Which example below is an example of a VARIABLE RATIO schedule of reinforcement?

• A. Tim gives his students a treat from the candy jar every time they get a 100% on their tests
• B. Grandma loves the slots in Vegas! On average, every 30th pull of the slot machine results in a small cash payout. Sometimes the payout occurs on the 15th pull... sometimes on the 45th... but, on average, payout occurs every 30 pulls on the slot machine. Grandma can't wait to hit the jackpot someday!
• C. Individuals who pass the RBT exam are given a $50 bonus on their next pay check at ACME ABA company.
• D. Every time Billy screams, his mother punishes him by taking away his toys for the night

Answer: (B)

Variable ratio schedules reinforce after an unpredictable number of responses, with reinforcement occurring on average after a given ratio. The slot-machine example fits this best because payouts happen after a varying number of pulls—sometimes 15, sometimes 45—and on average about every 30 pulls. This unpredictability keeps the person responding at a high and steady rate because they don’t know when the next reward will come. The other scenarios illustrate different patterns: rewarding after every correct test is continuous reinforcement, not variable; giving a bonus after passing is a one-time, event-based reinforcement rather than an ongoing ratio schedule; punishing after every scream is a punishment schedule, not reinforcement.