Van Leeuwen et al (2008) twin study:
- Created by: HarrietTammadge
- Created on: 18-12-18 18:23
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- Van Leeuwen et al (2008) twin study:
- Background
- Previous studies on mono-zygotic twins and dizygotic have estimated contribution of genetics to intelligence to be between 35 and 50 %.
- Aim
- Use twins, parents and family members to identify the relationship between family member and IQ.
- 100% shared genetic material for monozygotic twins and 50% for dizygotic, between siblings and parents and children.
- Participants
- 112 families studied
- either had MZ or DZ twins plus a sibling aged 9-14 and two parents.
- Volunteered to take part and passed the screening for disabilities, mental illness and metal materials such as pacemakers.
- 23 male MZ twins, 25 female MZ twins
- 20 DZ twins were of opposite sex
- 23 male DZ, 21 female DZ
- Method
- Raven's Standard Progressive Matrices for the children
- Advanced Progressive Matrices for the parents.
- This IQ tests covers a range of skills.
- Families arrived at 9-11 am and had three breaks.
- Testing period of around 5 hours.
- Rasch model was applied which takes into account the difficulty of each test question
- The IQ score they achieved was irrespective of which items were used as difficulty was controlled for.
- Results
- No sex differences in the group or in any of the three groups.
- Higher correlations for MZ twins than first degree relatives.
- High correlation between IQ of parents suggesting heritability estimate for intelligence wass at 67% with a 95% confidence level.
- For lower IQ groups, interaction between the genotype and environment was higher.
- Discussion
- Individual genetic differences can account for individual differences in intelligence.
- However, factors such as environment might impact low IQ groups more than high IQ groups.
- No indication that intelligent parents provide stimulating environments to promote intelligence but children with a predisposed IQ will either seek a stimulating (high IQ) or non-stimulating (low IQ) environments.
- Background
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