Bathtub Test

Name what accumulates, what fills it, and what drains it.

Your Spanish flashcard app shows 340 cards due for review. Last week it was 180. You are studying every day, so the pile growing feels unfair, and your instinct is to study harder. But you have not actually looked at the arithmetic of why the pile grows: how many cards you add per day versus how many you clear.

Bathtub Test forces you to name three things about any quantity that builds up: what accumulates (the stock), what fills it (the inflow), and what drains it (the outflow). The cue is any piling-up or running-down you keep reacting to: card backlogs, unread messages, debt, fatigue, unfinished chapters. The operation: name the stock in one phrase, list the inflows with rough rates, list the outflows with rough rates, then compare. If 40 new cards arrive daily and you clear 25, no amount of motivation talk changes the direction; you either slow the faucet or widen the drain. What changes when it works is that vague pressure becomes a solvable rate problem. Do not use it on things that do not accumulate; a one-time event or a pure flow with no storage gains nothing from bathtub language.