A Variable Ratio (VR) schedule of reinforcementReinforcement is a fundamental concept in Applied Behavior A... provides reinforcement after an unpredictable number of responses. The exact number of responses needed for reinforcement varies, but it averages out over time. This type of schedule is known to produce a high and steady rateRate refers to the number of times a behavior occurs within ... of responding because the individual does not know when the next reinforcement will come.
Example
A slot machine in a casino operates on a variable ratio schedule. A player might win after pulling the lever 5 times, then 20 times, then 10 times. The number of lever pulls required to win (reinforcement) is unpredictable, which keeps the player engaged and continuously responding.