Key Research - Van Leeuwen et al (2008)

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  • Created by: Rosa335
  • Created on: 18-06-17 07:42
Van Leeuwen et al - What did they aim to study?
To use not only twins but parents and siblings to identify the relationship between family member and IQ
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Van Leeuwen et al - Outline the sample used
112 families, either MZ or DZ twins, plus a sibling aged between 9-14 and 2 parents volunteered to take part. Mean age of twins 9.1, siblings 11.9, 23 male MZ twins, 23 DZ twins, 25 female MZ and 21 DZ, 20 DZ with opposite sex twins
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Van Leeuwen et al - Outline the procedure done
Completed a questionnaire and DNA test to see if MZ or DZ. Children completed Raven's standard progressive matrices (SPM) in separate rooms. Adults completed Raven's advanced progressive matrices 
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Van Leeuwen et al - Outline the SPM
Test consists of 60 problems divided into 5 sets of 12 questions that become increasingly difficult. It covers a range of cognitive skills, such as identifying missing puzzle pieces to completing analogies.
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Van Leeuwen et al - How was the difficulty of the questions controlled?
Rasch model, takes in account the difficulty of each test question and calculates the probability of the person being able to score high or low depending on their individual ability. IQ score achieved was therefore irrespective of which item was used
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Van Leeuwen et al - Outline the differences between the participants in terms of gender
No statistically significant sex differences were observed across the whole participant group.
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Van Leeuwen et al - Outline the results in terms of genetics and IQ
High correlation between IQ for parents. Suggests heritability estimate for intelligence was 67% rest was result of random environmental factors.
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Van Leeuwen et al - Outline the results Relating to high/low IQ and environment
Environmental factors were more important in children with a genetic disposition for low IQ, showing GE interaction, and means people with lower IQ are more sensitive to environmental influence than others.
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Van Leeuwen et al - Outline the results of spousal correlation
Spousal correlation was moderately high (0.33) which confirms previous evidence that individuals are likely to mate with someone of similar intellectual ability.
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Van Leeuwen et al - Outline the sample used

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112 families, either MZ or DZ twins, plus a sibling aged between 9-14 and 2 parents volunteered to take part. Mean age of twins 9.1, siblings 11.9, 23 male MZ twins, 23 DZ twins, 25 female MZ and 21 DZ, 20 DZ with opposite sex twins

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Van Leeuwen et al - Outline the procedure done

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Card 4

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Van Leeuwen et al - Outline the SPM

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Card 5

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Van Leeuwen et al - How was the difficulty of the questions controlled?

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