Lecture 6 Flashcards
how many genetic disorders have low IQ among their symptoms and who showed this?
more than 250 genetic disorders- Raymond and Tarpey.
define heritability of IQ
Heritability (h2) is the proportion of the total variation in intelligence in a given population that can be attributed to genetic differences between members of that population (the remainder being attributable to environmental factors).
with age what happens to the heritability of intelligence and why?
The heritability of intelligence generally increase with the age of the sample measured, because the environment becomes more similar.
How might we assess genetic influences on intelligence?
- family studies
- adoption studies
- twin studies
talk about family studies and their problems
-children share 50% of genes with each of their parents and brothers and sisters.
Problems:
- only 50 % of genes
- differences between family members may be due to environmental factors.
- heritability estimates from twin/adoption studies are more accurate
talk about adoption studies
Intelligence can be compared between parents and adopted children (→ no genetic heritability).
Variables are often compared between siblings, or twins, reared apart to examine the extent of genetic and environmental effects
Talk about twin studies
Identical (or monozygotic) twins occur when a single egg is fertilized to form one zygote.
Monozygotic twins are always of the same sex.
Monzygotic twins share 100% of genes with each other.
Fraternal (or dizygotic) twins usually occur when two fertilized eggs are implanted in the uterine wall at the same time.
Dizygotic twins share an estimated average of 50% of genes with each other.
Behavioural Genetics compares behaviours across non-twins, identical and fraternal twins to examine the relative influence of genetics.
give the equation for intra-class correlation
(Vb-Vw)/(Vb+Vw)
Vb- variation between scores of pairs of twins
Vw= variation between one twin and another within each pair
what did Bouchard & McGue, 1981 find?
Resemblance for general cognitive ability increases with genetic relatedness
talk about genes and intelligence
Genes play an important role (like other factors) The mechanism(s) are fully unknown
so far “no replicable, significant associations between particular genes and intelligence.”
who systematically reviewed sex IQ studies and what did they find?
J.H court
nearly 120 studies considered all used ravens progressive matricies
overall found no sex differences in IQ
who summarised Effect Sizes of Sex Differences on Intelligence Across the Age Range- what did they do/ find
Richard Lynn and Paul Irwing meta-analysed data of 57 studies from 30 countries, covering 195 samples, in total numbering more than 80,000 people.
- no difference among children up to age of 15
- slight difference from 15-19 yrs with men scoring 2+ points than women
- undergraduates men scores 3-5 points+ than women
- adults men=5+ points
sex difference in IQ is significant but effect is small (near the d=.20 criteria)
The effect size for sex differences in intelligence are relatively small when compared to other variables. list some
effect sizes for aggression variables range from .33 to .84
→ effect sizes for sexuality variables range from .30 to .96
→ effect sizes for personality variables (extraversion and agreeableness) range from .35 to .91
what is the result of z-scores on the sexes on tasks favouring men and women
tasks favoring men- large effect size
tasks favoring women- small effect size
