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Behaviour Towards Family & Friends:
Kin Selection and Reciprocal Altruism
Author Paul Kenyon
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Overview

Why do people engage in acts of heroism in which they lay down their lives for others, devote their working lives to alleviate human suffering, or donate to charity? This lecture explores altruistic behaviours because they appear to challenge Darwin's view that natural selection would never favour the development of behaviour that damaged the individual.

Hamilton's kin selection theory is based on the fact that relatives share genes. By co-operating with relatives, survival of these shared genes is encouraged. Hamilton worked out the conditions under which altruism pays off.

Trivers' reciprocal altruism theory explains why we co-operate with people who are not necessarily related to us. The essence of Trivers' theory is captured by the phrase "If you scratch my back, I'll scratch yours".

The lecture ends with a discussion of cheating - the opposite of co-operation. Humans are exquisitely sensitive to cheating . We are very good at detecting and remembering people who cheat.

Learning objectives
After studying the material on this page you should be able to:
  • Recognize the characteristics of altruism
  • Explain why altruism presented a challenge to Darwin's theory of evolution
  • Explain altruism in terms of kin selection
  • Describe the coefficient of relatedness between close relatives
  • Describe the conditions under which altruism would benefit kin selection according to Hamilton's Rule ( rb>c )
  • Design an experiment to illustrate kin selection theory
  • Describe Trivers' reciprocal altruism theory and compare it to kin selection theory
  • Compare the costs of co-operation and cheating in the prisoner's dilemma game
  • List three strategies that could be used in the iterated prisoner's dilemma game
  • List five conditions that encourage us to seek and give help
  • Design a fund raising initiative for charity based on our knowledge of the psychology of co-operation

Reflective exercise

This lecture considers relationships between people. Before you begin, you may find it useful to focus on who you are related to. This is not an experiment. There are no right / wrong answers. Your responses will not be recorded.

Write the first names of your relatives (if applicable) in the boxes, and then indicate how closely related you perceive yourself to be to this person:

How closely related do you perceive yourself to be to this person?
Distant
Name Close n/a
  • your twin brother or sister
  • your mother
 
  • your father
 
  • your sister(s)
  • your brother(s)
  • your aunt(s)
  • your uncle(s)
  • your grandmother(s)
 
  • your grandfather(s)
 
  • your niece(s)
  • your nephew(s)
  • your cousin(s)
  • your great-grandmother(s)
 
  • your great-grandfather(s)
 
  • your stepmother
  • your stepfather
  • your stepsister(s)
  • your stepbrother(s)
  • your best-friend
 

We will return to consider the pattern of your results later.

You may find it useful to view the video 'Tough Choices' from Scientific American Frontiers in which "Princeton researchers study the brain's of test subjects making tough ethical decisions to determine which part of the brain is the seat of morality". Choose the Play video option to jump to demonstrations of two topics  covered in this lecture: Decision making in life and death moral dilemmas and ultimatum games.


Altruism - a puzzle for natural selection

The phrases 'Survival of the fittest' and 'Nature, red in tooth and claw' are associated with Darwin's theory of evolution through natural selection . They portray a world populated by selfish organisms intent on their own survival. This lecture examines the paradox of altruism.

For example:

These are examples of altruism or self-sacrifice. The existence of altruism posed a significant challenge to Darwin's theory of evolution through natural selection. Recent evidence has highlighted the importance of co-operation to evolution. It turns out that an answer to the altruism-paradox may involve paying more attention to 'selfish genes' rather than selfish people.


Hamilton's kin selection theory

Kin share many common genes. Genes can spread by benefiting other carriers of the same gene. Hamilton proposed the inclusive fitness or kin selection theory to explain altruism or self-sacrifice.

In an altruistic encounter there is:

The probability that the altruist and the recipient share a gene is called the coefficient of relatedness ( r ). The diagram shows the extent to which we share genes with our relatives. The value of r varies between 0 and 1. On average we share half of our genes with our brothers, sisters and children ( r=0.5 ), and a quarter of our genes are identical with those of our grandchildren, nephews and nieces ( r=0.25 )

According to Hamilton's Rule altruism pays off if rb>c . In other words, shared genes will profit if the cost to the altruist is less than the benefit to the recipient multiplied by the probability that the recipient shares genes with the donor.

Costs and benefits are expressed in units of fitness or reproductive success with values between 0 and 1.

For the sake of argument assume you have spare food that you could give to your brother to feed him and his children.

We can test if your altruism would benefit kin selection by putting these values into Hamilton's Rule rb>c where:

You might wonder why b and c are not always equal. Why not use the spare food you have to increase your own reproductive success? Well there is a limit to how much you can eat. If you have an abundance of food and your brother is starving, the cost to you of sharing is small, but it may be a matter of life or death to your brother and his children.


Kin selection theory in action

Review your answers to the reflective exercise.

Colour coding was used to break up the table into groups of relatives who are more - or less - related to you.

Does the pattern of your perception of your relatedness to relatives correspond to their actual kinship with you.

You may not have a twin (r = 1.0), but you probably feel more related to

Read Study 1: Perceived and Actual Kinship in Burnstein, et al (1994). Journal of Personality and Social Psychology, 67/5, 733-789. Available online

Burnstein et al (1994) and Petrinovich et al (1993) asked people to imagine how they would react in life-and-death situations in which they could prevent the death of a relative.

For example imagine that a train is running out of control down a track that branches. You are in charge of the points at a track junction. If the train goes down the left track it will kill one of your relatives. If you send the train down the other track it will kill two strangers. The choice is yours!

  The results reflect what you may have predicted; we are more likely to help a near relative (e.g. brother or sister (r=0.50) than a stranger (r=0.00) in a life-and-death situation.

Recipient's age influences altruism

But what about the age of the relative involved. Would you have predicted that we are less likely to help a younger relative than one who is slightly older?

One explanation for our preference for helping young people is that they have higher reproductive value than children or older people. A person's reproductive value is a measure of the probability that they will have children. Older people have lower reproductive value because fertility declines with age. Children have lower reproductive value because they may die before they reach puberty.


Inheritance of wealth

Analysis of bequests (see Cartwright, 2000) made in wills shows that people leave more of their estate:



Paternal investment

According to a simple version of kin selection theory, men should give more resources to their genetic children than to stepchildren. Anderson et al (1999) looked at the odds that a man would give financial support to  'children' who were attending college.   A man's children were classified into one of four types

Man's relationship with child's mother
Man's relationship with child
Child's mother is man's current partner
Child's mother is man's previous partner
Man is child's genetic father Class 1 Class 2
Man is child's stepfather Class 3 Class 4

anderson_fig2.jpg (26418 bytes) Compared to a child fathered by the man, and whose mother was the man's previous partner (Class 2 child),
  • a man is 2.27 times more likely to support a child through college if he was the father of the child and his current partner is the child's mother. 
  • a man is very unlikely to support a child through college if the child's mother was a previous partner, and the man was the child's stepfather

Both of these effects are statistically significant.

One surprising finding is that a man does not discriminate financially between a child who was born to the man's current partner in a previous relationship (Class 3 child), and a child fathered by the man in a previous relationship (Class 2 child) even though the man is genetically related to the class 2 child, but is only the stepfather of the Class 3 child

Men may invest in the children of their current partners in order to convince the current partners that they are 'good providers' and thus persuade their current partner to bear him further children.

Men may invest less in their own children from previous relationships because they are not sure that they are the true fathers of the children born whilst they were living with their  previous partners: 'paternity uncertainty'


Parent - child conflict

Tony Robinson Ancestry Tutorial 300x250

Trivers applied Hamilton's mathematical formula for kin selection to within-family conflict.  According to Trivers:

"Parents are classically assumed to allocate investment in their young in such a way as to maximize the number surviving, while offspring are assumed to be passive vessels into which parents pour the appropriate care. Once one imagines offspring as actors in this interaction, then conflict must be assumed to lie at the heart of sexual reproduction itself-an offspring attempting from the very beginning to maximize its reproductive success would presumably want more investment than its parent is selected to give" (Trivers, 1974).


Here is a section from Buss (1999) which illustrates how conflict can arise from the application of the principles of kin selection.

bird_feeding_chicks.jpg (20039 bytes)goshawk_feeding_chicks.jpg (22845 bytes)"Suppose you have one sibling who has the same reproductive value as you. Your mother comes home from a day of gathering with two food items to feed her children. As with many resources, there are diminishing returns associated with each increase in consumption--that is, the value of the first unit of food consumed is higher than the value of the second unit of food. The first unit of food, for example, may prevent starvation, whereas the second unit of food just makes you a little fuller and fatter. Let's say that the first item would raise your reproductive success by four units and the second item of food would raise it an additional three units. Your sibling's consumption of these food items would have the same result, with diminishing returns associated with each added food item.

mother_children2.gif (34037 bytes)Now comes the conflict. From your mother's perspective, the ideal allocation would be to give one unit of food to you and one to your sibling. This would net her eight units of increase, four for you and four for your sibling. If either you or your sibling monopolized all the food, however, the gain would only be seven (four for the first item plus three for the second). So from your mother's perspective an equal allocation between her children would yield the best outcome.

From your perspective, however, you are twice as valuable as your sibling--you have 100 percent of your genes, whereas your sibling only has 50 percent of your genes (on average). Therefore, your mother's ideal allocation would benefit you by the four units that you receive plus only two of the units that your sibling receives (since you benefit by only 50 percent of whatever your sibling receives), for a total of six units benefit. If you manage to get all the food, however, you benefit by seven units (four for the first item plus three for the second). Therefore, from your perspective the ideal allocation in this simplified example would be for you to get all the food and your sibling none. This conflicts with your mother's ideal allocation, which is to distribute equally, however. The general conclusion is this: The theory of parent-offspring conflict predicts that each child will generally desire a larger portion of the parents' resources than the parents want to give. Although the above example is simplified in various ways, this general conclusion applies even when siblings differ in their value to the parents and even when the parents have only a single child. If the parents were to go along with the ideal allocation of resources desired by the child, it would take away from other channels through which the parents might be reproductively successful. Interestingly, parent-child conflict over the parent's resources is predicted not merely to occur at particular times such as adolescence, but at each stage of life (Daly & Wilson, 1988).

The theory of parent-offspring conflict yields a number of specific hypotheses that can be tested: (1) parents and children will get into conflict about the time at which the child should be weaned, with the parents generally wanting to wean the child sooner and the child wanting to continue to receive resources longer; (2) parents will encourage children to value their siblings more than children are naturally inclined to value them; and (3) parents will tend to punish conflict between siblings and reward co-operation. " Buss (1999).

This table shows how various allocations of food affect each relative's inclusive fitness

mother-children.gif (26546 bytes) Assume that:


  Mother's fitness Offspring A's fitness Offspring B's fitness
Offspring A gets 2 units of food value of 2 units of food to offspring A * coefficient of relatedness between mother and offspring A
= 7*0.5 = 3.5
value of 2 units of food to offspring A * coefficient of relatedness between offspring A and recipient of food (offspring A)
= 7*1 = 7
Best strategy for offspring A
value of 2 units of food to offspring A * coefficient of relatedness between offspring B and recipient of food (offspring A)
= 7*0.5 = 3.5
Offspring B gets 2 units of food value of 2 units of food to offspring B * coefficient of relatedness between mother and offspring B
= 7*0.5 = 3.5
value of 2 units of food to offspring B * coefficient of relatedness between offspring A and recipient of food (offspring B)
= 7*0.5 = 3.5
value of 2 units of food to offspring B * coefficient of relatedness between offspring B and recipient of food (offspring B)
= 7*1 = 7
Best strategy for offspring B
A and B each get 1 unit of food value of 1 unit of food to offspring A * coefficient of relatedness between mother and offspring A + value of 1 unit of food to offspring B * coefficient of relatedness between mother and offspring B
= (4*0.5) +(4*0.5) = 2+2 = 4
Best strategy for mother
value of 1 unit of food to offspring A * coefficient of relatedness between offspring A and recipient of food (offspring A) + value of 1 unit of food to offspring B * coefficient of relatedness between offspring A and recipient of food (offspring B)
= (4*1)+(4*0.5) = 4+2 = 6
value of 1 unit of food to offspring B * coefficient of relatedness between offspring B and recipient of food (offspring B) + value of 1 unit of food to offspring A * coefficient of relatedness between offspring B and recipient of food (offspring A)
= (4*1)+(4*0.5) = 4+2 = 6
Conflict arises between the mother and her offspring because
  • the best strategy for the mother is to give each of her offspring 1 unit of food. This division of food will increase the mother's fitness by 4 units, and each of her offspring by 6 units
  • the best strategy for offspring A is to obtain 2 units of food. This division of food will increase offspring A's fitness by 7 units, offspring B's fitness by 3.5 units, and the mother's fitness by 3.5 units
  • the best strategy for offspring B is to obtain 2 units of food. This division of food will increase offspring B's fitness by 7 units, offspring A's fitness by 3.5 units, and the mother's fitness by 3.5 units

Conflict between offspring

Before beginning this section, view the video from Scientific American Frontiers "Masked Killers. Stronger Masked Booby chicks kill their smaller siblings to better ensure their own survival, and that of their mothers as well."

Note that although this scenario is often described in terms of parent-offspring conflict, there is also conflict between the offspring for the mother's resources.

Potential conflict between siblings is magnified if they are only half siblings i.e. the offspring have separate fathers, but the same mother. This table shows how reducing the coefficient of relatedness from 0.5 (full siblings ) to 0.25 (half siblings ) affects the fitness outcomes.


adopted-children.gif (13437 bytes)Assume that:


  Mother's fitness Offspring A's fitness Offspring B's fitness
Offspring A gets 2 units of food value of 2 units of food to offspring A * coefficient of relatedness between mother and offspring A
= 7*0.5 = 3.5
value of 2 units of food to offspring A * coefficient of relatedness between offspring A and recipient of food (offspring A)
= 7*1 = 7
Best strategy for offspring A
value of 2 units of food to offspring A * coefficient of relatedness between offspring B and recipient of food (offspring A)
= 7*0.25 = 1.75
Offspring B gets 2 units of food value of 2 units of food to offspring B * coefficient of relatedness between mother and offspring B
= 7*0.5 = 3.5
value of 2 units of food to offspring B * coefficient of relatedness between offspring A and recipient of food (offspring B)
= 7*0.25 = 1.75
value of 2 units of food to offspring B * coefficient of relatedness between offspring B and recipient of food (offspring B)
= 7*1 = 7
Best strategy for offspring B
A and B each get 1 unit of food value of 1 unit of food to offspring A * coefficient of relatedness between mother and offspring A + value of 1 unit of food to offspring B * coefficient of relatedness between mother and offspring B
= (4*0.5) +(4*0.5) = 2+2 = 4
Best strategy for mother
value of 1 unit of food to offspring A * coefficient of relatedness between offspring A and recipient of food (offspring A) + value of 1 unit of food to offspring B * coefficient of relatedness between offspring A and recipient of food (offspring B)
= (4*1)+(4*0.25) = 4+1 = 5
value of 1 unit of food to offspring B * coefficient of relatedness between offspring B and recipient of food (offspring B) + value of 1 unit of food to offspring A * coefficient of relatedness between offspring B and recipient of food (offspring A)
= (4*1)+(4*0.25) = 4+1 = 5

 

  • Notice how the adverse effects on an offspring's fitness are magnified if all the mother's resources are directed towards a half sibling.
  • Note how co-operation between half-siblings can avoid this adverse effect
  • Co-operation between siblings for an equal allocation of resources is likely to succeed because this strategy maximizes their mother's fitness


The 'Wicked stepmother effect'

wicked-stepmother.gif (25066 bytes)Assume that:


  Mother's fitness Offspring A's fitness Offspring B's fitness
Offspring A gets 2 units of food value of 2 units of food to offspring A * coefficient of relatedness between mother and offspring A
= 7*0.5 = 3.5
Best strategy for mother
value of 2 units of food to offspring A * coefficient of relatedness between offspring A and recipient of food (offspring A)
= 7*1 = 7
Best strategy for offspring A
value of 2 units of food to offspring A * coefficient of relatedness between stepchild B and recipient of food (offspring A)
= 7*0 = 0
Stepchild B gets 2 units of food value of 2 units of food to stepchild B * coefficient of relatedness between mother and stepchild B
= 7*0 = 0
value of 2 units of food to stepchild B * coefficient of relatedness between offspring A and recipient of food (stepchild B)
= 7*0 = 0
value of 2 units of food to stepchild B * coefficient of relatedness between offspring B and recipient of food (offspring B)
= 7*1 = 7
Best strategy for offspring B
A and B each get 1 unit of food value of 1 unit of food to offspring A * coefficient of relatedness between mother and offspring A + value of 1 unit of food to stepchild B * coefficient of relatedness between mother and stepchild B
= (4*0.5) +(4*0) = 2+0 = 2
value of 1 unit of food to offspring A * coefficient of relatedness between offspring A and recipient of food (offspring A) + value of 1 unit of food to stepchild B * coefficient of relatedness between offspring A and recipient of food (stepchild B)
= (4*1)+(4*0) = 4+0 = 4
value of 1 unit of food to stepchild B * coefficient of relatedness between stepchild B and recipient of food (stepchild B) + value of 1 unit of food to offspring A * coefficient of relatedness between stepchild B and recipient of food (offspring A)
= (4*1)+(4*0) = 4+0 = 4

 

Notice how an unequal allocation of resources between her offspring A and her stepchild B maximizes the fitness of the mother, and her own offspring A
Notice how an equal allocation of resources between her offspring A and her stepchild B does not maximize the fitness of either the mother, or her own offspring A

 


A note on kin selection

cricket-field-positions.jpg (5015 bytes)Kin selection, reciprocal altruism, parental investment, sexual and natural selection are powerful concepts that have helped us gain a deeper understanding of the evolution of human behaviour. Although kin selection is an important concept, I have worries. Can you recognize your blood relatives before you are introduced to them? Who is your 'cousin once removed'? Are they blood relatives? Are all your uncles and aunts blood relatives? What is your mother's sister's husband called? Is he a blood relative? What is your mother's brother called? Is he a blood relative? Why are they both called uncle? Why is our language so clumsy when describing relatives, but so precise when describing where players are located on a cricket pitch?


Trivers' reciprocal altruism theory

Before tackling this section you may find it useful to view

Trivers (1971) has suggested another theory of why we co-operate with people who are not necessarily related to us. This works on the principle of " if you scratch my back, I'll scratch yours" This theory depends on important preconditions:

The prisoner's dilemma

The prisoner's dilemma game is a way of studying how people behave in a situation with different rewards for co-operating with, and cheating on, another person. For the purposes of this game you are asked to imagine that you and a colleague have committed a crime. You enter into a pact with your colleague-in-crime in which you both agree to say nothing to the police if you are interviewed. Subsequently the police interview both of you in separate rooms. They offer you a 'deal'. They have enough evidence to charge you both with a relatively minor crime for which you will both serve one year in prison. If you both confess to the major crime, you will each receive a five year sentence for co-operating with the authorities. But here's the twist! If you confess and your colleague does not confess, he will receive a ten year sentence and you will not be prosecuted. Likewise if you keep quiet about the major crime, but your friend confesses, you will serve ten years in prison and he will walk free. The choice is yours!. Here are your options:

    Prisoner B
    Silence (Co-operate) Confess(Cheat)
Prisoner A Silence (Co-operate) 1/1 10/0
Confess(Cheat) 0/10 5/5
       

As you can appreciate there is a great temptation to confess and thereby cheat on your earlier agreement with your colleague. If you were to play the prisoner's dilemma only once this might be your preferred strategy, but what happens if you had to face the same situation again. This variation of the game is called the iterated prisoner's dilemma . In this variation of the game you may be punished by your colleague on the next round of the game.

There is a great deal of interest in the prisoner's dilemma game because it is a model for real-world situations in which people and animals co-operate and compete with each other. For example the proliferation of nuclear arms during the Cold War can be analysed in terms of prisoner's dilemma strategies. Likewise the problem of persuading people to accept the inconvenience associated with abandoning private cars in favour of public transport, or separating their domestic rubbish for recycling are variations on the theme of the 'tragedy of the commons'.

What is the best strategy to adopt in the iterated prisoner's dilemma game. There are various possibilities:

It doesn't take much imagination to realize that finding the best strategy would be very important for foreign policy advisers to leaders of world superpowers.

It turns out a good strategy is to play tit for tat :

Soldiers in trenches on the Western front in World War 1 engaged in tit for tat shooting. The commanding generals stamped out this behaviour by court-martialling some soldiers.

Picture: "Humanity - Stretcher-bearer Post, 9th Field Ambulance" by Gilbert Rogers (Official War Artist). From Swedish University Network SUNET Archive ftp.sunet.se

 

But tit for tat can run into problems if you make an error . For example you might loose concentration, and imagine that the other player has cheated when in fact they made a co-operative move. A slight modification of the strategy overcomes this problem - only retaliate if the other player cheats twice in a row - the generous tit for tat strategy. Cartwright (2000) provides a clear explanation of the effectiveness of these strategies and variations such as the Pavlov 'win stay, lose shift' strategy.


Requesting and giving help

Gaulin & McBurney (2001) review the conditions that encourage us to ask for, and give help.

We are more likely to give assistance if:

We are more likely to ask for help if:

Ultimatum games indicate that people are more altruistic than mathematical game theory would predict.

Imagine I have 10 which you can split with someone else. If the other player accepts the split then you each get the amount you specified. If your offer is rejected, then you both get nothing. How much would you offer to share?

Game theory predicts that the best strategy is for you to offer 1 and keep 9 for yourself. But the majority of people offer the other player 5 and keep 5 for themselves.

Maybe you are worried that you will be punished for being mean. The other player might reject 1 in order to punish your selfishness.

Would you change your offer if the rules of the game are changed so that the other player cannot reject your offer?

This manipulation does have an impact on what people offer, but only 20% of subjects give away 1 and keep the remaining 9. And more than 20% of players split the money equally with the other player.

One explanation for people's niceness in ultimatum games is that they feel their reputation would be damaged if they behaved selfishly. However even under 'double-blind' conditions - in which anonymity is preserved - some people still fail to act selfishly.



Cheater-detection is easy, but valid inference is hard

Do you know who these men are, and why they are famous?

Humans are exquisitely sensitive to cheating . We scan our environment to detect people who cheat.

  • We remember the faces of people who have been introduced as cheaters more effectively than pictures of non-cheaters
  • we dislike 'free-riders'
  • we are interested in gossip about the exploits (often sexual) of people we know
  • we take steps to preserve our reputations (Gaulin & McBurney, 2001)
  • we feel guilt after cheating or failing to reciprocate a kindness

If you are a student at the University of Plymouth you may be familiar with the following logical problem:

You have been hired as a clerk. Your job is to make sure that a set of documents is marked correctly according to the following rule:

If the document has a D rating, then it must be marked code 3

You have been told that there are some errors in the coding of the documents, and that you need to find the errors. Each document has a letter rating on one side and a numerical code on the other. Here are four documents. Which document(s) do you need to turn over to check for errors?

D F 3 7

Here is another problem: You have been hired as a bouncer in a bar and you must enforce the following rule:

If a person is drinking beer, then they must be over twenty years old.

The cards below have information about four people at the bar. One side of each card lists a person's age and the other side shows what they are drinking. Which card(s) do you need to turn over to be sure no one is breaking the law?

beer coke 25 years 16 years

The bouncer's problem is easier to solve.

But the clerk's document checking problem is more difficult.

About 75% of students solve the bouncer's task but less than 25% get the clerical task correct. Don't worry if you are not one of the 25%. I didn't get it right first time and even now I can't solve that type of logical problems. But I can detect a 'cheater' at 20 paces!

It turns out that both tasks have exactly the same logical structure.

Logical structure of the 'bouncer' problem Logical structure of the 'clerk' problem
beer coke 25 years 16 years
D F 3 7
Rule : Beer drinkers must be over 20 Rule : D-rated documents must be marked code 3
Check person drinking beer to see if they are over 20 Check D-rated document to see if is marked code 3
Check anyone under 20 to ensure they are not drinking beer Check document coded 7 to check that it is not rated 3
No more checking necessary No more checking necessary
Anyone can drink coke. Therefore don't bother to check the age of the coke drinker Any document can be rated F. Therefore don't bother to check the code of the F-rated document
The rule does not apply to people over 20. Therefore ignore what the 25 year old is drinking Code 3 documents do not have to be D rated. Therefore ignore the rating of the 3-rated document.

 

andrew anna caroline
craig darren melanie nichola
Nasty Nick sada thomas  

Confused by the logic behind the clerk problem? I still am , and I'm writing this stuff. It turns out that you can solve the problem if you have been taught the rules of valid inference as part of a course on logic. These problems are examples of the Wason selection task . I get the impression that people who have been taught logic have spent years trying to figure out why the rest of us can't get our heads around the clerk problem.

It seems that the majority of us can solve Wason's selection tasks if they involves cheater detection -e.g. the bouncer problem. Cosmides and Tooby suggest that have evolved a mental ability to spot cheaters in order to be able to engage in reciprocal altruism .

The rules of logical inference are important to scientists because they need to check hypotheses for examples that would falsify them. The rest of us need to be equipped with the mental capacity to spot a rogue car dealer before we drive of in a gleaming 'death-trap'.

Can you pick out 'Nasty Nick' who cheated on the TV show 'Big Brother' and Caroline who replaced him from these pictures of contestants?

 

PSY364 Evolutionary Psychobiology Seminar discussion themes
  • View the Scientific American Frontiers (1992) video "The Power of Persuasion". What conclusions do you draw about sex differences, dominace and cheater detection?
  • What has evolutionary psychology taught us about human nature that we might not have already known? Question originally posed by Stangroom in  Discourse: Have Evolutionary Explanations Gone Too Far?

Read Caporael (2001). Evolutionary Psychology: Toward a Unifying Theory and a Hybrid Science. Annual Review of Psychology 2001, available online and consider the following issues:

  • How could 'altruistic genes' increase in a population?
  • Would evolutionary psychology exist without the work of Hamilton and Trivers?
  • What psychological processes can be explained in terms of inclusive fitness?
  • Is the finding that women with lower waist-to-hip ratios are more attractive than women with high waist-to-hip ratios an experimental artefact?. See also "1.3 Symposium: Examining the validity of the waist-to-hip ratio hypothesis of human female attractiveness " In Conference Proceedings The Annual Meeting of the Human Behavior and Evolution Society  June 2 - 6, 1999
  • Can the position of women in a society account for sex differences in mating preferences?
  • Is genetic determinism an inevitable consequence of inclusive fitness theory?
  • Does inclusive fitness explain many features of everyday family life, or is it merely a restatement - in 'scientific' language - of common beliefs about why families bicker and fight ?

Read Burnstein, Crandall and Kitayama (1994). Journal of Personality and Social Psychology, 67/5, 733-789. Available online and consider the following issues:

  • Are you convinced that individuals reliably distinguish their relationship with 'moderately close' kin (r=0.5) and 'distant' kin (r=0.125). Refer to Burnstein et al (1994) Study 1 and Figure 1
  • Examine the 'perceived relatedness' of 'step-kin' and 'acquaintances' in Figure 1. Is there a statistically reliable difference between these values?
  • Comment on the design of Study 2 in Burnstein et al (1994). How could the experiment be extended to investigate the possibility that we may behave differently towards our brother's and sister's children? Is there any reason (e.g. paternal uncertainty) to believe that we might behave differently towards these two types of child?
  • Comment on the design of Study 3 in Burnstein et al (1994). Is there a feature of the procedure that may have contributed to the finding of a significant reduction in the tendency to help the youngest children, and the oldest adults? What are the implications of your observations for a theory of evolutionary psychology?
  • On the basis of the results presented in Study 6, do we behave according to Haldane's criteria for altruism?
    • Would you rescue your 6 nephews or 2 brothers in a life-and-death situation?
    • Would you rescue your 4 nephews or 1 brother in a life-and-death situation?
    • Would you rescue your 4 nephews or 2 brothers in a life-and-death situation?
  • Would your decisions on these choices be modified if they involved your sisters and nieces?, and if so explain your reasons.

References

Online resources


Points to ponder

Here are some jaundiced views of human ethics / morals.

But maybe something of the human spirit is missing in these cogitations ...


Heroes and villains

Here are some people made famous by outstanding acts of altruism and cheating.

'I am just going outside, and may be away some time'

 

In the early years of the last century, a party of explorers led by Captain Scott set sail for the Antartic. In Scott's words "The main object of this expedition is to reach the South Pole, to secure for the British Empire the honour of this achievement."

On 17 January 1911, Scott's expedition reached the Pole; he wrote: "Great God! this is an awful place and terrible enough for us to have laboured to it without the reward of priority". Their disappointment was due to a Norwegian team having beaten them to the Pole.

The journey back to base was a nightmare. On the 17 February 1912 one of the expedition members, (Evans) died at the foot of the Beardmore Glacier after several bad falls.

The others struggled on, getting weaker and frost-bitten, especially Oates who, at the end of another month could go no further and knew he was holding back his companions. Scott wrote: "We knew the end had come. One morning he said, 'I am just going outside and may be some time'. He went out (of the tent) and we have not seen him since".

Scott, Wilson and Bowers knew that Oates was going out to die for their sakes. Scott wrote: "Though we tried to dissuade him, we knew it was the act of a brave man and an English gentleman. We all hope to meet the end with a similar spirit."

Down in the South where the blizzards blow,
Four men struggled along in the snow.
Bowers and Wilson and Captain Scott,
They could walk, but Oates could not.
Slower and slower, day by day,
They dragged the sled on which he lay.
Each man thought, though none would say,
But for Oates we might get away.....

'Never before have so many owed so much to so few'

The Battle of Britain was a crucial moment in World War II. Although short of planes and pilots, the Royal Air Force held off the Luftwaffe and prevented a German invasion. Churchill called it Britain's "Finest Hour".

 

 

.... and villains

The star Canadian sprinter Ben Johnson received a lifetime ban for steroid use after running 100 meters in 9.79 seconds at the Seoul Olympics.


Copyright Dr. C.A.P. Kenyon 1994-2006