1. Psyc311: Developmental Psychology
Chapter 2
Biological and Environmental Foundations

2. exercise What are some traits that you share with your family members?
What are some traits that make you different from your family members?
What factors (genes vs. environment) would you hold responsible for each of these traits?
Which are most likely genetic?
Which are most likely environmental?

3. nature vs. nurture
How do we explain the tremendous variability in human traits and behaviors?
It must be environment!
Humans have only 3x more genes than fruit flies.
Genes can’t explain behavioral flexibility
Plasticity argues against innate wiring
It must be genes!
Genes have tremendous combitorial power
Slight differences lead to large changes in behavior
Cascades of change
Innateness  pre-wiring
Plasticity  re-wiring

4. nature vs. nurture
Individual level: the extent to which any given child’s development the product of his/her genetic vs. environmental influences.
Population level: the degree to which observed variation in particular traits (in a given population) is due to environmental or to genetic factors.
Why does it matter?

5. ? nature vs. nurture phenotype genotype
The observable characteristics of a person, including appearance, personality, intelligence, and all other traits.
phenotype ?
An organism’s entire genetic inheritance or genetic potential.
genotype

6. View #1
genotype
phenotype

7. Not all variation in phenotypes can be explained by variation in genotypes.
Scientists have studied thousands of twins, both monozygotic and dizygotic, raised together in the same home and raised separately in different homes

8. Notice that identical twins are not identical, (there is clear evidence for the effect of environment).
Notice that DZ twins and regular siblings look the same.
Why isn’t this surprising?
Why is this surprising?

9. View #2
genotype
environment
phenotype

10. which contributes more?

11. which contributes more?
Trait B
High heritability (genes)
High shared environmental variance
High unshared (unique) environmental variance
Trait A
High heritability (genes)
High shared environmental variance
High unshared (unique) environmental variance
Trait C 
High heritability (genes)
High shared environmental variance
High unshared (unique) environmental variance

12. asking wrong question?
Asking: which (genes or environment) contributes more to child’s phenotype.
Is like asking: which (length or width) contributes more to the area of a rectangle?
The correct question to ask is which contributes more to variation within a given group (of children and rectangles)?

13. range of reaction

14. environments influence genes
Lots of genes are carried in a person’s genotype, but do not get expressed in their phenotype.
"The phenotype is the unique consequence of a particular genotype developing in a particular environment"
(Lewontin, 1982, pp. 22–23).
So environment can influence
Which genes get expressed
How they get expressed

15. genes influence environment
Passive genotype-environment correlation.
Evocative genotype-environment correlation.
Each child’s genes elicit other people’s responses, and these responses shape development.
In other words, a child’s environment is partly the result of his or her genes.
Active genotype-environment correlation.
Children, adolescents, and especially adults choose environments that are compatible with their genes (called niche-picking),
thus genetic influences in adulthood increase.

16. iclicker
A child is exposed to music because her parents enjoy music and frequently have it playing in the background.
A) passive
B) evocative
C) active
A child is exposed to music because she has colic and will only quiet down and fall asleep when her parents put on music, so they frequently have music playing in the background.
A) passive
B) evocative
C) active
A child is exposed to music because she asks her parents if she can go to music camp for the summer.
A) passive
B) evocative
C) active

17. View #3
genotype
environment
phenotype

18. epigenetic framework
Can you think of protective and risk factors in your own life?
neighborhood
family
SES
culture
Each layer can serve as either a protective or a risk factor for the developing child (and, at times, vice versa).

19. two important concepts
Phenotypic plasticity: the degree to which an organism's phenotype is determined by its genotype.
A phenotype is plastic if changes in the environment noticeably affect the physical properties of the organism.
Low plasticity: the phenotype can be reliably predicted from the genotype
The phenotype will express regardless of environmental variation.
Genetic canalization: the extent to which an organism's phenotype allows conclusions about its genotype.
A phenotype is canalized if changes in the genome do not noticeably affect the physical properties of the organism.
High canalization: the genotype cannot be reliably predicted from the phenotype
The phenotype will express regardless of genetic variation.
Examples
Language is low in plasticity and high in canalization.
Eye color is low in canalization.
Reading ability is high in plasticity.

20. exercise Name traits with low and high phenotypic plasticity
Sensitivity to environment
High sensitivity
High plasticity
Low sensitivity
Low plasticity
Name traits with low and high genetic canalization
Sensitivity to genetic variation
Low sensitivity
High canalization
High sensitivity
Low canalization

21. announcements Gattaca showing First debate – Friday 9/17
9/15 (Weds) 7-9pm, ECTR 118
First debate – Friday 9/17
Ask Yourself Q’s due – Monday 9/20
Meeting of the Psychology Majors & Minors
9/16 3:10pm Physician’s Auditorium
Psychology Club needs you!!
Psi Chi applications due 9/24/10
Sign up for ECDC observations!!

22. ADHD Genes Environment
Commonly found in boys who have male relatives with the same problem
Heritability rate 60-91%
Generates overactivity across environmental contexts
Home as well as school
Typically calmed by stimulants
Ritalin, Adderall, and even coffee
Environment
The rapid increase in ADHD
from 1 to 5 % of all U.S. children in the past 50 years
Many environmental factors correlated with ADHD
crowded homes, television, lead, food additives, rigid teaching, lack of sleep

23. ADHD

24. alcohol and drug addiction
Genes
Inherited biochemistry makes people vulnerable to various additions
Fewer dopamine receptors
People with high anxiety or quick tempers more likely to drink
Environment
Environments contribute to the likelihood that an addiction will form
College
Culture
Gender – genetic or environmental?

25. nearsightedness Environment also influences nearsightedness
Nearsightedness is a symptom in more than 150 genetic syndromes
Commonly inherited trait
Environment also influences nearsightedness
diet is deficient of vitamin A
large quantities of close-in vision (reading books/computer screens)

26. Type 2 diabetes Rapid increase due to environmental changes
What are some of these changes?
Also a genetic pre-disposition
Only some people vulnerable to the risk factors

27. IQ Interesting gene-environment interaction:
Fatty acids DHA and ARA promote neuronal growth/connectivity
Breast milk is rich in DHA and ARA
Absence of breast milk may negatively effect IQ
Certain genes play crucial role in metabolism of these fatty acids
Babies that have these genes benefit from breast milk; others don’t.

28. political orientation
How could political orientation be genetic?!
Liberal vs. conservative ideology
Instinctive emotional response