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Altruism

ÿNepotism

ÿCommon-Pool Resource (CPR)

ÿTragedy of the Commons

ÿPublic Good

ÿFree-riders

ÿCompetitive Altruism

A 1987 Florida news story reported that 22 blood donorswho had false positives on an HIV test were misinformed

that they were HIV positive, & 7 committed suicide.

This story prompted Gerd Gigerenzer and colleagues to studyhow HIV counsellors were explaining the results of HIV tests.

One of the researchers approached 20 HIV counselors for ablood test, presenting himself (truthfully) as a 25-year oldheterosexual with no history of drug use.

In each clinic he asked a standard set of questions including“What is the probability that a male in my risk categoryactually has HIV after a positive test?”

What’s the right answer? (Experts ought to know!)

Relevant facts that the expert counselors should have known :

HIV prevalence rate among low-risk men in Germany in 1990:0.01 %

Test sensitivity (probability of correct detection given disease):99.9 % (so the “miss” rate = 0.1 %)

Test specificity (prob of correct healthy diagnosis if no disease):99.99 % (so the “false positive” rate = 0.01 %)

The counselors’ answers:

2 refused to answer directly

10 said 100 % certain

5 said ≥ 99.9 % certain

1 said ≥ 99 % certain

2 said ≥ 90 % certain

Relevant facts that the expert counselors should have known :

HIV prevalence rate among low-risk men in Germany in 1990:0.01 %

Test sensitivity (probability of correct detection given disease):99.9 %

Test specificity (prob of correct healthy diagnosis if no disease):99.99 %

Working it out by Bayesian inference:

p ( + test given HIV+ )p ( HIV+ | + test) = p ( HIV+ ) x

p ( HIV+ ) x p ( + test | HIV+ ) + p ( HIV- ) x p ( + test | HIV- )

The counselors estimated between 90 and 100 %.

The correct (Bayesian) answer is 50 % !

And there’s an easy way to figure it out:

Imagine 10,000 men. Expected number HIV+ = 1 (and he’llalmost certainly test positive). 9999 men are not HIV+, and witha false positive rate of 0.01 %, one of them (on average) will testpositive, too. Result? 2 positive tests: 1 truly HIV+, 1 not.

10,000 men

1 HIV+ 9999 HIV-

1 pos test 0 neg test 1 pos test 9998 neg tests

G. Gigerenzer (2002) Calculated risks. Simon & Schuster

Why Are Organisms Ever Altruistic?

ÿ Kin Selection

ÿ Reciprocal Altruism

ÿ Costly Signaling

ÿ Group Selection?

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Spouse Non-Rel Child Parent Other RelHo

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Blood Kin are Relatively Immune, given their Availability

Daly & Wilson (1982) American Anthropologist 84: 372-378

The “problem of altruism” and its second solution (after nepotism) :Cooperation and Reciprocity (direct and indirect).

Common Pool Resources and the “Tragedy of the Commons”. … escaping the tragedy.

Public Goods Games : why contribute ?

Punishing non-cooperators is also hard to explain.

Reputation effects

Ultimatum Games

Non-Nepotistic Sociality

"Indirect Reciprocity” - Altruistic acts that are unlikely to be directlyreciprocated may still benefit the altruist later if his reputation isenhanced, and others reward those with altruistic reputations.

If an individual refuses to be altruistic, then it decreases his reputation,and lowers his chances of having others behaving altruistically towardshim. Thus, an individual can benefit from being altruistic if others notice.

Axelrod’s tournament showed that reciprocal altruism can evolve ifindividuals interact more than once.

Question: What if individuals meet each other individual only once?

Is cooperation doomed?

Nowak & Sigmund (1998) showed with a computer simulation thatindirect reciprocity can evolve if individuals help only those who havea good reputation. Using an evolutionary simulation, they found thatgradually, the amounts of altruism increased, and the number ofdefectors decreased because only the strategies that were selectivelyaltruistic thrived.

Nowak & Sigmund (1998), Nature, v.393, pp. 573-577

Wedekind and Milinski designed an experimentthat gave the opportunity for indirect reciprocity tooccur. They formed groups of 9-10, and gaveeach player 7 francs. Players were randomlyassigned to be “Donors” or “Recipients” (6 timeseach) with a different person each time. Donorscould pay 1 or 2 francs to give 4 francs toRecipients.

Identities were concealed, and players wereidentified only by number, but their past decisionsof giving or non-giving were displayed.

Do People Actually Do This?

This is themechanism usedby Wedekind &Milinski to ensureanonymity, yetprovide informationabout player’s pastdecisions

Wedekind & Milinski (2000) Science, 288(5467), 850-852

Participants had an image score. Every time they chose to givemoney, their image score increased by one. Every time they refused,their image score decreased by one.

Did a participant’s image score affect how others behavedtowards him/her?

The image scoreof recipients whowere givenmoney tended tobe higher thanthe image scoreof recipients whowere not givenmoney (in 7 outof 8 groups), p <0.01.

Donors were more likely to be altruistic towards those who had beenaltruistic in the past, even though the donors would not benefit fromthe recipients directly. Donors benefited from having an increasedimage score, which increased the amount money they received fromothers (indirect reciprocity).

Image Did Affect Amount Received

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Donors who onlydonated once ortwice only gavethose donations toplayers with highimage scores;donors who gavemore often wereless discriminate.

Wedekind & Milinski (2000) Science, 280(5467), 850-852

Common Pool Resources (CPRs)

CPRs are resources that people have collective rights and/or abilitiesto use, and whose value is depleted by each individual’s use.

CPRs "invite" free-riders :

Some CPRs (e.g. pastures and fisheries) exist regardless of humanlabour. Others (e.g. irrigation systems) are built. In either case, thereis a strong incentive to exploit CPRs without contributing to theirmaintenance or development:

If some take benefits without paying their share, those who do payare "suckers". This is the tragedy of the commons. In the classic e.g.,each shepherd keeps adding sheep to his flock despite evidence thatthe commons can’t sustain so many. Modern e.g.s of similar “socialtraps” include collapse of fisheries in the north Atlantic and elsewhere.

In group situations, people cannot always direct their actions towardsspecific individuals, e.g. public goods and common pool resources

Altruism Towards Groups

Like the necessity for “cheater detection” in dyadicreciprocity, Elinor Ostrom and others have identifiedthe monitoring and sanctioning of free-riders asessential for preventing “tragedy” and maintainingCPRs.

Ostrom’s claim that an institutionalized capability formonitoring and sanctioning free-riders is essential forsuccessful long-term maintenance of Common PoolResources in real world situations rests on analysis ofcase histories: both success stories and tragedies ofover-exploitation.

“Public goods” (CPR) experiments can test this claim.

Preventing Free-riding

Something that individuals have to expendeffort to provide (an altruistic effort), and once itis provided, everybody benefits from it. No onein the group can be excluded from benefiting.

Examples: national defense, public radio, publicradio, big-game hunting, group projects inuniversity

Public Goods

The group will do best if everyonecooperates, but it is in each individual’sinterest to defect and free-ride on thework of others. How is any groupcooperation sustained? How can publicgoods be provided?

Selfish Interest vs. Group Altruism

Some experimenters use Public Goods Games. Inthese games, each individual is given an amount ofmoney that they can either keep or donated to theirgroup.

Any money that is donated increases in value, andis then shared equally amongst all the participants.Group profits are highest if everyone donates alltheir money. However, each player does best if theydo not donate anything.

i.e. They take the benefit from the group (share ofthe profits) without paying the cost (donating)

How do we study this sort of problem?

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Each member of the group (e.g. 4people) receives some money (e.g. $10)each round which they may either keepfor themselves or donate to the publicgood.

The total amount donated is multiplied bya factor greater than 1 (e.g. it’s doubled),and this amount is shared equally by allthe players regardless of their individualdonations.

A Typical Public Goods Game

If A donates $10 to the group (and keeps nothing) andeveryone else also donates $10, the total amountdonated is $40. This amount is doubled = $80. Eachplayer gets a $20 share from that, so they each make$20 that round.

However, if A had kept his $10, but everyone elsedonated $10, the group would earn $60, and he wouldget a $15 share of that, for a total of $25, and the othersget $15 each.

Thus, each individual has a temptation to “sucker” theothers, or avoid being “suckered”.

Examples

Most players donate some (not all) of their money tothe public good, and donations fall over successiverounds because no one likes being the “sucker”. Thisfall is faster when players know individual contributionsrather than group averages.

Most public goods games are played anonymously, sothat no player knows the identity of any other player.Chapter 15 describes how donations in Dictator gamesare more selfish under double-blind conditions thanwhen the experimenter knows each person’s decisions.Might the donations in public goods be higher if otherplayers knew who donated and who defected?

Typical Results

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Data from Gächter & Fehr (1999), J. Econ. Beh. & Org, 39, 341-369

Donations were higher when participants knew how mucheach other person donated and the participants had a chanceto interact before the game (p < .001)

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What happens without anonymity?

Rege & Telle (2001) also found that donations increase whendonations are not anonymous, and the game is explicitly framed interms of “cooperating” and “free riding”.

However, there is a fairly constant proportion of people who free-ride regardless of anonymity or framing.

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Does everybody donate more?

Recall:

In reciprocal altruism and the repeatedPrisoner’s Dilemma, you can punish otherplayers by returning defection with defection.Punishment is selective.

However:

In a standard public goods game (N>2), youcan only punish by reducing your owncontribution. This punishes everyone elsewhether they are cooperators or defectors!

Why should we care if people know?

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Fehr & Gächter (2000) introduced a mechanismto selectively punish free-riders in public goodsgames.

After each round, each player was given theoption of paying a cost to reduce the payoff ofany other player. This is a financial punishment,but there was a cost of inflicting it.

Fehr & Gächter (2000), American Economic Review,90, 980-994

Why should we care if people know? When players couldpunish specific players,contributions stayedhigh, and evenincreased.

Without punishment,those same playersshowed a decline incontributions, just like inany other public goodsgame.

Notice the sharpcontrasts between theend of rounds withoutpunishment and roundswith punishment

People were even willingto punish other playerswhen the groups wererandomly shuffled everyround, and this keptcontributions stablewhen punishment wasallowed.

They later ran a session whereparticipants were randomlyshuffled, and guaranteed tonever encounter the same 4-person group. Punishmentsand contributions were similarto when there was still achance of meeting again.

Fehr & Gächter (1999) WorkingPaper No. 10

Fehr & Gächter (2000)

Free-riders got punished more than cooperators, and the amount ofpunishment was related to how badly the person free-rode.

Partner = group compositionremained the same all rounds

Stranger = group compositionshuffled each round

As a result of the opportunity to punish, group payoff increased whenpunishment was possible, even after subtracting the cost to punish.

Non-punishers do better than punishers, because they free-ride on the costly punishment of the punishers. Thus, thereis a “second-order free-rider problem” because punishmentis a public good.

We can try to solve this by punishing non-punishers.

Gintis (2000) proposes the model of “strong reciprocity” toexplain this. Strong reciprocators are individuals who arepredisposed to cooperate, or punish non-cooperators. Suchindividuals succeed because they cause the success andsurvival of whatever groups that they happen to be in.

Alternately, can rewards explain altruism? Might individualsbenefit from having a reputation for being altruistic?

Is punishment the best way to play?

Milinski et al. combined public goods games and their indirectreciprocity game. Participants were in one of two conditions:

1) 8 rounds of public goods, then 8 rounds of indirect reciprocity

2) Alternating rounds of indirect reciprocity and public goods (8 each)

Participants then played 4 final rounds of public goods, where they wereeither told that they would have no more rounds of indirect reciprocity, ornot given that information (and would thus expect future rounds ofindirect reciprocity).

This led them to 2 research questions;

1) Are donations to the public good higher when participants stand tobenefit from rounds of indirect reciprocity?

2) Are participants who contribute to the public good more likely to receivemoney via indirect reciprocity?

Milinski, Semmann, & Krambeck (2002), Nature, 415, 424-426

Can reputation explain giving?

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Red = public goods 1st,then indirect reciprocity

Blue = alternatingrounds

filled circles: rounds ofpublic goods

open circles: rounds ofindirect reciprocity

squares: group knewthat indirect reciprocityrounds were finished

diamonds: group didn’tknow that no moreindirect reciprocity left

Donations to public goods were significantly higher when they werealternated with rounds of indirect reciprocity (p < 0.0002), plus nodecline in contributions; players had the chance to be rewarded forcontributing to public goods. Contributions declined once participantsknew that no more rounds of indirect reciprocity remained.

Participants who donatedto public goods were lesslikely to be refusedmoney in the rounds ofindirect reciprocity (i.e.they were more likely toreceive money)

Groups that alternatedrounds of public goodsand indirect reciprocityearned more moneythan those that playedthe games in blocks of8 each.

Milinski, Semmann, &Krambeck (2002), Nature,415, 424-426

Take-Home Message:

There can be benefits from having a good reputationand being altruistic:

- you receive the benefits or mutual cooperation

- you receive more altruism from others

- you don’t get punished for being selfish

Under certain conditions, altruism can be selected for!

- Can signal willingness to cooperate

- Can signal abilities e.g. philanthropy, hunting

Could Competitive Altruism exist?

Altruism as a Costly Signal?