1
Q
Possible explanations to both sides of the Nature-Nurture debate in Intelligence
A
- Heredity: IQ has a genetic component
- Nurture: IQ is transmitted by nurture and high IQ parents transmit high IQ by the way they nurture their children
- Shared environment: There is some environmental factor that determines variation in IQ that tends to be shared within families
- Some combination of all the above
2
Q
Identical Twins and Intelligence
A
- Note that twins do not share 100% of their genetic code
- Correlations for MZ ranged between 0.58-0.96
- Correlations for dizygotic twins ranged between 0.21-0.87
- Correlations for MZ reared apart = 0.62-0.76 (less than reared tgt; support for env factor)
3
Q
Twins, Adoption Studies and Intelligence
A
- Mean correlation for MZ twins = 0.86
- Mean correlation for DZ twins = 0.60 (coud be higher than siblings because they have more similar shared environment)
- Mean correlations for siblings = 0.47
- Parent-child have higher corr (0.42) than adoptive parent-child (0.19)
4
Q
Heritability of IQ across Varying SES
A
- Analysed WISC scores from several hundred 70 MZ and DZ twins
- Explored how the additive effects of genotype, shared environment and non-shared environment interacted with SES
- Results show that proportions of IQ variance attributable to genes and environment vary non-linearly with SES
- Among lower SES families, about 60% of IQ variance was accounted for by shared environment and the contribution of genes was close to zero
- In higher income families, the reverse was true
BASICALLY:
- As SES increases, heritability goes up and environmental factor contribution goes down
5
Q
The Bell Curve: Group Differences between Races
A
- Many arguments are stated in this book but the most controversial concerns group differences
- In USA, African Americans viewed inferior to White Americans (lower scores, SES, achievements)
- Stated that African-As have lower IQ scores and that IQ is highly heritable
- Argued that lower attainment of African Americans is due to genetic diff between the races
- We should be thinking about the environmental factor here
6
Q
Increasing Heritability of IQ across the Lifespan
A
- Looked at changes across childhood, adolescence, and young adulthood in the heritability of IQ
- Found that the additive effect of genes rose from childhood to adolescence, and adolescence to young adulthood
- At the same time, the effect of environment is decreasing
- Robust effect; has been replicated multiple times
- MZ twins becoming more concordant with age; Reverse is true for DZ twins
7
Q
Explain the Wilson Effect
A
- Across one’s lifespan, the additive genetic effect on IQ increases whilst environmental factor contributions decrease
- We become more like our biological parents as we age
8
Q
Explain the multiplier effect
A
Genetic tendencies that guide behaviour will result in a change in the environment that magnifies the original tendency
9
Q
What other multiplier effects may be at work here?
A
- Educational institutions (ex. going to a private school)
- Sets of toys (ex. being given puzzles, sudoku)
- Basically factors that augment your environment
10
Q
GWAS and Genetic Effects on IQ
A
- GWAS studies found no common variants that explain much of genetic variance in IQ across normal range
- Brings up the problem of missing heritability
- GWAS studies suggest many mutations of small effects is most likely genetic architecture
11
Q
Explain Single Nucleotide Polymorphism (SNPs)
A
- Sometimes when a genome is copied to make a new cell, a single pair gets left out, added or substituted
- Single base pair substitutions create SNPs
- 10 millions snips in the human genome which account for many of the genetic diff between you and everyone else on the planet
- ex. physical appearances, diseases; BUT most SNPs correspond to no observable differences between people
- Can occur both in DNA and intergenic regions
12
Q
Individual SNPs and Intelligence/IQ
A
- SNPs across 22 chromosomes; excl. sex chromo
- Found 11,600 significant SNPs that was associated with IQ scores
- Having one SNP is often related to having another SNP, so they asked how many of these 11,600 SNPs were independent SNPs
- 434 were independent SNPs; these occurred at 148 regions along the 22 chromo (many in intergenic regions)
13
Q
Variation of SNPs Across Whole Genes and Intelligence
A
- Asked whether variation of SNPs across whole genes were associated with intelligence
- Tested 18,264 genes and found SNP variation at 709 genes was associated w IQ
- Concluded that intelligence is a polygenic trait that is associated with many genetic variants in many genes, and in many DNA locations that are not genes
- When they take into account all the tested SNPs, about 25% of the variation observed in participants intelligence test scores was accounted for by DNA SNP variation
14
Q
What are genes and DNA variations related to?
A
- Several of the genes were related to the development of nerve cells and the nervous system
- Some of the SNA SNP variations appear to also be related to health
15
Q
What are the genetic correlations found between IQ and traits & illnesses?
A
- Positive genetic correlations between intelligence and brain volume, birth weight, menopause age, lung function, hand grip strength, short-sightedness, autism, longevity
- Ex. The same genetic variants that are related to larger brains are also related to higher IQ
- Negative genetic correlations between intelligence and hypertension, BMI, smoking, heart attack, lung cancer, osteroarthritis, ADHD, Alzheimer’s, schizophrenia, major depressive disorder, neuroticism, low health satisfaction, sleeplessness, long-sightedness
16
Q
Correlates with g: Nerve Conduction Velocity
A
- NCV is measured by applying a burst of current through the skin over a nerve and picking up its time of arrival further up or down the nerve
- Good correlation with IQ
17
Q
Correlates of g: Inspection Time (IT)
A
- You see a pattern for a very short period of time (50msecs or less), followed immediately by a mask > You have to identify it as one of two possible shapes
- High IQ participants are faster
18
Q
Correlates of g: Reaction Times
A
- RT is the time taken to perform a task
- Simplest version of the task is just pressing 0 when a 0 appears on screen
- Choice task asks that the person presses 1, 2, 3 or 4 when that specific number shows
- Alice Heim Intelligence Test Scores; 30, 50 69yo
- Correlation is always stronger for the slightly more demanding task BUT correlation is present in every group
