What defines interval schedules of reinforcement?

Interval schedules of reinforcement are characterized by the fact that reinforcement is delivered after a specified period of time has elapsed, as long as the desired response has occurred. This can encourage behaviors that are more likely to happen at particular intervals rather than after a certain number of responses.

For example, in a fixed interval schedule, a response is reinforced only after a fixed amount of time has passed, such as receiving a paycheck every two weeks. In a variable interval schedule, reinforcement is provided after unpredictable amounts of time, such as checking for a text message or email at varying intervals.

The other options do not accurately describe interval schedules. While "require a number of responses" refers to ratio schedules, which depend on the number of responses instead of time, "always change" does not specifically relate to interval schedules as they can be either fixed or variable. Lastly, "based on the number of consequences" misrepresents the timing aspect that is essential to interval schedules.