Transcript Ch6 (part1 and 2)

Genetics of
Personality
Chapter 6
Nature vs Nurture
"A devil, a born devil, on whose
nature Nurture can never stick;
on whom my pains Humanely
taken, all, all lost, quite lost.“
“The Tempest”
-William Shakespeare
Decade of Doubt… 1970s
“Personality Coefficient”
r = .30
Maximum amount trait measures can ever predict !
Walter Mischel, 1981
The Human Genome
● The Human Genome Project
● 25,000 genes
● gene = one segment of DNA molecule
● genome = whole DNA molecule
● Body contains 100 trillion copies of
your own genome
● Rise of personal genomics….
Controversy
Personal Genomics
● Affordable DNA sequencers
● Health insurance premiums?
Designer Babies?
● Reduce variability
● Genetic elites?
Eugenics 2.0?
(“hybrid vigor” )
Eugenics
"good breeding"
Plato, in The Republic:
“…The best men must have intercourse with
the best women as frequently as possible,
and the opposite is true of the very inferior.“
●
●
●
●
Ancient Spartans leaving sick babies outside ….
20th Eugenics policies / programs
20th century  Blanqueamiento (Brazil)
Compulsory sterilization (Canada, up to 1970)
Francis Galton
● Cousin of Darwin
● “Heritability of Genius” (1869)
● Fear of dysgenic trends
“We greatly want a brief word to express the science of
improving the stock…the word EUGENICS would
sufficiently express the idea.“
● Great idea!! Gov. promote good genes!
(-) Good according to whom?
(-) Good for whom?
Am Breeders Assoc, 1920s
American Eugenics Movement
American Eugenics movement
● Alexander Graham Bell, 1881
– Study of Martha's Vineyard deaf population
● Proposed controlling immigration
● Immigration Restriction Act 1924
● Compulsory Sterilization Policies
● WW I… Treaty of Versailles.. Great
Depression… German Economic
collapse…
● 1930s rise of German
Nazi party
Haekel (1905)
"The mental life of savages rises little above
that of the higher mammals, especially the
apes, with which they are genealogically
connected. . . the lower races - such as the
Veddahs or Australian Negroes - are
psychologically nearer to the mammals apes and dogs - than to the civilized
European, we must, therefore, assign a
totally different value to their lives.."
Nazi Eugenics policies
Influenced by
American, Swedish,
and British Eugenics
movements
Eugenics
See flags of other
countries on 1936
Nazi poster
American laws
against interracial
marriage not
overturned until
1967
Cdn sterilization
laws exist up to
1970
Genes
Genetics
● Branch of biology that deals with the
mechanisms of heredity.
Heredity
● Transmission of genetic information
from one generation to the next
Behavior Genetics
● Study of how variation in genes affects
variation in behavior
Cell nucleus

23 pairs (46)
Chromosomes

DNA
molecule

Genes
Genes
Gene x Gene interactions
● Explains why only 35,000 needed
Comparative Genomics
● 99% of a mouse's genes are in humans too
● 17,000 of our 30,000 genes are also in dogs
● Our Rhodopsin pigment (in retina) is identical to
that in a 200 million year old horseshoe crab!!
Genes
● Alleles
Variation in some nucleotide sequences in a
gene
● Genetic variation
Presence of alleles in a population
● Gene pool
Total variety of alleles in the population
● Population Genetics
Study of distributions of alleles and their
effects
Genes
We have 98% of the genes a Bonobo
Chimpanzee has
We have 50% of the genes a banana has.
Human Genome Diversity Project
● Mapping genetic diversity by region
● Genghis Kahn
1/200 of all living males has his Y chrom
Australia
Africa
East Asia
How Genes Affect Behavior
Genotype
The underlying DNA sequence that an
individual inherits
Phenotype
An organism’s observable properties,
physical and behavioral
Polygenic
Involving many genes
Genes and personality
Genes and personality
Nature-Nurture Debate
Individual level? No, no debate—both
are important
Population level? -- yes, we can
disentangle the influence of genes and
environments.
Behavior Genetics
3 Goals of Behaviour Genetics
1. Determine the relative magnitude of
gene to environmental influences
2. Determining how genes influence
environments
3. Determine which kinds of
environmental influences are most
important (shared, nonshared, or
both).
Behavior Genetics
There exists phenotypic variation.
There exists genetic variation.
Q: What proportion of phenotypic
variance (e.g. extraversion variance)
is accounted for by genetic variance?
This proportion is called
heritability
Heritability
= A ratio statistic that
describes the proportion
of phenotypic variance
explained by genetic
variance
Heritability
Example:
If the heritability of extraversion was
estimated to be, H2= .50, this indicates
that about half of measurable variation in
extraversion is due to genetic variation.
Misconceptions of Heritability
1. Does it apply to an individual?
NO.
2. Are its values constant, or
unchangeable?
NO.
3. Is it a highly precise statistic?
NO.
Behavioural Genetics Methods
Selective Breeding
Tryon (1940): Maze Learning
Belyaev (1969)
Belyaev (1969)
Domestication / tameness
● Occurs quickly
● Changes are wide ranging
Appearance:
Ears, tail, coat color
Temperament: Friendliness, Cuddliness
More social --> Easily trainable
HPA reactivity ↓
Serotonin ↑
Are selective breeding experiments
ethicial to do with human subjects?
Family Studies
Amount of genetic overlap is known.
Siblings share 50% genes
1st Cousins share 12.5% genes
Measure similarity of phenotype.
Between siblings
Between cousins . . . .
(-) Gene & envir. influences are
confounded.
Twin Method
(MZ) Monozygote (identical)
● similar prenatal environment
● similar rearing environment
● 100% shared genes
(DZ) Dizygote (fraternal)
● similar prenatal environment
● similar rearing environment
● 50% shared genes
Twin Method
• Proportions of shared genes is known.
DZ= 50%, MZ= 100%,
1) Measure behavior phenotype
questionnaires, ratings, observation
2) Compare correlations.
DZ: Shyness corr = .40
MZ: Shyness corr = .60
Twin Method
DZ: shyness corr= .40
MZ: shyness corr= .60
Double the difference..
Heritability = .40
Twin Studies
Heritability,
2
h
=
(Corrmz– Corrdz) * 2
Heritability of shyness= (.60-.40)*2= .40
40% of shyness variance is attributable
to genetic variance
Riemann et al. (1997)
Big5 (FFI) correlations between raters
Riemann et al (1997)
Heritability of Self-reported Big5
Riemann et al. (1997)
Heritability of averaged peer ratings
Riemann et al (1997)
Heritability of self+peer ratings (merged)
Riemann et al (1997)
Proportion of self-peer corr due to genes
Attitudes?
Yes, but depends which attitudes
Tough on crime/punitiveness?
(yes, > .30)
Religious Fundamentalism?
(yes, >.30)
Kirk et al. (1999)
Spirituality VS Church Attendance ?
Self-Transcendence scale
1. Sometimes I have felt my life was being
directed by a spiritual force greater than any
human being.
2. I sometimes feel a spiritual connection to other
people that I cannot explain in words.
3. I have had personal experiences in which I felt
in contact with a divine and wonderful spiritual
power.
4. I often feel that I am a part of the spiritual force
on which all life depends.
Self-Transcendence Scale
What is it correlated with?
Heritability of spirituality
Kirk et al. (1999)
Self-transcendence
● 48% variance is genetic
● 0 % variance is shared environment
● 50% non-shared environment effects
Church attendance
● 22% variance is genetic
● 43 % variance is shared environment
● 35% non-shared environment effects
Comparative heritabilities (TCI)
Drinking and Smoking?
Yes
2
h
> .40
Drinking and smoking habits
show evidence of heritability.
Typical Twin findings:
IQ
Personality
Soc attitudes
50-80%
30-50 %
20-30 %
Concordance rates for disorders
Adoption Method
Child vs Adoptive parent
● Shared environment
● 0 shared genes
Child vs Biol parent
● No shared environment
● 50% shared genes
Adoption Studies
● Corr between adopted children and
adoptive parents must be due to
environment
● Corr between adopted children bioparents
must be due to genes
(+) Adoption method avoids“equal
environment” issue in twin designs
Bio parents share 0% envir with offspring
Example: IQ correlations:
r = .31
adoptive parents/child
r = .36
biol parents/child
Gene AND environmental effects!
Twin+Adoption Method
Minnesota Study of Twins
Reared Apart
● 2 Jim's from Ohio
● separated at birth
● met at age 39
● U Minnesota calls them up
● located 57 more MZ-Raised Apart twins
Twin+Adoption Method
Minnesota Study of Twins
Reared Apart
● 2 Jim's of
Ohio (1979)
Minnesota Personality Questionnaire (MPQ)
Well-Being
Social Potency
Achievement
Social Closeness
Neuroticism
Alienation
Aggression
Self-Control
Low Risk-Taking
Traditionalism
Absorption (Imagination)
.49
.57
.38
.15
.70
.59
.67
.56
.45
.59
.74
Twin+Adoption Method
Results
1. Just as similar as MZ raised
together.
2. 30-50% of the adult variation in a
behavior trait are due to inherited
genetic differences
3. Which environment influences?
Influences that are NOT shared
between twins growing up.
Environmental Influences
Q: Which environmental influence has
more impact on personalilty?
Shared?
Presence of a TV, number of books…
Non-Shared?
Different friends, hobbies…
Genes and the Environment:
Genotype-Environment Interaction
Genotype-Environment Correlation
Genotype-Enviro Interaction
● Differential response to the same
environment
Task performance of introverts versus
extraverts interacts with caffeine
Genotype-Enviro Interaction
● Low MAO
x DeliqPeers = DELIQUENCY
Interaction
Genotype-Envir Correlation
Different genotypes may
systematically experience
different environments.
Genotype-Envir Correlation
Active
● A genotype seeks a particular
environment
High sensation seekers
exposed to more dangerous
environments
Genotype-Envir Correlation
Passive
e.g., Parents provide both genes
and environment to children
Child’s verbal ability and
reading to children at bedtime
Genotype-Envir Correlation
Reactive
● Parents (or others) respond
differently to diff genotype
Baby likes cuddling; so
mother cuddles that
baby a lot.
Genotype-Envir Correlation
Genotype-environment correlations
can be positive or negative
e.g. shy child…
(-) corr:
(+) corr:
boldness encouraged
avoiding people
Molecular Behavior Genetics
Specific genes and personality traits
(e.g.) Dopamine Receptor Gene
"Long repeat" allele of D4DR
--> “novelty seeking”
Novelty-Seeking
Variety
“I like to begin new things”
Recklessness
“I rush into things.”
Extravagance
“I spend more money than I have.”
Rebelliousness
“I break rules.”
Molecular genetic findings
1. Twin studies implies some genes
2. Schizophrenia Family Linkage studies
D4DR gene variation found to correlated
with a “Novelty-Seeking” trait measure.
3. Meta-analysis of allelic association
studies (10 studies): 5 found +corr,
5 were null; no studies found -corr.
Novelty-seeking probably is assoc with
D4DR dopamine gene variation.
RGS2 gene
(Smoller et al. 2008)
1. RGS2 mice bred to lack it  fearful
2. Allelic association study
1. Genotyped blood samples from 700 students
2. RGS2 allele: higher freq in introverts
3. MRI study
1. Those having a mood or anx disorder vs
controls. Each student was genotyped.
2. Viewed emotional faces during MRI
3. RGS2 allele, higher activ in amygdala and
insula
Serotonin Transporter



Full scan of whole human genome.
No correlation with extraversion for any
single-nucleotide DNA variation in humans
Some effects found but only for broad
groupings of many genes
…these results show that extraversion is
a highly polygenic personality trait…”
Summary
● Heritability evidence has become much stronger
over the past 20 years.
● Enviromental influences, especially non-shared
environmental influences, play just as important a
role as genetic differences do in shaping
personality.
● Gene-Environment correlations and interactions
also play important roles in shaping personality.
● Molecular genetics findings remain elusive for
many traits.