Variable-interval reinforcement is characterized by which of the following?

Variable-interval reinforcement is indeed characterized by rewards being provided at unpredictable time intervals. This type of reinforcement schedule means that the individual cannot predict when the next reward will occur, making it difficult to gauge exactly when to expect a response. This unpredictability can lead to a steady and consistent rate of response, as the individual continues to engage in the behavior in hopes of receiving a reward.

For instance, in a situation where a person receives a paycheck at random times rather than at fixed intervals, they are likely to continuously put in effort, much like a gambler who plays a slot machine without knowing when the next payout will occur. This schedule is effective in maintaining behavior over time, as the element of chance keeps individuals engaged.

The other choices describe different types of reinforcement schedules. One describes a fixed ratio schedule, where rewards are given after a set number of responses; another describes a fixed interval where a reward is given after a specific time; and the last option suggests a fixed schedule where rewards are delivered after a predefined duration. These descriptions do not align with the nature of variable-interval reinforcement, which emphasizes the unpredictability of the timing of rewards.