Chapter 64. Schedules of Reinforcement

Learning Objectives

acquisition
learning a conditioned behavior; in operant conditioning, occurs when a behavior is followed by a reinforcer
continuous reinforcement
in operant conditioning, providing a reinforcer for every instance of the desired behavior
extinction
weakening or eliminating a conditioned behavior; in operant conditioning, occurs when the reinforcers are stopped
fixed-interval schedule
in operant conditioning, providing a reinforcer after a set time period, as long as the desired behavior occurred
fixed-ratio schedule
in operant conditioning, providing a reinforcer after a set number of behaviors
interval schedule
in operant conditioning, reinforcement is tied to the elapsed time since the previous reinforcer, as long as at least one instance of the desired behavior has occurred
learning
changing your behavior or your knowledge as a result of experience
operant chamber
a controlled environment for operant conditioning research, containing a bar or key that an animal can press to receive a reinforcer
operant conditioning
type of learning in which a behavior is influenced by the favorable or unfavorable consequences that follow it
partial reinforcement
in operant conditioning, providing a reinforcer for some, but not all, of the desired behaviors
ratio schedule
in operant conditioning, reinforcement is tied to the number of desired behaviors
reinforcer
in operant conditioning, a pleasant consequence that increases the frequency of the behavior it follows
reinforcement
in operant conditioning, applying a pleasant consequence to strengthen a behavior
variable-interval schedule
in operant conditioning, providing a reinforcer after a varying (unpredictable) time period, as long as the desired behavior occurred
variable-ratio schedule
in operant conditioning, providing a reinforcer after a varying (unpredictable) number of behaviors
Schedules of Reinforcement
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Learning Objectives:

Understand the difference between continuous and partial reinforcement.

Describe the four schedules of partial reinforcement.

Review

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1. Real life does not provide continuous reinforcement for learned behaviors. Instead, behaviors are typically rewarded on a partial reinforcement schedule, in which responses are sometimes reinforced, and sometimes not. The principles of operant conditioning predict that the type of reinforcement schedule will influence the rate of learning and the frequency of the behavior.

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2. Partial reinforcement, also called intermittent reinforcement, generally produces slower initial learning (also called acquisition), but the behavior is more resistant to extinction.

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3. In real life and in the laboratory, partial reinforcement is administered according to either a ratio schedule (which counts the number of behaviors) or an interval schedule (which counts the passage of time).

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4. Fixed-ratio schedules reinforce behavior after a set number of responses, while variable-ratio schedules provide reinforcers after an unpredictable number of responses. In this illustration, each response is shown in gray, and the reinforcers are shown as red squares.

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5. With fixed-interval schedules, reinforcement is given for the first response that occurs after a fixed period of time has elapsed, while variable-interval schedules reinforce the first response after varying time intervals. In this illustration, each response is shown in gray, and the reinforcers are shown as red squares.

Practice 1: Introduction to the Schedules

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Practice 1: Introduction to the Schedules

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In the laboratory and in real life, behavior is usually reinforced intermittently, according to the four schedules listed above. The rat in this operant chamber (also called a "Skinner box") is being trained to press a bar; the training is reinforced with food pellets.


On the next pages, you will see four simulations illustrating how each of the schedules of reinforcement influences the rat’s behavior.

Practice 2: Fixed-Ratio Schedule

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Practice 2: Fixed-ratio Schedule

Select the PLAY button to watch the rat’s behavior when being reinforced on a fixed-ratio schedule of reinforcement.

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This rat is being reinforced with 1 food pellet for every 5 bar presses. That means the first time the rat presses the lever, nothing will happen—and the same is true for presses 2, 3, and 4. But on press 5, a pellet of food will slide down the dispenser. Then, the counter starts again, and the apparatus rewards the rat for every fifth press.

Practice 3: Variable-Ratio Schedule

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Practice 3: Variable-ratio Schedule

Select the PLAY button to watch the rat’s behavior when being reinforced on a variable-ratio schedule of reinforcement.

Variable-ratio
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This rat is being reinforced with 1 food pellet for an average of 3 bar presses. Sometimes, the food pellet will appear the very first time the rat presses the lever, but at other times, the rat will be reinforced after press 2, 3, 4, or 5. Over the course of several minutes, the rewards will average out to one for every three presses—but the timing is unpredictable.

Practice 4: Fixed-Interval Schedule

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Practice 4: Fixed-interval Schedule

Select the PLAY button to watch the rat’s behavior when being reinforced on a fixed-interval schedule of reinforcement.

Fixed-interval
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This rat is being reinforced with 1 food pellet for the first bar press during every 4-minute time period. The first time the rat presses the lever, a food pellet appears. But, no matter how many times the rat presses after that, the next reward will not appear until 4 minutes have passed. Then, the timer resets, and the cycle repeats.

Practice 5: Variable-Interval Schedule

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Practice 5: Variable-interval Schedule

Select the Play button to watch the rat’s behavior when being reinforced on a variable-interval schedule of reinforcement.

Variable-interval
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This rat is being reinforced with 1 food pellet for the first bar press during a variable time period that averages 3 minutes. Sometimes, the interval will be 1 or 2 minutes, but at other times, it will be 4 or 5 minutes. The interval is unpredictable, but the rat must press the bar at least once during the interval in order to get the reward.

Quiz 1

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Quiz 1

Drag each of the terms for reinforcement schedules to the area in front of of the appropriate description. When all the schedules have been placed, select the CHECK ANSWER button.

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Reinforcement occurs after an unpredictable number of responses.

Reinforcement occurs after a specified number of responses.

Reinforcement occurs after a specified amount of time.

Reinforcement occurs after an unpredictable time period.

Quiz 2

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Quiz 2

Match the terms to the situations by dragging each colored circle to the appropriate gray circle. When all the circles have been placed, select the CHECK ANSWER button.

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Rat is rewarded with 1 food pellet for first bar press after an average of 3 minutes.
Rat is rewarded with 1 food pellet for every 4 bar presses.
Rat is rewarded with 1 food pellet after an average of 7 bar presses.
Rat is rewarded with 1 food pellet for first bar press after every 5 minutes.

Conclusion

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