Technique · Actionable Gamification
Magnetic Caps (GT#68)
A limit on how often a Desired Action can be taken, which makes the action more appealing and pulls people toward the limit. Chou's calibration rule is to cap at or just above the natural upper bound, for example the 90th percentile, and to raise caps for proven power users.
Plain label: calibrated usage limitAlso known as: Magnetic Caps, usage caps, daily limits
How it works
A capped action feels valuable and gets used eagerly, while unlimited features often go ignored (CD6), and abundance dulls motivation, so any windfall should stay temporary. The cap must add more activity than it suppresses, and power users should always see a next cap. The purchase-limit evidence Chou cites comes from Brian Wansink, whose research record was later heavily discredited, and the 90th-percentile rule is a practitioner heuristic.
Evidence warning
The cited study comes from Brian Wansink, who left Cornell in 2018 after many of his papers were retracted; confirm this particular study holds up, and test caps on your own users.
Tightening caps mainly to force upgrades reads as manipulation and erodes trust.
What the research says
Chou reports that a grocery sign limiting a product to 12 per person lifted purchases 30-105% over a no-limit sign.
AG Ch10 citing Wansink, Mindless Eating (author's research record later discredited), 2006
How to build it
- Mobile
- 'Five super-likes a day' with a refill and a visible next cap for proven users.
- Web
- 'Pick up to five interests' or 'nominate three teammates this month'.
- E-commerce
- 'Limit three per customer' only when supply is genuinely limited.
What can go wrong
- A cap below the natural bound that suppresses activity.
- Caps tightened to force upgrades.
- Post-purchase abundance that never ends.
Pairs well with
- Raise caps for proven power users and always show the next one.
- Judge the cap by total activity, not only per-user use.
In practice
Where it shows up
Limits
What we don’t claim
- Octalysis is a practitioner framework built from observing games, not a validated scientific model.Actionable Gamification Ch.15, pp.399-400
- Left Brain and Right Brain are a metaphor for extrinsic and intrinsic motivation, not a claim about neuroscience.Actionable Gamification Ch.13, pp.342-343
- This is a practitioner heuristic (grade D): test it in your own product before relying on it.
- The threshold is a heuristic, not a measured cut-off.
Sources
Actionable Gamification · Yu-kai Chou
Ch.10, p.253 · Ch.10, p.254 · Ch.10, p.255 · Ch.10, p.267 · Ch.10, p.230
Source IDs: GT#68CD6
Book content is paraphrased, never quoted at length. Last verified October 24, 2026.
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