Public Goods Game
In each round, you receive an endowment and choose how much to contribute to a shared public pool. The sum of all contributions is multiplied and evenly split among all group members. This simulates tension between private interest and collective benefit.
- Choose your contribution using the slider and submit.
- Your payoff = endowment - contribution + public return.
- Public return = (group contribution × multiplier) ÷ group size.
- Others' contributions are simulated for demonstration.
Frequently Asked Questions
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What is the Public Goods Game?
A group of players decide how much of their private endowment to contribute to a public pool. The multiplied total is shared equally among all players.
What is the trade-off?
Contributing benefits the group but may reduce your private payoff; withholding helps you personally but reduces the group return.
Why do researchers use this game?
It explores how contributions behave when private and group interests pull in opposite directions — how much people contribute at first, how contributions respond to what others do, and why they tend to decline over rounds without communication or enforcement. It is a paradigm for studying collective action, not an assessment of any individual.
Why do contributions typically decline over rounds?
Free-riding pays individually in the short run; without communication or punishment, contributions erode — one of social science's most replicated findings.
What sustains cooperation?
Communication, reputation, punishment of free-riders, and group identity all reliably raise contributions in research versions of the game.
Show Details
About the Public Goods Game
Economic Background
The Public Goods Game is a cornerstone of experimental economics, first formalized by Marwell and Ames in 1981. It models a fundamental tension in economics: individuals benefit from shared resources, but each has an incentive to free-ride on others' contributions.
Psychological Mechanisms
Contribution behavior is driven by a combination of social preferences (warm glow from contributing, norms of fairness) and strategic considerations (conditional cooperation, expectations about others). Research shows that people often contribute 40-60% of their endowment initially, but this decays over rounds without enforcement.
Real-World Applications
The game models collective action problems from environmental conservation (reducing pollution) to public infrastructure funding. Understanding what promotes cooperation has implications for policy design, from reward systems to peer sanctioning mechanisms.
References
- Isaac, R. M., & Walker, J. M. (1988). Group size effects in public goods provision: The voluntary contributions mechanism. Quarterly Journal of Economics, 103(1), 179-199. 10.2307/1882648
- Ledyard, J. O. (1995). Public goods: A survey of experimental research. In J. H. Kagel & A. E. Roth (Eds.), The handbook of experimental economics (pp. 111-194). Princeton University Press.
- Fischbacher, U., Gächter, S., & Fehr, E. (2001). Are people conditionally cooperative? Evidence from a public goods experiment. Economics Letters, 71(3), 397-404. 10.1016/S0165-1765(01)00394-9
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About This Experiment
This experiment is an educational adaptation for demonstration purposes. It is not a clinical diagnostic tool. Results reflect your performance in this specific session and should not be interpreted as an assessment of your cognitive abilities.
Data Privacy
Your experiment data is processed and stored locally in your browser. No data is uploaded to any server unless you explicitly export it.
