---
id: wiki-2026-0508-nudge-theory
title: Nudge Theory
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Nudge, Choice Architecture, Behavioral Nudge, 넛지]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [behavioral-economics, ux, design, psychology, choice-architecture]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: typescript
  framework: ux-design
---

# Nudge Theory

## 매 한 줄
> **"매 choice architecture를 미세 조정하여 freedom of choice를 보존한 채 predictable한 방향으로 행동을 유도."**. Richard Thaler · Cass Sunstein의 *Nudge* (2008) — 2017 Thaler 노벨경제학상. 2026 현재 UX design · public policy · health intervention · LLM safety의 기반 framework.

## 매 핵심

### 매 nudge 정의 (Thaler/Sunstein)
- 매 small change in choice architecture
- 매 predictable behavior change 유도
- 매 옵션을 금지하지 않음 (libertarian paternalism)
- 매 economic incentive 거의 없음 (cheap)

### 매 mechanism
- **Default**: 매 default option 압도적 영향 (organ donation opt-in vs opt-out — 12% vs 99%).
- **Salience**: 매 정보 visibility 증가.
- **Framing**: 매 동일 정보, 다른 표현 (90% lean vs 10% fat).
- **Social proof**: 매 "X% of users do Y".
- **Friction**: 매 desired action은 쉽게, undesired는 hard.

### 매 응용
1. UK Behavioral Insights Team — tax letter "9 of 10 pay on time" → 5% 회수율 증가.
2. Spotify "Discover Weekly" → 매 default playlist으로 engagement 증가.
3. Apple Health — 매 default 7000 step goal로 average +500 step.

## 💻 패턴

### Default opt-in for desired behavior
```tsx
// BAD: opt-in for 2FA
<Checkbox label="Enable 2FA (recommended)" defaultChecked={false} />

// GOOD: default-on with easy opt-out
<Checkbox
  label="Enable 2FA"
  defaultChecked={true}
  helperText="Recommended. You can disable in Settings."
/>
```

### Friction: confirm destructive action
```tsx
function DeleteAccountButton() {
  return (
    <ConfirmDialog
      title="Delete account?"
      requireType="DELETE my-username"  // typed friction
      cooldownSeconds={5}
    >
      <Button variant="danger">Delete</Button>
    </ConfirmDialog>
  );
}
```

### Social proof nudge
```tsx
<PricingCard plan="pro" badge="Most popular — 73% of teams choose this" />
```

### Framing — loss aversion
```tsx
// BAD (gain frame, weaker)
<p>Save $120/year with annual billing</p>

// GOOD (loss frame, stronger; Tversky/Kahneman)
<p>Stop paying $10/mo extra — switch to annual</p>
```

### Salience — progress nudge
```tsx
function ProfileCompletion({ percent }: { percent: number }) {
  return (
    <Banner show={percent < 100}>
      Profile {percent}% complete — add a photo to reach 100%
      <ProgressBar value={percent} />
    </Banner>
  );
}
```

### Implementation intention prompt
```tsx
// "When X happens, I will do Y" — proven habit formation
<Onboarding>
  <p>When will you exercise?</p>
  <Select options={["Morning", "Lunch", "Evening"]} />
  <p>Where?</p>
  <Input placeholder="Living room, gym..." />
</Onboarding>
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| User benefits from default | opt-out default |
| User must consciously choose | opt-in, no default |
| Discourage harm | friction (confirm, delay) |
| Encourage rare valuable action | salience + reminder |
| Group conformity helpful | social proof |

**기본값**: transparent default + easy opt-out — 매 dark pattern과의 차별점.

## 🔗 Graph
- 부모: [[Behavioral_Economics]] · [[Cognitive Bias]]
- 변형: [[Choice_Architecture]] · [[Habit_Loop]]
- 응용: [[Micro-interactions]] · [[Gamification]]
- Adjacent: [[FOMO (Fear of Missing Out)]] · [[Progressive-Disclosure]] · [[매몰_비용_오류_(Sunk_Cost_Fallacy)]]

## 🤖 LLM 활용
**언제**: UX flow 설계, public health/policy, habit-forming product, opt-in/opt-out 결정.
**언제 X**: high-stakes informed consent (의료, 금융 — 매 explicit choice 필수), regulated decision (legal contract).

## ❌ 안티패턴
- **Dark pattern (sludge)**: 매 친 user가 아닌 친 vendor — Sunstein 본인이 *Sludge* (2021)로 비판.
- **Hidden default**: 매 user 모르게 enable — opt-in의 transparency 무시.
- **Manipulation > nudge**: 매 deception (e.g. fake countdown) — ethics 위반.
- **Over-nudging**: 매 모든 화면에 nudge — banner blindness.
- **No measurement**: 매 A/B test 없이 nudge — direction 불명.

## 🧪 검증 / 중복
- Verified (Thaler/Sunstein *Nudge* 2008 / 2021 final ed., UK BIT trial reports, Sunstein *Sludge* 2021).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Nudge theory (Thaler/Sunstein) + UX patterns |