How Localized How Localized How Localized
E l ti
Evolution o Evolution o
C (
Chiho Kaito (Evolution and Ecology Pr Chiho Kaito (Evolution and Ecology Pr
H J ) Aki S ki (E l t
Hayama, Japan), Akira Sasaki (Evolut Hayama, Japan), Akira Sasaki (Evolut
Ad d St di H J )
Advanced Studies, Hayama, Japan), Advanced Studies, Hayama, Japan),
U i it f Vi A t i ) Ulf D University of Vienna, Austria), Ulf D U e s ty o e a, ust a), U
1 Background 1 Background g
L li d i f ti
Gl b l i f ti Localized information Global information
Interaction
ith b d
with everybody
Long time no see!
Interaction only with neighbors
Our study Our study
Reputations among interacting individuals are Reputations among interacting individuals are
k f i t i i ti i t ti
key for maintaining cooperative interactionsy g p
2 Method 2 Method
Non participants Non-participants
❸
❸
Good reputation
❸
Good reputation
or
❶
❶
❶
Bad reputation
Ob
Observers
❷ ❷
❷
Cooperation
or o
Donor Defection Recipient Donor Defection Recipient
St ❶ R d l h d i i t d b ithi
Step ❶: Randomly choose a donor, a recipient, and observers within range.
Step p ❷❷❷: Play the game: If the recipient’s reputation in the eyes on the donor y g p p y exceeds the donor’s donation threshold the donor regards the recipient
exceeds the donor s donation threshold, the donor regards the recipient
b i d d t
as being good and cooperates.g g p
Step ❸: Each observer evaluates the donor’s action and updates his/her reput Step ❸: Each observer evaluates the donor s action and updates his/her reput Donation thresholds are either fixed at 0 or are allowed to evolve through muta Donation thresholds are either fixed at 0 or are allowed to evolve through muta
4 S & F t W k 4 Summary & Future Work 4 Summary & Future Work
● The Kandori strategy imposes stricter judgment on the donor and c
● The Kandori strategy imposes stricter judgment on the donor and, c individuals diminishes cooperation and decreases payoffs
individuals, diminishes cooperation, and decreases payoffs.
● The Sugden strategy by contrast avoids this problem and promotes
● The Sugden strategy, by contrast, avoids this problem and promotes
● We plan to study three extensions: to well-mixed populations to par
● We plan to study three extensions: to well-mixed populations, to par loss in reputation records
loss in reputation records.
d Information Affects the d Information Affects the d Information Affects the
f I di t R i it
of Indirect Reciprocity of Indirect Reciprocity p y
S G f S
rogram IIASA; Graduate University for Advanced Studies rogram, IIASA; Graduate University for Advanced Studies,
ti d E l P IIASA G d t U i it f
tion and Ecology Program, IIASA; Graduate University for tion and Ecology Program, IIASA; Graduate University for
K l Si d (E l ti d E l P IIASA Karl Sigmund (Evolution and Ecology Program, IIASA;
Karl Sigmund (Evolution and Ecology Program, IIASA;
Di k (E l ti d E l P IIASA)
Dieckmann (Evolution and Ecology Program, IIASA) ec a ( o ut o a d co ogy og a , S )
Indirect reciprocity is a basic mechanism to Indirect reciprocity is a basic mechanism to s stain cooperation based on rep tations in sustain cooperation based on reputations inp p
triangular relationshipstriangular relationships
Observer
Observer Observer
Observer
Cooperation Cooperation
R i i
D Recipient
Donor Recipient
Donor Recipient p
Donor
Observer strategy: Sugden Observer strategy: Kandori Observer strategy: Sugden Observer strategy: Kandori
Cooperation with a badly reputed person Cooperation with a badly reputed person gives donor a good reputation gives donor a bad reputation
Whi h b t t b t t th
Which observer strategy best promotes the gy p evolution of cooperation?
evolution of cooperation?
3 Results 3 Results
D ti th h ld fi d t 0 Donation thresholds fixed at 0 Reputations of 100 persons Reputations of 100 persons
after 50 000 000 games after 50,000,000 games.
A point represents a person.
A point represents a person.
Donation thresholds evolving Donation thresholds evolving
Reputationp Reputationp
Good
Bad Bad Good
Donation
Donation Donation
threshold Donation
threshold threshold
G ti
threshold
G ti Generations
Generations
Payoffy Payoffy
Donation
Donation Donation
threshold Donation
threshold threshold
threshold
tation record accordingly.
tation record accordingly.
ation and selection ation and selection.
consequently gradually increases the donation threshold of consequently, gradually increases the donation threshold of
s the evolution of cooperation s the evolution of cooperation.
rticipants that can make mistakes and to different rates of memory rticipants that can make mistakes, and to different rates of memory
