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Variable reward: why we keep scrolling

About this app

Two feeds, both rewarding every fourth video on average: one on a fixed schedule, one unpredictably. When the hits stop, 20 simulated people quit the fixed feed after 5 to 11 swipes and the variable one only after 11 to 26. Plus endless feed versus feed with stopping points.

With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.

Unpredictable reward

Learning psychology calls it a variable ratio when a reward follows a changing, unpredictable number of actions. Experiments since Ferster and Skinner (1957) show that a variable ratio produces steady, persistent responding, and when the rewards stop, the behaviour takes longer to stop than with a fixed ratio. Someone who has already lived through long dry spells recognises the end later. A feed in which only some videos are a hit follows this pattern; how strong the effect is in scrolling has not been measured precisely.

What the app shows

Two feeds side by side, both with one hit in four videos. On the left it comes on time every fourth video, on the right irregularly. Columns show the current dry spell and, dashed, the longest one so far. After 40 videos the hits stop, and a curve shows how many of 20 simulated people keep swiping. In the second comparison the hits continue and one feed gets stopping points.

Try it yourself

Let both feeds run to swipe 80 and watch when the curves fall: on the left after 5 to 11 videos without a hit, on the right only after 11 to 26. Change the ratio to every 2nd or every 8th video. Then switch to “Endless or with breaks” and compare how many people are still there after 80 videos with a stopping point every 10, 20 or 30 videos. All numbers are model values.

Frequently asked questions

What is a variable reinforcement schedule?
A reinforcement schedule defines when a behaviour is rewarded. On a variable ratio the reward comes after a changing number of actions, for example after every fourth on average, but never predictably. In the lab this schedule produces particularly steady and persistent behaviour.
Why is it harder to stop when rewards are unpredictable?
If you have already experienced long stretches without a reward, you cannot tell another dry spell from the final end. On a fixed ratio the missing reward is noticed at once. That is why behaviour lasts longer after variable reward; the technical term is resistance to extinction.
Do breaks help when scrolling?
An endless feed has no natural stopping point. Notices like “You’re all caught up”, time limits or breaks create moments where you decide deliberately. In February 2026 the European Commission preliminarily asked a large short-video service, among other things, for effective screen-time breaks.
What can I try out in this app?
You compare a feed with fixed and one with variable reward and see how long 20 simulated people keep swiping after the last hit. In the second comparison you set the spacing of stopping points. The values are a model, not a measurement of people.

Subject: Film & media

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