Which instance reflects a variable ratio schedule?

A variable ratio schedule is characterized by delivering rewards after an unpredictable number of responses or actions, creating a scenario in which reinforcement is not given at fixed intervals. In this case, offering free soup randomly at a restaurant fits this definition because customers do not know when they will receive the reward, creating sporadic and unexpected moments of reinforcement.

In contrast, cash rewards for participating in a survey represent a fixed reward tied directly to a specific action rather than a variable schedule of rewards. Every tenth purchase receiving a bonus reflects a fixed ratio schedule, as it is a predictable and consistent trigger for receiving the reward based on a set frequency. Monthly draws for gift cards have a fixed time aspect rather than a variable amount of responses, thereby also distinguishing them from a variable ratio schedule.