Home / Summaries / Behavioral genetics / correlation-cognitive-abilities

Cognitive disabilities

Q: Adoptive siblings correlation direct estimate of.

A doptive siblings --> Children that grow up together but are not genetically related to each other. Adoptive siblings correlation tells you something about C. Adoptive siblings correlation is 0,25 during childhood. However this correlation will drop to 0,01 when they are in adulthood. At childhood they still resemble each other but in adulthood they don't resemble anymore because they do not share their environment. Anymore. --> The influence of C has vanished.

Q: Generalist genes hypothesis

M ost genes associated with common learning disabilities -- developmental language disorder dyslexia and dyscalculia are generalists: Genes that affect common learning disability are largely the same genes responsible for normal variation in learning abilities. Genes that affect one learning disability are also likely to affect other learning disabilities. Genes that put a child at risk for developing dyslexia will also put the child at risk for other learning disabilities.

6 important questions on Cognitive disabilities

Resemblance for general cognitive ability and genetic relatedness

Resemblance for general cognitive ability increases with genetic relatedness.
The correlation for IQ between third degree relatives (share 12,5 of their genes is 0,15%. While the correlation of identical twins is 0,85 --> There is genetic influences.
There is also an environmental factor because the correlation between first-degree relatives is different than the correlation between fraternal twins even though their genetic relatedness is the same (50%)

Adoptive siblings correlation direct estimate of.

Adoptive siblings --> Children that grow up together but are not genetically related to each other.
Adoptive siblings correlation tells you something about C.
Adoptive siblings correlation is 0,25 during childhood.
However this correlation will drop to 0,01 when they are in adulthood.
At childhood they still resemble each other but in adulthood they don't resemble anymore because they do not share their environment. Anymore. --> The influence of C has vanished.

Additive genetics effect are quantitative like our phenotypes

1 gene with 2 alleles yields:
3 genotypes 3 phenotypes. 2 genes with 2 alleles 5 pheno 9 geno, 3 genes with 3 alleles, 7 pheno 27 geno.
Normal bell-shaped curve of continuous variation
There a lot of different genes that all have a tiny effect on your phenotype.

Generalist genes hypothesis

Most genes associated with common learning disabilities -- developmental language disorder dyslexia and dyscalculia are generalists:
Genes that affect common learning disability are largely the same genes responsible for normal variation in learning abilities.
Genes that affect one learning disability are also likely to affect other learning disabilities. Genes that put a child at risk for developing dyslexia will also put the child at risk for other learning disabilities.

3 findings about cognitive abilities

Heritability increases during development.
Assorive mating is substantial (like marries like) --> Assortative mating is much greater for cognitive abilities than for other traits such as personality and height and weight.
The same genes affect diverse cognitive and learning abilities. (generalist genes)

Gene-environment interaction for reading ability

Twin studies lower heritability of reading ability for families in low income neighborhoods and greater heritability of reading ability for students with better teachers.

The question on the page originate from the summary of the following study material:

Behavioral genetics | 9781429205771 | Robert Plomin

View summary