Van Leeuwen Flashcards
Van Leeuwen participants
Opportunity sampling via letter or phone
112 families from the Netherlands
Two parents, twins aged 8.9-9.5 during study, a sibling
Exclusion criteria: pacemaker, metal materials in head, physical / sensory disabilities, participated in special education
Van Leeuwen aim
To investigate the genetic relationship between family members and IQ
To build on previous research by including parents and siblings too
Van Leeuwen method
Parents signed consent forms. Children got a present for taking part. Collected biological data, hormonal data and did MRI scans.
The cognitive testing was based on Raven’s Standard Progressive Matices for children, and Raven’s Advanced Progressive Matrices for adults. 60 items divided into 5 sections.
Van Leeuwen results
67% heritability estimate for intelligence, high correlation between parents IQ and child’s
Monozygotic twins had more similar IQ than dizygotic twins
Parents had similar IQ scores
For lower IQ groups, environment seemed to have more of an effect on their IQs than high IQ groups
No difference in male or female IQ scores
Van Leeuwen conclusions
The more similar the genetic makeup, the more similar the IQ. IQ could therefore be inherited.
Environment could be more important for children with a genetic predisposition for low IQ.
BACKGROUND: Lucas’s study on nutrition
Premature babies had higher cognitive skills at 7.5-8 if they were breastfed than bottle fed,
however Geoff found no impact of breastfeeding on intelligence in full term babies implying nutrition only has an effect on intelligence for especially susceptible individuals.
BACKGROUND: King’s study on Quebec Ice Storm and Maternal Stress
Ppts: 140 children born after the Quebec ice storm 1998 and other local children who’s mothers experienced less stress
Procedure: asked mothers about their stress during the ice storm and performed IQ tests on their children
Findings: children with stressed mothers scored 15 points lower than children of less stressed mothers
Conclusion: cortisol negatively affects intelligence of the child during pregnancy
