Social Cognition
Public Goods Game
Also called: public goods experiment, voluntary contribution game, linear public goods game
Measure cooperation in a group: participants put points into a shared project with three programmed members over repeated rounds, scored by the share they put in and how they follow the group.
7-10 minUntimed
Free to start: 10 free participants per account, then $0.99 per participant for academic research, or any yearly plan. Preview any test free after you sign up.
- Papers, 2021 to 2025
- 778
- Evidence grade
- C
- Registered clinical studies
- 3
What it measures
Measures cooperation in a group: in each round the participant and three programmed members each put part of 20 points into a project that is multiplied by 1.6 and shared equally.
Constructs
- Cooperation
- Conditional cooperation
- Social preferences
- Social decision making
Research uses
- Behavioral economics research
- Cooperation and social dilemma studies
- Social decision-making research in clinical groups
- Within-study group comparison
How the paradigm works
The Public Goods Game measures cooperation in a group. In each round the participant and three other members each have 20 points and choose how many to put into a group project. The project total is multiplied by 1.6 and shared equally, so each point put in returns 0.4 points to every member. The group earns most when all members put in everything, but each member earns most by keeping their own points. The other members are computer programs that follow set rules, and by default the instructions say so.
More about the paradigm
The task follows Fehr and Gächter (2000): groups of four, 20 points per round and a return of 0.4 per point, for 10 rounds with the same members and the number of rounds shown. After each round the participant sees what each member put in and their own points. One comprehension question with feedback comes first. As standard the members follow a conditional rule: each opens with 6 to 14 points, then puts in 0.9 times the mean of the other members' amounts in the round before, with a small adjustment drawn from the session's seed. After the rounds, the contribution table of Fischbacher, Gächter and Fehr (2001) asks for a first choice and then an amount for each average the other members could put in, from 0 to 20 points; a draw picks the member whose table answer counts. Researchers can set 1 to 20 rounds, choose cooperative or selfish members, move the table before the rounds or leave it out, use a neutral wording for the members, and choose the payment line.
Scores
- Mean Contribution%
- Points put into the project as a proportion of the 20 points, averaged over rounds.
- Higher means more cooperation
- First-Round Contributionpoints
- Points put into the project in the first round.
- Higher means more cooperation at the start
- Contribution Trendscore
- Least-squares slope of the points put in on the round number, in points per round. Negative when contributions fall.
- Informational
- Conditional Cooperation Slopescore
- Least-squares slope of the points put in on the mean of the other members' amounts in the round before, from round 2.
- Positive means the participant followed the group
- Total Pointspoints
- Points earned over the rounds.
- Informational
- Comprehension Check%
- Share of the comprehension questions answered correctly.
- 1 supports interpretation
- Unconditional Contributionpoints
- The first choice in the contribution table: points put in without knowing the other members' amounts.
- Higher means more cooperation
- Contribution Table Slopescore
- Least-squares slope of the table answers on the other members' average, from 0 to 20 points. A slope of 1 matches the others exactly.
- Higher means stronger conditional cooperation
- Conditional Cooperator0/1
- 1 when the table answers rise with the other members' average, by the rule of Fischbacher, Gächter and Fehr (2001). Free riding, a hump shape and other patterns are reported the same way.
- Informational
Use and evidence
778 papers from 2021 to 2025 name this task in their title or abstract, up 10% compared with 2016 to 2020. That ranks it 32 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 201 |
| 2024 | 150 |
| 2023 | 158 |
| 2022 | 134 |
| 2021 | 135 |
| 2020 | 145 |
| 2019 | 140 |
| 2018 | 158 |
| 2017 | 153 |
| 2016 | 114 |
| 2015 | 132 |
| 2014 | 115 |
| 2013 | 95 |
| 2012 | 81 |
| 2011 | 78 |
| 2010 | 74 |
| 2009 | 45 |
| 2008 | 30 |
| 2007 | 33 |
| 2006 | 22 |
| 2005 | 15 |
| 2004 | 14 |
| 2003 | 15 |
| 2002 | 7 |
| 2001 | 13 |
| 2000 | 6 |
Use grade B
300 to 999 papers from 2021 to 2025.
Evidence grade C
At least 2 test-retest papers, 30 reliability or validity papers or 3 registered clinical studies.
- Papers on test-retest reliability
- 1
- Papers on reliability or validity
- 66
- Registered clinical studies using it as an outcome
- 3
Note on the counts: includes theory papers.
How the grades work
Use: A is 1,000 or more papers from 2021 to 2025, B 300 to 999, C 100 to 299, D 30 to 99 and E fewer than 30. Evidence: A means at least 25 papers report its test-retest reliability and at least 25 registered clinical studies use it as an outcome; B, at least 8 test-retest papers, and either 5 registered clinical studies or 150 reliability or validity papers; C, at least 2 test-retest papers, 30 reliability or validity papers or 3 registered clinical studies; D, little published measurement evidence found. The counts measure use. They include every paper that names the task in its title or abstract. Grades describe the published research on this task, not ConductCognition's version of it.
Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Group
- The participant and three computer programs that follow set rules. The standard instructions say so; a neutral wording says only "the other members".
- Points
- 20 per member in each round. The project total is multiplied by 1.6 and shared equally among the four members, so each point put in returns 0.4 to every member.
- Rounds
- 10 (standard; 1 to 20) with the same three members. The number of rounds is shown.
- Member rule
- Conditional (standard): an opening amount of 6 to 14 points, then 0.9 times the mean of the other three amounts in the round before, plus an adjustment of -2 to 2 points drawn from the session's seed. Or cooperative, 15 to 20 points, or selfish, 0 to 4 points, in every round.
- Results
- After each round: every member's amount, the project total and the participant's points.
- Contribution table
- After the rounds (standard), before them or off: a first choice, then an amount for each average of the other members' amounts from 0 to 20 points, 22 answers in all. A draw picks the member whose table answer counts.
- Check
- One question with feedback before the first round: the points for an example amount and project total drawn from the seed. One more before the table.
- Money
- Points are hypothetical by default; a setting changes the instruction line to say the study pays.
In Fehr and Gächter (2000) all four group members were participants paid for their points. Here the other three members are computer programs, the instructions say so by default, and the points are hypothetical unless the study pays.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: the scored run's amounts in the rounds and in the contribution table. No amount is correct, so accuracy is not judged against chance, and the same amount on every decision is accepted. A wrong answer to a comprehension question is flagged for review. Decisions confirmed under 200 ms on at least half the decisions invalidate.
Why these rules
There is no correct option to compare with chance, so accuracy is not judged against chance. Putting in the same amount every time, including nothing or everything, is a stable preference, so repeated amounts are not checked. A participant who misreads how the project pays may choose the opposite of what they intend, so a wrong answer to a comprehension question is flagged for review and never invalidates. An answer under 200 ms is faster than a simple visual reaction, so it cannot reflect the item. Following response-time effort screening for untimed tests (Wise and Kong 2005), the session is invalid only when at least half the answers are that fast.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Rounds | 10 | 1 to 20 |
| Member rule | Conditional: 0.9 times the others' mean in the round before, from an opening of 6 to 14 points (standard) | Conditional: 0.9 times the others' mean in the round before, from an opening of 6 to 14 points (standard), Cooperative: 15 to 20 points in every round, Selfish: 0 to 4 points in every round |
| Contribution table | After the rounds (standard) | After the rounds (standard), Before the rounds, Off |
| Group member wording | Computer programs (standard) | Computer programs (standard), Neutral: the other members |
| Payment line | Hypothetical points (standard) | Hypothetical points (standard), The study pays for points |
Yearly plans can change settings within these limits. Free and pay-as-you-go studies use the standard settings.
Need a setting this test does not have?
Devices and languages
- Untimed test: runs on desktops, laptops, tablets and phones. Participant devices
- Languages: English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese.
- Available on: Every plan, including the free plan.
- No percentile. Scores and quality flags only. How norms work
- Recruiting online? See the setup guides for Prolific, Sona Systems, CloudResearch Connect and Qualtrics.
Cite and describe
Participants completed the Public Goods Game in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Isaac RM, Walker JM, 1988; Fehr E, Gächter S, 2000; Fischbacher U, Gächter S, Fehr E, 2001), with the standard settings (rounds: 10; member rule: Conditional: 0.9 times the others' mean in the round before, from an opening of 6 to 14 points; contribution table: After the rounds; group member wording: Computer programs; payment line: Hypothetical points). The main score was mean contribution (points put into the project as a proportion of the 20 points, averaged over rounds).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Fehr, E., & Gächter, S. (2000). Cooperation and punishment in public goods experiments. American Economic Review, 90(4), 980-994. https://doi.org/10.1257/aer.90.4.980
- Fischbacher, U., Gächter, S., & Fehr, E. (2001). Are people conditionally cooperative? Evidence from a public goods experiment. Economics Letters, 71(3), 397-404. https://doi.org/10.1016/S0165-1765(01)00394-9The contribution table and its patterns.
- 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. https://doi.org/10.2307/1882648Group size and the return per point.
Source papers
- Fehr and Gächter (2000): the repeated public goods game with these parameters. Fischbacher, Gächter and Fehr (2001): the contribution table and its patterns.Paradigm source, Adults
Questions
How long does the Public Goods Game take?
About 7 to 10 minutes, as listed in the test library.
What device does a participant need?
Untimed test: runs on desktops, laptops, tablets and phones. The browser must be Chrome, Edge, Firefox or Safari.
What scores does it produce?
Mean Contribution, First-Round Contribution, Contribution Trend, Conditional Cooperation Slope, Total Points, Comprehension Check, Unconditional Contribution, Contribution Table Slope and Conditional Cooperator. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Public Goods Game used in research?
778 papers from 2021 to 2025 name it in their title or abstract, up 10% compared with 2016 to 2020. That ranks it 32 of 395 test families in the ConductCognition test census (use grade B). Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Public Goods Game have?
In the published research, 1 paper reports its test-retest reliability and 3 registered clinical studies use it as an outcome (evidence grade C in the ConductCognition test census).
Does it report a percentile?
No. Scores and quality flags only.
Which settings can a researcher change?
Rounds (1 to 20), member rule (Conditional: 0.9 times the others' mean in the round before, from an opening of 6 to 14 points (standard), Cooperative: 15 to 20 points in every round, Selfish: 0 to 4 points in every round), contribution table (After the rounds (standard), Before the rounds, Off), group member wording (Computer programs (standard), Neutral: the other members) and payment line (Hypothetical points (standard), The study pays for points). Settings can be changed on yearly plans; free and pay-as-you-go studies use the standard settings.
Which languages can participants use?
Participants can take this test in English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese. English is on every plan, and the other languages come with yearly plans. Have a native speaker read the machine-translated text before launch.
Is this a clinical test?
No. ConductCognition is for research use only. It runs, scores and exports the test; clinical interpretation is outside the platform.
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