Variable ratio reinforcement schedule is when reinforcement occurs on average after every nth response. Which option correctly describes this?

• A. After a fixed number of responses
• B. After a fixed time
• C. On average after every nth response
• D. After a fixed percentage of responses

Answer: (C)

Reinforcement occurs after an unpredictable number of responses, with the average number of responses around a specified value. That means you might get a reward after 1, then after 5, then after 2, but over time the average approaches the target nth response. This unpredictability keeps responding high and steady because you never know exactly when the next reward will come, and it also makes the behavior harder to stop if rewards cease. The other descriptions describe different schedules: a fixed number of responses is a fixed-ratio schedule, a fixed time is a fixed-interval (or fixed-time) schedule, and a fixed percentage of responses refers to a different, non-variable percentage-based setup.