Week 14: The Commons Simulation
When Individual "Best" Choices Lead to Group Failure
The Prisoner's Dilemma showed the tension between individual and group benefit with TWO players. This week we scale up to see what happens with a shared resource and MULTIPLE players.
We run the most dramatic simulation in the course: The Fishing Game. A shared resource is available to everyone. Each person can take as much as they want. If everyone takes a little, the resource lasts forever. If people get greedy, it collapses — and EVERYONE loses. This is the Tragedy of the Commons, and it explains everything from overfishing to climate change to why the milk in a shared fridge always runs out.
- The Fishing Game needs 2–4 players. Recruit siblings, friends, or family members if possible.
- The game is designed to fail in the first round (without communication). That failure IS the lesson.
- Rounds 2–4 introduce different "solutions." The discussion about which works best is the real learning.
- This is the capstone of Phase 4. It brings together ripple effects, cooperation, and the Prisoner's Dilemma.
Week at a Glance
| Component | Details |
|---|---|
| Key Vocabulary | commons, tragedy of the commons, shared resource, sustainability, regulation |
| Difficulty | Advanced |
| Prep Time | ~15 minutes |
| Guided Session 1 | The Fishing Game |
| Guided Session 2 | Solving the Commons |
| Independent Practice | My Commons + Design a Fair Rule |
Facilitator Preparation
- Gather 20 tokens (coins, buttons, counters, LEGO bricks — anything countable) as "fish"
- Prepare a bowl or plate to serve as the "pond"
- Make small paper cups or bags for each player's "catch"
- Prepare a score sheet to track rounds
- Read through the full game rules below before starting
Resist the urge to "fix" the first round. Let the commons collapse. The emotional experience of watching a shared resource vanish because everyone took too much is unforgettable. THEN introduce the solutions.
If Round 1 doesn't collapse (cautious players may cooperate naturally), that's a valuable discussion too. Ask why it worked, then play a "maximum catch" round where each player's goal is to maximize their personal haul regardless of the group.
For Younger Learners (Ages 8–9)
Simplest version of the concept: "When everyone shares something, each person has to decide: 'Do I take a lot for me, or leave some for everyone?' If everyone takes a lot, there's nothing left."
What to shorten or skip:
- Focus on the Fishing Game — it's the centerpiece and works at any age.
- Skip the formal Tragedy of the Commons terminology. Use "The Sharing Problem" instead.
- Keep the real-world examples simple: shared snacks, shared crayons, the last piece of pizza.
- Keep sessions to 20 minutes.
Adapting the activities:
- For the Fishing Game, use physical tokens (goldfish crackers, coins, small blocks). Start with 10 tokens in a bowl. Each round, each player takes 1–3, then the pool "grows back" by adding half of what's left (rounded down). If the bowl empties, the game is over.
- Even with one learner + facilitator, this works well as a 2-player game.
- Skip the spreadsheet/graphing version. The physical tokens tell the story.
Journal alternative: "In the Fishing Game, the fish ran out when ___. We could have kept them going if ___." Spoken is fine.
What success looks like: The learner can explain "If everyone takes too much, there's none left for anyone" and suggest a rule that would help.
- Full simulation with tracking, graphing the fish population over rounds.
- Discuss real-world commons: climate change, overfishing, shared bandwidth, public parks.
- Have students design and test their own rules for sustaining the commons.
- Introduce the concept of enforcement: "Rules only work if people follow them — what makes people follow them?"
Guided Session 1
The Fishing Game
Learning Goal
By the end of this session, the student can:
- explain the Tragedy of the Commons in their own words
- describe why individually rational choices can lead to collectively terrible outcomes
- explain the connection between this game and the Prisoner's Dilemma
Activities
1. Game Setup
- The Pond: Place 20 tokens in a bowl. These are fish.
- Players: 2–4 players. Each has a cup for their catch.
- Goal: Earn as many fish as possible over multiple rounds.
Round Rules:
- Each player secretly writes down how many fish they want to take (0-5).
- Everyone reveals simultaneously.
- If the total taken ≤ total fish available, everyone gets what they asked for. Remove those fish from the pond.
- Replenishment: After each round, the remaining fish in the pond double (but the pond can never hold more than 20).
- If the pond hits 0, the game is OVER. No more fishing. Ever.
Key math:
- If 4 players each take 2 fish (8 total), and the pond started with 20, it drops to 12. Then 12 doubles to 20 again. Sustainable!
- If 4 players each take 5 fish (20 total), the pond drops to 0. Game over.
Diminishing returns: As more fish are taken from the pond, the remaining fish yield less and less — this is diminishing returns at the group level. A pond with 4 fish left can only double to 8, while a pond with 12 left doubles to 20. Every extra fish taken reduces the pond's ability to recover.
If only 2 players (learner + facilitator): The Fishing Game works great with 2. Each round, each player secretly writes how many fish to take (1–3), then reveal simultaneously. Add half the remaining fish back each round.
If truly solo: Run a simulation against imaginary players. "Round 1: You take 2 fish. Two imaginary players each take 3. There were 20 fish. How many are left? How many grow back?" The learner tracks the population on paper and discovers when it collapses.
2. Round 1: No Communication
Rules for Round 1: Players cannot talk to each other. No discussion.
Play it out. Track what happens:
| Round | Fish in Pond (start) | Player 1 | Player 2 | Player 3 | Player 4 | Fish Taken | Fish Left | After Doubling |
|---|---|---|---|---|---|---|---|---|
| 1 | 20 | |||||||
| 2 | ||||||||
| 3 | ||||||||
| ... |
What usually happens: At least one player takes a lot, thinking "If I don't, someone else will." This depletes the pond faster. Within 2–4 rounds, the fish are gone.
Debrief:
- "Why did the pond collapse?"
- "Was anyone 'wrong' for trying to take a lot?"
- "This is EXACTLY the Prisoner's Dilemma at scale. Each person's 'best move' (take more) leads to the worst collective outcome."
- "Did anyone take extra because they were afraid of losing out? That's loss aversion from Week 6. Did anyone keep taking more because they'd already committed to a big haul? That's sunk cost from Week 7. These aren't just individual biases — they drive group disasters too."
3. The Real-World Tragedy
Share age-appropriate examples:
- The family fridge: Everyone grabs the best snacks as fast as they can. The snacks run out by Wednesday.
- Shared crayons in a classroom: Nobody puts them back carefully. Soon they're broken and scattered.
- A park: If nobody picks up their trash, the park becomes a mess and nobody wants to go there.
- Fishing (for real): Overfishing has collapsed fish populations in many oceans because each fishing boat took as much as it could.
"The Tragedy of the Commons happens whenever a shared resource has no rules. Everyone acts 'rationally' and the result is disaster."
Guided Session 2
Solving the Commons
Learning Goal
By the end of this session, the student can:
- describe at least 3 different approaches to solving a commons problem
- explain the role of communication, transparency, and rules
- evaluate which solution works best for different situations
Activities
1. Round 2: Communication Allowed
Reset the pond to 20 fish. Replay the game with ONE change:
Before each round, players can discuss strategy for 1 minute.
Play 6-8 rounds. Track results.
Debrief:
- "Did the outcome change? Why?"
- "What did you discuss? Did everyone stick to the agreement?"
- "Communication alone helps a LOT. But what happens if someone breaks the agreement?"
2. Round 3: Transparent Catches
Reset again. This time:
After each round, everyone can see how many fish each person took.
Play 6-8 rounds.
Debrief:
- "Did knowing that others could see your catch change your behavior?"
- "This is called transparency. When people know their choices are visible, they tend to be more cooperative."
- "Real-world equivalent: public recycling bins, energy usage reports, screen time trackers."
3. Round 4: Group Rules
Reset one more time. Now:
Before playing, the group votes on a maximum number of fish anyone can take per round. This rule is binding.
Let the group create their rule. Play 6-8 rounds.
Debrief:
- "Did the rule work?"
- "Was the limit too strict? Too loose?"
- "What if someone had disagreed with the rule?"
- "This is how real societies solve commons problems: fishing quotas, speed limits, park rules, HOA guidelines."
4. Which Solution Worked Best?
Compare all four rounds:
| Version | Outcome | Why? |
|---|---|---|
| No communication | Probably collapsed | No way to coordinate |
| Communication | Probably sustained | People could agree on a plan |
| Transparency | Probably sustained | Social pressure reduces greed |
| Rules/Quotas | Most reliably sustained | Clear limits enforced fairly |
Discussion:
"In real life, the best solutions usually combine all three: people talk about the problem, behavior is visible, and there are agreed-upon rules. This is why communities, teams, and families need clear expectations."
5. The Big Connection
Tie together the whole Phase 4 arc:
- Week 12: Your choices create ripple effects beyond yourself.
- Week 13: In the Prisoner's Dilemma, individual logic fails without cooperation.
- Week 14: When shared resources are involved, cooperation isn't optional — it's survival.
"The world's biggest problems — climate change, traffic, pollution — are all commons problems. The solutions all involve the same ingredients: communication, transparency, and fair rules. Now you understand WHY."
This week completes Phase 4: Game Theory & Social Systems. You've learned that your choices ripple outward, that cooperation beats defection in repeated interactions, and that shared resources need communication, transparency, and rules. In Phase 5, we'll take everything you've learned and apply it to the biggest decisions of all — the ones that shape your future.
Independent Practice
Goal
Identify commons problems in your own life and design simple solutions.
Activities
The Fishing Game requires 2–4 players — recruit family members or friends if revisiting independently.
1. My Commons
List 3 shared resources in your life:
- At home (bathroom, fridge, Wi-Fi, TV, etc.)
- At school (classroom supplies, playground equipment, library books)
- In your community (parks, sidewalks, public spaces)
For each one:
- Has it ever suffered from a "Tragedy of the Commons"?
- What solution is currently in place (if any)?
- What solution would you recommend?
Minimum viable version (younger learners): Pick one shared resource at home (like a bag of chips or shared screen time). Watch what happens for 2 days. Ask: "Is anyone taking more than their share? Did it run out faster?" Tell a grown-up what you noticed.
2. Design a Fair Rule
Pick one commons problem from your list. Design a simple rule that could help:
- The rule should be clear and easy to follow
- It should be fair to everyone
- It should allow the resource to replenish/stay healthy
- Write it down as if you were proposing it to your family or class
Decision Journal
Write about a time when everyone acting in their own interest made things worse for the group. What happened? What would you change? Which of the four Fishing Game versions (no communication, communication, transparency, rules) best describes the situation, and which version would have fixed it?
Reflection Questions
- Why is it harder to solve a commons problem with more people?
- Is it fair to limit what individuals can do to protect a shared resource?
- What's the difference between a rule that people follow because they agree with it and a rule they follow because they have to?
Quick Mastery Check
After this week, check whether the learner can:
- Identify a commons: "What do you share at home or school that could run out if people aren't careful?" (Looking for: any shared resource — snacks, art supplies, hot water, Wi-Fi bandwidth, clean common spaces.)
- Explain the dilemma: "In the Fishing Game, why is it tempting to take a lot of fish even though everyone would be better off taking less?" (Looking for: "Because if I take less but others don't, I lose out" or "I want more for myself.")
- Propose a solution: "If you were in charge of the fishing pond, what rule would you make?" (Looking for: limits per person, communication/agreements, taking turns, monitoring.)
If the learner can explain why shared resources get overused AND suggest a rule to prevent it, they've grasped the core lesson.
Pause and Notice
After the Fishing Game, ask:
"When you saw someone else take a lot of fish, what did you feel? Did it make you want to take more too — like 'I'd better grab mine before it's gone'? Or did it make you frustrated?"
"The urge to take more when you see others taking more is completely natural. It's a mix of fairness instinct ('Why should they get more than me?') and fear ('There might not be enough'). Recognizing that feeling is the first step to choosing differently."
This week is really about the tension between self-interest and community. There's no single "right" answer — but being aware of the tension helps you make choices you're proud of.
This week's takeaway: You can't control what everyone else does. But you CAN decide what kind of community member you want to be — and sometimes that inspires others to follow.
Spiral Review
- From Week 13: "The Fishing Game is a multiplayer Prisoner's Dilemma. Each person faces the same cooperate-or-defect choice — but now with shared consequences."
- From Week 12: "Every fish you take creates ripples. Taking too many now means less for everyone later — including future you."
- From Week 9: "You can calculate expected value on your fish-taking strategy. But the EV changes based on what everyone else does — that's what makes commons problems so tricky."
- From Week 6: "Loss aversion makes you grab MORE when the pool is shrinking — 'Take it now before it's gone!' That instinct accelerates the tragedy."
- Use 10 fish instead of 20, and play fewer rounds — the collapse happens faster and is easier to grasp.
- Focus on the physical, hands-on experience of the Fishing Game rather than the math.
- Keep real-world examples close to home: the family fridge, shared crayons, the playground.
- Run full multi-round simulations and have students graph the fish population over time.
- Discuss real-world commons: ocean fisheries, air quality, climate change, shared digital resources.
- Have students design their own rules, test them in the game, and compare effectiveness across approaches.