2nd/10_Wiki/Topics/Game_Design/Prisoners-Dilemma-Models.md

---
id: wiki-2026-0508-prisoners-dilemma-models
title: Prisoner's Dilemma Models in Game Design
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Prisoners Dilemma, PD Game Design, Cooperation Games]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [game-design, game-theory, multiplayer, cooperation, axelrod]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: python
  framework: numpy
---

# Prisoner's Dilemma Models in Game Design

## 매 한 줄
> **"매 PD model은 매 multiplayer game design의 매 cooperation tension의 매 mathematical core — 매 individual rational choice가 매 collective suboptimal로 leads하는 매 모든 trust mechanic의 base."** Robert Axelrod 'Evolution of Cooperation' (1984)이 매 iterated PD에서 매 'tit-for-tat' winning strategy 증명. 매 game design에서 매 The Resistance / Werewolf social deduction, 매 EVE Online corp wars, 매 Among Us, 매 Trust (Nicky Case 2017 interactive)까지 매 explicit application 광범. 매 2026 시점, 매 Multi-Agent RL (Llama 3 / Claude 3.5)이 매 inter-agent cooperation 학습에 매 PD framework 활용.

## 매 핵심

### 매 PD payoff matrix
- **Standard PD**: T (Temptation, 5) > R (Reward, 3) > P (Punishment, 1) > S (Sucker, 0).
- **Constraint**: 2R > T + S — 매 mutual cooperation이 매 alternating defection보다 better.
- **One-shot**: 매 rational defect (Nash). 매 iterated: 매 cooperation 가능.

### 매 winning strategies (Axelrod tournament)
- **Tit-for-Tat (TFT)**: 매 first move cooperate, 매 then mirror opponent. 매 nice + retaliating + forgiving + non-envious.
- **Tit-for-Two-Tats**: 매 noise tolerant — 매 2회 연속 defect 후에야 retaliate.
- **Generous TFT**: 매 retaliate 90% of time — 매 forgive 10%.
- **Pavlov (Win-Stay, Lose-Shift)**: 매 last round 'win' (R or T)이면 매 same action repeat.

### 매 game design 응용
- **Trust mechanic**: 매 player가 매 다른 player에게 매 currency 맡기면 매 returner는 매 더 많이 받기 가능. EVE Online stockpiling.
- **Punishment mechanic**: 매 betrayal에 매 reputation system — 매 public visible defection history.
- **Communication tool**: 매 chat / signal로 매 commitment make 가능 — 매 cheap-talk vs costly signal.
- **Endgame revelation**: 매 final round 시 매 cooperation 붕괴 (backward induction).

## 💻 패턴

### IPD simulator
```python
import numpy as np
from typing import Callable

PAYOFF = {
    ('C', 'C'): (3, 3),
    ('C', 'D'): (0, 5),
    ('D', 'C'): (5, 0),
    ('D', 'D'): (1, 1),
}

def play(strat_a: Callable, strat_b: Callable, rounds=200, noise=0.0):
    history_a, history_b = [], []
    score_a, score_b = 0, 0
    for r in range(rounds):
        move_a = strat_a(history_a, history_b)
        move_b = strat_b(history_b, history_a)
        if np.random.random() < noise: move_a = 'D' if move_a == 'C' else 'C'
        if np.random.random() < noise: move_b = 'D' if move_b == 'C' else 'C'
        pa, pb = PAYOFF[(move_a, move_b)]
        score_a += pa; score_b += pb
        history_a.append(move_a); history_b.append(move_b)
    return score_a, score_b
```

### TFT + variants
```python
def tit_for_tat(my_hist, opp_hist):
    return 'C' if not opp_hist else opp_hist[-1]

def tit_for_two_tats(my_hist, opp_hist):
    if len(opp_hist) < 2: return 'C'
    return 'D' if opp_hist[-1] == 'D' and opp_hist[-2] == 'D' else 'C'

def generous_tft(my_hist, opp_hist):
    if not opp_hist: return 'C'
    if opp_hist[-1] == 'D' and np.random.random() < 0.1: return 'C' # 매 forgive
    return opp_hist[-1]

def pavlov(my_hist, opp_hist):
    if not my_hist: return 'C'
    last_payoff = PAYOFF[(my_hist[-1], opp_hist[-1])][0]
    return my_hist[-1] if last_payoff >= 3 else ('D' if my_hist[-1] == 'C' else 'C')
```

### Reputation system (multiplayer game)
```python
class Reputation:
    def __init__(self):
        self.scores = {}  # player_id → reputation float

    def record_action(self, player: str, action: str, target: str):
        delta = +0.1 if action == 'cooperate' else -0.3
        self.scores[player] = self.scores.get(player, 0) + delta
        self.scores[player] = max(-1, min(1, self.scores[player]))

    def is_trustworthy(self, player: str) -> bool:
        return self.scores.get(player, 0) > 0.3
```

### Costly signal mechanic
```python
# 매 player가 매 commitment를 매 escrow로 demonstrate
class CostlySignal:
    def __init__(self):
        self.escrows = {}

    def signal_commitment(self, player: str, amount: int):
        # 매 player가 매 amount를 lock — 매 betray시 매 lose
        self.escrows[player] = amount

    def reward_or_punish(self, player: str, betrayed: bool):
        amt = self.escrows.pop(player, 0)
        if betrayed:
            return 0  # 매 escrow 몰수
        else:
            return amt + (amt * 0.5)  # 매 50% bonus return
```

### Endgame anti-defection (finite-game prevention)
```python
# 매 final round를 매 hidden — 매 backward induction 차단
class HiddenEndgame:
    def __init__(self, expected_rounds: int, jitter: int):
        self.actual_rounds = expected_rounds + np.random.randint(-jitter, jitter+1)

    def is_final(self, current_round: int) -> bool:
        return current_round >= self.actual_rounds
    # 매 player에게 매 actual_rounds 매 공개 안 함
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Social deduction (Werewolf 식) | 매 information asymmetry + 매 PD |
| Persistent MMO | Reputation + costly signal |
| Co-op survival (Don't Starve Together) | 매 mutual benefit dominant — 매 PD weak |
| Competitive 1v1 | Pure PD only at meta level |
| Multi-agent RL | TFT-family baseline |

**기본값**: 매 iterated PD with reputation + 매 hidden endgame. 매 one-shot은 매 always defect dominant.

## 🔗 Graph

## 🤖 LLM 활용
**언제**: 매 LLM 두 instance를 매 IPD opponent로 simulate — 매 emergent strategy 분석.
**언제 X**: 매 deep human social dynamic — 매 emotion / context는 매 LLM-PD simulation으로 안 잡힘.

## ❌ 안티패턴
- **Pure cooperation reward without defection option**: 매 PD 아닌 just co-op.
- **No reputation persistence**: 매 betrayal 후 매 anonymity → 매 cooperation collapse.
- **Known finite endgame**: 매 backward induction → 매 always defect.
- **No noise tolerance**: 매 single mistake → 매 permanent defection spiral (TFT vs TFT trap).

## 🧪 검증 / 중복
- Verified — Axelrod "Evolution of Cooperation" (1984), Nicky Case "The Evolution of Trust" (2017), 매 Multi-Agent RL papers (DeepMind 'Sequential Social Dilemmas' 2017).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — PD payoff matrix, TFT variants, reputation / costly signal / hidden endgame patterns |