Welcome to this experiment
on decision making
Centre for Ecological and Evolutionary Studies
dept. of Theoretical Biology
General overview
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Instructions (ca. 15 minutes)
Receiving desk number
Going to lab
Experiment (max. 120 minutes)
Payment (outside laboratory)
• Earnings: 30 +/- 30 Euros
General overview
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Instructions (ca. 15 minutes)
Receiving desk number
Going to lab
Experiment (max. 120 minutes)
Payment (outside laboratory)
• Earnings: 30 +/- 30 Euros
In the lab…
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Instructions are on your desk
Quiz
Experiment itself
Questionnaire
Payment (outside of the lab…)
The experiment
• Do not talk inside the laboratory
• You will earn money depending on your decisions and
the decisions of others
• You get a show-up fee of XXX Euros
• Payments are anonymous
• You start out with XXX points
• 10 points are worth 1 Euro
The experiment
• Lasts for 10 periods
• Each period you will be part of a group
• Randomly assigned
• Anonymous
• You get a ‘symbol’
• #, $, %, etc
Interacting in your group
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‘Contribution game’
At least 1 round
New round will start with a 80% chance
Period ends with a 20% chance
Initially, your group will consist of 3 players
The contribution game
• Each round, you can contribute to a project
• Costs: 4 points
• Contributions are made simultaneously
• The revenues of the project are the sum of the group’s
investments x 1.5
• Equally split among the group members
• Both contributors and non-contibutors
The contribution game: example I
• Example 1: all three group members contribute
• Cost per player = 4 points
• Total contributions to the project
• 3 x 4 = 12 points
• Project’s revenue
• 12 x 1.5 = 18 points
• All group members get 6 points
• Earnings in this round: 2 points for all group members
The contribution game: example II
• Other group members contribute, you do NOT contribute
• Cost for you = 0 points
• Total contributions to the project
• 2 x 4 = 8 points
• Project’s revenue
• 8 x 1.5 = 12 points
• Your group-mates earn 0 points
• You earn in this round: 3 points
Hiring a ‘supervisor’
• Before the contribution game starts
• Your group can decide to hire a supervisor
• Rigorous supervisor
• Lenient supervisor
• No supervisor
• Supervisor is hired for 1 period
• Supervisor is a computer program
Hiring a ‘supervisor’
• Each round of the period that the supervisor is hired
• Non-contributors will NOT get revenues with chance
• Rigorous supervisor 100%
• Lenient supervisor 50%
• No supervisor 0%
• Supervisor is hired for 1 period
Hiring a ‘supervisor’
• Each round of the period that the supervisor is hired
• Non-contributors will NOT get revenues with chance
• Rigorous supervisor 100% cost: 2 points
• Lenient supervisor 50% cost: 1 point
• No supervisor 0% cost: 0 points
• Each round of that period, all group
members have costs for the supervision
Hiring a ‘supervisor’
• Which supervisor is hired, depends on majority voting
• Before voting, you can discuss which supervisor to hire in
a chat box
• If none of the options gets the majority, the computer
program will select a random option
Hiring a ‘supervisor’: example
• You are in a group with 2 others
• You hired a ‘lenient supervisor’ for this period
• Cost: 1 point per player per round
• One of your group-mates (‘#’) contributes
• The other (‘$’) does not contribute
• What are the earnings of the players
in this round if you do (not) contribute?
Hiring a ‘supervisor’: example
• What are the earnings of the players
in this round if you do (not) contribute?
Your
decision
Contribute
Do not
contribute
Total
amount
invested
Project
revenue
Your
earnings
Earnings of
‘#’
Earnings of
‘$’
8
12
–1
–1
3 or –1
(2x4)
(8x1.5)
(12/3 – 4 – 1)
(12/3–4–1)
(12/3–1) or (12/3
– 1 – 12/3)
4
6
1 or –1
–1
1 or –1
(1x4)
(4 x 1.5)
(6/3–1) or (6/3 –
1 – 6/3)
(6/3-4-1)
(6/3–1) or (6/3
– 1 – 6/3)
50-50 chance
Recapitulation
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As far as we have seen, a period looks like this:
1. Chatting
2. Voting for hiring a supervisor
3. Playing the ‘contribution game’ for a number of
rounds
• The number of rounds per period
is equal for all groups
Group growth, splitting and elimination
• At the end of each period, average earnings of the groups
are compared
Group growth, splitting and elimination
• At the end of each period, average earnings of the groups
are compared
• One group will have the highest average
Group growth, splitting and elimination
• At the end of each period, average earnings of the groups
are compared
• This group will grow, two participants
are added to this group
Group growth, splitting and elimination
• At the end of each period, average earnings of the groups
are compared
• The next period will start, one group being larger
Group growth, splitting and elimination
• After a number of growth events, it may occur that a
group of 5 players has the highest average earnings
Group growth, splitting and elimination
• After a number of growth events, it may occur that a
group of 5 players has the highest average earnings
• In this case, the group with the
lowest average earnings will
be eliminated
Group growth, splitting and elimination
• After a number of growth events, it may occur that a
group of 5 players has the highest average earnings
• In this case, the group with the
lowest average earnings will
be eliminated
•Questionnaire
•Payment
Group growth, splitting and elimination
• After a number of growth events, it may occur that a
group of 5 players has the highest average earnings
• One participant is added to the this group
Group growth, splitting and elimination
• After a number of growth events, it may occur that a
group of 5 players has the highest average earnings
• The group splits in two
Group growth, splitting and elimination
• After a number of growth events, it may occur that a
group of 5 players has the highest average earnings
• A new period starts
Summary of a period
2. Playing contribution game
(a number of times)
1. Hiring a supervisor
3. Growth, splitting and
elimination of groups
• In total, the session will last for 10 periods
Session end: questionnaire & payment
• After 10 periods, the experiment ends
• You are asked to fill out a few questions about your
personal background
• Please remain seated until your desk number is called
• You will be paid in cash individually and
anonymously
Questions ?