Biological processes and personality Flashcards
Biological Premises
❖Human behaviour is generated by complex biological
systems
• focus is on how neuroanatomy & neurophysiology influences action & experience
❖Personality characteristics are genetically determined
• biological perspective explores which aspects of personality are influenced by heredity, evolution and brain function
Behavioural genetics
❖ How is personality inherited?
Similarities in personality are compared between people with different degrees of genetic similarity.
❖ Methods to establish genetic-behaviour relationships
• adoption studies
• twin studies
• selective breeding
Adoption studies
❖ If children had no influence from biological
parents / compare children’s personality to that of biological parents (shared genes) & adoptive parents (no shared genes).
❖ If families have biological & adoptive children –
compare personalities of adopted to biological
children.
❖ Correlations – estimate how much variation
due to genetic factors – heritability coefficient.
>. Overall heritability personality traits = 40%
Twin studies: Part 1
❖ Dizygotic – (DZ different genetically) two separate fertilized eggs –as genetically similar as any pair of siblings.
❖ Brought up together – provides some environmental control
❖ Individuals with different genotypes experience same environment differently & act to shape the environment.
Twin studies: Part 2
❖ Monozygotic (MZ – identical genes) same fertilized egg
❖ Differences must be environmental
❖ Reared apart – still have same attitudes, hobbies and preferences for pets
Temperaments
❖ Inherited personality traits present at birth are:
• genetically based
• wholly pervasive – affecting how and what people do
❖ Three fundamental temperaments:
• activity level – overall output of behaviour
• sociability – preference for being with others
• emotionality – ease of being emotionally aroused
Environmental influences
❖ Environmental effects may be underestimated:
• judged as that which is not explained by genetics
• some environmental and genetic effects may have shared influence on an outcome (e.g., intelligence)
• if shared variance is attributed to genetics, the
environmental effect is underestimated
❖ Environmental influences on personality operate primarily at the individual level
❖ Sources of non-shared environmental influences
• peer, friends, social networks
• complementary, but diverging, roles within families
• parental preference
Shared & non-shared environments
❖ Shared – environments shared by siblings by growing up together
❖ Nonshared – environments not shared by siblings growing up together, due to different gender, birth order, illnesses, peers, experiences etc.
Plomin & Daniels (1987): Why are children from same family so different? • 40% to 50% genetics • 35% non-shared environment • 5% shared environment • remainder – attributed to measurement error
Genetic-environment interactions
❖ Cooper & Zubeck (1958) – research on how early
environmental experiences influenced adult problem
solving in genetically different rats.
❖ Used rats previously bred to be “maze-bright” & “mazedull”
>. Each then raised in:
a) enriching stimulating environment
b) impoverished environment
❖ Enriched environment improved later learning ability in dull rats (new environment) but not bright ones.
❖ Impoverished environment handicapped bright rats but not dull ones.
Evolutionary theory
> . “We are part of nature, but we like to see ourselves as otherwise” (Goldsmith 1991)
. “Natural selection has built us, and it is natural selection we must understand if we are to comprehend our own identities” (Trivers, 1976)
Evolved psychological mechanisms
> . Psychological mechanisms – results of evolution by natural selection
. Aspects of human nature such as fundamental motives and emotions can be
understood in terms of their adaptive value
Adaptive value implies:
• reproductive success/ passing on of genes
• time lag – adaptive to hunter and gatherer life
• adaptive value for specific tasks/problems in specific context
Sociobiology & evolution
❖Social behaviours exist because they confer adaptive advantage
❖Example: Altruism???
• may confer a biological disadvantage at an individual level
• may help others in the same gene pool survive and reproduce (inclusive fitness)
• may form the evolutionary basis of cooperation
Summary of types of nature-nurture interactions
- Same environment experiences different effects on individuals with different
genetic constitutions - Individuals with different genetic constitutions may evoke different responses from environment
- Individuals with different constitutions select and create different environments as soon as they are physically able to “In the dance of life, genes and environment are absolutely inextricably partners”
(Hayman 1999)
More to it than genes & evolution!
❖ Premise: two evolutionary processes influence behaviour
• biological evolution—slow
• cultural evolution—much faster
❖ Problems arise when the behavioral tendency from biological evolution conflicts with current cultural environment
Neurotransmitters (brain chemicals): Part 1
Neurotransmitters travel across the synaptic cleft between neurons Example of relationship to behaviour ❖ excess of dopamine associated with – schizophrenia ❖ underproduction of dopamine associated with Parkinson’s disease
