Fixed-Interval Schedule: Definition and Examples

A fixed-interval schedule of reinforcement is a reward system where someone gets a reward after a set amount of time passes, but only if they perform the desired behavior. A kid getting a weekly allowance for keeping their room clean is an example of a fixed-interval reinforcement schedule. They get a reward every seven days, but only if their room is at an acceptable level of cleanliness when it comes time to give the reward. 

Reinforcement schedules are ways to encourage certain behaviors by using rewards. The idea of reinforcement schedules was first introduced by the behavioral psychologist B.F. Skinner. Skinner discovered that different patterns of giving rewards could lead to different patterns of behavior. 

Along with fixed-interval schedules, there are several other types of reinforcement schedules, each with its own effect on how people or animals learn and maintain behaviors.

What Is a Fixed-Interval Schedule?

You can think of a fixed-interval schedule as similar to a timer that needs to run out before you can earn a reward. The key is the specific amount of time that must pass. The amount of time needed varies depending on the situation; it could be an hour, a week, or even a month. However, just waiting for the required time isn’t enough–you also need to perform the right behavior when the time is up to get your reward.

Let’s imagine this in a situation you might encounter while training your pet. Imagine you have a pet hamster that you’re training to press a lever. Using a fixed-interval schedule, you might set up the system so that pressing the lever only gives the hamster a treat once every 5 minutes. Even if your hamster presses the lever 100 times during those 5 minutes, it won’t get a treat until the time is up–and then, it still has to press the lever to receive the reward.

This makes fixed-interval schedules different from other types of reinforcement. For instance, they’re not like fixed-ratio schedules, where you get a reward after doing something a certain number of times (like getting a free coffee after buying 10). They also differ from variable-interval schedules, where the time between possible rewards changes unpredictably (like catching fish–you never know exactly when you’ll get a bite).

Examples of Fixed-Interval Schedules

You might not notice or be aware of them all the time, but fixed-interval schedules are all around us. One of the most common examples is getting a paycheck. Most people get paid every two weeks or once a month–it doesn’t matter how hard you work during that time, you’ll still get paid on the same schedule. However, the amount of time that passes isn’t the only factor; you do need to show up and do your job to receive that paycheck when payday comes around.

Students experience fixed-interval schedules through report cards and weekly quizzes. For example, a student who has a spelling test every Friday might not study much early in the week, but they’re more likely to start practicing their spelling words as Friday approaches. This pattern—where activity increases as the reward time gets closer–is super common with fixed-interval schedules.

Fixed-interval behavior can also be seen in social media use. Many people check their social media accounts at specific times, like during lunch breaks or right after work. They’ve learned that these times usually yield new posts or responses from friends. Similarly, many of us check our email at set intervals throughout the day, knowing that’s when we’re most likely to find new messages that need our attention.

People tend to show the same pattern in fixed-interval schedules. They’re most active right before the reward is due, but then there is a slowdown right after the reward is given.

Scientists call this the “scallop pattern” because if you drew it on a graph, it would look like the wavy edge of a scallop shell.

The Pattern of Response

When someone is on a fixed-interval schedule, they develop a distinctive response pattern. The most noticeable feature is what happens right after someone gets their reward: they tend to take a break or slow down. This “post-reinforcement pause” is perfectly normal. Think about how most people relax a bit right after payday, or how students might take it easy right after turning in a big project.

As time moves on, though, activity starts to pick up. The closer it gets to the next reward time, the more frequent or intense the behavior becomes. This creates what psychologists call the “scallop pattern.” Imagine a student with a test every Friday. They might do very little studying over the weekend, pick up the pace a bit by Wednesday, and then really hit the books on Thursday night. Sometimes, this might happen because people are procrastinating, but in many cases, it’s just a natural result of how the reward is timed. 

This pattern is really consistent across different situations and even different species. Whether it’s office workers approaching a deadline, animals in a laboratory experiment, or kids working toward allowance day, the same basic pattern appears: minimal activity after the last reward, followed by gradually increasing activity until the next reward is due.

The downside of this pattern is that it can lead to uneven effort.

In work settings, this might mean projects move slowly at first and then turn into a rush at the end. In learning situations, it could result in cramming rather than steady studying. Understanding this pattern helps us recognize when it’s happening and potentially adjust our approach when more consistent effort would be beneficial.

Strengths and Limitations

Fixed-interval schedules have their advantages, but that doesn’t mean they are right for every situation.

Strengths

Fixed-interval schedules can work really well in certain situations. For example, they’re often great for tasks that naturally take place in specific time periods, like weekly reports at work or regular homework assignments.

Using this type of schedule can help provide structure and predictability. That way, people are able to plan their time and know exactly when to expect rewards. This schedule also works well when it isn’t practical or possible to monitor the behavior constantly. A teacher can’t observe students studying every minute of the day, but they can test their knowledge weekly.

Potential Limitations

It’s essential to be aware of the drawbacks of a fixed-interval schedule. The biggest limitation is that performance tends to be really uneven. You’ll see lots of activity right before the deadline, followed by very little activity afterward. This “scallop pattern” isn’t always ideal, especially when you want steady, consistent behavior. 

For example, if you’re trying to learn a new language, studying for 30 minutes each day would be more effective than cramming for 3.5 hours once a week.

How to Make a Fixed-Interval Schedule Work

There are some things you can do to help use fixed-interval schedules effectively:

• Break longer intervals into shorter ones if you want more consistent behavior. Instead of one monthly review, try weekly check-ins.
• Combine fixed-interval schedules with other types of reinforcement. For instance, you might have both a weekly reward and surprise bonuses for exceptional work.
• Set reasonable time intervals. If the time between rewards is too long, motivation might drop too low. If it’s too short, the reward system might become impractical to maintain.
• Make sure the reward is meaningful enough to motivate the desired behavior. Small rewards might not be worth the effort, especially during the early part of the interval.

It’s important to remember that no reinforcement schedule is perfect for every situation. The key is to match your schedule to your specific goals and the type of behavior you are encouraging or teaching.

Key Takeaways

Fixed-interval schedules of reinforcement can help us understand how behaviors form and help us to teach new behavior. Whether in classrooms, workplaces, or our habits, these schedules influence how we behave and when we’re most likely to take action. Understanding that the “scallop pattern,” where we tend to increase our effort as a deadline approaches, is a natural response can help us better manage our time and effort.

Recognizing when we’re under a fixed-interval schedule and understanding its effects allows us to make better choices about approaching tasks and goals. That might involve breaking down longer intervals into shorter ones, combining different types of reward schedules, or simply being more aware of our natural response patterns. By understanding, this, we can gain more control over our behaviors and habits.

Sources:

Watson, S.T., Griffes, C. (2011). Fixed interval schedule. In: Goldstein, S., Naglieri, J.A. (eds) Encyclopedia of Child Behavior and Development. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-79061-9_1147