Operant Conditioning

Basic Principles of Operant Conditioning: Thorndike’s Law of Effect

Thorndike’s law of effect states that behaviors are modified by their positive or negative consequences.

Learning Objectives

Relate Thorndike’s law of effect to the principles of operant conditioning

Key Takeaways

Key Points

  • The law of effect states that responses that produce a satisfying effect in a particular situation become more likely to occur again, while responses that produce a discomforting effect are less likely to be repeated.
  • Edward L. Thorndike first studied the law of effect by placing hungry cats inside puzzle boxes and observing their actions. He quickly realized that cats could learn the efficacy of certain behaviors and would repeat those behaviors that allowed them to escape faster.
  • The law of effect is at work in every human behavior as well. From a young age, we learn which actions are beneficial and which are detrimental through a similar trial and error process.
  • While the law of effect explains behavior from an external, observable point of view, it does not account for internal, unobservable processes that also affect the behavior patterns of human beings.

Key Terms

  • Law of Effect: A law developed by Edward L. Thorndike that states, “responses that produce a satisfying effect in a particular situation become more likely to occur again in that situation, and responses that produce a discomforting effect become less likely to occur again in that situation.”
  • behavior modification: The act of altering actions and reactions to stimuli through positive and negative reinforcement or punishment.
  • trial and error: The process of finding a solution to a problem by trying many possible solutions and learning from mistakes until a way is found.

Operant conditioning is a theory of learning that focuses on changes in an individual’s observable behaviors. In operant conditioning, new or continued behaviors are impacted by new or continued consequences. Research regarding this principle of learning first began in the late 19th century with Edward L. Thorndike, who established the law of effect.

Thorndike’s Experiments

Thorndike’s most famous work involved cats trying to navigate through various puzzle boxes. In this experiment, he placed hungry cats into homemade boxes and recorded the time it took for them to perform the necessary actions to escape and receive their food reward. Thorndike discovered that with successive trials, cats would learn from previous behavior, limit ineffective actions, and escape from the box more quickly. He observed that the cats seemed to learn, from an intricate trial and error process, which actions should be continued and which actions should be abandoned; a well-practiced cat could quickly remember and reuse actions that were successful in escaping to the food reward.

Thorndike’s puzzle box: This image shows an example of Thorndike’s puzzle box alongside a graph demonstrating the learning of a cat within the box. As the number of trials increased, the cats were able to escape more quickly by learning.

The Law of Effect

Thorndike realized not only that stimuli and responses were associated, but also that behavior could be modified by consequences. He used these findings to publish his now famous “law of effect” theory. According to the law of effect, behaviors that are followed by consequences that are satisfying to the organism are more likely to be repeated, and behaviors that are followed by unpleasant consequences are less likely to be repeated. Essentially, if an organism does something that brings about a desired result, the organism is more likely to do it again. If an organism does something that does not bring about a desired result, the organism is less likely to do it again.

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Law of effect: Initially, cats displayed a variety of behaviors inside the box. Over successive trials, actions that were helpful in escaping the box and receiving the food reward were replicated and repeated at a higher rate.

Thorndike’s law of effect now informs much of what we know about operant conditioning and behaviorism. According to this law, behaviors are modified by their consequences, and this basic stimulus-response relationship can be learned by the operant person or animal. Once the association between behavior and consequences is established, the response is reinforced, and the association holds the sole responsibility for the occurrence of that behavior. Thorndike posited that learning was merely a change in behavior as a result of a consequence, and that if an action brought a reward, it was stamped into the mind and available for recall later.

From a young age, we learn which actions are beneficial and which are detrimental through a trial and error process. For example, a young child is playing with her friend on the playground and playfully pushes her friend off the swingset. Her friend falls to the ground and begins to cry, and then refuses to play with her for the rest of the day. The child’s actions (pushing her friend) are informed by their consequences (her friend refusing to play with her), and she learns not to repeat that action if she wants to continue playing with her friend.

The law of effect has been expanded to various forms of behavior modification. Because the law of effect is a key component of behaviorism, it does not include any reference to unobservable or internal states; instead, it relies solely on what can be observed in human behavior. While this theory does not account for the entirety of human behavior, it has been applied to nearly every sector of human life, but particularly in education and psychology.

Basic Principles of Operant Conditioning: Skinner

B. F. Skinner was a behavioral psychologist who expanded the field by defining and elaborating on operant conditioning.

Learning Objectives

Summarize Skinner’s research on operant conditioning

Key Takeaways

Key Points

  • B. F. Skinner, a behavioral psychologist and a student of E. L. Thorndike, contributed to our view of learning by expanding our understanding of conditioning to include operant conditioning.
  • Skinner theorized that if a behavior is followed by reinforcement, that behavior is more likely to be repeated, but if it is followed by punishment, it is less likely to be repeated.
  • Skinner conducted his research on rats and pigeons by presenting them with positive reinforcement, negative reinforcement, or punishment in various schedules that were designed to produce or inhibit specific target behaviors.
  • Skinner did not include room in his research for ideas such as free will or individual choice; instead, he posited that all behavior could be explained using  learned, physical aspects of the world, including life history and evolution.

Key Terms

  • punishment: The act or process of imposing and/or applying a sanction for an undesired behavior when conditioning toward a desired behavior.
  • aversive: Tending to repel, causing avoidance (of a situation, a behavior, an item, etc.).
  • superstition: A belief, not based on reason or scientific knowledge, that future events may be influenced by one’s behavior in some magical or mystical way.

Operant conditioning is a theory of behaviorism that focuses on changes in an individual’s observable behaviors. In operant conditioning, new or continued behaviors are impacted by new or continued consequences. Research regarding this principle of learning was first conducted by Edward L. Thorndike in the late 1800s, then brought to popularity by B. F. Skinner in the mid-1900s. Much of this research informs current practices in human behavior and interaction.

Skinner’s Theories of Operant Conditioning

Almost half a century after Thorndike’s first publication of the principles of operant conditioning and the law of effect, Skinner attempted to prove an extension to this theory—that all behaviors are in some way a result of operant conditioning. Skinner theorized that if a behavior is followed by reinforcement, that behavior is more likely to be repeated, but if it is followed by some sort of aversive stimuli or punishment, it is less likely to be repeated. He also believed that this learned association could end, or become extinct, if the reinforcement or punishment was removed.

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B. F. Skinner: Skinner was responsible for defining the segment of behaviorism known as operant conditioning—a process by which an organism learns from its physical environment.

Skinner’s Experiments

Skinner’s most famous research studies were simple reinforcement experiments conducted on lab rats and domestic pigeons, which demonstrated the most basic principles of operant conditioning. He conducted most of his research in a special cumulative recorder, now referred to as a “Skinner box,” which was used to analyze the behavioral responses of his test subjects. In these boxes he would present his subjects with positive reinforcement, negative reinforcement, or aversive stimuli in various timing intervals (or “schedules”) that were designed to produce or inhibit specific target behaviors.

In his first work with rats, Skinner would place the rats in a Skinner box with a lever attached to a feeding tube. Whenever a rat pressed the lever, food would be released. After the experience of multiple trials, the rats learned the association between the lever and food and began to spend more of their time in the box procuring food than performing any other action. It was through this early work that Skinner started to understand the effects of behavioral contingencies on actions. He discovered that the rate of response—as well as changes in response features—depended on what occurred after the behavior was performed, not before. Skinner named these actions operant behaviors because they operated on the environment to produce an outcome. The process by which one could arrange the contingencies of reinforcement responsible for producing a certain behavior then came to be called operant conditioning.

To prove his idea that behaviorism was responsible for all actions, he later created a “superstitious pigeon.” He fed the pigeon on continuous intervals (every 15 seconds) and observed the pigeon’s behavior. He found that the pigeon’s actions would change depending on what it had been doing in the moments before the food was dispensed, regardless of the fact that those actions had nothing to do with the dispensing of food. In this way, he discerned that the pigeon had fabricated a causal relationship between its actions and the presentation of reward. It was this development of “superstition” that led Skinner to believe all behavior could be explained as a learned reaction to specific consequences.

In his operant conditioning experiments, Skinner often used an approach called shaping. Instead of rewarding only the target, or desired, behavior, the process of shaping involves the reinforcement of successive approximations of the target behavior. Behavioral approximations are behaviors that, over time, grow increasingly closer to the actual desired response.

Skinner believed that all behavior is predetermined by past and present events in the objective world. He did not include room in his research for ideas such as free will or individual choice; instead, he posited that all behavior could be explained using learned, physical aspects of the world, including life history and evolution. His work remains extremely influential in the fields of psychology, behaviorism, and education.

Shaping

Shaping is a method of operant conditioning by which successive approximations of a target behavior are reinforced.

Learning Objectives

Describe how shaping is used to modify behavior

Key Takeaways

Key Points

  • B. F. Skinner used shaping —a method of training by which successive approximations toward a target behavior are reinforced—to test his theories of behavioral psychology.
  • Shaping involves a calculated reinforcement of a “target behavior”: it uses operant conditioning principles to train a subject by rewarding proper behavior and discouraging improper behavior.
  • The method requires that the subject perform behaviors that at first merely resemble the target behavior; through reinforcement, these behaviors are gradually changed or “shaped” to encourage the target behavior itself.
  • Skinner’s early experiments in operant conditioning involved the shaping of rats’ behavior so they learned to press a lever and receive a food reward.
  • Shaping is commonly used to train animals, such as dogs, to perform difficult tasks; it is also a useful learning tool for modifying human behavior.

Key Terms

  • successive approximation: An increasingly accurate estimate of a response desired by a trainer.
  • paradigm: An example serving as a model or pattern; a template, as for an experiment.
  • shaping: A method of positive reinforcement of behavior patterns in operant conditioning.

In his operant-conditioning experiments, Skinner often used an approach called shaping. Instead of rewarding only the target, or desired, behavior, the process of shaping involves the reinforcement of successive approximations of the target behavior. The method requires that the subject perform behaviors that at first merely resemble the target behavior; through reinforcement, these behaviors are gradually changed, or shaped, to encourage the performance of the target behavior itself. Shaping is useful because it is often unlikely that an organism will display anything but the simplest of behaviors spontaneously. It is a very useful tool for training animals, such as dogs, to perform difficult tasks.

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Dog show: Dog training often uses the shaping method of operant conditioning.

How Shaping Works

In shaping, behaviors are broken down into many small, achievable steps. To test this method, B. F. Skinner performed shaping experiments on rats, which he placed in an apparatus (known as a Skinner box) that monitored their behaviors. The target behavior for the rat was to press a lever that would release food. Initially, rewards are given for even crude approximations of the target behavior—in other words, even taking a step in the right direction. Then, the trainer rewards a behavior that is one step closer, or one successive approximation nearer, to the target behavior. For example, Skinner would reward the rat for taking a step toward the lever, for standing on its hind legs, and for touching the lever—all of which were successive approximations toward the target behavior of pressing the lever.

As the subject moves through each behavior trial, rewards for old, less approximate behaviors are discontinued in order to encourage progress toward the desired behavior. For example, once the rat had touched the lever, Skinner might stop rewarding it for simply taking a step toward the lever. In Skinner’s experiment, each reward led the rat closer to the target behavior, finally culminating in the rat pressing the lever and receiving food. In this way, shaping uses operant-conditioning principles to train a subject by rewarding proper behavior and discouraging improper behavior.

In summary, the process of shaping includes the following steps:

  • Reinforce any response that resembles the target behavior.
  • Then reinforce the response that more closely resembles the target behavior. You will no longer reinforce the previously reinforced response.
  • Next, begin to reinforce the response that even more closely resembles the target behavior. Continue to reinforce closer and closer approximations of the target behavior.
  • Finally, only reinforce the target behavior.

Applications of Shaping

This process has been replicated with other animals—including humans—and is now common practice in many training and teaching methods. It is commonly used to train dogs to follow verbal commands or become house-broken: while puppies can rarely perform the target behavior automatically, they can be shaped toward this behavior by successively rewarding behaviors that come close.

Shaping is also a useful technique in human learning. For example, if a father wants his daughter to learn to clean her room, he can use shaping to help her master steps toward the goal. First, she cleans up one toy and is rewarded. Second, she cleans up five toys; then chooses whether to pick up ten toys or put her books and clothes away; then cleans up everything except two toys. Through a series of rewards, she finally learns to clean her entire room.

Reinforcement and Punishment

Reinforcement and punishment are principles of operant conditioning that increase or decrease the likelihood of a behavior.

Learning Objectives

Differentiate among primary, secondary, conditioned, and unconditioned reinforcers

Key Takeaways

Key Points

  • ” Reinforcement ” refers to any consequence that increases the likelihood of a particular behavioral response; ” punishment ” refers to a consequence that decreases the likelihood of this response.
  • Both reinforcement and punishment can be positive or negative. In operant conditioning, positive means you are adding something and negative means you are taking something away.
  • Reinforcers can be either primary (linked unconditionally to a behavior) or secondary (requiring deliberate or conditioned linkage to a specific behavior).
  • Primary—or unconditioned—reinforcers, such as water, food, sleep, shelter, sex, touch, and pleasure, have innate reinforcing qualities.
  • Secondary—or conditioned—reinforcers (such as money) have no inherent value until they are linked or paired with a primary reinforcer.

Key Terms

  • latency: The delay between a stimulus and the response it triggers in an organism.

Reinforcement and punishment are principles that are used in operant conditioning. Reinforcement means you are increasing a behavior: it is any consequence or outcome that increases the likelihood of a particular behavioral response (and that therefore reinforces the behavior). The strengthening effect on the behavior can manifest in multiple ways, including higher frequency, longer duration, greater magnitude, and short latency of response. Punishment means you are decreasing a behavior: it is any consequence or outcome that decreases the likelihood of a behavioral response.

Extinction , in operant conditioning, refers to when a reinforced behavior is extinguished entirely. This occurs at some point after reinforcement stops; the speed at which this happens depends on the reinforcement schedule, which is discussed in more detail in another section.

Positive and Negative Reinforcement and Punishment

Both reinforcement and punishment can be positive or negative. In operant conditioning, positive and negative do not mean good and bad. Instead, positive means you are adding something and negative means you are taking something away. All of these methods can manipulate the behavior of a subject, but each works in a unique fashion.

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Operant conditioning: In the context of operant conditioning, whether you are reinforcing or punishing a behavior, “positive” always means you are adding a stimulus (not necessarily a good one), and “negative” always means you are removing a stimulus (not necessarily a bad one. See the blue text and yellow text above, which represent positive and negative, respectively. Similarly, reinforcement always means you are increasing (or maintaining) the level of a behavior, and punishment always means you are decreasing the level of a behavior. See the green and red backgrounds above, which represent reinforcement and punishment, respectively.

  • Positive reinforcers add a wanted or pleasant stimulus to increase or maintain the frequency of a behavior. For example, a child cleans her room and is rewarded with a cookie.
  • Negative reinforcers remove an aversive or unpleasant stimulus to increase or maintain the frequency of a behavior. For example, a child cleans her room and is rewarded by not having to wash the dishes that night.
  • Positive punishments add an aversive stimulus to decrease a behavior or response. For example, a child refuses to clean her room and so her parents make her wash the dishes for a week.
  • Negative punishments remove a pleasant stimulus to decrease a behavior or response. For example, a child refuses to clean her room and so her parents refuse to let her play with her friend that afternoon.

Primary and Secondary Reinforcers

The stimulus used to reinforce a certain behavior can be either primary or secondary. A primary reinforcer, also called an unconditioned reinforcer, is a stimulus that has innate reinforcing qualities. These kinds of reinforcers are not learned. Water, food, sleep, shelter, sex, touch, and pleasure are all examples of primary reinforcers: organisms do not lose their drive for these things. Some primary reinforcers, such as drugs and alcohol, merely mimic the effects of other reinforcers. For most people, jumping into a cool lake on a very hot day would be reinforcing and the cool lake would be innately reinforcing—the water would cool the person off (a physical need), as well as provide pleasure.

A secondary reinforcer, also called a conditioned reinforcer, has no inherent value and only has reinforcing qualities when linked or paired with a primary reinforcer. Before pairing, the secondary reinforcer has no meaningful effect on a subject. Money is one of the best examples of a secondary reinforcer: it is only worth something because you can use it to buy other things—either things that satisfy basic needs (food, water, shelter—all primary reinforcers) or other secondary reinforcers.

Schedules of Reinforcement

Reinforcement schedules determine how and when a behavior will be followed by a reinforcer.

Learning Objectives

Compare and contrast different types of reinforcement schedules

Key Takeaways

Key Points

  • A reinforcement schedule is a tool in operant conditioning that allows the trainer to control the timing and frequency of reinforcement in order to elicit a target behavior.
  • Continuous schedules reward a behavior after every performance of the desired behavior; intermittent (or partial) schedules only reward the behavior after certain ratios or intervals of responses.
  • Intermittent schedules can be either fixed (where reinforcement occurs after a set amount of time or responses) or variable (where reinforcement occurs after a varied and unpredictable amount of time or responses).
  • Intermittent schedules are also described as either interval (based on the time between reinforcements) or ratio (based on the number of responses).
  • Different schedules (fixed-interval, variable-interval, fixed-ratio, and variable-ratio) have different advantages and respond differently to extinction.
  • Compound reinforcement schedules combine two or more simple schedules, using the same reinforcer and focusing on the same target behavior.

Key Terms

  • extinction: When a behavior ceases because it is no longer reinforced.
  • interval: A period of time.
  • ratio: A number representing a comparison between two things.

A schedule of reinforcement is a tactic used in operant conditioning that influences how an operant response is learned and maintained. Each type of schedule imposes a rule or program that attempts to determine how and when a desired behavior occurs. Behaviors are encouraged through the use of reinforcers, discouraged through the use of punishments, and rendered extinct by the complete removal of a stimulus. Schedules vary from simple ratio- and interval-based schedules to more complicated compound schedules that combine one or more simple strategies to manipulate behavior.

Continuous vs. Intermittent Schedules

Continuous schedules reward a behavior after every performance of the desired behavior. This reinforcement schedule is the quickest way to teach someone a behavior, and it is especially effective in teaching a new behavior. Simple intermittent (sometimes referred to as partial) schedules, on the other hand, only reward the behavior after certain ratios or intervals of responses.

Types of Intermittent Schedules

There are several different types of intermittent reinforcement schedules. These schedules are described as either fixed or variable and as either interval or ratio.

Fixed vs. Variable, Ratio vs. Interval

Fixed refers to when the number of responses between reinforcements, or the amount of time between reinforcements, is set and unchanging. Variable refers to when the number of responses or amount of time between reinforcements varies or changes. Interval means the schedule is based on the time between reinforcements, and ratio means the schedule is based on the number of responses between reinforcements. Simple intermittent schedules are a combination of these terms, creating the following four types of schedules:

  • A fixed-interval schedule is when behavior is rewarded after a set amount of time. This type of schedule exists in payment systems when someone is paid hourly: no matter how much work that person does in one hour (behavior), they will be paid the same amount (reinforcement).
  • With a variable-interval schedule, the subject gets the reinforcement based on varying and unpredictable amounts of time. People who like to fish experience this type of reinforcement schedule: on average, in the same location, you are likely to catch about the same number of fish in a given time period. However, you do not know exactly when those catches will occur (reinforcement) within the time period spent fishing (behavior).
  • With a fixed-ratio schedule, there are a set number of responses that must occur before the behavior is rewarded. This can be seen in payment for work such as fruit picking: pickers are paid a certain amount (reinforcement) based on the amount they pick (behavior), which encourages them to pick faster in order to make more money. In another example, Carla earns a commission for every pair of glasses she sells at an eyeglass store. The quality of what Carla sells does not matter because her commission is not based on quality; it’s only based on the number of pairs sold. This distinction in the quality of performance can help determine which reinforcement method is most appropriate for a particular situation: fixed ratios are better suited to optimize the quantity of output, whereas a fixed interval can lead to a higher quality of output.
  • In a variable-ratio schedule, the number of responses needed for a reward varies. This is the most powerful type of intermittent reinforcement schedule. In humans, this type of schedule is used by casinos to attract gamblers: a slot machine pays out an average win ratio—say five to one—but does not guarantee that every fifth bet (behavior) will be rewarded (reinforcement) with a win.

All of these schedules have different advantages. In general, ratio schedules consistently elicit higher response rates than interval schedules because of their predictability. For example, if you are a factory worker who gets paid per item that you manufacture, you will be motivated to manufacture these items quickly and consistently. Variable schedules are categorically less-predictable so they tend to resist extinction and encourage continued behavior. Both gamblers and fishermen alike can understand the feeling that one more pull on the slot-machine lever, or one more hour on the lake, will change their luck and elicit their respective rewards. Thus, they continue to gamble and fish, regardless of previously unsuccessful feedback.

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Simple reinforcement-schedule responses: The four reinforcement schedules yield different response patterns. The variable-ratio schedule is unpredictable and yields high and steady response rates, with little if any pause after reinforcement (e.g., gambling). A fixed-ratio schedule is predictable and produces a high response rate, with a short pause after reinforcement (e.g., eyeglass sales). The variable-interval schedule is unpredictable and produces a moderate, steady response rate (e.g., fishing). The fixed-interval schedule yields a scallop-shaped response pattern, reflecting a significant pause after reinforcement (e.g., hourly employment).

Extinction of a reinforced behavior occurs at some point after reinforcement stops, and the speed at which this happens depends on the reinforcement schedule. Among the reinforcement schedules, variable-ratio is the most resistant to extinction, while fixed-interval is the easiest to extinguish.

Simple vs. Compound Schedules

All of the examples described above are referred to as simple schedules. Compound schedules combine at least two simple schedules and use the same reinforcer for the same behavior. Compound schedules are often seen in the workplace: for example, if you are paid at an hourly rate (fixed-interval) but also have an incentive to receive a small commission for certain sales (fixed-ratio), you are being reinforced by a compound schedule. Additionally, if there is an end-of-year bonus given to only three employees based on a lottery system, you’d be motivated by a variable schedule.

There are many possibilities for compound schedules: for example, superimposed schedules use at least two simple schedules simultaneously. Concurrent schedules, on the other hand, provide two possible simple schedules simultaneously, but allow the participant to respond on either schedule at will. All combinations and kinds of reinforcement schedules are intended to elicit a specific target behavior.