Download PD delft - June

Who can I trust in the P2P
Noosphere?
does
… make you nice?
Jeremy Goslin
School of Psychology
University of Plymouth
Getting beyond tit-for-tat..

● Enforced altruism
● Expensive
● Circumvention
●Social Networks?
●Social relationships can improve trust
●Increase cooperation/altruism
●P2P
●Tribler
●e.g. cooperative download
Group Identity
● Social Identity Theory (Billig & Taijfel, 1973)
● In-group members treated more positively than out-group
members
● Self-identity partly derived from group identity
● Motivated to enhance positive group distinctiveness
● Or seek out alternative groups that are more positively distinct
● Profound effects on social strategies
● Group membership tends to lead to within group altruism
● Expectation of reciprocation
● Communication not required
● Group membership can be ad-hoc
How can P2P benefit from Social Identity?
● Question: Do groups need to be extrinsic?
● Can self defined dynamic groups lead to the same effect, or
better?
● Question: What are the optimum group-conditions?
● Maximal peer cooperation
● Psychology experiments for P2P:
● Control of information, communication, interaction
● Endogenous vs. exogenous groups
● Information
● Group vs. Individual information
● Reputation (over time)
● Group Entry
● Tags (Subsuming action to the group)
● Voting
Experimental Paradigm
● Game theory
● The study of conflict between thoughtful and potentially deceitful
opponents
● Assumptions:
● Rationality
● Maximisation of individual gain
● Provides robust basis for behavioural experimentation
● Already know what rational players should do
● Nash equilibrium point
● Why don’t players act rationally?
● What are the conditions for optimum irrationality?
● Game for experiments
● n-Persons iterated Prisoner’s Dilemma
Experiment Game
Moreover, whilst the college will initially assign you to a group, the university
allows students to change groups whenever they like, and even to set up new
groups.
…
What you decide to do is up to you, but finding the right group is likely to be
the key to getting good marks whatever you choose.
● Computer mediated multiplayer text-based game
● Scenario
● Students involved in group projects
● Maximise course credits:
For next week you have the chance to start a new group, to join the group of
● Fully contribute
toorgroup
(cooperate)
your friend,
stay inassignment
your current group.
● Concentrate
individual
Presson
space
to continuework
in your(defect)
current group
● Information
Press N to go to a new group
Press course
F to join
same
groupatas
friend
You have just enrolled on a new degree
in the
social
studies
theyour
College
● Themselves and a ‘friend’
of Princeton. This course in very progressive, they believe that to study
● Decision
sociology the students must gain a direct and first hand experience of working
● Reward
with others. To this end half
of the course credits required by the degree are
for group assignments, and
only half assigned to individual study.
● Fortune
However, as Princeton standards are very high they will only let the best
Each week you have to decide whether you want to focus on getting high
students graduate each year, and you know that competition for course credits
marks your individual assignment, at the cost of putting less time into your
●need
Groups
is fierce. You
good marks on both your individual and group
group assignment.
However
if lots
ofcontribution
people in your
group
alsoassignment
decide to do
You chose
to make
a full
to the
group
and managed
assignments, which
are
averaged outwithin
each week.
●
Interaction
group
this then thetogroup
will be
lower,
and your
grade
average
for thatthis
week
earn mark
6 between
your
individual
and
group
assignments
week.
will suffer. On
thefar
other
hand,
everyone
contributes
fully to the group
Thus
have if
earned
18 course
credits.
● you
Group
movement:
assignment then
the marks
will
be
high, and
may compensate
you
This that
weekpart
your
heard
thatgroup
a friend
managed
to receive 10
course credits
●ofhave
Stay
within
for the time after
lost on
theconcentrated
individual
they
on their individual assignment, they now have a total
● New assignment.
group
of 26 credits. ● Join ‘friend’
Experiment 1: Endogenous vs. Exogenous Groups
● Question: Does inter-group movement improve
cooperation?
● Condition 1: Game of two fixed groups
● No inter-group interaction
● Condition 2: Dynamic inter-group movement
● Two initial groups
● Every round players may either:
● Stay in their group
● Move to group of a ‘friend’
● Set up a new group
● Comparison: System wide proportion of
cooperation between conditions
● Fixed time frame (first 20 game rounds)
Experiment 1: Results
First 20 rounds of play
*
Proportion of Co-operation
*
*
0.6
0.45
0.5
0.38
0.4
0.3
0.25
0.2
0.1
0
fixed
groups
dynamic
groups
illusory
groups
n=62
n=71
n=74
● Cooperation effect of dynamic groups
● psychological
● structural
● Illusory group condition
● Interaction as no group condition
Experiment 1: Summary
● Question: Does inter-group movement improve
cooperation?
● Freedom of movement between groups improves
systemic cooperation
● Even if the groups have no actual effect over interaction
● How to reduce the prevalence of freeriders raiding
cooperative groups?
● Ejection from groups?
● Entry restrictions?
Tags (e.g. Hales, 2000)
Shared tags (group)
Game
Interactions
Copy tag and strategy
● Basic
Evolutionary
Cooperation
computer
process
models
●
●
●
Defectors
very
Initial
simple
random
quickly
agents
groups
surrounded
that evolveby
(replication/mutation)
other defectors because
based
new
on
payoff
entrants
to group copy
their get
behaviour
Groups containing
defectors
smaller as agents leave them for
“tag” code
better
Hence
defection
groups
strategy
or form
notand
sustainable
new
group
groups
membership
strategy => it destroys your own
groups cooperation
● Dynamical process with groups constantly forming and dissipating
but maintain high cooperation
Experiment 2: Group info and tags movement
● Questions:
● How does the provision of group information affect
cooperation?
● Can ‘tags’ based group movement improve cooperation
over free movement in endogenous groups?
● Condition 1: Group information
● Number and ratio of cooperators and defectors within group
● Rewards for cooperation and defection
● Condition 2: Tags
● Initial cooperate/defect decision (round 1)
● Decision carried forward to subsequent rounds
● 10% chance each round of changing decision
● To move groups you must take on game decision of your
‘friend’
Experiment 2: Results
First 20 rounds of play
Proportion of Co-operation
*
*
**
0.6

0.5
0.45
0.5
0.38
0.4
0.33
0.31
0.25
0.3
0.2
0.1
0
fixed
groups
dynamic
groups
illusory
groups
group
info
Tags +
group info
Tags group info
n=62
n=71
n=74
n=40
n=40
n=35
● Tags
●Initial
● Include
choice
group
of action
information
(co-operate / defect)
● Proportion
of co-operators
defectors
●Thereafter
probability
of changeand
= 0.1
per round
● groups
Co-operator and defector rewards
●Moving
●Copy game decision of compatriot
Experiment 2: Summary
● Question: How does the provision of group information
affect cooperation?
● Group information provides excellent source of
information on the best cooperative groups
● for defectors and cooperators
● Defectors more pro-active so ‘raiding’ results in reduced systemic
cooperation
● Question: Can ‘tags’ based group movement improve
cooperation over free movement in endogenous groups?
● Trading decisions for group membership does increase
cooperation?
● Possible effect of the reduction of decision ‘churn’
● Can simplistic voting match this strategy?
Experiment 3: Voting and reputation
● Questions:
● Can group members protect themselves from defectors
voting to bar them entry?
● How does longer term ‘reputation’ influence voting
decisions?
● Condition 1: Friend voting on group entry
● ‘Friend’ votes to let new members join group
● Information on previous decision and reward
● Condition 2: Reputation
● ‘Friends’ given information on the proportion of
cooperation/defection decisions on previous 5 rounds
Experiment 3: Results
First 20 rounds of play

*
Proportion of Co-operation
*
0.6
0.5

0.52
0.45
0.48
0.42
0.42
0.4
0.3
0.2
0.1
6E-16
-0.1
dynamic
groups
n=71
Voting
n=47
illusory
voting
n=43
Reputation Reputation
and voting
n=37
n=32
● ●Long-term
Voting toreputation
group entry
has
increases
no effectcooperation
on cooperation
● ●With
psychological
or without voting
● Structural
● Illusory voting condition
● No difference in cooperation to no-voting condition
Experiment 3: Analysis of voting
● In authentic voting conditions:
● 176 attempts to move group
● From 1440 group decisions (12%)
● 64% were successful
● Cooperative voters:
● Rejected prospective cooperator:
● Rejected prospective defector:
5.5%
18.9%
● Defector voters:
● Rejected prospective cooperator:
● Rejected prospective defector:
42.8%
70.3%
● Defectors as wolves turned sheepdogs?
● Protecting their ‘herd’ of co-operative sheep
Experiment 3: Voting and reputation
● Question: Can group members protect themselves from
defectors voting to bar them entry?
● The action of voting does improve systemic cooperation
● No psychological effect of being ‘judged’
● Defectors protecting themselves better than cooperators
● Question: How does longer term ‘reputation’ influence
voting decisions?
● No effect
●
With complete anonymity and no control over the selection of interactions
long term reputation is not important – no long term relationship
Conclusions
Exploring social freedom for social P2P
● Movement
● Endogenous groups significantly increase cooperation
● But so does the illusion of groups
● Information
● Group information significantly undermines beneficial group
dynamics
● Too much information can be a bad thing
● Reputation is moot with anonymous and ephemeral
relationships
● Action
● Restriction of choice can be socially beneficial
● Subsuming freedom of choice to others for group inclusion (Tags)
● Voters can be your friends
● Even if they are the enemy