You post a photo and put your phone down. A minute later you pick it up again. Two likes. Then seven. That’s nice for about as long as it takes to read the number. What should you post next?
You wait, you get a result, you feel good for a second, you go again. Short videos, puzzle games and slot machines all run some version of this. The gaps differ, and so does what decides the result.
Likes change when you post
This one’s been measured. A Nature Communications study went through more than a million posts from over 4,000 users on Instagram and three online forums (two on fashion, one on gardening). People’s posting fit reward learning models: they posted more often after lots of likes and less often after few. A separate experiment with 176 people found the likes themselves were shaping the posting.
That’s a finding about when people post. It doesn’t say a like feels the same as any other reward.
Short video skips the wait
When you post, the wait comes from other people. Short video mostly gets rid of it. TikTok’s For You page lines the clips up in a sequence. You get bored halfway through, and swipe. The clip ends, and the next one is already waiting.
Take autoplay away and the feed feels different, at least in the lab. People in a preliminary study presented at CHI 2026 got explicit playback instead. They reported more control and estimated time more accurately.
One level, one spin
Candy Crush Saga takes longer. You get a goal, you play, and you either clear the level or go again. Then the next one shows up.
King treats that timing as a design problem. At GDC in 2024 it said longer levels are less likely to be fun, and that a really hard level should also be really short. It judges levels partly by how long players take to pass them or give up.
A slot machine squeezes the cycle tighter. You press spin. The reels run for a few seconds, which is the whole wait, then they stop. Experienced players on an authentic machine, tested in a lab, got through 10.5 to 16.6 spins a minute. That’s one every 3.6 to 5.7 seconds. Picture a slot game at an online casino in Saudi Arabia and the order doesn’t change: a press, a few seconds of reels, a result, and the button ready again.
From a distance, Candy Crush and a slot look alike. Up close they don’t. Your moves in a Candy Crush level change what happens. The goal is stated up front, and King even profiles player skill from wins, losses and attempts. A slot gives you nothing like that. The result comes from a random number generator. It is decided at the moment you press “spin”, and nothing you do affects whether it wins.
So one leans toward predictable achievement and the other toward uncertain reward. Neat, except a Candy Crush level can still beat you, so it isn’t fully predictable either. And none of this means they produce the same psychological or neurological response. What they share is timing and structure.
Uncertainty does seem to matter when it clears up fast. In a 2018 consumer study, people were more likely to repeat a task like running a lap for an uncertain reward than for a certain one, even when the certain one was worth more. That only held when they found out straight after each round.
Rings, stars and a unicorn
Designers build versions of this cycle elsewhere. That doesn’t mean they copied it from gambling.
Apple Watch is the predictable kind. Three Activity rings track daily goals for Move, Exercise and Stand, and you can change the goals. Stand counts the hours in which you stood for at least a minute. The ring fills as you go, so you always know how close you are. Close one and you may get an animation on the watch. Then the day ends and the rings start again. Apple stacks longer cycles on top, like a January 2026 award for closing all three rings seven days in a row.
Starbucks Rewards moves slower, more like a meter. Since the March 10, 2026 relaunch, you earn by level: 1 Star per dollar at Green, 1.2 at Gold, 1.7 at Reserve. A new 60-Star tier takes $2 off any item, so at Green that’s about $60 of spending for $2 off. Every purchase moves you a known distance. Not much suspense there.
Asana is odder. Ticking off a task is already a visible milestone. Turn on its optional celebrations and a unicorn might cross your screen as well, but not every time. So a routine click in project management software gets a small, unpredictable bit of feedback. The idea started as an April Fool’s joke. Later the unicorn got a team.
