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Psyc311: Developmental
Psychology
Chapter 2
Biological and Environmental
Foundations
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?
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
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?
nature vs. nurture
phenotype
?
genotype
• The observable characteristics
of a person, including
appearance, personality,
intelligence, and all other
traits.
• An organism’s entire genetic
inheritance or genetic
potential.
View #1
• genotype
phenotype
• 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
• 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?
View #2
• genotype
• environment
phenotype
which contributes more?
which contributes more?
Trait B
A. High heritability (genes)
B. High shared environmental
Trait A
variance
A. High heritability
(genes)
unshared (unique)
TraitC.C High

environmental
variance
High shared environmental
variance
A. High heritability B.
(genes)
C. High unshared
(unique) environmental
B. High shared environmental
variance
variance
C. High unshared (unique) environmental
variance
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)?
range of reaction
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
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.
iclicker
• A child is exposed to
• A child is exposed to music
music because her
because she has colic and
childmusic
is exposed towill
music
parentsAenjoy
onlybecause
quiet down and
she asks have
her parents
if she
can when
go to her parents
and frequently
it
fall
asleep
music
camp
for
the
summer.
playing in the
put on music, so they
background. A) passive
frequently have music
– A) passive B) evocative playing in the background.
– A) passive
– B) evocativeC) active
– C) active
– B) evocative
– C) active
View #3
• genotype
• environment
phenotype
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).
two important concepts
• Phenotypic plasticity: the
• Genetic canalization: the extent to
degree to which an organism's
which an organism's phenotype
phenotype is determined by its
allows conclusions about its
genotype.
genotype.
– A phenotype is plastic if
– A phenotype is canalized if
changes in the environment
changes in the genome do not
noticeably
affect the physical
noticeably affect the physical
• Examples
properties
of the
of the organism.
• Language
is organism.
low in plasticity and properties
high in canalization.
– Low
phenotype
– High canalization: the genotype
• plasticity:
Eye color the
is low
in canalization.
can be reliably predicted
cannot be reliably predicted from
• Reading ability is high in plasticity.
from the genotype
the phenotype
• The phenotype will express
regardless of environmental
variation.
• The phenotype will express
regardless of genetic variation.
exercise
• Name traits with low and high phenotypic plasticity
Sensitivity to environment
Low sensitivity
Low plasticity
High sensitivity
High plasticity
• Name traits with low and high genetic canalization
Sensitivity to genetic variation
Low sensitivity
High canalization
High sensitivity
Low canalization
announcements
• Gattaca showing
– 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!!
ADHD
• Genes
– 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
ADHD
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?
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)
Type 2 diabetes
• Rapid increase due
to environmental
changes
•What are some
of these changes?
• Also a genetic predisposition
•Only some
people vulnerable
to the risk factors
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.
political orientation
• How could political orientation be
genetic?!
• Liberal vs. conservative
ideology
– Instinctive emotional response