What is the difference between fixed-interval and fixed-ratio reinforcement schedules? Give a few examples of each.
With a schedule of fixed ratio, reinforcement is unforeseen on a predictable, fixed number of responses. For example, on a schedule with fixed ratio of 10 (abbreviated as FR 10), a rat will press the lever 10 times in order to obtain the pellet of food.
Likewise, when a person is earning one dollar for every 5 carburetors put together on a line would be an example of FR 5 schedule, whereas earning the same amount of money for every carburetors would be an example of FR 1 schedule.
FR 1 schedule is also termed as continuous reinforcement (CRF) where every response will be reinforced. Therefore, such kind of schedule is appropriately termed as either a CRF or an FR 1 schedule.
A response with high rate is usually produced in FR (fixed ratio) schedules accompanied with a brief pause chasing the attainment of every reinforcer. Such a kind of brief pause is termed as postreinforcement pause.
For example, a rat on a schedule of FR 20 will briskly press the lever 20 times, will eat the food it will receive and then roam around inside the chamber for a short period of time before briskly pressing the lever again for 20 times.
The rat would take a brief break chasing every reinforcer, in much the similar way, as a student might go for brief breaks after reading every chapter in a book, or during the completion of a specific assignment.
Every pause if generally chased by an approximately fast return to a higher response rate. Therefore, a common FR pattern would be characterized as “break-and-run” pattern-a brief break chased by a constant responses run.
On a schedule of fixed interval (FI), reinforcement is unforeseen on the first response followed by a predictable, fixed period of time. If a rat on a schedule of FI 50-sec, the first press of the lever followed by a 50 sec interval would result into the pellet of food.
Ensuing that, another 50 second should pass before the press of lever would result into the pellet of food again. Any pressing of the lever occurring during the interval, that is, before the time of 50 sec would elapse, will be ineffective.
Likewise, trying to make a call to a business firm which is yet to be opened and would open in exactly 20 minutes will be ineffective if called during the interval of those 20 minutes. The call would be effective only after the elapse of 20 minutes.
Schedules on fixed intervals (FI) generally result into an upwardly curved (or scalloped) responding pattern, which consists of a pause of postreinforcement followed by a gradual increase in the response rate as the interval moves closer to its closure.
For example, a rat scheduled on an FI 40-sec schedule would show no pressing of the lever in the beginning of the 40 sec interval. It would be followed by a less temporary pressing of lever in the midway of the interval, with the slowly elevating response rate afterwards.
When the interval has moved forward for its closure and the reinforcer is immediate, the rat would emit a higher response rate, such that the reinforcer is attained immediately it is available.