Free · 2026 · ABA and psychology Schedules of reinforcement: fixed ratio, variable ratio, fixed interval and variable interval, with a simulator
Schedules of reinforcement are the rules that decide which responses get reinforced: every response (continuous reinforcement) or only some (intermittent, or partial, reinforcement). The four basic intermittent schedules come from two choices: count responses (ratio) or time (interval), and keep the requirement fixed or let it vary around an average. A fixed ratio (FR) schedule reinforces after a set number of responses, such as every 5th; a variable ratio (VR) schedule after a number that varies, like a salesperson's sale after an unpredictable number of calls. A fixed interval (FI) schedule reinforces the first response after a set time, such as 2 minutes; a variable interval (VI) schedule the first response after a time that varies, like checking your phone for a reply. Ratio schedules produce faster responding than interval schedules, and variable schedules produce steadier responding than fixed ones, so VR gives the highest, steadiest rates and the most resistance to extinction. In ABA, continuous reinforcement teaches a new skill and the schedule is then thinned to an intermittent one to keep it, which is part of task C.1 on the RBT Test Content Outline. Below: the four schedules compared with examples, what each looks like on a cumulative record, a simulator to try each one, and a free 14-question drill with answers.
- FRFixed ratioAfter a set number of responses.
- VRVariable ratioAfter a number of responses that varies around an average.
- FIFixed intervalThe first response after a set time has passed.
- VIVariable intervalThe first response after a time that varies around an average.
Fixed ratio vs variable ratio vs fixed interval vs variable interval
Two questions name any schedule: does reinforcement depend on how many responses (ratio) or how much time has passed (interval)? And is the requirement the same every time (fixed) or does it change around an average (variable)?
| Schedule | Reinforcer comes | Response pattern | Everyday example | ABA example |
|---|---|---|---|---|
| Fixed ratio (FR) | After a set number of responses | High rate, with a pause after each reinforcer (the post-reinforcement pause) | A worker is paid $10 for every 5 boxes packed. | A token after every 3 correct answers (FR 3). |
| Variable ratio (VR) | After a number of responses that varies around an average | The highest, steadiest rate, with almost no pauses; the most resistant to extinction | A salesperson makes a sale after an unpredictable number of calls. | Praise after about every 4th correct answer, never knowing which one (VR 4). |
| Fixed interval (FI) | The first response after a set time has passed | A "scallop": little responding right after reinforcement, speeding up as the time runs out | Only the first oven check after the 30-minute bake finds the cake done. | The first hand raise after each 5 minutes earns a token (FI 5 min). |
| Variable interval (VI) | The first response after a time that varies around an average | A moderate, steady rate without pauses | Checking your phone for a reply: the first check after it lands is reinforced. | The teacher checks work at unpredictable times, about every 5 minutes on average (VI 5 min). |
| Schedule | Rule | Used for |
|---|---|---|
| Continuous reinforcement (CRF) | Every response is reinforced (the same as FR 1) | Teaching a new skill: fast learning, but fast extinction once reinforcement stops |
| Extinction (EXT) | No response is reinforced | Reducing a behavior that used to be reinforced |
| Fixed time / variable time (FT / VT) | The reinforcer comes on a timer, with no response needed | Noncontingent reinforcement (NCR). Not an interval schedule: interval schedules need a response |
What each schedule looks like on a cumulative record
A cumulative record is a graph of total responses over time: the line climbs with every response and stays flat when there are none, so a steeper line means faster responding. Ferster and Skinner used it to show that each schedule leaves its own shape. The ticks mark reinforcers. These are idealized drawings on one shared scale.
Try it: the schedule simulator
Pick a schedule and press the button for 20 seconds to earn points. Your own cumulative record draws as you go. Try all four and compare the table at the end: most people press far more on the ratio schedules and learn to wait on fixed interval.
Fixed ratio (FR 5). Every 5th press earns a point. You have 20 seconds; the clock starts on your first press.
Schedules of reinforcement in ABA
In ABA, a new skill starts on continuous reinforcement, because reinforcing every correct response teaches fastest. Once the skill is learned, the BCBA thins the schedule step by step (every response, then every 2nd, then about every 4th) so the skill keeps going with less reinforcement, closer to how it's reinforced in everyday life, and holds up when reinforcement is missed. That is maintenance rather than acquisition (task C.9). Thinning too fast can make the skill fall apart, so RBTs follow the schedule the plan sets.
Schedules matter for problem behavior too. A behavior that was reinforced only sometimes (an intermittent schedule) is harder to extinguish, which is why giving in now and then during an extinction burst makes it last longer. And reinforcement on a timer with no response needed (fixed time) isn't an interval schedule at all: it's noncontingent reinforcement, an antecedent intervention, compared with DRO on our differential reinforcement page.
Name the schedule: 14 practice questions with answers
Everyday and ABA scenarios like the ones on the RBT exam and in intro psychology. The reason shows after each answer.
Question 1 of 14 · 0 right so far
A garment worker is paid $5 for every 10 shirts sewn. Which schedule is this?
Schedules of reinforcement on the RBT exam
On the 3rd edition RBT Test Content Outline, Behavior Acquisition is 19 of the 75 scored questions. Task C.1 covers delivering reinforcement immediately, contingently and according to schedules of reinforcement, and C.9 covers telling maintenance apart from acquisition. Expect scenarios that ask which schedule a plan describes, or why a schedule is thinned.
- Ratio counts responses; interval counts time. "Every 5 minutes" is interval; "every 5 responses" is ratio.
- Interval schedules still need a response: the first one after the time passes. A reinforcer on time alone is fixed time (NCR).
- Variable means the requirement changes around an average; it isn't random or unplanned.
- Continuous reinforcement (FR 1) is for teaching; intermittent schedules are for keeping a skill.
- The scallop is FI; the post-reinforcement pause is FR.
- VR, not FR, is usually the most resistant to extinction.
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Schedules of reinforcement FAQ
What are the 4 schedules of reinforcement?
Fixed ratio (FR): reinforcement after a set number of responses. Variable ratio (VR): after a number of responses that varies around an average. Fixed interval (FI): the first response after a set time. Variable interval (VI): the first response after a time that varies around an average. They are the four basic intermittent schedules; continuous reinforcement, where every response is reinforced, is the other end.
What is the difference between ratio and interval schedules?
Ratio schedules count responses: the more you respond, the sooner reinforcement comes, so they produce high rates. Interval schedules count time: reinforcement comes for the first response after a time passes, so responding faster doesn't bring it sooner, and rates are lower.
What is the difference between fixed and variable schedules?
A fixed schedule keeps the same requirement every time (every 5th response, every 2 minutes). A variable schedule changes the requirement around an average, so the next reinforcer is unpredictable. Variable schedules produce steadier responding, without the pauses fixed schedules show.
Which schedule of reinforcement is most resistant to extinction?
Variable ratio, in most accounts. More broadly, any intermittent schedule makes a behavior more resistant to extinction than continuous reinforcement, because the learner is used to responses that don't pay off (the partial reinforcement extinction effect).
What is an example of a variable ratio schedule?
A salesperson who makes a sale after an unpredictable number of calls, or a learner praised after about every 4th correct answer. The classic textbook example is a slot machine, which pays out after an unpredictable number of plays.
What is continuous reinforcement?
Continuous reinforcement (CRF) reinforces every response; it's the same as FR 1. It's the fastest way to teach a new behavior, but the behavior also stops quickly when reinforcement stops, so in ABA the schedule is thinned to an intermittent one once the skill is learned.
What is intermittent reinforcement?
Intermittent (partial) reinforcement reinforces only some responses. Fixed and variable ratio and interval schedules are the basic kinds. It keeps a learned behavior going and makes it more resistant to extinction than continuous reinforcement.
What is a cumulative record?
A cumulative record is a graph of the total number of responses over time. The line rises with each response and stays flat when there are none, so a steeper line means faster responding. Skinner used it to show each schedule's pattern, such as the FI scallop and the FR pause.
Sources, checked October 28, 2026: BACB: RBT Test Content Outline (3rd ed.) · Ferster & Skinner: Schedules of Reinforcement (1957) · Cooper, Heron & Heward: Applied Behavior Analysis (3rd ed., 2020). For study, not clinical guidance: in ABA, the supervising BCBA sets and thins reinforcement schedules, and RBTs follow the plan.