Variable Interval Reinforcement (Examples)

It’s always nice to be recognized for good work, even if that recognition or reward comes at random times. Some people appreciate only receiving praise or rewards randomly. Accountability in the form of surprise check-ins keeps many people on their toes, working to the best of their ability at all times. 

This isn’t the only way to encourage good behavior, but health inspections, pop quizzes, and other forms of variable interval reinforcement can work. Whether you are trying to lock in a new habit or motivate your students to study every night, this reinforcement schedule is one of a handful that is available for your use.

Curious about variable interval reinforcement and other ways to encourage behavior? Keep reading! 

What is Variable Interval Reinforcement? 

Variable interval reinforcement is a schedule in which reinforcements are distributed at varying intervals of time, depending on whether or not the desired behavior has been performed. These intervals may be completely random or within a range of times, but they are not fixed.

Who “Discovered” Variable Interval Reinforcement? 

B.F. Skinner is considered by many to be the “father of operant conditioning” and also the first to write about reinforcement schedules. His experiments were mostly conducted on animals rather than humans, in what psychologists now call the “Skinner box.” Even though these experiments largely took place in a small, contained area, reinforcement schedules can be used on humans, in large groups, across the globe!

What Are Reinforcements? 

In case you have not recently read up on other concepts in behaviorism, here is a quick refresher. Reinforcements strengthen a conditioned response. Let’s say you want to condition a child to respond to getting up by immediately making their bed. It’s great if they can do this on their own, but reinforcement will help encourage that behavior again and again. 

Reinforcements aren’t necessarily rewards. Positive reinforcements, or the things given to a subject after their conditioned response, are typically rewards. Giving a child a candy bar or access to their laptop are forms of positive reinforcement. Negative reinforcements can also strengthen conditioned responses; these are things taken away from the subject. Turning off a high-pitched sound or an uncomfortable harness after an animal completes a conditioned response are both considered negative reinforcements. 

To psychologists, this system of reinforcements and behavior is one way to approach operant conditioning. Operant conditioning is a process in which reinforcements or punishments are used to consciously encourage (or discourage) behavior. Reinforcement can happen through many approaches or schedules, including the variable interval reinforcement schedule. 

Variable Interval Reinforcement vs. Continuous Reinforcement 

Variable interval reinforcement is a partial schedule of reinforcement, as opposed to a continuous set of reinforcement. Not every behavior is immediately reinforced. A kid could spend their whole day choosing to study instead of playing video games, but they are not going to be rewarded for every minute or hour that they study. Reinforcements are given seemingly at random. 

Real-Life Examples of Variable Interval Reinforcement 

Not everyone who schedules this type of operant conditioning knows that they are operating on a variable interval reinforcement schedule, but it works just the same. Some of the most commonly used forms of variable interval reinforcement include:

  • Health inspections
  • Pop quizzes
  • Speed traps or DUI checkpoints 
  • Verbal praise
  • Random gifts 

1) Health Inspections

One classic example of variable interval reinforcement is having a health inspector or secret shopper come into a workplace. Store employees or even managers may not know when someone is coming in to inspect the store, although they may know it’s happening once a quarter or twice a year. The secret shopper goes into the business, interacts with employees, and sends a report back about their experience. If the employees did their job well, they might get a bonus or just congratulations from managers.

a health inspector visits a restaurant randomly

2) Pop Quizzes

Another classic example of variable interval reinforcement is a pop quiz. Teachers won’t tell students when these pop quizzes will happen, so students are expected to pay attention and study throughout the week, month, or semester. If the student has displayed this good behavior, they will likely get an A on their quiz and their grade will go up. 

3) Speed traps and DUI checkpoints

Not all reinforcements have to be a reward. Things may also be removed from a situation in order to encourage certain behaviors. One example is speed traps and DUI checkpoints. These “traps” are set up at various times, dates, and places along the highway. The stress of running into one of these traps is always lingering over drivers, especially in states where these traps are common. But if you aren’t speeding or you encounter a checkpoint with a blood alcohol content below the legal limit (.08,) that stress will be removed and you will be free to go. 

4) Verbal Praise 

You may be able to think about a time when your parent walked into your room, saw you studying for school instead of goofing off, and told you they were proud of you. That praise feels great! Of course, no parent offers this praise every time they see their child doing well; they might be too tired or distracted to do so. Verbal praise likely comes at varying intervals. It’s still a form of variable interval reinforcement, even if there is less intention behind the reinforcement.

giving praise as a reinforcement

5) Random Gifts 

Maybe your parents decided one day that, because you’ve been practicing the violin a lot, they are going to buy you a ticket to a concert that you’ve been wanting to go to. They can’t buy you a concert ticket every time you play the violin or they will go into debt! Small reinforcements like this likely encouraged you to continue that good behavior, even though you don’t know exactly when you’ll get another “treat” or reward like the ones you’ve received in the past. 

Does Variable Interval Reinforcement Work? 

Psychologists have found that this variable interval reinforcement schedule can increase the likelihood that a behavior will be formed, especially when reinforcements are frequent. This reinforcement schedule definitely keeps subjects on their toes! However, this is more effective for humans than animals. Animals may not connect a reinforcement to behavior that happened one week or one day or even two minutes prior. 

Running into a DUI checkpoint is a strong motivator to stay sober or have a designated driver. Random health inspector visits are a strong motivator to keep your restaurant clean. If you know that you are going to run into a speed trap at some point during the week, you are more likely to drive the limit than you would if speed traps only were set once a year. But distributing treats to dogs at random times is not likely to be effective unless the dog can immediately connect the treat with good behavior. Dogs don’t have long attention spans, so good luck with that!

Even in humans, there is a brief dip in performance once the behavior is reinforced; but overall, the rate of performing the behavior remains steady. 

What Is the “Best” Reinforcement Schedule? 

Subjects are most likely to perform a behavior if reinforcement is administered every time, but continuous reinforcement is not always possible or practical. Costs, time, and other factors play into how often reinforcements can and will be distributed. Of the partial reinforcement schedules, the variable ratio is a pretty solid reinforcement schedule. (No wonder slot machines so popular!) Factors like the reinforcement itself, the conditioned response, and the ratio or intervals themselves may also play a role in how likely the subject will perform a behavior. If you only give a child a small amount of allowance once a year for making their bed, they are not likely to make it every day. If that allowance becomes a trip to an amusement park, the child may be more motivated. 

How to Use Variable Interval Reinforcement In Training

If you want to encourage your child to do their homework or encourage your employees to greet every customer, consider a variable interval reinforcement. Pick a random date of the year to check up on your “subjects” and see if they are performing the behaviors you expect. If they are, provide a reward that is memorable and motivating. 

For example, if you want your child to keep their room clean, let them know that you’re going to enforce “surprise inspections” of their room. Tell them what reinforcement you will share ahead of time. Allowance? A new video game? The latest iPhone? When you share the reinforcement ahead of time, your child will know the stakes and be more motivated to clean their room. Pick a number at random – maybe six – and remind yourself to check on their room in six days. Don’t wait too long! 

You may have a harder time setting this schedule for yourself because you can’t surprise yourself, but this is where an accountabilibuddy or a trainer can come in handy. Tell them about a variable interval reinforcement and ask them to incorporate it into your meetings or training sessions. Share the reinforcements that will motivate you to stick to your goals. You might find yourself behaving better than you did before!

Other Schedules of Reinforcement 

Does reinforcement have to be distributed at various intervals? Not necessarily! Psychologists have identified variable interval reinforcement as one of four main partial schedules of reinforcement. The other partial reinforcement schedules are: 

  • Fixed Interval Reinforcement
  • Fixed Ratio Reinforcement
  • Variable Ratio Reinforcement 

partial reinforcement schedules

Fixed Interval Reinforcement 

When reinforcements are distributed at the same time of day, the same day a week, or after a fixed passage of time, psychologists call it a “fixed interval reinforcement.” One example of fixed interval reinforcement is offering an allowance at the end of the week if a child has completed their chores. Even if there is just one chore on the list and the child completes it one hour before “time is up,” they will still receive the reinforcement. 

Fixed Ratio Reinforcement 

Schedules may also rely on how many times the response is recorded. If you give out a reward once your child logs five hours of studying, for example, you are working on a fixed-ratio reinforcement schedule. The most common example of this type of reinforcement is a rewards cards at coffee shops or other retail locations. Buy nine coffees, get one free!

Variable Ratio Reinforcement 

You can also go by a variable ratio reinforcement schedule. This type of schedule distributes reinforcements at various ratios. Sometimes, the reinforcement is given after two of the same conditioned responses are performed. Other times, you have to perform the response 100 times to receive the reinforcement. Slot machines are a great example of variable ratio reinforcement. Gamblers are encouraged to keep pulling the lever with the hopes that the reinforcement will be distributed next time. 

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