PS28C Psychometrics

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PS28CPsychometrics

• Lecture 8
• Intelligence and Cognitive Abilities

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Introduction

• Review three perspectives on intelligence
• Psychometric
• Genetic
• Neuropsychological
• Review common measures of intelligence

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Definition of Intelligence and Abilities

• Cognitive abilities are cognitive traits
  implicated in solving problems. (Kline, 2000)
• Intelligence is a general reasoning ability,
  general because it is applicable in many fields.
  (Kline, 2000)

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The Psychometric Perspective

• Focuses on identifying a set of abilities
  associated with intelligence
• Administer a large number of tests to respondents
• Correlate scores on tests
• Conduct Factor Analysis to identify larger
  cognitive abilities

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The Psychometric Perspective

• Many competing findings
• Spearman found one large ability he called g
• Thurstone identified 9 core mental abilities but
  no g

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The Psychometric Perspective

• Cattell identified 3 levels of intellectual
  abilities
• 21 primary mental abilities
• 5 second order mental abilities
• Fluid and Crystallized Intelligence are two of
  the five
• 1 general mental ability corresponding to
  Spearmans g

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The Psychometric Perspective

• Provides a detailed description of mental
  abilities
• Little theoretical explanation for presence of 3
  hierarchical factors
• Heavily dependent on factor analysis
• Fails to suggest how intelligence develops or
  originates

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The Genetic Perspective

• Provides an explanation for basic source of
  intelligence
• Does not suggest what intelligence is
• Suggests that the most powerful influence on
  intelligence is genetics
• Intelligence is a complex genetic trait
• No single gene causes intelligence

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The Genetic Perspective

• Relies heavily on a statistical technique called
  biometric analysis
• Compares intelligence of people of varying
  degrees of relatedness
• Two types of twins
• Identical (Monozygotic)
• Non-Identical (Dizygotic)

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The Genetic Perspective

• Compare intelligence of identical twins raised
  together versus apart
• Compare intelligence of non-identical twins
  raised together versus apart
• If intelligence completely determined by
  genetics there should be no difference in
  identical twins intelligence scores

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The Genetic Perspective

• If intelligence is strongly genetically based
  identical twins should have greater correlation
  in intelligence scores than non-identical twins
• Difference in size of correlations of
  intelligence for identical twins raised together
  versus apart is the contribution of environment
  to intelligence

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The Genetic Perspective
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The Genetic Perspective

• Several criticisms of analyses
• Environments of identical twins raised together
  are more similar than non-identical twins raised
  together
• Identical twins raised apart are a very rare
  group
• Identical twins when separated are usually in
  close proximity
• Studies done in countries with small differences
  in social environments

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Neuropsychological Perspective

• Intelligence determined by two factors
• Neurological health of person
• Quality of early environment
• Emerges from clinical assessment of people with
  head injuries
• Specific injury associated with greater deficits
  in specific aspects of intelligence

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Neuropsychological Perspective

• Environment important for protecting or enhancing
  brain development
• More environmental threats the greater the
  impairment
• Psychologically stimulating environments promote
  brain growth

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Neuropsychological Perspective

• Major problem is source of data
• Case studies of small numbers of people
• People with head injuries may not be
  representative of normal intellectual functioning
• Children living in extremely deprived environments

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Tests of Intelligence

• Two categories of intelligence test
• Individually administered
• Group administered
• Individual tests more accurate
• Require high level of training to administer and
  interpret
• Usually given in schools, clinics, or hospitals

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Tests of Intelligence

• Two major individual tests of intelligence
• Wechsler Tests
• Standford-Binet
• Wechsler tests cover preschool to elderly
• 3 specific tests, but all Wechsler tests are
  similar in content

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Tests of Intelligence

• WAIS consists of 11 subtests
• Divided into Verbal and Performance scales
• Verbal scale includes subtests on
• Information
• Comprehension
• Arithmetic
• Similarities
• Vocabulary
• Digit Span

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Tests of Intelligence

• Performance scale includes subtests
• Digit symbol
• Picture completion
• Block design
• Picture arrangement
• Object Assembly
• Verbal and Performance scales yield IQ scores
  Total IQ

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Tests of Intelligence

• Stanford-Binet originally developed for children
  but extended to adults
• Items organized by difficulty level rather than
  type of task
• Only generates a total IQ score
• Can not assess adults with very high levels of
  intelligence

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Tests of Intelligence

• Several group tests of intelligence
• Ravens Matrices
• Mill-Hill Vocabulary Test
• Culture Fair Test