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Introduction

Welcome to the experiment. This is an experiment funded by a research foundation to study decision making. For showing up on time, you will be paid a $5 show-up fee. In addition, you may receive additional earnings as the result of the outcomes in this session. All earnings that you make will be in “points”. At the end of the experiment we will pay you in cash an amount equal to $0.05 for every point you earn.

Today’s session will take about an hour and a half. Please work on your own and avoid communicating with anyone else during the experiment.

Decisions and payoffs

At the beginning of this decision-making experiment you will be matched with three other people, randomly selected from the people in this room, to form a group of four. You will remain in this group of four people for the duration of the whole decision-making experiment. The names of the other members of your group will not be revealed.

At the beginning of each period, you and each other person in your group will receive 20 points. You must decide how much of this amount to keep, and how much to contribute to the POOL: you can contribute any number between 0 and 20. Only whole numbers will be accepted. Contributions in one period do not carry over to the next.

Each point that you contribute to the POOL will earn you 1 point. The sum of your and others’ contributions to the POOL is multiplied by β and subtracted from your earnings. Thus,


Your Earnings = 20 - YOUR contribution to the POOL
+ β*(Total GROUP contribution to the POOL)

The β’s for you and the other three participants in your group are:

Person A: 0.30 Person B: 0.40
Person C: 0.50 Person D: 1.20

You are going to make decisions with the other participants in your group for 10 periods. The computer screen will display the period number and the value of β assigned to you. The value of β assigned to you will remain the same for the entire experiment.

Example

Suppose that your β=0.40 and all the other people in your group contributed a total of 50 points. If you decide to contribute 12 points, the total group contribution to the POOL will be 50 + 12 = 62 points. This will yield you earnings of 32.8 points (20 initial points – 12 points contributed to the pool + (0.40 * 62) points from the POOL).

Results

Once everyone in the room has entered their contribution to the POOL, you will see the results screen. The results screen shows your contribution to the POOL, the sum of all contributions, and your earnings for the period.