Shared threshold project: rules and printable materials

Choose private contributions, reveal together, and see whether the group funds a shared project. Use points only, never real money.

Players

3–6

Plan for

15–20 minutes

Bring

Six choice slips per player, score ledger

Agree a point-only experiment

Use three to six players. Each begins every round with ten imaginary points and may contribute an integer from zero to five. The group threshold equals twice the number of players: six with three people, eight with four, and so on. Write the threshold where all can see it. Play three rounds. Do not collect money, private financial information or real possessions.

Reveal contributions simultaneously

Allow one minute of voluntary group discussion, then each person secretly writes a contribution on a slip. All reveal at once; nobody may change after seeing another slip. If the contribution total reaches or exceeds the threshold, the project succeeds and every player receives five bonus points. If it falls short, nobody receives the bonus. Contributions are spent in either case and excess is not refunded.

Calculate the score

A player’s round score is ten minus their contribution, plus five only if the project succeeds. With four people and contributions 0,2,3,3, the total is eight: scores are 15,13,12,12. If the last contribution were two instead, the total would be seven and the scores 10,8,7,8. Show both examples before making real game choices; their difference explains the threshold and failed-project cost.

Discuss without labels

The group’s goal is to explore coordination, not expose who is selfish or generous. Do not require an explanation for someone’s choice. After each round announce only the recorded choices and arithmetic, then invite observations about the total and threshold. Participants may pass before a round; if the number changes, start a fresh round with a newly announced threshold. Never secretly adjust the target after seeing contributions.

Close after three rounds

Add personal points across exactly three rounds and separately count successful group projects. These are two different results; do not call the highest individual score the most cooperative player. For a comparison session agree in advance to refund contributions on failure, then treat it as a separate variant. Record the changed rule prominently because its incentives and outcomes differ from the nonrefunded starter.

Printable materials

Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.