3100- Lecture 19 March 19, 2013
Preamble: Person vs. Situation?
- Fundamental Attribution Error: attributing behavioural variability to others’ personality rather than
the situations they’re in.
- Power of the situation relative to personality.
- Nevertheless, there are consistent individual differences
o Humans- personality
o Non-humans- behavioural syndromes
- What causes these individual differences?—they are consistent
Individual Differences at Different Levels of Analysis
- Proximate psychological mechanisms: how do the brains and emotional responses differ?
o There has to be something different about their brains!
All behaviour comes from the brain/CNS—no longer controversial that brain causes
behaviour. Therefore, logically, if two individuals behave different in exact same
situation, this must mean something different happening in their brains.
Experience changes your brain.
Right now professor is changing our brain, and we are changing his brain in some way
- Developmental causes: what caused those brain differences? What differs among people... Genes?
Environments? Gene/environment interactions?
- Ultimate/ Functional Causes: why do these differences persist? Why respond those ways to the
Why are there any Differences between people?
- Shouldn’t the best strategy out-compete other strategies?
o You receive $1 if raise hand, and $0 if don’t raise your hand
Cleary everyone would raise their hand—payoff higher
Why do people not raise their hand?
- What about continuous traits?
o Shouldn’t stabilizing selection make everyone at or close to the optimum?
Should expect people to stabilize at optimum if there is one—natural selection will select
against those at the tails.
Any universal adaptation will be possessed by everyone and any variation will be errors
Potential Functional Causes of Individual Differences
- Developmental differences: how differences have come about during individual’s lifetime.
o Malfunctions, pathologies, errors
o Something causing changes in the brain—very possible cause of individual differences
o Facultative responses to environment—individuals will differ in their response based on
situation they find themselves in—based on circumstances
If big, be aggressive; if small, be conciliatory o This can be:
Conditional yes/no strategy (e.g. if dad is present...)
Differential learning: (e.g. Do I attract mates?)
Always in same situation (e.g. high/low status, married to someone of higher mate
value & jealousy)
There are different social roles/positions that one could take within a group.
Better to not compete with roles that are already taken—better to differentiate
from the others.
- Heritable differences: difference between individuals due to different genes
o Reactive heritability is when a single-design psychological mechanism uses other heritable
qualities as input to determine one’s strategy (it’s a facultative response), e.g. ‘if big, be
i.e. body size—differences in genes? This difference in size changes people’s behaviour
o Hair colour—most variability due to genetic make-up and some due to environment (hair
dye)—Variability in heritable= HIGH
o Differences in number of arms globally—in this case due to environment (war, landmines,
amputations)—Variability in heritable= LOW
- Potential causes of heritable differences:
o Low selection pressure (i.e. selectively neutral)
o Changing selection pressures
If environments change, that means new selective pressures
o Migration and mixing of populations
Skin colour—due to mixing genetics, or because of the sun
Behaviour—poor quality to attribute behaviour due to genes/ethnicity—no good date
on heritable ‘race differences’ in behaviours, nor do I expect any.
o By-products of something else that is adaptive and heritable
Imagine there were heritable difference in tendency to pursue ST/LT mating
strategies—what would happen?
People more inclined to purse ST strategies would behave different- go out for
often. Where as those in LT would behave different
This could result in differences in musculature that arise from differences in
inclination (by-product of something else!)
o Frequency-dependent selection
Payoff depends on if trait is common or rare in population
Game theory—raise hand and get $1 for every hand