AP Psychology

Module 27 - Operant Conditioning


Operant Conditioning

FOCUS QUESTION: What is operant conditioning, and how is operant behavior reinforced and shaped?

It's one thing to classically condition a dog to salivate at the sound of a tone, or a child to fear moving cars. To teach an elephant to walk on its hind legs or a child to say please, we turn to operant conditioning. Classical conditioning and operant conditioning are both forms of associative learning, yet their difference is straightforward:

Skinner's Experiments

B. F. Skinner (1904-1990) was a college English major and an aspiring writer who, seeking a new direction, entered psychology graduate school. He went on to become modern behaviorism's most influential and controversial figure. Skinner's work elaborated on what psychologist Edward 1. Thorndike (1874-1949) called the law of effect: Rewarded behavior is likely to recur (FIGURE 27.1) . Using Thorndike's law of effect as a starting point, Skinner developed a behavioral technology that revealed principles of behavior control. These principles also enabled him to teach pigeons such unpigeon-like behaviors as walking in a figure 8, playing Ping-Pong, and keeping a missile on course by pecking at a screen target.

For his pioneering studies, Skinner designed an operant chamber, popularly known as a Skinner box (FIGURE 27.2). The box has a bar (a lever) that an animal presses-or a key (a disc) the animal pecks-to release a reward of food or water. It also has a device that records these responses. This design creates a stage on which rats and others animals act out Skinner's concept of reinforcement: any event that strengthens (increases the frequency oD a preceding response. What is reinforcing depends on the animal and the conditions. For people, it may be praise, attention, or a paycheck. For hungry and thirsty rats, food and water work well. Skinner's experiments have done far more than teach us how to pull habits out of a rat. They have explored the precise conditions that foster efficient and enduring learning.

Shaping Behavior

Imagine that you wanted to condition a hungry rat to press a bar. Like Skinner, you could tease out this action with shaping, gradually guiding the rat's actions toward the desired behavior. First, you would watch how the animal naturally behaves, so that you could build on its existing behaviors. You might give the rat a bit of food each time it approaches the bar. Once the rat is approaching regularly, you would give the food only when it moves close to the bar, then closer still. Finally, you would require it to touch the bar to get food. With this method of successive approximations, you reward responses that are ever-closer to the final desired behavior, and you ignore all other responses. By making rewards contingent on desired behaviors, researchers and animal trainers gradually shape complex behaviors.

Shaping can also help us understand what nonverbal organisms perceive. Can a dog distinguish red and green? Can a baby hear the difference between lower-and higherpitched tones? If we can shape them to respond to one stimulus and not to another, then we know they can perceive the difference. Such experiments have even shown that some animals can form concepts. When experimenters reinforced pigeons for pecking after seeing a human face, but not after seeing other images, the pigeon's behavior showed that it could recognize human faces (Herrnstein & Loveland, 1964). In this experiment, the human face was a discriminative stimulus. Like a green traffic light, discriminative stimuli signal that a response will be reinforced. After being trained to discriminate among classes of events or objects-flowers, people, cars, chairs-pigeons can usually identify the category in which a new pictured object belongs (Bhatt et a1., 1988; Wasserman, 1993). They have even been trained to discriminate between the music of Bach and Stravinsky (Porter & Neuringer, 1984).

In everyday life, we continually reinforce and shape others' behavior, said Skinner, though we may not mean to do so. Isaac's whining, for example, annoys his dad, but look how he typically responds:

Isaac: Could you take me to the mall?
Father: (Ignores Isaac and stays focused on his phone)
Isaac: Dad, I need to go to the mall.
Father: (distracted) Uh, yeah, just a minute.
Isaac: DAAAD! The mall!!
Father: Show some manners! Okay, where are my keys ...

Isaac's whining is reinforced, because he gets something desirable-his dad's attention. Dad's response is reinforced because it gets rid of something aversive-Isaac's whining.

Or consider a teacher who pastes gold stars on a wall chart beside the names of children scoring 100 percent on spelling tests. As evetyone can then see, some children consistently do perfect work. The others, who take the same test and may have worked harder than the academic all-stars, get no rewards. The teacher would be better advised to apply the principles of operant conditioning-to reinforce all spellers for gradual improvements (successive approximations toward perfect spelling of words they find challenging).

Types of Reinforcers

FOCUS QUESTION: How do positive and negative reinforcement differ, and what are the basic types of reinforcers?

Up to now, we've mainly been discussing positive reinforcement, which strengthens a response by presenting a typically pleasurable stimulus after a response. But, as we saw in the whining Isaac story, there are two basic kinds of reinforcement (TABLE 27.1 on the next page).

Negative reinforcement strengthens a response by reducing or removing something nega- tive . Isaac's whining was positively reinforced, because Isaac got something desirable- h i s fa- ther's attention. His dad's response to the whining (taking Isaac to the mall) was negatively reinforced, because it ended an aversive event-Isaac's whining. Sinlliarly, taking aspirin may relieve your headache, and pushing the snooze button will silence your anl10ying alarm. These welcome results provide negative reinforcement and increase the odds that you will repeat these behaviors. For drug addicts, the negative reinforcement of ending withdrawal pangs can be a compelling reason to reSLUne using (Baker et al., 2004). Note that negative reinforcement is not punishment. (Some friendly advice: Repeat the last five words in your mind.) Rather, nega- tive reinforcement removes a punishing (aversive) event. Think of negative reinforcement as something that provides relief-from that whining teenager, bad headache, or annoying alarm.

Sometimes negative and positive reinforcement coincide. Imagine a worried student who, after goofing off and getting a bad test grade, studies harder for the next test. This increased effort may be negatively reinforced by reduced anxiety, and positively reinforced by a better grade.Whether it works by reducing something aversive, or by giving something desirable, reinforcement is any consequence that strengthens behavi01:


Getting food when hungry or having a painful headache go away is innately satisfying. These primary reinforcers are unlearned. Conditioned reinforcers, also called secondary reinforcers, get their power through learned association with primaly reinforcers. If a rat in a Skinner box learns that a light reliably signals a food delivery, the rat will work to turn on the light. The light has become a conditioned reinforcer. Our lives are filled with conditioned reinforcers-money, good grades, a pleasant tone of voice-each of which has been linked with more basic rewards.


Let's return to the imaginary shaping experiment in which you were conditioning a rat to press a bar. Before performing this "wanted" behavior, the hungry rat will engage in a sequence of "unwanted" behaviors-scratching, sniffing, and moving around. If you present food immediately after anyone of these behaviors, the rat will likely repeat that rewarded behavior. But what if the rat presses the bar while you are distracted, and you delay giving the reinforcer? If the delay lasts longer than about 30 seconds, the rat will not learn to press the bar. You will have reinforced other incidental behaviors - more sniffing and moving - that intervened after the bar press.

Unlike rats, humans do respond to delayed reinforcers: the paycheck at the end of the week, the good grade at the end of the term, the trophy at the end of the season. l1"\deed, to function effectively we must learn to delay gratification. In laboratOlY testing, some 4-year-olds show this ability. In choosing a candy, they prefer having a big one tomorrow to munching on a small one right now. Learning to control our impulses in order to achieve more valued rewards is a big step toward maturity (Logue, 1998a,b). No wonder children who make such choices have tended to become socially competent and high-achieving adults (Mischel et a!., 1989).

To our detriment, small but immediate consequences (the enjoyment of latenight videos or texting, for example) are sometimes more alluring than big but delayed consequences (feeling alert tomorrow). For many teens, the immediate gratification of risky, unprotected sex in passionate moments prevails over the delayed gratifications of safe sex or saved sex. And for many people, the immediate rewards of today's gas-guzzling vehicles, air travel, and air conditioning prevail over the bigger future consequences of global climate change, rising seas, and extreme weather.

Reinforcement Schedules

FOCUS QUESTION: How do different reinforcement schedules affect behavior?

In most of our examples, the desired response has been reinforced every time it occurs. But reinforcement schedules vary. With continuous reinforcement, learning occurs rapidly, which makes this the best choice for mastering a behavior. But extinction also occurs rapidly. When reinforcement stops - when we stop delivering food after the rat presses the bar - the behavior soon stops. If a normally dependable candy machine fails to deliver a chocolate bar twice in a row, we stop putting money into it (although a week later we may exhibit spontaneous recovery by trying again).

Real life rarely provides continuous reinforcement. Salespeople do not make a sale with every pitch. But they persist because their efforts are occasionally rewarded. This persistence is typical with partial (intermittent) reinforcement schedules, in which responses are sometimes reinforced, sometimes not. Learning is slower to appear, but resistance to extinction is greater than with continuous reinforcement. Imagine a pigeon that has learned to peck a key to obtain food. If you gradually phase out the food delivery until it occurs only rarely, in no predictable pattern, the pigeon may peck 150,000 times without a reward (Skinner, 1953). Gambling machines and lottelY tickets reward gamblers in much the same way-occasionally and unpredictably. And like pigeons, slot players keep trying, time and time again. With intermittent reinforcement, hope springs eternal.

Lesson for child caregivers: Partial reinforcement also works with children. Occasionally giving in to children's tantrums for the sake of peace and quiet intermittently reinforces the tantrums. This is the very best procedure for making a behavior persist.

Skinner (1961) and his collaborators compared four schedules of partial reinforcement. Some are rigidly fixed, some unpredictably variable.

Fixed-ratio schedules reinforce behavior after a set number of responses. Coffee shops may reward us with a free drink after every 10 purchased. In the laboratOly, rats may be reinforced on a fixed ratio of, say, one food pellet for every 30 responses. Once conditioned, animals will pause only briefly after a reinforcer before returning to a high rate of responding (FIGURE 27.3 on the next page). Variable-ratio schedules provide reinforcers after a seemingly unpredictable number of responses. This is what slot-machine players and fly-casting anglers experience unpredictable reinforcement-and what makes gambling and fly fishing so hard to extinguish even when both are getting nothing for something. Because reinforcers in crease as the number of responses increases, variable-ratio schedules produce high rates of responding. Fixed-interval schedules reinforce the first response after a fixed time period. Animals on this type of schedule tend to respond more frequently as the anticipated time for reward draws near. People check more frequently for the mail as the delivelY time approaches. A hungry child jiggles the Jell-O more often to see if it has set. Pigeons peck keys more rapidly as the time for reinforcement draws nearer. This produces a choppy stop-start pattern rather than a steady rate of response (see Figure 27.3). Variable-interval schedules reinforce the first response after varying time intervals. Like the longed-for responses that finally reward persistence in rechecking e-mail or Facebook, variable-interval schedules tend to produce slow, steady responding. This makes sense, because there is no knowing when the waiting will be over (TABLE 27.2).

In general, response rates are higher when reinforcement is linked to the number of responses (a ratio schedule) rather than to time (an interval schedule). But responding is more consistent when reinforcement is unpredictable (a variable schedule) than when it is predictable (a fixed schedule). Animal behaviors differ, yet Skinner (1956) contended that the reinforcement principles of operant conditioning are universal. It matters little, he said, what response, what reinforcer, or what species you use. The effect of a given reinforcement schedule is pretty much the same: "Pigeon, rat, monkey, which is which? It doesn't matter.... Behavior shows astonishingly similar properties."


FOCUS QUESTION: How does punishment differ from negative reinforcement, and how does punishment affect behavior?

Reinforcement increases a behavior; punishment does the opposite. A punisher is any consequence that decreases the frequency of a preceding behavior (TABLE 27.3). Swift and sure punishers can powerfully restrain unwanted behavior. The rat that is shocked after touching a forbidden object and the child who is burned by touching a hot stove will learn not to repeat those behaviors. A dog that has learned to come running at the sound of an electric can opener will stop coming if its owner runs the machine to attract the dog and banish it to the basement.

Criminal behavior, much of it impulsive, is also influenced more by swift and sure punishers than by the threat of severe sentences (Darley & Alter, 2011). Thus, when Arizona introduced an exceptionally harsh sentence for first-time drunk drivers, the drunk-driving rate changed very little. But when Kansas City police started patrolling a high crime area to increase the sureness and swiftness of punishment, that city's crime rate dropped dramatically.

How should we interpret the punishment studies in relation to parenting practices? Many psychologists and supporters of nonviolent parenting note four major drawbacks of physical punishment (Gershoff, 2002; Marshall, 2002) .

  1. Punished behavior is suppressed, not forgotten. This temporary state may (negatively) reinforce parents' punishing behavi01: The child swears, the parent swats, the parent hears no more swearing and feels the punishment successfully stopped the behavior. No wonder spanking is a hit with so many U.S. parents of 3-and 4-year-olds-more than 9 in 10 of whom acknowledged spanking their children (Kazdin & Benjet, 2003).
  2. Punishment teaches discrimination among situations. In operant conditioning, discrimination occurs when an organism learns that certain responses, but not others, will be reinforced. Did the punishment effectively end the child's swearing? Or did the child simply learn that it's not okay to swear around the house, though okay elsewhere?
  3. Punishment can teach fear. In operant conditioning, generalization occurs when an organism's response to similar stimuli is also reinforced. A punished child may associate fear not only with the undesirable behavior but also with the person who delivered the punishment or the place it occurred. Thus, children may learn to fear a punishing teacher and try to avoid school, or may become more anxious (Gershoff et al., 2010). For such reasons, most European countries and most U.S. states now ban hitting children in schools and child-care institutions (www.stophitting.com).Thirty-three countries, including those in Scandinavia, further outlaw hitting by parents, providing children the same legal protection given to spouses.
  4. Physical punishment may increase aggression by modeling aggression as a way to cope with problems. Studies find that spanked children are at increased risk for aggression (and depression and low self-esteem). We know, for example, that many aggressive delinquents and abusive parents come from abusive families (Straus & Gelles, 1980; Straus et al., 1997).

Some researchers note a problem. Well, yes, they say, physically punished children may be more aggressive, for the same reason that people who have undergone psychotherapy are more likely to suffer depression-because they had preexisting problems that triggered the treatments (Larzelere, 2000, 2004). Which is the chicken and which is the egg? Correlations don't hand us an answer.

If one adjusts for preexisting antisocial behavior, then an occasional single swat or two to misbehaving 2-to 6-year-olds looks more effective (Baumrind et al., 2002; Larzelere & Kuhn, 2005). That is especially so if two other conditions are met:

  1. The swat is used only as a backup when milder disciplinaty tactics, such as a time-out (removing them from reinforcing surroundings), fail.
  2. The swat is combined with a generous dose of reasoning and reinforcing.

Other researchers remain unconvinced. After controlling for prior misbehavior, they report that more frequent spankings of young children predict future aggressiveness (GroganKaylor, 2004; Taylor et al., 2010) .

Parents of delinquent youths are often unaware of how to achieve desirable behaviors without screaming at or hitting their children (Patterson et al., 1982). Training programs can help transform dire threats ("Apologize right now or I'm taking that cell phone away!") into positive incentives ("You're welcome to have your phone back when you apologize."). Stop and think about it. Aren't many threats of punishment just as forceful, and perhaps more effective, when rephrased positively? Thus, "If you don't get your homework done, I'm not giving you money for a movie!" would better be phrased as ....

In classrooms, too, teachers can give feedback on papers by saying, "No, but try this ... " and "Yes, that's it!" Such responses reduce unwanted behavior wlUle reinforcing more desirable alternatives. Remember: Punishment tells you what not to do; reinforcement tells you what to do.

What punishment often teaches, said Skinner, is how to avoid it. Most psychologists now favor an emphasis on reinforcement.

Skinner's Legacy

FOCUS QUESTION: Why did Skinner's ideas provoke controversy?

B. F. Skinner stirred a hornet's nest with his outspoken beliefs. He repeatedly insisted that external influences (not internal thoughts and feelings) shape behavior. And he urged people to use operant principles to influence others' behavior at school, work, and home. Knowing that behavior is shaped by its results, he said we should use rewards to evoke more desirable behavior.

Skinner's critics objected, saying that he dehumanized people by neglecting their personal freedom and by seeking to control their actions. Skinner's reply: External consequences already haphazardly control people's behavior. Why not administer those consequences toward human betterment? Wouldn't reinforcers be more humane than the punishments used in homes, schools, and prisons? And if it is humbling to think that our history has shaped us, doesn't this very idea also give us hope that we can shape our future?

Before You Move On

ASK YOURSELF: Does your social media behavior (such as checking for new messages) make sense now that you've learned about the different kinds of reinforcement schedules?

TEST YOURSELF: Fill in the three blanks below with one of the following terms: negative reinforcement (NR), positive punishment (PP), and negative punishment (NP). The first answer, positive reinforcement (PR) is provided for you.