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INTELLIGENCE, THINKING AND PERSONALITY

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Title: INTELLIGENCE, THINKING AND PERSONALITY


1
INTELLIGENCE, THINKING AND PERSONALITY
  • Factor Analytic Theories of Intelligence

2
BASIS OF THEORIES
  • Based on Factor-analytic treatment of
    psychometric tests
  • How do scores on individual test items or on
    subtests correlate with one another?
  • Do some scores correlate more than others?
  • How should these correlations be accounted for?

3
PURPOSE OF THEORIES
  • To explain individual differences in intelligence
  • NOT (primarily) to explain how intelligent
    behaviour comes about
  • i.e. not concerned with the cognitive apparatus
    underlying intelligence

4
SPEARMAN
  • Invented the first form of factor analysis
  • Proposed a two-factor theory of intelligence
  • Every activity involves a general factor a
    specific factor (g s)
  • g general intelligence and is innate
  • the specific factors need not be innate

5
SPEARMAN - cont
  • Spearman had noted that results of different
    intelligence tests (or subtests) almost always
    correlated positively.
  • His method of tetrads or the later principal
    components version of factor analysis finds a
    factor (g) that accounts for these correlations.

6
SPEARMAN - cont
  • However, this technique can miss clusters of
    strong correlations (e.g. verbal test results
    might go together in one cluster, and
    mathematical tests in another).
  • Gould gives a detailed presentation in Chapter 6
    of The Mismeasure of Man

7
DIAGRAMMATIC REPRESENTATION OF TEST RESULTS AND
FACTORS
  • Each test is represented as a line
  • Angle between lines (actually cosine of angle)
    represents correlation
  • Cosine of 0o is 1, so perfect correlation if
    lines are in same direction
  • Cosine of 90o is 0, so no correlation if lines
    are at right angles

8
PRINCIPAL COMPONENTSANALYSIS
  • Note - in general it is not possible to represent
    all correlations in two dimensions

g
maths tests
Verbal tests
2nd principal component
9
PRINCIPAL COMPONENTS ANALYSIS - cont
  • The first principal component is the best single
    summary of the results.
  • If the subtests are positively correlated, which
    is what Spearman observed, the first principal
    component will provide a resonable summary.
  • Technically, it will account for a substantial
    proportion of the differences between one person
    and another (variance) and more than any other
    possible principal component
  • It is Spearmans g factor (general intelligence)
  • So, the claim is that differences in g (IQ)
    explain differences in test performance quite
    well.

10
BURT AND VERNON
  • Proposed a hierarchical model, with three levels
  • g (as in Spearmans model)
  • group factors, suggested by the fact that some
    subtests correlate more strongly than others (but
    identified indirectly using the principal
    components method)
  • ve, verbal-educational ability
  • km,spatial-mechanical ability
  • specific factors (as in Spearmans model)

11
PRINCIPAL COMPONENTSANALYSIS (REPEATED)
g
km tests
ve tests
2nd principal component
12
THE SECOND PRINCIPAL COMPONENT
  • The second principal component has to be
    orthogonal (at right angles in the diagram) to
    the first).
  • If we take the second component to run from left
    (negative) to right (positive), in the example
    given the ve tests load negatively on that
    component and the km tests load positively.
  • The second component, therefore, provides an
    indirect representation of group factors.

13
THURSTONE - PRIMARY MENTAL ABILITIES
  • Thought g was not real enough
  • Disliked the idea of negative loading
  • Thought that abilities should be identified
    positively

14
THURSTONE - cont
  • Started with 56 different tests and identified(7)
    primary mental abilities, which he original
    wanted to claim were independent
  • S - spatial
  • P - perceptual speed
  • N - numerical reasoning
  • V - verbal meaning
  • W - word fluency
  • M - memory
  • I - inductive reasoning

15
THURSTONE - cont
  • Argued that g has no real significance, but just
    reflects correlations between test results (which
    may change if different tests are used).
  • Spearman and Burt later applied the same argument
    to Thurstones PMAs
  • Also argued that the use of a composite score, or
    a system of overall ranking (i.e. an IQ score)
    is inappropriate

16
THURSTONE - cont
  • Invented a method of rotating factors so that
    each one fell close to a cluster of strong
    correlations.
  • Produces a so-called simple structure (not
    inevitable that a matrix of correlations will
    yield a simple structure).
  • Wanted to eliminate negative projections of
    tests onto factors.

17
ROTATED, ORTHOGONAL FACTORS
  • Note that factors are at right angles (zero
    correlation) so lie outside clusters of tests if
    all tests positively correlated

Verbal PMA
Maths PMA
18
THURSTONE -cont
  • Thurstone later related g to the results of
    second order factor analysis
  • He realised that correlated factors would lie
    closer to his clusters than uncorrelated ones.
  • i.e. he realised there were correlations between
    his PMAs, even though he originally suggested
    they were independent

19
ROTATED, NONORTHOGONAL FACTORS
Verbal PMA
Maths PMA
  • Factors now lie within clusters, but are not
    independent, so harder to interpret

20
WHY SUCH DIFFERENT CONCLUSIONS?
  • There is no single correct way to do factor
    analysis
  • Spearmans method is bound to find a single
    factor, provided subtests are correlated to some
    degree
  • Thurstones will find separate factors if the
    subtests group to some degree

21
WHY SUCH DIFFERENT CONCLUSIONS? - cont
  • Exploratory factor analysis (the kind used in
    work on intelligence) is just a mathematical
    technique of data reduction and summarisation
  • By itself it cannot show the existence of
    things in the world that correspond to the
    factors it identifies (general intelligence or
    Thurstones PMAs)

22
LATER DEVELOPMENTS
  • Within the psychmetric framework
  • Guilford - Structure of the Intellect
  • Cattell - Crystallised and Fluid Intelligence

23
GUILFORD - STRUCTURE OF THE INTELLECT
  • Attempted a more systematic description of the
    Structure of the Intellect
  • He classified tasks/tests according to
  • content (4 types) e.g. visual figures, verbal
    meanings
  • operations (5 types) e.g. evaluation, memory
  • products (6 types), e.g. relations, implications

24
GUILFORD cont.
  • So, identified 4 x 5 x 6 120 distinct mental
    abilities
  • Guilford tried to develop tests for each
  • But scores on those tests were often strongly
    correlated

25
CATTELL - FLUID AND CRYSTALLISED INTELLIGENCE
  • Cattell 1963 - distinguished between crystallised
    and fluid intelligence, which has subsequently
    been of some importance
  • He regarded them as subdivisions of g, and so
    labelled them gf and gc

26
FLUID INTELLIGENCE
  • Deals with abstract relations
  • Is not taught
  • Is culture free
  • Declines with age in adulthood
  • Represents the ability to deal with new problems

27
CRYSTALISED INTELLIGENCE
  • Represents cumulative learning experience
  • wisdom?
  • expertise?
  • Increases with age

28
DOES INTELLIGENCE DECLINE WITH AGE?
  • According to Cattell, fluid intelligence
    decreases with age and crystallised intelligence
    increases.
  • Previous, cross-sectional work had tended to
    conclude that intelligence in general declines
    with age
  • However, this finding was probably an artefact of
    increasing educational opportunities in the 19th
    and 20th centuries

29
DOES INTELLIGENCE DECLINE WITH AGE? - cont
  • The older people in the studies had poorer
    education and so less accumulated knowledge, so
    overall their intelligence measured lower than
    expected.
  • Younger people had more accumulated knowledge
    that might have been expected because their
    education had been better.
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