# Reciprocal Altruism _cont_

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```					Reciprocal Altruism II

Psych 250
10/2/07
Announcements
• First Research Opportunity (2 credits)
– Posted across from Gartley 210B
– Don’t show up during last ½ hour
• Second Research Opportunity (1 credit)
– Also posted across from Gartley 210B
• Alternate Assignments posted on the web
1   2   3                 4          TOTAL

TFT

Strategy   D   D   C                 D
X

Strategy X
Cooperate      Defect

Cooperate
TFT: 5          TFT: 1
X: 5            X: 8
TFT
Defect

TFT: 8         TFT: 3
X: 1           X: 3
From last time
•   Modus Ponens
•   Modus Tollens
•   Wason selection task
•   Do we use the rules of formal logic to reason?
•   The descriptive problem
•   The drinking problem
•   What was the difference?
Told that the following cards have a letter on the top half and a number on the bottom half.
Which, if any, of the pieces of paper do you need to remove to see if the following rule has
been violated?

If the card has a 7 on top, then there is an E on the bottom.

Ponens: Given P  Q                                                Tollens: Given ~Q  ~P

7                    3                    6                      7

X                      E                     E                      S

P                    ~P                      Q                     ~Q
Told that the following cards have a letter on the top half and a number on the bottom half.
Which, if any, of the pieces of paper do you need to remove to see if the following rule has
been violated?

If you are drinking beer, then you must be 21 or older.

Ponens: Given P  Q                                                Tollens: Given ~Q  ~P

beer                  soda                 water                   beer

17                    23                    23                     19

P                    ~P                      Q                     ~Q
Cheating
• Why was the drinking problem easier?
• The evolution of reciprocal altruism required
that individuals be able to detect cheaters.

• What is cheating in a social exchange?
– Taking the benefit without paying the associated
cost or meeting the requirement.
Features of a cheater detection system
    Shouldn’t need to be familiar with the content
    Should use the rules of adaptive logic not necessarily
formal logic
    Should be sensitive to perspective
    Should be sensitive to costs and benefits
    Should be sensitive to intentional cheating versus
innocent mistakes
    Should be able to detect cheaters not altruists
1. Shouldn’t need to be familiar with the problem
100
90   familiar
80   unfamiliar
Percent Correct

70
60
Drinking   Cassava
50                                    Age       Root

40
30
20
If a yellow
If 7 then E     canary,
10                    then blue
bananas

0
Descriptive                 Social Contract
Adaptive vs Formal Logic
• From an adaptive point of view, is there any
difference between the following:
– If you give me your watch, then I’ll give you \$10
– If I give you \$10, then you give me your watch

• Is there a difference according to the rules
of formal logic?
2. Rules of adaptive logic not necessarily formal logic
• Normal social contract:
If you take the benefit, then you pay the cost

p                       q

Formal logic violation:

• Switched social contract:
If you pay the cost, then you take the benefit

p                       q

Formal logic violation:
2. Rules of adaptive logic not necessarily formal logic
• Normal social contract:
If you are drinking beer, then you must be over 21.

p                          q
Formal logic violation:

• Switched social contract:
If you are over 21, then you (can) drink beer.

p                          q

Formal logic violation:
2. Rules of adaptive logic, not necessarily formal logic
Standard Social Contract:
If you take a benefit, then you pay the cost
Switched Social Contract:
If you pay the cost, then you (can) take the benefit

Benefit     Benefit not    Cost      Cost not
accepted    accepted       paid      paid

Standard     P            ~P           Q         ~Q

Switched     Q            ~Q           P         ~P
• How do subjects perform on the
switched social contract?
– __% pick Q and ~P which is the correct
adaptive response but the incorrect logical
response.
• So it looks as if people follow an
adaptive logic, not modus ponens or
modus tollens.
• This makes sense if people are looking
for cheaters and not just logic violators.
3. Should be sensitive to perspective
• You would expect reasoning mechanisms
to be sensitive to perspective.

• Example:
– If an employee gets a pension, then he
must have worked more than 10 years.
Rule:
If an employee gets a pension then he
must have worked more than 10 years.

Gets     Doesn’t get      Gets        Gets
a pension    a pension    a pension   a pension

Worked      Worked
8           24          30 yrs      2 yrs

What counts as a violation to this rule for the employer?
What counts as a violation to this rule for an employee?
Perspective Matters!
• Depends on perspective!
• This would not follow from the rules of
formal logic.
• We possess circuits that follow an
ecological rationality.
Features of a cheater detection system
   Shouldn’t need to be familiar with the content
   Should use the rules of adaptive logic not necessarily
formal logic
   Should be sensitive to perspective
   Should be sensitive to costs and benefits
   Should be sensitive to intentional cheating versus
innocent mistakes
   Should be able to detect cheaters not altruists
Dissociations as evidence for
specialized neural circuitry
Daffy has a lesion
to a particular
brain region.
Test him and a
control (bugs)
on two different
tasks (A & B).

Performs well on A Performs well on A
Performs well on B Does not perform well on B
Neuropsychology of Social Exchange
• Are there areas of the brain that have been
associated with the ability to reason about
social exchange and cheaters?
• To look at impairments in the brain, good to
look at two abilities that are hypothesized to
use different reasoning circuits.
• Double dissociations
• We have been talking about reasoning
about cheating in a social context
• Also reasoning about precautions:
– If you handle blood, then you wear gloves

Did not
Did not
Handled    Handle     Wore
Wear
Blood      Blood     Gloves
gloves

p          ~p        q          ~q
Same circuits?
• Are there specialized circuits for reasoning about
social contracts?
• Hypothesis 1:
– No specialized circuits: general reasoning abilities
– Should see either poor performance on both or intact
performance on both
• Hypothesis 2:
– Yes, there are specialized circuits for reasoning about
social contracts.
– Should see poor performance on social contracts but
intact performance on precautions
• RM suffered a bicycle
accident in 1974, when
he was 25.
• Damage to the medial
OFC and anterior
temporal cortex.
• Gave RM social
contract problems –
only got 39% correct.
This is in contrast to
control subjects who
got >65%.
• However, he did fine
on precautions.
Summary
• How do we get altruism between non-relatives?
• Social exchange/ reciprocal altruism is possible.
– TFT strategy in repeated prisoner’s dilemma
• Properties: retaliatory and forgiving
• Iterated (one time  defection)
• Requires:
– Person recognition, attribute memory, reason about cheating.
• How do we reason about cheating?
– Do we use general purpose reasoning abilities or specialized
reasoning ability that are specific for cheating?
• What would a general reasoning ability look like?
– Modus ponens and modus tollens
• What is cheating?
Adaptive Problem     Altruism toward non-relatives

Individual recognition
Cognitive Programs     Person memory

Parts of frontal and
Neurophysiology         temporal lobes??
• Humans are not the only creatures that
possess mechanisms designed to
detect cheaters.
• All organisms that participate in
cooperative relationships are expected
to have such mechanisms.
• Let’s look at 4 examples:
–   spawning in the black hamlet fish
–   regurgitation of blood by vampire bats
–   alliances in primates
–   fig trees
Cooperation among Vampire Bats
• Common for bats to fail to find
a blood meal. However, they
need this blood meal to stay
alive.
• Blood sharing:
– A hungry bat will beg for
food from another lucky bat
who was able to find a
blood meal during the
evening.
• It has been shown
experimentally that well-fed
bats will donate blood to
hungry bats who roost near
them and are familiar to them.
These individuals are likely
ones who in the past have
donated their extra blood.
Donor -- give 10% of blood will lose only ~2 hours
Amount of blood gathered

110
Recipient -- if given 10% of blood will gain ~20 hours
(% of pre-fed body wt)

100

90
D
80

70
R

50       40       30       20       10
Hours to death
Under what circumstances will
reciprocity evolve?
• Donors must be able to recognize
cheats, and refuse to feed previous
recipients who fail to reciprocate.
• Sufficient pair-wise interactions so that
there are interchanges of roles and
therefore net benefits to all donors.
• The benefits of receiving aid must
outweigh the cost of donating it.
Fig Wasps
• A very neat story...

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