutive Discontinued after 4 consecutive incorrect responsesincorrect responses


ArithmeticArithmetic Requires working memory in Requires working memory in

addition to mathematical abilityaddition to mathematical ability How many blocks are there How many blocks are there

altogether?altogether? The price of shirts is 2 for 31 pounds. The price of shirts is 2 for 31 pounds.

What is the price of 1 dozen shirts?What is the price of 1 dozen shirts? If 8 machines are needed to finish the If 8 machines are needed to finish the

job in 6 days, how many machines are job in 6 days, how many machines are needed to finish the job in one-half day? needed to finish the job in one-half day?



SimilaritiesSimilarities In what way are a In what way are a fork fork and a and a spoonspoon alike? alike? In what way are In what way are workwork and and playplay alike? alike?

2 points – basic human activities, valued 2 points – basic human activities, valued activities, both require effort for successactivities, both require effort for success

1 point – part of life, actions, need energy to 1 point – part of life, actions, need energy to do bothdo both

0 points – do them with other people, 0 points – do them with other people, recreation, oppositesrecreation, opposites

In what way are an In what way are an enemyenemy and a and a friendfriend alike?alike?



VocabularyVocabulary Tell me what ______ meansTell me what ______ means

BedBed TranquilTranquil

2 points – peaceful, calm, serene2 points – peaceful, calm, serene 1 point – relaxed, laid back, satisfied, peace1 point – relaxed, laid back, satisfied, peace

Tirade Tirade Discontinued after 6 consecutive Discontinued after 6 consecutive

incorrect responsesincorrect responses


Digit spanDigit span Forwards and backwardsForwards and backwards 2 attempts on each span length 2 attempts on each span length

before discontinued before discontinued 1 point for each correctly produced 1 point for each correctly produced

spanspan Maximum 9 forward and 8 Maximum 9 forward and 8

backwardsbackwards


Letter- number sequencing (optional)Letter- number sequencing (optional) Examinee is read a combination of Examinee is read a combination of

numbers and letters and is asked to numbers and letters and is asked to recall numbers first in ascending recall numbers first in ascending order followed by letters in order followed by letters in alphabetical orderalphabetical order L-2L-2 D-1-R-9-B-4-K-3D-1-R-9-B-4-K-3

Requires working memoryRequires working memory

Performance SubtestsPerformance Subtests Picture Picture

completioncompletion Determine the Determine the

missing part in missing part in the picturethe picture

Discontinued Discontinued after 5 after 5 consecutive consecutive incorrect incorrect responsesresponses

Performance SubtestsPerformance Subtests

Digit Symbol –Digit Symbol –codingcoding

(optional)(optional) Need to draw Need to draw

correct symbol correct symbol for each numberfor each number

Complete as Complete as many as can in many as can in 120 seconds120 seconds

Performance SubtestsPerformance Subtests Block designBlock design 4 or 9 block 4 or 9 block

designsdesigns Required to Required to

replicate pattern replicate pattern with blockswith blocks

Time limitTime limit Discontinued Discontinued

after 3 after 3 consecutive consecutive incorrect incorrect responsesresponses

Performance SubtestsPerformance Subtests Matrix reasoningMatrix reasoning

(optional)(optional) Nonverbal task Nonverbal task Requires pattern Requires pattern

completion, completion, classification, classification, analogy & serial analogy & serial reasoningreasoning

Discontinued after Discontinued after 4 consecutive 4 consecutive incorrect responsesincorrect responses

Performance SubtestsPerformance Subtests Picture Picture

arrangementarrangement Picture cards Picture cards

need to be need to be rearranged to rearranged to tell a storytell a story

Time limitTime limit Discontinued Discontinued

after 4 after 4 consecutive consecutive incorrect incorrect responsesresponses


Symbol searchSymbol search Need to visually Need to visually

scan a group of scan a group of symbols to symbols to determine whether determine whether either of 2 target either of 2 target symbols are symbols are includedincluded

Complete as many Complete as many as can in 120 as can in 120 secondsseconds


Object assemblyObject assembly

Like a puzzle but Like a puzzle but without picture without picture to guide designto guide design

Time limitTime limit Administer all Administer all

itemsitems

WAIS Mental IndicesWAIS Mental Indices

1) 1) Verbal comprehensionVerbal comprehension Thinking in Thinking in language, a left hemisphere abilitylanguage, a left hemisphere ability

2) 2) Perceptual organisationPerceptual organisation Thinking in Thinking in visual images, predominantly a right visual images, predominantly a right hemisphere functionhemisphere function

3) 3) Working memoryWorking memory Ability to hold and Ability to hold and manipulate items in memory to solve manipulate items in memory to solve problems, involving the frontal lobesproblems, involving the frontal lobes

4)4) Processing speed Processing speed Time to apprehend, Time to apprehend, scan, retrieve, and respond to stimuliscan, retrieve, and respond to stimuli

Assist with neuropsychological Assist with neuropsychological diagnosisdiagnosis

Measuring Premorbid IQMeasuring Premorbid IQ

Tests of irregular word reading Tests of irregular word reading National Adult Reading Test-Revised (Nelson)National Adult Reading Test-Revised (Nelson) Wechsler Test of Adult Reading (Wechsler)Wechsler Test of Adult Reading (Wechsler)

Although patients with Although patients with neurodegenerative disease may not be neurodegenerative disease may not be able to give definitions, their correct able to give definitions, their correct pronunciation of words when reading pronunciation of words when reading provides evidence of their premorbid provides evidence of their premorbid familiarity with that word. familiarity with that word.

Problems with IQ TestsProblems with IQ Tests

Lack of theoretical basisLack of theoretical basis social and political need that led to social and political need that led to

IQ testsIQ tests Tests not based on cognitive and Tests not based on cognitive and

brain models brain models Binet set out only to address an Binet set out only to address an

educational aim, not to measure educational aim, not to measure innate abilityinnate ability

They do not assess creativity or They do not assess creativity or interpersonal skillinterpersonal skill


IQ tests are modestly related to IQ tests are modestly related to adaptive ability in achieving adaptive ability in achieving practical goals in life practical goals in life IQ scores and academic IQ scores and academic

achievement .50achievement .50 IQ scores and income .30IQ scores and income .30 IQ scores and occupational IQ scores and occupational

performance .15–.30performance .15–.30


Cultural bias?Cultural bias? Why do white, middle class have Why do white, middle class have

better scores?better scores? Apparently culture-free cognitive Apparently culture-free cognitive

tests of categorising geometric tests of categorising geometric stimuli according to size or shape, stimuli according to size or shape, actually require experience with actually require experience with abstract geometric shapes that are abstract geometric shapes that are taken out of context and reproduced taken out of context and reproduced on paperon paper

…….Cultural bias.Cultural bias

Serpell (1979) asked Zambian and Serpell (1979) asked Zambian and English children to reproduce English children to reproduce patterns in three media: wire patterns in three media: wire models, clay models, or pencil and models, clay models, or pencil and paper. Zambian children excelled in paper. Zambian children excelled in the wire medium. English children the wire medium. English children were best with pencil and paper. were best with pencil and paper.

Timed tests reflect cultural Timed tests reflect cultural emphasis on emphasis on speedspeed

Psychometric Psychometric ApproachesApproaches

Most common tests assess Most common tests assess gg – – general general intelligenceintelligence

Scores on individual tasks are Scores on individual tasks are correlatedcorrelated

Spearman Spearman Two-Factor TheoryTwo-Factor Theory (1904, UCL) (1904, UCL) (of Spearman’s correlation fame) (of Spearman’s correlation fame) factor factor

analysedanalysed IQ subtests and found - IQ subtests and found - gg an an all-round cognitive abilityall-round cognitive ability - being good - being good

at one test made it likely one would be good at one test made it likely one would be good at another at another

Specific Specific ss abilities abilities of which there were two of which there were two types - verbal/numerical and types - verbal/numerical and spatial/mechanicalspatial/mechanical

Fluid & Crystallised IQFluid & Crystallised IQ

Cattell, 1957Cattell, 1957 Fluid intelligenceFluid intelligence capacities which capacities which

have no specific content but are have no specific content but are used in processing information used in processing information and approaching novel problemsand approaching novel problems ((gfgf))

Crystallised intelligenceCrystallised intelligence an an individual’s store of knowledge, individual’s store of knowledge, much of which is learned from much of which is learned from cultureculture ( (gcgc))

……factor analysisfactor analysis

A recent reanalysis of 400 data A recent reanalysis of 400 data sets collected over several sets collected over several decades has shown a 3 level decades has shown a 3 level hierarchy (hierarchy (Carroll, 1993)Carroll, 1993) a general factora general factor primary abilitiesprimary abilities specific abilitiesspecific abilities

Gardener’s Theory of Gardener’s Theory of Multiple Intelligences Multiple Intelligences

(1983)(1983) 7 intelligences7 intelligences musicalmusical bodily/kinaesthetic as in athletes and bodily/kinaesthetic as in athletes and

dancersdancers spatial as in mental mapsspatial as in mental maps Linguistic/verbalLinguistic/verbal logical/mathematicallogical/mathematical intrapersonal- self understandingintrapersonal- self understanding interpersonal - social skillsinterpersonal - social skills

……Multiple Intelligences-Multiple Intelligences-evidence?evidence?

Each could be isolated Each could be isolated neuropsychologicallyneuropsychologically with its own rules, with its own rules, procedures and memory systemsprocedures and memory systems

SavantsSavants - individuals with pockets of - individuals with pockets of superior ability against a background of superior ability against a background of disabilitydisability

PProdigiesrodigies - Mozart could write music - Mozart could write music before he could read, i.e., musical IQ before he could read, i.e., musical IQ independent of verbal abilityindependent of verbal ability

Differential childhood developmental Differential childhood developmental coursescourses

Extra Intelligences?Extra Intelligences?

Gardener examined several possible Gardener examined several possible additionsadditions Naturalist intelligence Naturalist intelligence enables human enables human

beings to recognize, categorize and draw beings to recognize, categorize and draw upon certain features of the environment upon certain features of the environment

? Existential intelligenceExistential intelligence, a concern with , a concern with 'ultimate issues' 'ultimate issues'

? Moral intelligenceMoral intelligence concern with those concern with those rules, behaviours and attitudes that rules, behaviours and attitudes that govern the sanctity of life govern the sanctity of life

……Multiple IntelligencesMultiple Intelligences

LimitationsLimitations what of evidence of general abilities?what of evidence of general abilities? how to measure?how to measure? potential proliferation of IQ categories potential proliferation of IQ categories

(e.g. musical composition, music (e.g. musical composition, music performance, improvisation, etc)performance, improvisation, etc)

are some “intelligences” (bodily-are some “intelligences” (bodily-kinesthetic for example) appropriately kinesthetic for example) appropriately described as forms of intelligence or described as forms of intelligence or are they special talents?are they special talents?

What determines What determines IQ?IQ?

Developmental Developmental progressionsprogressions

Piaget – intelligence develops in Piaget – intelligence develops in children through the assimilation of children through the assimilation of new information into existing new information into existing cognitive structurecognitive structure

Vygotsky – all intellectual abilities Vygotsky – all intellectual abilities are social in originare social in origin

Heredity and Heredity and EnvironmentEnvironment

Relative independence of academic Relative independence of academic and practical intelligence. and practical intelligence.

Women shoppers in California who Women shoppers in California who had no difficulty in comparing had no difficulty in comparing product values at the supermarket product values at the supermarket were unable to carry out the same were unable to carry out the same mathematical operations in paper-mathematical operations in paper-and pencil tests (Lave, 1988)and pencil tests (Lave, 1988)

gene action always involves an gene action always involves an environmentenvironment

at least a biochemical environmentat least a biochemical environment often an ecological (interpersonal, often an ecological (interpersonal,

cultural) onecultural) one

Family environmentFamily environment a sizable part of the variation a sizable part of the variation

in intelligence test scores is in intelligence test scores is associated with genetic associated with genetic differences among individuals. differences among individuals.

Overall, heritability (h2) Overall, heritability (h2) works out to about .50 and works out to about .50 and the between-family variance the between-family variance (shared environment) (c2) to (shared environment) (c2) to about .25 (Chipuer et al, about .25 (Chipuer et al, 1990)1990)

……Family EnvironmentFamily Environment

These overall figures are misleading, These overall figures are misleading, however, because most of the relevant however, because most of the relevant studies have been done with childrenstudies have been done with children

h2 goes up and c2 goes down from h2 goes up and c2 goes down from infancy to adulthood (McCartney et al, infancy to adulthood (McCartney et al, 1990)1990)

Correlation between MZ twins reared Correlation between MZ twins reared apart, which directly estimates h2, apart, which directly estimates h2, ranged from .68 to .78 in five studies ranged from .68 to .78 in five studies involving adult samples from Europe involving adult samples from Europe and the U.S. (McGue et al., 1993)and the U.S. (McGue et al., 1993)

……Family EnvironmentFamily Environment

Correlation between unrelated Correlation between unrelated children reared together in adoptive children reared together in adoptive families, which directly estimates c2, families, which directly estimates c2, was approximately zero for was approximately zero for adolescents in two studies (Scarr & adolescents in two studies (Scarr & Weinberg, 1978; Loehlin et al, 1989)Weinberg, 1978; Loehlin et al, 1989)

Biological variablesBiological variables Malnutrition in childhoodMalnutrition in childhood Blood lead levels of children growing up Blood lead levels of children growing up

near a lead smelting plant were near a lead smelting plant were negatively correlated with IQ scores negatively correlated with IQ scores (Baghurst et al, 1992)(Baghurst et al, 1992)

Foetal alcohol syndromeFoetal alcohol syndrome Mothers who drank >4 units of alcohol Mothers who drank >4 units of alcohol

daily during pregnancy had children with daily during pregnancy had children with 5 points below controls at age 4. 5 points below controls at age 4. (Streissguth et al 1989) (Streissguth et al 1989)

Prenatal exposure to aspirin and Prenatal exposure to aspirin and antibiotics had similar negative effects in antibiotics had similar negative effects in this studythis study

The Flynn effectThe Flynn effect

like heightlike height Mean IQs have increased more than Mean IQs have increased more than

15 points-a full standard deviation-in 15 points-a full standard deviation-in the last fifty yearsthe last fifty years

Why?Why? Richer cultural environmentRicher cultural environment NutritionNutrition ArtefactArtefact

Sex DifferencesSex Differences Most standard tests of intelligence have Most standard tests of intelligence have

been standardised so that there are no been standardised so that there are no overall score differences between females overall score differences between females and malesand males

There is little evidence for an overall There is little evidence for an overall difference in IQdifference in IQ

Males better on visual-spatial tasks like Males better on visual-spatial tasks like mental rotation and spatio-temporal tasks mental rotation and spatio-temporal tasks like tracking a moving object through space like tracking a moving object through space

Females better on some verbal tasks Females better on some verbal tasks including synonym generation and verbal including synonym generation and verbal fluency fluency

……Sex DifferencesSex Differences Biological explanation e.g. sex related Biological explanation e.g. sex related

differences in the sizes of some portions of differences in the sizes of some portions of the corpus callosum; these differences are the corpus callosum; these differences are correlated with verbal fluency (Hines et al, correlated with verbal fluency (Hines et al, 1992).1992).

Social explanation – play in childhoodSocial explanation – play in childhood Hormonal influence - studies of individuals Hormonal influence - studies of individuals

who were exposed to abnormally high who were exposed to abnormally high androgen levels in utero (congenital androgen levels in utero (congenital adrenal hyperplasia; CAH). Adult CAH adrenal hyperplasia; CAH). Adult CAH females score significantly higher than females score significantly higher than controls on tests of spatial ability (Resnick controls on tests of spatial ability (Resnick et al, 1986)et al, 1986)

Learning DisabilityLearning Disability

MILD MILD 50-7050-70 No demonstrable CNS abnormalityNo demonstrable CNS abnormality Social class bias, predominantly in lower Social class bias, predominantly in lower

classesclasses Concerns 1 million in UKConcerns 1 million in UKSEVERE SEVERE <50<50 CNS aetiology - chromosomal - Down’s CNS aetiology - chromosomal - Down’s

syndromesyndrome No social class biasNo social class bias Psychological training greatest gains in Psychological training greatest gains in

this groupthis group Concerns 150,000 in UKConcerns 150,000 in UK

Intelligence Dr Verity Leeson Imperial College. Learning Objectives What is Intelligence? What is...

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