Infrared simulation and processing on Nvidia platforms
Simulpast may v2
1. Social Mechanisms, Agent-Based Modelling
and the Evolution of Cooperation
Mauricio Salgado
PhD
Analytical Sociology and Institutional Design Group
(GSADI) – UniversitatAutònoma de Barcelona
Mauricio.Salgado@uab.cat
Barcelona – May 2013 1
3. Why cooperation?
3
Definitions
Cooperation: when two or more individuals engage in costly joint
actions that result in mutual benefit
Altruism (Unconditional Cooperation): Acts that benefit others at
a personal cost
Donor
(c)
Recipient
(b)
5. Why cooperation?
5
Ingrid Loyau-Kennett (48)
―Being a cub leader I have my first aid so when
I saw this guy on the floor I thought it was an
accident then I saw the guy was dead‖
―And then when I went up there was this black
guy with a revolver and a kitchen knife (…) and
he said 'move off the body‘.‖
(…)
―I started to talk to him and I started to notice
more weapons and the guy behind him with
more weapons as well. By then, people had
started to gather around. So I thought OK, I
should keep him talking to me before he
noticed everything around him.‖
7. Why cooperation?
7
―If you try to do something cooperative with a
chimp—point out something, show them where
some food is—their attention wanders all over
the place, but if you compete with them over
food, they are zeroed in like a laser. All their
cognitive skills are on.‖
Michel Tomasello
But we still have to explain how did we go from ―chimp-like-selfishness‖ to
―human super-cooperation‖
10. Social Mechanisms
10
Two main advantages:
1. Knowledge about mechanisms increases the possibility of
causal analysis in the absence of nomological laws, and
2. it helps to open the ‗black box‘ of social dynamics in order to
provide the microfoundations of the observed phenomena.
11. Social Mechanisms
11
Definition
A mechanism consists of entities and activities, organized such that they are
productive of regular changes from start or set-up to finish or termination
conditions.
Entities (and their properties) are the things that engage in activities, and
activities are the producers of change.
The dualistic nature of this definition makes it adequate for social sciences
that deal with individual agents (‗entities‘) and their actions (‗activities‘).
12. ―Mechanisms consist of entities (with their
properties) and the activities that these entities
engage in, either by themselves or in concert with
other entities. These activities bring about change,
and the type of change brought about depends on
the properties of the entities and how the entities
are organized spatially and temporally‖
Hedström, P. Dissecting the Social (2005)
Opening the black box
Social Mechanisms
12
13. Social Mechanisms
13
1. A set of entities, e1 to en, vary with respect
to a property pi
2. In a certain environment the
benefit, b1, bestowed on entity i is a
function of its property p1
3. The value of bi, influences the relative
frequency of entities with different
properties at subsequent time periods.
(Properties that perform better in the
environment will become more frequent)
Selection Mechanisms
14. Social Mechanisms
14
Evolutionary game dynamics describe:
• Frequency-dependent selection.
• The outcome of the game is related to reproductive success.
• Payoff determines fitness.
• Reproduction can be genetic or cultural.
Genetic Reproduction
It means that individuals leave genetic offspring
that inherit their strategy.
Cultural Reproduction
It means that individuals are imitated by others;
thereby strategies reproduce by imitation or
learning.
15. 15
Ontology
Is the mechanisms made of ‘real’ entities and
activities or is it just an as-if story?
Regularity
In which instances can the mechanisms be
generalized from one case to another?
Transparency
Is the presence of the mechanism clearly
observable?
Intelligibility
Dos the presence of the mechanism improve the
intelligibility of the explanation?
Reduction Base
What are the mechanism ‘microfoundations’, the
local rules that bring about the ‘macro-properties’?
Generative Sufficiency
Can the model’s microfundations generate the
observed macroproperties?
Empirical Adequacy
Are the model’s microfundationsplausible in
relation to some theory or empirical data?
22. Kin Selection
22
Agents cooperate only with those related genetically
―I will jump into the river to save two brothers or eight cousins‖
C
DD
First Generation
C
CC
N Generation
Selection
23. Kin Selection
23
Definition
The beneficiaries share some genes with the altruist; the survival and
reproduction of the beneficiaries contribute to the propagation of the
altruist’s genes.
Ontology Realist
Regularity It works in small familial groups
Transparency Yes Intelligibility Yes
Reduction
Base
Individuals’ genes
Generative
Sufficiency
Yes
Empirical
Adequacy
Although it might work in small and familial groups with little migration, it
does not explain cooperation to unrelated individuals (commitment falls off
precipitously as genetic distance increases between individuals)
24. Kin Selection
24
In meerkats, helpers vary widely in the number
of food items they gave to pups. The level of
contributions that helpers make to rearing pups
is not significantly correlated with variation in
kinship to the litters they are rearing.
(Clutton-Brock et al., 2001)
In this picture, a male golden lion tamarin at
Colchester Zoo (The United Kingdom) took the
unusual step of carrying other primates‘
offspring that he shares his enclosure with. This
tamarin male has taken on the role of carrying
for two silvery marmoset youngsters.
Limitations: It cannot explain cooperative breeding
26. Direct Reciprocity
26
Agents play the Iterated Prisoner's Dilemma (IPD)
―You scratch my back and I'll scratch yours‖ Tit for Tat Interactions
Alter Ego
T1
T2
27. Direct Reciprocity
27
Definition
Both the beneficiaries and the cooperators face repeated encounters; the
cooperator’s decision to cooperate is based on what the beneficiary has
done to her in previous encounters
Ontology Realist
Regularity It works in contexts of repeated encounters within small groups
Transparency Yes Intelligibility Yes
Reduction
Base
Individuals in repeated interactions
Generative
Sufficiency
Yes
Empirical
Adequacy
Although it might work in small groups, it is a weak mechanism in larger
groups (ability to directly monitor trustworthiness in reciprocation decreases
rapidly as the number of transactions multiply)
28. Direct Reciprocity
28
Limitations:
• It cannot explain short-term or one-shot cooperative interactions in games
such as ―The Ultimatum Game‖ or ―The Dictator Game‖
• It cannot explain the production of ―public goods‖
• In natural populations, errors occur: occasional mistakes between two TFT
players cause long runs of mutual backbiting.
C
C C
C
C
C
D
D
D
D
D
TFT
TFT‘
Error!
C
…
30. Indirect Reciprocity
30
Reputation ―I help you and somebody will help me‖
D R
W
Ct1
D R
WCt1+n
D R
W
Dt1
Dt1+n
Donor‘s reputation
increases
Donor‘s reputation
decreases
31. Indirect Reciprocity
31
Definition
Both the beneficiaries and the altruists interact with each other only
occasionally; the altruist’s decision to cooperate is based on information about
what the beneficiary has done to others in previous encounters
Ontology Realist
Regularity It works when information about the beneficiaries’ reputation is available
Transparency Yes Intelligibility Yes
Reduction
Base
Individuals in occasional interactions
Generative
Sufficiency
Yes
Empirical
Adequacy
Although it might work in larger groups, it requires dense connections or
cultural artifacts that register individuals’ reputation
32. Indirect Reciprocity
32
―Indirect reciprocity is a plausible mechanism to sustain
cooperation within dense, bounded social networks that are stable
through time‖
Limitations:
Heroism in warfare?
35. Group Selection
35
Definition
The altruists’ genes can become fixed within certain groups because of the
benefits they bestow on those groups as wholes, even when the effect of
these alleles on individuals’ fitness is negative. These groups reproduce faster
Ontology Realist
Regularity
It works when the group benefit of the altruists’ actions is higher than the
altruists’ individual costs
Transparency Yes Intelligibility Yes
Reduction
Base
Individuals’ genes within groups that compete with each other
Generative
Sufficiency
Yes
Empirical
Adequacy
Although it might work in small or medium-size groups, it requires within-
group homogeneity, between group heterogeneity and low migration rates
36. Group Selection
36
―Most human populations do not meet these conditions. Thus, it does
not seem that group selection can provide a genetic basis for altruism (…)
Group selection mechanism depends on the relative amount of variation
within and between groups. If group members are closely related, most of
the variation will occur between groups. This is easiest to see if groups are
composed of clones (as in colonial invertebrates such as corals). Then
there is almost no genetic variation within groups; all the variation is
between groups, and selection acts to maximise group benefit.‖
Limitations:
38. Parochial Altruism
38
Multilevel Model ―I help you because you belong to my group
(… and, therefore, my group will be stronger)‖
Declining Average Fitness (Extinction)
Intergroup Conflict
39. Parochial Altruism
39
Definition
The altruists cooperate with group members and are hostile to individuals
from other groups. In contexts of intergroup conflict, internally cooperative
groups prevail over less cooperative rival groups
Ontology Realist
Regularity It works when there is severe intergroup conflict
Transparency Yes Intelligibility Yes
Reduction
Base
Individuals within groups that compete with each other
Generative
Sufficiency
Yes
Empirical
Adequacy
Although it might work in contexts of violent intergroup conflict, it does not
apply in contexts in which groups cooperate among them
40. Parochial Altruism
40
―However, such generalisations are unlikely to correctly describe the
conditions in which our Pleistocene ancestors lived, so parochial altruism
seems to be implausible. Small bands of hunter-gatherers, numbering 25
or so individuals, under chronic climate fluctuation, widely dispersed over
large areas and unable to fall back on staple foods, would have suffered
from high mortality rates, particularly child mortality, due to starvation as
well as predation and disease, so they hardly would have been able to
sustain warfare against competing groups ‖
Limitations:
42. Concluding Remarks
42
Explaining the evolution of cooperation requires the
identification of some mechanism at work
A mechanism consists of entities and activities, organized such that
they are productive of regular changes from start or set-up to finish
or termination conditions. Entities (and their properties) are the
things that engage in activities, and activities are the producers of
change.
Ontology, Regularity, Transparency, Intelligibility, Reduction
Base, Generative Sufficiency, Empirical Adequacy
43. Concluding Remarks
Five Mechanisms for the Evolution of Cooperation
• Kin Selection: Cooperate with genetic relatives
• Direct Reciprocity: I help you, you help me
• Indirect Reciprocity: I help you, somebody will help me
• Group Selection: Groups of cooperators out-perform other
groups
• Parochial Altruism: Groups of cooperators out-compete other
groups
43
44. Concluding Remarks
44
Punishment (e.g., ‗Strong Altruism‘) is not a mechanism
for the evolution of cooperation Parsimony
If you punish someone who has defected with you, then you are
using direct reciprocity
If you punish someone who has defected with others, then you are
using indirect reciprocity
If you punish someone who is not a member of your group, then
you are using parochial altruism (a special case of group selection)
(Winners do not punish)
46. Thank you!
Mauricio Salgado
PhD
Analytical Sociology and Institutional Design Group
(GSADI) – UniversitatAutònoma de Barcelona
Mauricio.Salgado@uab.cat
Barcelona – May 2013 46
Notas del editor
Tales about the origins of our species always start off like this: A small band of hunter-gatherers roams the savannah, loving, warring, and struggling for survival under the African sun. They do not start like this: Brave mom Ingrid Loyau-Kennett faced Woolwich terrorists.
Parochial altruism has gained recent popularity among scholars: these models highlight the idea that individuals are altruistic with group members and are hostile to individuals not of one’s own group (Arrow, 2007; Bowles, 2006; Choi and Bowles, 2007; Sa ̈äksvuori et al., 2011). Since internally cooperative groups prevail over less cooperative rival groups, parochial altruism rests on the evolutionary belief that violent intergroup conflict played a key role in the dawn of human cooperation.
