Biological Bases of Personality Flashcards
(47 cards)
Whats the problem with looking for family resemblance as an indicator of genetics?
Could be resemblance for reasons other than genetic
- i.e. children’s personality can elicit certain behaviours from parents that lead them to resemble each other
- or parents provide an environment that encourages children to become like them
ex. Bach’s family
3 factors involved in Personality
- Genetics
- Shared Environment
- Things in the environment that makes us like others who share that same environment
- I.e. parents, schools, cultures, country - Non-shared Environment
- Things that happen to us uniquely and shape us in directions that are different from others
define Phenotype
Set of all Measureable or observable aspects of who we are
- hair color, eye color, IG, Personality(may not be observable but definitely measureable)
Define genotype
Set of genes we have inherited from our parents
if some phenotypic characteristic (say, intelligence or IQ) is completely determined by genes, then the correlation between IQ scores of MZ twins reared apart, and the correlation between IQ scores of MZ twins reared together should be What?
- what do we actually see?
should both be equal to 1.00
→ We do not see this, there is lower correlation for those raised apart thus there is an affect of environment
if we compare the phenotypic similarity of MZ twins with that of DZ twins (with both sets either raised apart or raised together) assuming 100% genetic determination, then we still expect to find a _____ correlation between the scores of MZ twins, but only a ___ correlation between the scores of DZ twins
1.00, .50
if a phenotypic characteristic is 100% determined by genes, we expect there to be essentially __ correlation between children and their adoptive parents, but a ____ correlation between children and their biological parents.
0, 50%
What are the problems with twin studies?
→ DZ twins (of the same sex) confused as MZ
= underestimate influence of genes
ALL other problems lead to overestimate of genetic influence
→ Selective placement: Correlated environments in adopted twins
→ Differences between MZ and DZ twins in environmental similarity
→ Assortive Mating: Greater parent-child similarity
the total variance (VT) of a distribution is equal to …
to the sum of the genetic variance (Vg) and the environmental variance (Ve)
Define hereditability
portion of total variance that is due to genetic variability in the population at large
what is The heritability coefficient for some phenotypic characteristic
the ratio of the genetic variance (Vg)to the total variance (VT).
→ h2 = Vg/Vt
what equation is used when the data available consists of correlations between pairs of monozygotic twins reared apart (MZA).
→ h2 = r(mza)
What equation is used for calculating the heritability coefficient when the data consists of DZ twins reared apart (DZA).
→ h2 = 2r(dza)
What equation is used when the data consists of both correlations between pairs of monozygotic (MZ) twins, and pairs of dizygotic (DZ) twins. It doesn’t matter whether the twins have been reared together or apart, so long as both groups of twins have been reared in the same way (together or apart).
→ h2 = 2(rmz – rdz)
→ The heritability quotient merely tells what?
how much of the total variability in some phenotypic characteristic can be attributed to genetic variability within our sample.
Does heritability apply to groups or individuals
GROUPS
- If a group shows that 50% of IQ is due to genes, it does not mean 50% of your genes are from your parents
• Heritability Coefficient is NOT a constant, how does is vary?
Varies from population to population, and over time
→ Whenever you get MZ correlation more than ____ the correlation of DZ twins means there is a problem with your data
half
There are 2 limits to our interpretation of the heritability coefficient, explain.
- h2 tells us nothing about how much of an individual’s phenotype can be attributed to his or her genes: h2 is about the source of variation between individuals.
- h2 is not a constant. The relative contribution of genetic variability to phenotypic variability may change over time, and may be different in different populations.
what is Temperament
Something general about an individual’s behaviour/personality
what did Thomas, Chess and Birth (1970) do?
Tested 9 personality traits on a 3 point scale(high,medium, low) for 9-10month old infants for their: • Level of motor activity • Positive response to new objects • Regularity in biological functions • Friendliness or good mood
what did Thomas, Chess and Birth (1970) find?
2 major clusters of variables that were highly intercorrelated traits: EASY infants • Regular rhythms • Good mood • Accepts novelty • Adapts well to change • Low to moderate levels of energy → laid back, easy to deal with infants DIFFICULT infants • Irregular rhythms • Poor mood – often cry • Dislikes novelty • Adapts poorly to change • High levels of energy
what happened when they They assessed these individuals all the way to 14 -15
→ It is consistent: They found a high correlation b/w their ratings at age one and groupings at age 14
→ It causes differences is psychology: ?? difficult infants showed various kinds of psychological problems and only 20% of easy infants were referred for help
→ also premature infants are more likely to be classified as difficult and the bulk of them retain the same grouping at 4.5 years, while some did change
→ they were interested in those who change from difficult to easy – and the only difference is that they had especially warm and present mothers
what is a contrast effect
DZ correlations are much smaller than they should be (much less than half the MZ correlation) given the relative genetic similarity of MZ and DZ twins.
