In a fixed interval schedule, reinforcement is provided after what occurs?

In a fixed interval schedule, reinforcement is contingent upon the first response occurring after a predetermined amount of time has passed. This means that there is a specific timeframe that must elapse before reinforcement can be delivered, and the reinforcement is given only when the first response is made after that time period.

For example, if a rat is on a fixed interval schedule of 30 seconds, it will only receive reinforcement after it makes its first response following the completion of that 30-second interval. This type of schedule tends to produce a "scalloped" response pattern, where the subject may respond more frequently as the time for reinforcement approaches, reflecting an understanding of the delay before reinforcement is available.

This is in contrast to the other choices: reinforcement given after every response would characterize a continuous reinforcement schedule, a random time interval refers to a variable interval schedule where the timing of reinforcement varies unpredictably, and a set number of responses points to a fixed ratio schedule where reinforcement is provided after a specific number of responses. Each of these alternatives has distinct characteristics that differentiate them from the fixed interval schedule.