---
id: wiki-2026-0508-cognitive-load
title: Cognitive Load
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Mental Load, Working Memory Pressure, Code Complexity Tax]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [engineering, design, code-quality, devex]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: any
  framework: software-engineering
---

# Cognitive Load

## 매 한 줄
> **"매 working memory 에 동시에 매 잡고 있어야 하는 정보의 양"**. Sweller 의 cognitive load theory (1988) 에 기반 — intrinsic, extraneous, germane 의 3-tier. 매 modern software design 의 first-principle metric — 작은 cognitive load 가 매 maintainable code 를 결정.

## 매 핵심

### 매 3 종류
- **Intrinsic**: 문제 자체의 본질적 복잡도 (e.g., distributed consensus).
- **Extraneous**: 표현/도구 가 만드는 인위적 복잡도 (bad naming, deep nesting).
- **Germane**: schema 형성 과정 (learning) — useful load.

### 매 7±2 rule
- Working memory 는 약 4-7 chunk 만 동시 처리 (Miller 1956, refined Cowan 2001).
- Code 가 이 한계 넘으면 → bug, slow review, onboarding 지연.

### 매 응용
1. Function 의 line / parameter 제한 (small functions).
2. Module boundary 설계 — high cohesion, low coupling.
3. PR size 제한 (200-400 line max).
4. Naming convention — domain language 사용.

## 💻 패턴

### Guard clause 로 nesting 줄임
```python
# BAD: deep nesting (high extraneous load)
def process(user):
    if user is not None:
        if user.is_active:
            if user.has_permission('write'):
                return do_work(user)
    return None

# GOOD: early return
def process(user):
    if user is None: return None
    if not user.is_active: return None
    if not user.has_permission('write'): return None
    return do_work(user)
```

### Extract domain primitive
```typescript
// BAD: primitive obsession — caller must remember semantics
function transfer(from: string, to: string, amount: number, currency: string) {}

// GOOD: types carry semantics
type AccountId = string & { __brand: 'AccountId' };
type Money = { amount: bigint; currency: Currency };
function transfer(from: AccountId, to: AccountId, money: Money) {}
```

### 매 colocation
```tsx
// BAD: scattered — must context-switch
// styles.css, validation.ts, component.tsx, types.ts

// GOOD: single-file feature unit (Astro/Svelte/RSC era)
export function Form() {
  const validate = (v: string) => v.length > 0;
  return <input onBlur={e => validate(e.target.value)} />;
}
```

### Boundary objects
```python
# Each layer translates — caller doesn't need to know inner schema
class UserDTO:  # external API shape
    ...
class User:  # domain entity
    ...
class UserRow:  # DB schema
    ...
def to_domain(dto: UserDTO) -> User: ...
def to_row(user: User) -> UserRow: ...
```

### Team Topologies pattern
```yaml
# Stream-aligned team owns a single bounded context
# Platform team provides self-service infra
# Goal: each team's cognitive load fits one team's working memory
team: payments
owns: [PaymentService, RefundService, payment-db]
depends_on:
  platform: [k8s-cluster, observability]
  enabling: []
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Function > 50 lines | Extract sub-functions or strategy |
| Class > 7 public methods | Split by responsibility |
| Team owns > 1 product area | Reorg per Team Topologies |
| Domain logic mixed w/ infra | Hexagonal / Clean Architecture |
| Onboarding > 2 weeks | Reduce coupling, write decision records |

**기본값**: Optimize for reader, not writer — 매 reduce extraneous, accept intrinsic.

## 🔗 Graph
- 부모: [[Software Design]] · [[Cognitive Psychology]]
- 변형: [[Intrinsic Load]] · [[Extraneous Load]] · [[Germane Load]]
- 응용: [[Team Topologies]] · [[Hexagonal Architecture]] · [[Clean Code]]
- Adjacent: [[Working Memory]] · [[Code Smell]] · [[Naming Things]]

## 🤖 LLM 활용
**언제**: Code review, refactoring decision, team structure 설계, PR size 판단.
**언제 X**: Pure performance optimization (different metric).

## ❌ 안티패턴
- **Cleverness 자랑**: dense one-liner, clever bitwise — high extraneous.
- **God object**: 30+ method class — exceeds chunking capacity.
- **Magic constants**: `if x > 86400` 대신 `SECONDS_PER_DAY`.
- **Implicit context**: global mutable state — reader 가 매 trace 해야 함.
- **Premature abstraction**: framework-itis — abstraction 이 intrinsic 아닌데 추가됨.

## 🧪 검증 / 중복
- Verified (Sweller 1988, Skelton & Pais 2019 Team Topologies).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — cognitive load theory + practical refactoring patterns |
