How to Master Which Curve
TLDR: Which Curve shows you two graphs of the same phenomenon and asks which one is real. Don’t guess from the picture · reason from the thing itself. Ask four questions in order: does it compound, is it seasonal, does it saturate, does it decay? The decoy is almost always a boring straight line, so the moment you know the real world bends, you know which graph to reject.
What You’re Actually Learning
Which Curve is a streak game about the shapes change makes. Each round names something that moves over time · world population since 1800, daylight across a year, the price of storage per gigabyte, the daily views of a viral video · and draws two curves. One is the honest shape; the other is a plausible fake. Tap the real one, read a one-line explanation, build your streak.
The skill is not graph-reading, it is first-principles reasoning. You are not meant to recall a dataset · you ask “what must this look like?” before you glance at the lines. Storage cannot get cheaper in a straight line forever; it collapses toward zero. A viral video cannot ramp up slowly; attention arrives almost at once. Reason your way to the shape and the correct graph is obvious.
The Decoy Is Usually a Straight Line
The most useful pattern in the game: the fake graph is, more often than not, a plain straight line · rising or falling steadily. The real world rarely moves in straight lines; it accelerates, peaks, plateaus, crashes. So your first move on almost every round is one question: is this phenomenon actually linear, or does it bend? If it bends, reject the straight line and you are usually done.
When one of the two graphs is a clean straight diagonal, treat it as the prime suspect. Things that compound, saturate, or decay all curve · a ruler-straight line is the game’s favourite disguise, and almost always the lie.
Compounding Means Exponential
If a quantity grows by a percentage of itself · more people make more people, more debt accrues more interest · it compounds, and compounding draws an exponential: nearly flat at first, then bending sharply upward. World population since 1800 and US national debt since 1980 are both exponential here · the truth curves up and away, not in a straight ramp.
The compounding test. Does more of this thing create even more of it? Population, debt, anything earning interest all compound · pick the curve that starts gentle then rockets up, not the steady diagonal. For population the decoy is a straight rising line; for debt it is a falling line, doubly wrong · the debt did not shrink and did not rise evenly.
Seasonal and Daily Things Make Bells and Waves
Anything tied to the calendar or the clock rises to a peak and falls back. Hours of daylight over a year peak at midsummer and dip in winter · a smooth seasonal bell. Outdoor temperature over a single day peaks in the afternoon and is coldest before dawn · a daily bell. Same shape, different timescale. The giveaway is a natural cycle in the prompt · “over a year,” “over a single day.” Look for a hump that climbs then falls, and reject any graph that only climbs.
Cycle words are your cue: “over a year,” “over a day,” “monthly.” Nature returns to where it started after one cycle, so the real curve must come back down · a line that only rises cannot be a single year of daylight.
Adoption Saturates Into an S-Curve
New technology does not spread in a straight line and does not grow forever. It starts slow, hits a tipping point, races upward, then flattens as it runs out of new people to reach · the logistic S-curve. The share of people owning a smartphone since 2007 is the classic case: slow start, rapid take-off, then levelling near saturation, since you cannot pass one hundred percent.
The ceiling test. When something is a share or percentage of a fixed population · ”% who own,” “share who adopted” · there is a hard ceiling it cannot cross. Reject the line that sails past the ceiling and pick the S that flattens near the top. Saturation, not infinity, is the tell.
Obsolescence and Decline Make a Decay
When something is being replaced or steadily falling, it decays · a steep drop that flattens toward a floor. The price of computer storage per gigabyte since 1990 collapses toward zero as technology improves. The birth rate in a developed country over the last century falls steadily as the country develops. Both are downward curves, and in both rounds the decoy is a rising line · “it goes up” is the wrong answer before you judge the bend.
Watch the direction first. For storage price and birth rate the fake graph rises · but prices crashed and birth rates fell. If you check only the shape and ignore which way it points, a decoy that climbs when the truth falls will catch you. Confirm the trend goes the right way before fussing over the curve.
Fads Spike Then Fade
Some things do not ramp up at all · they explode almost instantly, then burn out. The daily views of a viral video after it blows up spike right at the start and fade away; attention burns bright and fast. Unlike exponential growth, which is slow at first, a fad’s peak is at the beginning. Reject the gentle ramp and pick the curve already near its top on day one.
Distinguish a spike from exponential growth by where the action is. Exponential is quiet early, loud late; a viral spike is loud immediately, quiet later. “After it blows up” tells you the explosion already happened · the curve should start high and decline.
U-Shapes: Down Then Up
A few phenomena fall and then climb back · a valley, or U. Vinyl record sales from 1970 to today nearly died as CDs and streaming took over, then revived: down, then up. The number of deaths each month over a year rises in winter at both ends of the calendar and dips in the warmer middle · a gentle U. The trap is a graph that only goes one way: if a trend reversed, neither a pure rise nor a pure fall fits.
Your four-question checklist, in order: (1) Does it compound? Then exponential · gentle then steep. (2) Is it on a cycle · a day, a year? Then a bell that returns to where it began. (3) Is it a share with a ceiling? Then an S-curve that flattens near the top. (4) Is it being replaced or declining? Then a decay toward a floor · and check the direction. Anything that reversed is a U. When none of these fit a straight line, reject the straight line.
Building a Long Streak
Once the shape vocabulary is automatic, the game becomes fast. Read the prompt, name the shape before looking, then find the matching graph and confirm the decoy is wrong. Reasoning first, picture second, keeps you from being fooled by a fake that merely looks tidy. Master the four questions and exponential, bell, S-curve, decay, spike and valley all feel obvious · the straight-line decoy never tricks you again.
Which Curve
Two graphs over time · pick which curve is the real shape of a phenomenon, from world population to a year of rainfall
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