PSYCH 2B03 Lecture Notes - Epistasis, Collective Unconscious, Somatotype And Constitutional Psychology
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Psych 2B03 – November 12th
BIOLOGICAL BASES OF PERSONALITY
- Freud – the characteristics of the ID, organic development of the ego, lesser of the superego
- Jung – in the collective unconscious
- Maslow – many biologically based instinctoids motives that follow one another as they are
satisfied, then self-actualization
- Rogers – OVP and the actualizing tendency, both built in.
- Mishel and Bandura don’t specifically say it.
- Esyenck and Zuckermann – very intensely into finding the specifics.
- To estimate how important the biological bases are important for personality.
- The similarity among families. Just bc there’s family similarity, does not mean that it’s due to
genetics. Family resemblance and similar habits and traits does not pass down. Like parents
being doctors does not pass down ‘doctor genes’ to their kids.
Factors Involved in Personality:
-Genetics – we inherit things from our parents that lead us to have certain personality
characteristics over others.
-Shared environment – separately may shape personality and behavior. Families have similar
shared environments of house, city, learn same values, etc. They tend to shape them in the
same/common direction. It can contribute to similarity in personality for those that share the
-Non-shared environment – Even people living together will experience different things. No
friends or teachers or activities in common.
- They thought genetics > shared > non-shared. BUT actually what is shared uniquely is one of
the most important factors in determining our personality!!! Non-shared is the greatest.
Phenotype and Genotype:
•Phenotype – that set of observable or measurable characteristics. Height, weight, eye colour,
hair colour, intelligence. Phenotypic characteristic is any characteristics that can be measured.
Personality is part of your phenotype, measure aspects of your personality.
•Genotype – the set of genes that we inherited from our parents. To what extent is our observable
characteristics determined by our genes?
•To what extent to variability in phenotype is determined by genotype.
•To compare the similarity of phenotypic by differing those in genes:
oMonozygotic twins – identical. Both developed form a single fertilized egg that then
spilt that created genetically the same genes. ~100% same genes.
oDizygotic twins – born at the same time. Developed from two different separately
fertilized eggs. Not genetically identical. Can be of different sexes. Share approximately
~50% genes in common.
•1) Comparisons we can make. We can compare their IQ scores, of twins that are reared and
raised together, and that correlation of monozygotic twins reared together, with the
monozygotic twins that are reared apart.
oIf genes are 100% determined, then the correlation should be r = 1.00 correlation.
oWith the ones reared together, and reared apart then it should be the SAME correlation
in both of them. Even for the monozygotic and dizygotic reared together or apart, then
it’s r = 1.0 and r = 0.50. Same as genetics.
•2) Family similarities. 12% genes shared with cousins. 50% shared with parents. 50% shared
with siblings. 25% with grandparents or uncles/aunts.
oYou can come up with relative importance of genotype and phenotype with genes.
•3) Adoption studies. They shared 50% with biological parents, but 0.0 with adopted parents. See
how similar they are to their adopted parents. If genes are really significant, then there should
be a high correlation to the biological parents. Looking at the relative size of the correlation,
look at the importance of IQ made by genes. And also the shared or non-shared environments.
•Problems with these techniques:
oDizygotic twins are confused as monozyotic twins - When they are of the same sex and
look very similar, they are misclassified as identical twins. Then there are dizygotic
twins in the monozygotic twins, they will dilute similarity and you will underestimate
the genes impact. The only problem that leads to the problem of genes in phenotype.
oSelective placement – correlated environments in adopted twins. Twins reared apart are
unrelated and uncorrelated environments. Twin A doesn’t share the same environment as
Twin B. Only similar in genes, right? When twins are separated for adoption. They
always try to place them both in similar homes, just about everything is similar. They
are very often reared in similar environments. The differences are due to the
environments if they are separated. This leads to an overestimate power of genetic
oDifference in monozygotic and dizygotic twins in environmental similarity. Assume the
monozygotic twins, and the dizygotic twins are sharing their own similarity in homes.
Roughly similar for the two members of the pair. Not true!!! Parents treat monozygotic
twins differently, almost treated identically as the same. So many things about their life
is identical, treat them as if they are the same person. Very similar treatment, parents
work to make their environments so identical. Dizyotic twins are treated differently, so
they emphasize their individuality. Work to have them separated and different. Then
when you look at the monozygotic twins environments are treated as exactly the same,
and their genes are exactly the same. Then the dizygotic twins have 50% same genes,
but 10% same environment. … It now looks like genes are much higher, power of
genetics, but they are wrong!
oAssortive mating – Greater parent-child similarity. The two parents of any child will not
have alike genes in common, 50/50 from mom and dad. A child will resemble a parent
by 50%. That is if mating is random. Hopefully correlation between you and your
spouse’s genes is 0. Assortive mating happens for IQ.
It happens when mom and dad have similar genes. IQ is substantially shaped by
genetics, and smart people marry smart people. So they may have similar genes. A child
can inhert those similar genes from a parent, it makes a child more similar to one parent.
Can get one parent’s genes from another parent, making them more similar to one
more common or introverts to marry introverts, maybe shaped by genes, then it’s
assertive mating. More similar to parents than just 50%. Can get mom’s genes from both
mom and dad. It will also make genes look more powerful.
Distributions and Variance:
Quantify the relative contributions of genes vs environmental factors for any phenotypic
characteristics. Single most widely used method in almost everything – heritability coefficient.
Variance: (he won’t ask about variance)
Mean/Avg is meu = u. There is much variability in the distribution of IQ scores, a range of scores
above or belong the mean. How big is this variability? Quantify it by using variance. It is each of the