A schedule of reinforcement is the rule that decides when a behaviour gets rewarded. B.F. Skinner charted them on a cumulative recorder — the scrolling pen you see here. Its slope is the response rate; each short mark is a payout.
Reward every N actions (fixed-ratio) and you get bursts with a pause after each payout. Reward the first action after a set time (fixed-interval) and you get the tell-tale scallop: a long pause, then a rush toward the deadline.
Reward on a random schedule — variable-ratio, the slot machine and the loot box — and the behaviour becomes fast, steady, and remarkably hard to stop. The brain rewards surprise, and an unpredictable payout stays surprising no matter how long you play.
That is why variable-ratio is the most extinction-resistant schedule: cut the rewards and a variable-ratio habit keeps going long after a predictable one would quit. Knowing this is the ethical line every monetisation designer has to decide where to draw.
This lab hit a snag — the lesson continues without it.