Reading Notes

**Systems Thinking — Legend Cheat Sheet**

**Stock (Level)**

Symbol: □

Meaning: A quantity that accumulates—inventory, trust, CO₂, cash.

Why it matters: Stocks give systems inertia and memory. They’re slow to change, which is why short-term actions often fail to move long-term outcomes.

**Flow (Rate)**

Symbol: →⧈→

Meaning: Pipes and valves controlling inflows/outflows.

Why it matters: If a system behaves strangely, it’s usually because a flow—not a stock—is constrained or misaligned.

**Source / Sink**

Symbol: ☁️

Meaning: Represents what lies outside your defined system.

Why it matters: The choice of boundary changes the analysis. Make the boundary too small, and the “clouds” hide essential drivers.

**Causal Link**

Symbol: A → B

Meaning: A influences B.

Why it matters: Systems behaviour emerges from interconnections, not elements. This is the primary building block.

**Polarity of Link**

Symbol: (+) or (–) on the arrow

Meaning:

• **( + )** → A moves B in the same direction.

• **( – )** → A moves B in the opposite direction.

**Reinforcing Loop (Positive Feedback)**

Symbol: 🔁 R

Meaning: A self-amplifying loop—growth or collapse.

Why it matters: These loops create runaway behaviour: hypergrowth, bubbles, viral spread, or death spirals.

**Balancing Loop (Negative Feedback)**

Symbol: 🔁 B

Meaning: A stabilising loop pushing the system toward a target.

Why it matters: These loops keep systems in equilibrium—the body maintaining temperature, markets finding price, staff maintaining workload.

**Delay**

Symbol: // on the arrow or a delay box

Meaning: A time lag between cause and effect.

Why it matters: Delays cause oscillation, overshoot, and unintended consequences. Most management mistakes trace to ignoring delays.

**System Boundary**

Symbol: Dashed enclosure

Meaning: What’s inside vs outside the analysis.

Why it matters: Change the boundary, change the problem—and the solution. Many “unsolvable” issues are boundary errors.

**Rule**

Symbol: text annotation

Meaning: Constraints shaping behaviour (formal or informal).

Why it matters: Change the rules and you change outcomes dramatically—often more than changing resources or people.

**Purpose (Goal)**

Symbol: label

Meaning: The goal the system’s behaviour reveals.

Why it matters: The true purpose is what the system consistently does, not what people claim it is. This explains many organisational frustrations.

**Paradigm (Mindset)**

Symbol: conceptual box at a higher level

Meaning: The worldview or assumptions shaping the rules.

Why it matters: Deepest leverage point. Change the paradigm, and the entire system transforms.

**Behaviour-Over-Time Graph (BOTG)**

Symbol: 📈 curved line over time

Meaning: Time-series showing a stock’s pattern.

Why it matters: Patterns—growth, collapse, oscillation—tell you which structures and loops dominate the system.