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Biology of human behaviour summary
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Summary about all the lectures in the course "Biology of human behaviour" (WBBY031-05)
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Biology of human behaviour notesLecture 1
Introduction to the course
Statement; Humans are product of evolution → not completely true for human
behaviour - culture is also a part
For evolution you need heredity, variability and selection
Look at evolution:
Differences in building plan → anatomy, physiology and behaviour (!)
Behaviour: proximate (how, development and mechanism) and ultimate (why, function and
evolution)
What distinguishes us (from the rest of the animal kingdom)?
● Language (but communication is also present in animals in a less
complicated way)
● Tool use is also not unique
● Self awareness → hard to study in animales
● Learning
Identity - gender
Traits on slide are not unique for humans but are very pronounced in humans
Super stimulus → humans do it as well → ornaments
Kindenschema → baby like face- attractive (also more attractive in other species -
we breed animals to this extend- short noses)
What is the role of a scientist (in our society)
● Facts
● Solutions
● Advice
● Inventing
● Asking the right questions
● Pointing out mistakes
● The scientific method
○ Transparent, neutral and objective
Assignment → biological point of view
Essay → newspaper like, also with some sort of opinion
Movie (5min) → for children (klokhuis), no difficult words, nice illustration ect.
,Presentation of het movies, pick one or two topics and start a discussion
Lecture 2
Behavioural immunity
Behaviour has a strong effect on disease risk → wearing masks and lockdown
Behaviour saves a lot of lifes in the covid crisis
This lecture: example of birds → illness and evolution
Illness has strong negative effect on fitness
→ natural selection favors anti-disease behaviors
Behaviour immune system is a set of behaviors that reduce disease risk
- Detecting pathogens
- Trigger disease relevant emotions and cognitive responses
- Facilitate behaviour to avoid infections
- Reactive behavior
- When ill, behavioural change should increase one’s own fitness (and the
fitness of close relatives
- Proactive behaviour
- Prevention is better than cure (Hippocrates?): behavioural adaptations to
avoid sources of infection
In endotherms:When should fever take place? A fever develops in an individual that is healthy
enough to withstand the fever but kill the pathogens in the body. When someone has a poor
physical state, they will not develop a fever. It is questionable if this is behaviour
In ectotherms → they can change behavior to mimic a fever
- Experiment: Fish treated with viral RNA (ds) move to the warmer side of the
tube → direct behavioral response to suppress pathogens. Exposure of
dangerous warm environment to mimic a fever and the fish only need to
survive longer than the bacteria can
Behavioral immunity in birds
1. Preening
a. Removing lice from feathers
b. Traits of beak → hooked (overhang) beak in some species to remove
lice
c. There is an optimal length of the overhang
d. Social birds preening each other (allopreening) → more pronounced effect
than self preening
i. Unmated penguins (self preening) have 2-3 times more head ticks than
mated penguins (allopreen)
2. Scratching
a. Function similar to preening
, b. Adaptation on claws (to came through the feathers)
c. Species with short beaks tend to scratch more than preen, best option
3. Water bathing
a. Would make sense that sanitation behavior to remove parasites (but poorly
proven)
b. Water doesn't really harm pathogen
c. Floating pathogen in water are attracted to oily feathers → unbeneficial
to bath
d. Reason of bathing is unclear
4. Dust bathing
a. Environmental dependent
b. Dust bath to remove lice
c. But soil with clay have less effect
5. Sunbathing
a. Behavioral fever
b. Energetically expensive
c. Not a pleasant experience for the birds, thus must have a beneficial effect
d. experiment: Wings of a black bird has a warmer temperature than environment -
the warmer the temperature the more likely that the lice die
6. Social distancing
a. Reduce the transmission of pathogens
7. Avoidance of pathogen
a. When reusing old nests: Wait longer with laying eggs till the pathogen leaves the
nest
b. Trait off nutrition content with disease risk and prefer medium size of cockle (less
nutritious)
8. Sanitation
a. Clean nest by eating ectoparasites
b. Starlings incorporate fresh plant materials in the nest → releasing
volatile compounds, insecticidal properties and reduce lice and mites
in nest
i. Complex behaviour adaptation of starling
These are examples of behavioral strategies that birds have to adapt
Insect behavioral immunity
- Same kind of examples as with the bird study → see slide
Social immunity
- Inclusive fitness; Removal of sick offspring → detection of different sickness
cues → mostly in animals that live in large social groups
Humans
Way more complicated than birds and insects → we have culture and inherited
mammalian strategies
, - Difficult to distinguish between this innate mammal strategies and learned culture
behavior
- Maybe we want to avoid this innate behavior,
● In human beings it is important to look normal
● People with low levels of averageness → lower assessment of other people of
how healthy they are
○ More average → look more healthy in their experience
○ Symmetry is a cue → important in mate choice.
○ Disease increases level of asymmetry
○ Humans like average symmetrical people
● disgust
● Dominant behavior is common sense of disgust
○ Like vomiting by seeing a dead body
○ Is a avoidance behaviour → wanting to get away of the feeling of
disgust
○ Humans vary in level of disgust they experience → can also change in
the course of your life
○ Disgust against: food (rotted food, monkey meet), animals, sex (sex between two
men), body products (vomit, poo), envelope violation (how your body is meant to
enclose) death, hygiene (toilet seat), magic (like not wanting to sleep in a room
where a man died in the past)
○ Aversion against injections studied at different aspects;
■ Core disgust
■ Animal reminder → humans are actually just animals
■ Blood-injection injury → injection reminds one of blood
■ Drives disease/injury avoidance
Immune system like a smoke alarm
● Does Not goes of when there is fire → severe and you will die
● Goes of when there is no fire→ not that bad
● A high false positive rate is acceptable
● True positive → big response for avoidance
● False positive → not a real trigger for behavioral immune system (like people
that doesn't look average) → but still triggers the avoidance response (like
discrimination)
When seeing a slideshow with pictures of diseases → people tend to help (donate
money) to humans of their own group (only in europe) - avoidance of outgroups
When seeing a slideshow with pictures of external accidents → also donate to
people outside europe
Lecture 3
gender identity, sex hormones and the brain
Sex and gender
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