What was the approximate magnitude of the correlation between the IQs of monozygotic twins reared apart reported by Bouchard, Lykken, McGue, Segal, and Tellegen (1990)?
0.75
What did this correlation lead these authors to conclude about the heritability of IQ?
h2 of IQ is ~0.75; that is, three-quarters of the variance in IQ is caused by genetic differences.
How do the correlations between the IQs of adoptive relatives reinforce their conclusion?
Low correlation between the IQ of adoptive siblings
- Environment play a small role
How does the heritability of IQ change from childhood to adulthood?
As people age, heritability goes up
How does the influence of shared family environment on IQ change from childhood to adulthood?
Effects of shared environment go down.
What is a genome-wide association study (GWAS)?
If studies find that a trait is heritable, it seems justified to search for the actual causal sites in the genome affecting that trait.
Genetic correlation
The correlation between just the genetic parts of two traits
- The correlation between these two quantities is the genetic correlation between traits 1 and 2.
With what traits does years of
education show moderate to high genetic correlations?
Intracranial volume and IQ (cognitive performance)
How is it that DNA variation comes to bring about trait (phenotypic) variation?
Through protein
DNA - protein - trait
What is the underlying biology suggested by the GWAS “hits” for years of education (and, by inference, intelligence)?
Many expressed in the brain at steady or peak levels well after birth.
- proteins important in brain function
- these proteins are important in the development of the brain
What have been the results of the three quasi-experimental designs about the effect of education on IQ?
- One cannot infer from an education-IQ correlation that more education causes higher IQ. But such an inference becomes more plausible if prior IQ is controlled.
- Look at happens to IQ scores when the mandatory duration of schooling is legally increased.
- Norway increased the mandatory duration of schooling from 7 to 9 years. - Look at the difference in IQ between children who fall right before or after a school-age cutoff.
- being born right before the cutoff and thus starting school one year early confers a ~5-IQ advantage over those born right after the cutoff.
What is the causal nature of the relationship between birth order and IQ?
Family sizes have shrunk, the average IQ will have increased because there are fewer people with older siblings.
- IQ increase due to shrinking family size, however, can only account for a fraction of the Flynn Effect
What is the causal nature of the relationship between breastfeeding and IQ?
Having been breastfed is correlated with IQ.
- Weak: breastfeeding will increase a child’s IQ
- High-IQ mothers are more likely to breastfeed and have high-IQ children.
What is the causal nature of the relationship between parental wealth and IQ
If your parents suddenly become wealthier, your IQ is virtually unaffected
What is the Flynn Effect?
IQ test scores worldwide have been increasing over time: younger generations perform better than older generations.
How does the Flynn Effect manifest itself differently across different types of IQ subtests?
Higher to low:
- Raven’s Progressive Matrices
- Vocabulary
- Similarities
- Block Design
- Information
- Arithmetic
Does the Flynn Effect occur within families?
Yes
What kind of explanation of the Flynn Effect is made less likely by this fact?
causes of the Flynn Effect seem not to coincide with environmental influences experienced by all children growing up under the same roof
How does exposure to air pollution affect test scores?
Standard deviation has a negative effect on verbal test scores not math test
- A 1-SD increase in average exposure over 3 years leads to a decline of ~0.10 SDs
What kind of test is most affected by exposure to air pollution?
Verbal test
Does air pollution have different effects on males and females?
Yes, males are more adversely affected than females
Ten personality disorders listed in the DSM
- Schizoid
- Schizotypal
- Paranoid
- Antisocial
- Borderline
- Histrionic
- Narcissistic
- Avoidant
- Dependent
- Obsessive-Compulsive
Which personality disorder can be easily confused with another serious mental illness with a nearly identical name that is not classified as a personality disorder?
Do not confuse obsessive compulsive personality disorder with plain obsessive-compulsive disorder (OCD)!
- OCD is defined by repetitive behaviors such as hand washing, counting, etc.
- It is typically a more serious impairment than the personality disorder.
What criticisms have been made of the traditional DSM system for classifying personality disorders?
1: Some symptoms of a disorder are not correlated. Someone with one symptom is not that likely to show another symptom.
2: Two disorders, despite being listed separately, often share many symptoms in common.
3: The DSM system, with its three clusters, does not match up well with the results of factor analysis.
4: The DSM treats a personality disorder as a binary category: either you have it, or you don’t.
