1. Genetics vs. Environment
Their Role in Intelligence

2. Nature vs. Nurture in IQ
“Is a person’s intelligence due more to genes or to environment?”
Both genes & intelligence crucial for any trait
Environmental factors determines which genes get switched on.
Example of nutrition effecting you reaching your genetic potential in height.
Clearly, IQ is not the only psychological construct for which this debate applies, and instructors may wish to take a moment to name the other areas (i.e., personality, mental disorders, etc.) for which heritability is hotly debated.

3. Heredity and Environment
Heritability
The variation among individuals caused by genetic factors
Estimates for Intelligence are between 50-80%
Environment
Degree to which variation is due to environmental rather than genetic differences
Environmental Factors can be early intervention, schooling and family life

4. Twin Studies & Family Influence Thomas Bouchard & the Minnesota Twins studies
If trait genetic:
closely related more similar than less closely related
Many close relatives share environments too
Types of studies to separate effects
monozygotic twins reared together
monozygotic twins reared apart
siblings/dizygotic reared together
siblings/dizygotic reared apart
adoptive siblings reared together
MSClip art
Discussion here about the higher correlation between identical twins’ IQ scores than fraternal twins’ and whether siblings were reared together or apart and the genetic role then in intelligence

5. Twin Studies
figure scanned in from Gray's text, pg. 370, figure 10.7

6. Data Analysis
The data show that both genetics and environment have an effect on IQ scores.
The more closely two individuals are related genetically, the more similar their IQ scores:
Identical twins reared together are more alike than are fraternal twins reared together.
Also show the importance of environmental influences:
Identical twins reared together are more alike than are identical twins reared apart
siblings who are reared together are more alike than are siblings reared in different homes.

7. Both genetics and environment have an effect on IQ scores

8. Adoption Studies
Children's verbal ability scores became modestly more like their biological parents' scores.
(Adapted from Plomin & DeFries, 1998.)

9. Environmental Influences
Children growing up in extreme neglect and impoverished environments have lower IQ
When interventions take place like tutored human enrichment in Iranian orphanages, children verbal and intellectual skills improved.
Programs like Head Start helped disadvantaged children early in their educational careers get caught up to others
No evidence though shows you can make your child into a genius by exposing them to special programs at a early age.
Belief that intelligence can grow (growth mindset) can help people have more motivation to succeed academically.
Those who see intelligence as biological (fixed mindset) may feel there is nothing they can do to improve and lead to a self-fulfilling prophecy.