Task 5 Flashcards
Heritability of Personality
.50-.65, little if any nonadditive (comparing MZ and HZ)
• Nearly always at least moderate factor even in attitudes
Environmental factors influence personality
decrease to near zero after adolescence
Behavioural genetic studies
studies of human twins and adoptees
Comparing identical and fraternal twins raised together
o Alternative to raised apart studies
o Any extra similarities of identicals is supposed to be caused by genes, double the difference and you get the heredity
Additive genetic influence
genes contributing separately to making ones level of trait a bit higher or lower
effects of genes can be estimated by adding together their sperate effects
Non-additive genetic effects
Effect is only seen if the person has two alleles, the effects depend on the presence or absence of other allele (specific combinations of traits)
How to detect non-additive effects
o when nonadditive genetic influences on a trait are important, identical twins will be considerably more than twice as similar as fraternal twins will be. If we see that identical twins are more than twice as similar as fraternal twins, this tells us that nonadditive genetic influences are involved
Common environment influences
o 2(heritability MZ – heritability DZ) the difference to the heritability is the influence of the environment o Or just compare biological unrelated persons that live in the same environment
Unique environmental influences
o Sampling siblings and determine which were treated differently by there parents an then compare it to same treated siblings, same with friend groups
o Or they just figure out how much variance in a trait is left over
o Caused by differences in parental treatment and different peer groups (only .15 correlation)
Assimilation effect
the tendency to emphasise similarities between related persons
Contrast effect
the tendency to emphasise differences between related persons (comparing to the other twin can falsify self-report)
Use other-report of someone who only knows one twin or behaviour Reports
Two assumptions for heritability of Personality
No assortative mating and no contrast/assimilation effect
Womb environment
features of the womb environment can constitute aspects both of the common and the unique (for normal siblings) environment (not significant)
Equal environment assumption
There is a influence of environment but it is rather small
Molecular genetic studies
identified different alleles that account for differences in Neurotransmitter production and are so weakly correlated to some traits (serotonin=harm avoidance dopamine=novelty seeking)
Genotype-environment interaction
the same environment will influence peoples levels of a given characteristic in different ways depending on their genetic characteristics (not very strong)
Genotype-environment correlation
genetic tendencies might actually cause you to be exposed to some kinds of environments more than other kinds, and the differences between those environments might then influence the development of your personal characteristics (correlation can be positive or negative)
Passive genotype-environment correlation
children inherit this combination of genes and environment passively, e.g. sporty parents pass on mindset and sporty genes, and not as result of their own behaviour
Reactive genotype-environment correlation
other peoples reaction to the child’s genetic tendencies, e.g. supporting the child in sports, end up influencing the environment that he child experiences
Active genotype-environment correlation
the child actively chooses environments, e.g. finds sport satisfying so it sticks to it, as a function of his or her genetic predisposition
sex differences
o Genes that influence personality traits do not differ in the two sexes
o Sometimes there are sex differences in heritability
Assortative mating
tendency for parents to be similar in their levels of the trait
o Is not actually happening
Psychological interests
heritability is around .36 and environmental influence accounts for 10% for each trait
Psychiatric illnesses
o Schizophrenia has heritability of about .80 mostly additive
o Major depression has heritability of .40
o Panic disorders, generalized anxiety disorder and phobias are moderately heritable, largely additive, few if any sex differences
o Alcoholism .50-.60 mostly because of additive genetic effects
o Antisocial behaviour: additive and in the range .41-.46, shared environment influences decrease from childhood to adulthood
Social attitudes
o Conservation: only environmental influence on conservationism to age 19, heritability .65 for males .45 for females, some is nonadditive
o Religiousness: in 16 years olds .11 for girls .22 for boys and strongly influenced by shared environment .60 girls .45 boys.
Heritability is moderately in adults with some environmental influences
Difference-detecting adaptions
humans have evolved specialized adaptions for tracking and acting on these important induvial differences (e.g. attractiveness, intelligence, health etc.)
Life-history theory
broad formulation of the major trade-offs in an individual’s life with respect to capturing and allocating energy (e.g. investing in growth, kin selection or parenting)
o Individuals choose by their own sometimes based on already existing feature where the allocate their energy
Costly signalling theory
individuals compete with each other in sending signals to others about their qualities
o They are so costly that an individual has on focus on one which creates differences between individuals
Balancing selection
when genetic variation is maintained by selection, such that different levels on a trait dimension are favoured, or are adaptive, in different environmental conditions to the same degree
Environmental Heterogeneity in Fitness Optima: (Fluctuating optimum)
if selection pressures vary over time and space, then selection can favour different levels of a personality trait in these different environments
7R allele, associated with novelty seeking and extraversion, occurs in dramatically different rates in different geographical regions
Frequency-dependent selection
occurs when two or more strategies are maintained within a population at a particular frequency relative to each other
Mutation load
o Individuals differ in their mutation load
o Heritability of some traits originates from individual differences in mutation
Reactive heritability
refers to selection for species-typical psychological mechanisms that are flexibly responsive to changes in environmental conditions (e.g. becoming more risk averse after becoming father)
