PSY 544 Lecture Notes - Lecture 9: Diminishing Returns, Inclusive Fitness, Golden Rule
• (9) Problems of Group Living: Cooperation
• Is cooperation a puzzle, evolutionarily speaking?
How can evolutionary theory account for cooperation b/w unrelated individuals - so evo
theory from kin altruism/inclusive fitness can provide an explanation for why we help
other people given that those people are genetically related to us but
• Most of humait’s greatest ahieeets ould ot e possile ithout ooperatio
between unrelated individuals. So how do we explain this
•
• Is cooperation a puzzle, evolutionarily speaking?
• Yet a great of evolutionary thinking seems to suggest that selfish, uncooperative
individuals – those who seek to maximize gains and minimize costs to the self (while also
inflicting costs on rivals) – should be the ones to survive and reproduce more effectively.
• We might think that cooperation b/w unrelated individuals is a bit of a puzzle
evolutionarily speaking because evolutionary thinking seems to suggest that selfish
uncooperative individuals seeking maximizing gains and minimizing costs to self and
inflicting costs on rival should be the ones to survive and reproduce more effectively - this
is from the perspective of your genes
• So, how could cooperation evolve?
• Kin altruism:
• Another way called: Reciprocal altruism: it relies on various conditions being met but
as long as those conditions are met, you can see that even through the evolutionary
framework, how it is beneficial to genes in you to promote you being cooperative
with others
• Overview
• Cooperation through Reciprocal Altruism (RA): how dose it work
• Game theory
• Tit-for-Tat as a winning strategy
• A non-human animal example of RA
• Social Contract Theory: Do humans have specialized adaptations for cooperation?
o Cheater detection
o Cheater punishment
• The role of emotion in the evolution of cooperation
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• Cooperation
• Can evolution create cooperation?
• Imagine you and I are hunter-gatherers: I have learned where the potatoes grow and you
have learned where the carrots grow. Each potatoes or carrot that we get is going to be
beneficial to our survival. Considering the assumption of diminishing returns, because
potatoes and carrots have different nutrients in them, if your diet is all potatoes or all
carrots it will be a weaker diet.
• Now imagine that the first one of each we gather is worth 3 Nus to our survivals but the
second is only worth 1
• So you go out and gather 2 carrots and no potatoes so first is worth 3 units and second is
worth 1 NU so you have a total of 4 Nus
• I go out gather 2 potatoes and no carrots I also have 4 NU first is worth 3 units and second
is worth 1 NU
• One ans to how we can do better is to swap because if I swap my potato for your carrot,
now the ones that we swap will be the first one each of us has so I will have 1 carrot and
you will get your first potato now our Nus will be 6 so we will do better if we swap
• There's a prb here that we will both get - so lets supposed we go out all day and gather
our item and at the end of the day we each go to a central location and you'll put one
carrot in a box and I'll put 1 potato In another box and we'll collect - now I can either
cooperate with you and give you the potato or I could not cooperate and keep both my
potatoes. And you could do the same, you can either give me or not give me a carrot
• Imagine you gather carrots and I gather potatoes. The first one of each we gather is
worth 3 Nutritional Units (NU), the second only 1NU.
• You have two carrots, but no potatoes (4NU)
• I have two potatoes, but no carrots (4NU)
• Lets look at the outcomes in this table:
• Imagine we both cheat: we get 0 additional NUs
• Imagine we both keep our word and we give a potato and a carrot - the addition for
both of us will be 2 NUs because it's worth 3 and if we switch we both get addition 2
NUs that we would not have received before
• Prb is what happens if one of us cooperates and the other cheats?
Imagine I am cooperatie ad put the potato i the o ut ou do’t put the arrot
- now you will gain +3 because you took my potato which is worth 3NUs but you
didn't pay any cost for it you have the 2nd carrot worth 1 NU so your gain is +3 and
inflicting a cost of -1 on me
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Similarly if you give me a carrot and I don't give you a potato - now I will gain +3
because I took your carrot which is worth 3NUs but I didn't pay any cost for it, I have
the 2nd potato worth 1 NU so my gain is +3 and inflicting a cost of -1 on you
In these cases we both one ends up with 7 Nus (+3 gain) while the other gets only
3NU (-1 NU lose)
If this is a one time trade, then it is always be to your benefit to cheat me and vice
versa
If I am going to cheat and not give you the potato the only two outcomes are that:
Either you pay -1 and you give me the carrot and I gain +3
Or you give me nothing and that's 0 cost to you and 0 benefit to me
And so if I will cheat and not give you a potato your best option is to cheat as well
and have 0 gain than -1 loss
Now if I were to uphold our deal, your best option is also to cheat because that will
be the best out come for you - if I've given you the potato then if you give me the
carrot your benefit is +2 but if you don't then your benefit is +3
So in a one time deal it is always to your advantage to cheat no matter what the
other person does.
If the other person doesn't cheat, and you're really trying to maximize your benefit
and minimize your benefit, you should still cheat by taking my potato and not giving
me your carrot
•
• Cooperation
• In this case (a one-time deal), it is always to your benefit to cheat me, and vice versa.
• If I’ goig to heat, ou’re etter off if ou heat.
• But if I a goig to uphold our deal, ou’re also etter off if ou heat.
• So, how can cooperation evolve?
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find more resources at oneclass.com
Document Summary
Imagine you and i are hunter-gatherers: i have learned where the potatoes grow and you have learned where the carrots grow. Each potatoes or carrot that we get is going to be beneficial to our survival. And you could do the same, you can either give me or not give me a carrot. Imagine you gather carrots and i gather potatoes. The first one of each we gather is worth 3 nutritional units (nu), the second only 1nu: you have two carrots, but no potatoes (4nu) I have two potatoes, but no carrots (4nu) Lets look at the outcomes in this table: Imagine we both cheat: we get 0 additional nus. Imagine we both keep our word and we give a potato and a carrot - the addition for both of us will be 2 nus because it"s worth 3 and if we switch we both get addition 2.
