Evolutionary Psychology Week 5 Cooperation & Interdependence.

Evolutionary Psychology

Week 5

Cooperation & Interdependence

Running order

Group Selectionism

Recap on Kin Altruism

Reciprocal Altruism

Social Identity Theory & Virtual Kin Altruism

Moral sentiment

Evolutionary PsychologyWeek 5 – Cooperation & interdependence


Group Selection ‘for the good of the species’.

• Zoology and ethology refuted ‘selfish selection’

– Co-operation amongst members of species, as diverse as ants and birds, offered what seemed to be sound reasons for believing that individual characteristics pertaining to fitness were pertinent to the survival of the species as a whole.

• On a human level, group selectionism seemed to offer the prospect that the good of the species orchestrated some of the most acute human behaviours such as aggression and altruism.

• Thus, in an attempt to shore up a Darwinian approach, group selectionism took hold.


What’s wrong with Group Selection?

Q. Why can’t a species (or a population therein) come to be for the good of itself?

A. Given that NS is about differential reproduction, a competitor species identical in all respects bar the Group Selection gene would out-reproduce it.

John Maynard-Smith


Inclusive Fitness Theory & The distributed individual

The idea is that any given gene is selfish but not necessarily unique. A clone is expected to be extant in a number of other individuals;

i.e. there are multiple copies of all genes and, given the Mendelian rules of inheritance, the proximity of exact copies are likely to be closest in kin-groups.

Thus ...

The answer to the question why ‘Group’ rather than ‘Species Selection’?, is due to the observation that altruism seemed to be more prevalent in groups comprised of related individuals.


Try it this way ...

Suppose that the K locus carries alleles that code for exchange relations toward kin.

This allele comes in four forms ...

k Cheat - i.e. take but don’t give.

k Grudger - i.e. give only having been given to but defect if defected against thereafter.

K Initiator - i.e. give before being given to but defect if defected against thereafter.

K Altruist - i.e. give unconditionally to others with K, otherwise adopt Grudger, Initiator or Cheat.


Try it this way ...

Generation 1

Pop Ma

Kk kK

K Altruist k Cheat k Grudger K Initiator


Try it this way ...

Generation 2

Baby1 Baby 2 Baby 3 Baby 4

Kk kK KK kk

Note:If K is dominant it will be expressed in two of the four.

If K is recessive it will be expressed in one of the four.


Try it this way ...

All that is required for All that is required for KK to spread is for to spread is for KK to have the effect of to have the effect of producing more RS in other bodies with producing more RS in other bodies with KK than will K, k or k. than will K, k or k.

Thus, Pop’s KK helps children with KK to have greater RS compared. to others in the population.

Notice: There is no cost to Pop because the Babies just are his RS.Notice: There is no cost to Pop because the Babies just are his RS.

So, if Babies 1 and 3 have, say, six Babies against the average of four then KK is likely to have a greater representation in generation 3 than K, k or k.K, k or k.


Scenario 1. Population of Suckers

In a population comprised mainly of Suckers, Cheats would do well. Payoffs exceed their costs because they have no costs and meet Suckers most of the time. This strategy would proliferate mainly at the cost of Suckers.

Grudgers also do well. Their payoffs will also exceed their costs. Meeting Suckers who give but do not insist on reciprocation Grudgers will also spread in the population.

Initiators do as well as Cheats by happenstance. They would be ready to give, but take without reciprocation from the Suckers they meet most of the time.

Suckers do relatively badly. They loose more points than they gain because although they accumulate points from other Suckers they give to all.


Scenario 3. Population of Cheats

Suckers do very badly. They are exploited by the majority Cheats.

Grudgers would not do well. In a population of cheats they don’t loose points because they don’t initiate, but because neither do Cheats they have limited chances to build point scoring exchanges.

Initiators would do badly. Although they would only be exploited by any given Cheat strategy once, they would move from interaction to interaction loosing points.

Cheats don’t do well either. In a population comprised mainly of Cheats the Cheat has few opportunities to cheat!


Scenario 3. Population of Grudgers

Suckers would do fairly well because the majority of favours would be returned by the numerous Grudgers.

Cheats would not accumulate many points because Grudgers do not give before having taken.

Initiators would do well because favours would be returned.

Grudgers would not do so well. Being a Grudger in a population mainly of Grudgers means that few positive point accumulating exchanges would begin.


Scenario 4. Population of Initiators

Suckers would do well because favours would be returned by the Initiators.

Cheats would do very well by exploiting the tendency of Initiators to begin exchanges with a favour and responding with nothing.

Grudgers do well because positive exchanges would be initiated and their response would be reciprocation.

Initiators would do almost as well as Grudgers – almost because the tendency to initiate means they would be carrying IOU’s from Grudgers and would loose against Cheaters.


Which strategy would win over time?

Across scenarios Suckers don’t do well.

Unconditional giving leaves it vulnerable to Cheats. Suckers hold their own best amongst themselves.

Cheats thrive in two scenarios – against Suckers and Initiators.

Don’t do well against themselves and Grudgers.

Grudgers don’t do badly or particularly well.

Immune to Cheats, thrive amongst Suckers.

Accumulate with Initiators but don’t thrive amongst themselves.



Initiators appear to fair best.

Reciprocal exchanges are advantageous for both parties in terms of overall fitness - those who engage in more of them win over time.

Exposed by cheats but they gain from suckers to an equal extent as do Cheats and Grudgers.

Trigger exchanges in a population of Grudgers.

Exchange amongst themselves.



Initiators appear to fair best.

Evolutionary stable strategy.

‘tit-for tat’ strategy which begins generously but adopts a ‘do unto others as they do onto you hereafter’.

But CheatsCheats can survive in small numbers.


How could Initiator get started?

Kin selection.

Error Management Theory.



3 assumptions

Self-concept is comprised of personal and social aspects.

We are motivated to achieve a positive self-concept.

Our social identity is built upon the positive identity of the group(s) to which we belong.



Group memberships are internalised.

We are inclined to affiliate with others and this inclination is promiscuous.

The need to affiliate is so great that when we define ourselves as members of a group, we perceive ourselves to be interchangeable with members of that group.

‘Fictive kin’.

Kin altruism & SIT both predict favouritism toward an in-group.

‘Good tricks’, ‘no brainers’.


The psychological basis of RS

There are a number of ways in which a sense of fairness could be selected for ...

• Seen as simple cooperation it can be selected for because those organisms that assist one another may enhance one another's fitness over non co-operators.

• Seen as an ability to detect cheaters it will be selected for because the organism won't be consistently cheated by a conspecific.

• Seen as a pressure to reciprocate, it will be selected for because the pressure will facilitate critical acts of reiterated cooperation and help to insure that the natural co-operator is not cheated.


The psychological basis of RS

• Warmth - signalling for initial altruistic move in a possible exchange.

• Sympathy - signalling for awareness of another’s need for altruism.

• Friendship - ongoing state of mutual reciprocal altruism.

• Gratitude - signal of thanks and acceptance of the size of repayment required.

• Guilt - feeling of indebtedness to another/reminder of indebtedness.

• Suspicion - result of calculation that a debt may not be repaid.

• Anger - realisation that debt will not be repaid.

• Revenge - desire for punishment of cheater.

• Indignation - response to another’s accusation of cheating.

• Forgiveness - hope that another desists from cheating.

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Evolutionary Psychology Week 5 Cooperation & Interdependence.

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