Regarding understanding behavior, psychologists have a secret weapon: reinforcement. The influential B.F. Skinner realized that we can shape behavior through consequences. He termed this “operant conditioning.”
A key component is the “reinforcement schedule” – when and how often rewards are given. Today, we’ll zero in on one schedule: the fixed interval. Like clockwork, this schedule delivers rewards at set intervals. Understanding this schedule helps uncover the inner workings of behavior.
What Is a Fixed Interval Schedule
For example, on a fixed interval 30-second schedule, a reward would be provided every 30 seconds, regardless of the number of responses. An animal on this schedule would learn to respond rapidly just before the next scheduled reward.
Fixed interval schedules produce predictable “scalloped” patterns of responding. There is a pause after reinforcement until the next interval begins, followed by a high response rate as the time for the next reward approaches. The high response rate continues until the delivery of the next reinforcer.
In everyday life, many activities happen on a fixed interval schedule. For example, receiving a paycheck every two weeks or checking social media feeds every 10 minutes. Fixed interval schedules help maintain behaviors over long periods without continuous reinforcement.
Characteristics of Fixed Interval Schedules
Fixed interval schedules involve reinforcing after a set amount of time has passed, no matter how many responses have occurred. This type of schedule produces a characteristic pattern of responding, such as:
- There is a high response rate near the end of the interval as the subject anticipates the upcoming reinforcement.
- Earlier in the interval, there is typically a lower response rate. This is because the subject knows reinforcement will not come until the interval has elapsed.
- The overall response rate remains fairly consistent over many intervals and trials. Subjects adjust their pattern of responding to match the fixed interval.
Some key characteristics of fixed interval schedules are:
- Reinforcement is delivered after a set amount of time has passed, no matter how many responses occur.
- The timing of reinforcement delivery is predictable.
- There are high response rates near the end of the interval but lower rates earlier.
- Overall response rates remain steady across many intervals.
- Behavior is persistent since reinforcement is guaranteed after the interval elapses.
Examples of Fixed Interval Schedules
Let’s look at some real-world examples to understand better how fixed interval schedules work:
- Paychecks: Most people receive paychecks on a fixed interval, such as every two weeks or twice a month. The paycheck arrives at the same fixed interval, no matter how much or little they work during those two weeks. This is a fixed interval reinforcement schedule.
- Quizzes/tests in school: Students typically take quizzes or tests on a fixed interval schedule, such as every Friday or at the end of every chapter. The opportunity to earn points arrives at a fixed time. This motivates students to study consistently.
- Subscriptions/memberships: Services like magazines, streaming sites, or gym memberships operate on a fixed interval. You pay the subscription fee each month and gain access to the benefits, regardless of how much you use them. The reward comes on a fixed schedule.
- Performance reviews: Many companies conduct annual or bi-annual performance reviews on a fixed schedule. Employees know when to expect their next review, which motivates them to work hard leading up to it in hopes of earning a positive evaluation, promotion, or raise. The fixed interval schedule creates an incentive.
Examples in Psychology
Fixed interval schedules have been studied extensively in psychology, particularly behavioral psychology and operant conditioning experiments. Some key examples include:
1. Animal Research
Many early experiments on fixed interval schedules were done with pigeons and rats. In a classic experiment, B.F. Skinner used a fixed interval schedule to deliver food to pigeons.
He found that the pigeons would rapidly increase their rate of pecking on the keys as the time for reward delivery approached. Rats pressing levers for food rewards have shown similar response patterns under fixed-interval schedules.
2. Token Economies
Token economies use conditioned reinforcers, or tokens, that can later be exchanged for other rewards. Points, stars, chips, or fake money are common tokens.
Patients can earn tokens on a fixed interval schedule in institutions like psychiatric hospitals, schools, or prisons by demonstrating desired behaviors. They can later exchange the tokens for privileges, goods, or services.
3. Addiction Treatment
Research has explored using fixed-interval schedules of methadone delivery to treat heroin addiction. Methadone helps reduce cravings and withdrawal symptoms.
Providing methadone doses at fixed intervals rather than allowing people with an addiction to self-administer has been found in some cases to reduce illicit opiate abuse. The predictability of the dosing in a clinic may be beneficial.
Advantages of Fixed Interval Schedules
Fixed interval schedules have some key advantages that make them useful in many situations:
- Predictable reinforcement delivery: With fixed interval schedules, the reinforcement is delivered at predictable, regular intervals. This means that the subject (person, animal, etc.) can anticipate when the next reinforcer is coming. This predictability can help maintain consistent responses over time.
- Less strain on reinforcer source: In certain situations, the source of reinforcement may be limited or difficult to obtain. For example, financial bonuses or other rewards may have budget constraints in the workplace. With a fixed interval schedule, reinforcements are delivered periodically but consistently, putting less strain on the reinforcer source than continuous reinforcement.
- Lower supervision needed: Once a fixed interval schedule is implemented, it requires less effort and supervision. The reinforcer delivery happens automatically at the set intervals without the need for constant monitoring. This frees up supervisors and managers to focus on other tasks.
Disadvantages of Fixed Interval Schedules
Fixed interval schedules have some potential drawbacks to consider:
- Pause after reinforcement: There is often a pause in responding right after the reinforcement is delivered on a fixed interval schedule. This makes sense – if the organism knows that the next reinforcement won’t come until the interval has passed again, it may take a break immediately following reinforcement.
- Inefficient use of time: With fixed intervals, there are often periods of very low response rates at the beginning of the interval, followed by higher rates toward the end. This means that the early portion of each interval is not used efficiently.
- Higher rates closer to reinforcement: As the next reinforcement gets closer, response rates accelerate. This scalloping pattern of low early and higher later rates makes the response inefficient overall.
How Does a Fixed Interval Schedule Differ from a Fixed Ratio Schedule?
Fixed interval and fixed ratio schedules are both methods of reinforcement in operant conditioning to influence an individual’s behavior. However, they differ in their key characteristics and how the reinforcement is delivered.
|Fixed Ratio Schedule
|Fixed Interval Schedule
|Involves reinforcing a specific number of responses.
|Involves reinforcing after a specific amount of time has elapsed.
|The salesperson gets a bonus for every 10th sale made.
|The employee receives a monthly paycheck, regardless of the work done.
|Tends to have a high response rate which increases as the individual gets close to meeting the required number of responses.
|Typically shows ‘scalloping behavior’ where responses increase as the time for reinforcement approaches and slow down immediately after.
|Best Used When
|Motivating individuals to produce high levels of work or responses consistently.
|Encouraging consistent work or responses over a set period.
Fixed Interval Schedule Vs. Variable Interval Schedule: What’s the Difference
Fixed interval schedules and variable interval schedules are two critical types of reinforcement schedules in operant conditioning. Let’s delve into understanding their distinctions.
As discussed above, in a fixed interval schedule, behaviors are reinforced after a certain time has passed. Since the time frame remains constant, individuals can predict when reinforcement is available.
In contrast, a variable interval schedule refers to a scenario where behavior is reinforced after an unpredictable or variable amount of time has passed. Because individuals cannot predict when the reinforcement will come, they repeat the behavior consistently.
This type of schedule leads to steady and consistent behavior, with fewer pauses after reinforcement because the next reinforcement could come at any time. Here’s a quick comparison:
|Fixed Interval Schedule
|Variable Interval Schedule
|The reinforcement is given after a fixed amount of time.
|The reinforcement is given after an unpredictable or variable amount of time.
|A student receives a grade at the end of each semester.
|Checking emails or social media. You don’t know when a new message will come, but you check regularly.
|Behavior tends to increase just before the next reinforcement is due – a pattern known as “scalloping”.
|Behavior tends to be steady because the exact timing of the next reinforcement is unpredictable.
|Used for behaviors that need to be done consistently but not continuously (e.g., monthly reports).
|Used for behaviors that must be done persistently and consistently (e.g., checking equipment for safety).
The Behavioral Influence of Fixed Interval Schedules
The fixed interval schedule is a powerful behavior modifier. It doles out rewards on a rigid timeline, motivating ever-escalating responses as the next payoff approaches. From monthly paychecks to semester grades, these predictable patterns permeate our lives, subtly shaping our actions and habits.
Though fixed intervals can promote “scalloping” and inactivity between reinforcements, their ability to elicit target behaviors is proven. In short, grasping this schedule illuminates operant conditioning’s intricate influence and the outsized impact of timing rewards on human conduct.