key research (part A)

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Created by
Ayanna vickerson

Cards (9)

  • aim

    to investigate whether biological factors and/or environmental factors affect intelligence using twins, parents and siblings
  • research methods

    mini case studys
    correlation study
  • participants

    112 families (with twins and an extra sibling)
    between the ages 9-14
    Netherlands
    the Netherlands twin registry
    VU university of Amsterdam
  • characteristics

    23 pairs of male monozygotic twins
    23 pairs of male dizygotic twins
    25 pairs of female monozygotic twins
    21 pairs of female dizygotic twins
    20 pairs of opposite sex dizygotic twins
  • procedure

    both parents and children signed a consent form.
    families asked to take part in a number of measures (MRI scans, cheek swabs, cognitive testing)
    data collection took place over two days
    children asked to complete Ravens standard progressive matrices (SMP)
    parents asked to complete Ravens advanced progressive matrices (AMP)
  • Ravens Standard Progressive Matrices (SMP)
    - 60 problems divided into 5 sets of 12
    - in each set the first problem is as nearly as possible self-evident and then the problems becoming progressively more difficult
    - it provides an index of general intelligence
  • Ravens Advanced Progressive Matrices (APM)

    - this is administered to adults as the SMP is too easy
    - the test is comparable to the SMP but more difficult
    - consists of two sets
    set 1 has 12 practice items to familiarise the participant with the test
    set 2 consists of 26 items which are identical in presentation
    - the items progressively get more difficult and complex
  • key quantitative findings
    • the variance for siblings was significantly larger than for twins (may be due to age difference)
    • correlations were higher in monozygotic twins than any other first degree relatives
    • genetics accounts for 67% of variation in intelligence and the remainder is due to random environmental factors
  • conclusions
    1. variability in fluid intelligence (as measured by Raven) is largely explained by genetic effects that are passed from parents to children
    2. individual differences in intelligence are largely accounted for by genetic differences
    3. environmental factors are significantly more important in children with a genetic predisposition for a lower IQ