Final answer:
Slot machines operate on a variable ratio reinforcement schedule, where the number of responses (such as inserting quarters) before a reward varies and is unpredictable. This can lead to high engagement and is resistant to extinction, explaining gambling's addictive nature.
Step-by-step explanation:
The type of reinforcement at play with slot machines involves unpredictability as to when the reward will be given, which aligns with a variable ratio reinforcement schedule. In such a schedule, the number of responses (in this case, inserting quarters) required before a reward is issued varies. This is a powerful form of reinforcement because it is unpredictable, hence why it is highly addictive and resistant to extinction. Gamblers, like Christopher in the provided scenario, continue to insert quarters without knowing after how many quarters they might win, which keeps their behavior steady.
To compare, in a fixed ratio schedule, there is a set number of responses before a reward; in a fixed interval schedule, the behavior is rewarded after a set amount of time; and in a variable interval schedule, the rewards are given after an unpredictable amount of time has passed. Due to the slot machine's nature of providing unpredictable rewards based on the number of responses, the best answer is C. Variable-ratio schedule.