20-2 Who was Skinner, and how is operant behavior reinforced and shaped?

B. F. Skinner (1904–1990) was a college English major and aspiring writer who, seeking a new direction, studied psychology in graduate school. He went on to become modern behaviorism’s most influential and controversial figure. Skinner’s work elaborated on what psychologist Edward L. Thorndike (1874–1949) called the law of effect: Rewarded behavior tends to recur (FIGURE 20.1). Using Thorndike’s law of effect as a starting point, Skinner developed a behavioral technology that revealed principles of behavior control. By shaping pigeons’ natural walking and pecking behaviors, for example, Skinner was able 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.

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For his pioneering studies, Skinner designed an operant chamber, popularly known as a Skinner box (FIGURE 20.2). 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 other animals act out Skinner’s concept of reinforcement: any event that strengthens (increases the frequency of) 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.

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 higher-pitched 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 pigeons’ behavior showed that they 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 were usually able to identify the category in which a new pictured object belonged (Bhatt et al., 1988; Wasserman, 1993). They have even been trained to discriminate between the music of Bach and Stravinsky (Porter & Neuringer, 1984).

Skinner noted that we continually reinforce and shape others’ everyday behaviors, though we may not mean to do so. Isaac’s whining annoys his father, for example, but look how he typically responds:

Isaac: Could you take me to the mall?

Father: (Continues reading paper.)

Isaac: Dad, I need to go to the mall.

Father: Uh, yeah, just a minute.

Isaac: DAAAAD! The mall!

Father: Show me 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 sticks gold stars on a wall chart beside the names of children scoring 100 percent on spelling tests. As everyone can then see, some children consistently do perfect work. The others, who 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).

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20-3 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 20.1). Negative reinforcement strengthens a response by reducing or removing something negative. Isaac’s whining was positively reinforced, because Isaac got something desirable—his father’s attention. His dad’s response to the whining (doing what Isaac wanted) was negatively reinforced, because it ended an aversive event—Isaac’s whining. Similarly, taking aspirin may relieve your headache, and hitting snooze will silence your annoying alarm. These welcome results provide negative reinforcement and increase the odds that you will repeat these behaviors. For those with drug addiction, the negative reinforcement of ending withdrawal pangs can be a compelling reason to resume using (Baker et al., 2004). Note that negative reinforcement is not punishment. (Some friendly advice: Repeat the italicized words in your mind.) Rather, negative reinforcement—psychology’s most misunderstood concept—removes a punishing (aversive) event. Think of negative reinforcement as something that provides relief—from that whining teen, bad headache, or annoying alarm.

Sometimes negative and positive reinforcement coincide. Imagine a worried student who, after goofing off and getting a bad exam grade, studies harder for the next exam. This increased effort may be negatively reinforced by reduced anxiety, and positively reinforced by a better grade. We reap the rewards of escaping the aversive stimulus, which increases the chances that we will repeat our behavior. The point to remember: Whether it works by reducing something aversive, or by providing something desirable, reinforcement is any consequence that strengthens behavior.

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PRIMARY AND CONDITIONED REINFORCERS 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 primary 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.

IMMEDIATE AND DELAYED REINFORCERS 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 any one 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. It will have moved on to other incidental behaviors, such as scratching, sniffing, and moving, and one of these behaviors will instead get reinforced.

Unlike rats, humans do respond to delayed reinforcers: the paycheck at the end of the week, the good grade at the end of the semester, the trophy at the end of the season. Indeed, to function effectively we must learn to delay gratification. In one of psychology’s most famous studies, some 4-year-olds showed this ability. In choosing a candy or marshmallow, they preferred having a big one tomorrow to munching on a small one right away. 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 delay gratification have tended to become socially competent and high-achieving adults (Mischel, 2014).

To our detriment, small but immediate pleasures (the enjoyment of watching late-night TV, for example) are sometimes more alluring than big but delayed rewards (resting, then 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.

20-4 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 it 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. It extinguishes. 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). Slot machines 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.

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Lesson for parents: 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. Once conditioned, 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 20.3).

Variable-ratio schedules provide reinforcers after a seemingly unpredictable number of responses. This unpredictable reinforcement is what slot-machine players and fly fishers experience, and it’s what makes gambling and fly fishing so hard to extinguish even when they don’t produce the desired results. Because reinforcers increase 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 delivery 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 (see FIGURE 20.3).

Variable-interval schedules reinforce the first response after varying time periods. Like the longed-for message that finally rewards 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 20.2).

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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.”

20-5 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 20.3). 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.

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 swiftness and sureness 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 have noted four major drawbacks of physical punishment (Gershoff, 2002; Marshall, 2002):

Some researchers have noted a problem with this logic. Well, yes, they’ve said, 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 (Ferguson, 2013; 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:

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

Parents of delinquent youths are often unaware of how to achieve desirable behaviors without screaming, hitting, or threatening their children with punishment (Patterson et al., 1982). Training programs can help transform dire threats (“You clean up your room this minute or no dinner!”) into positive incentives (“You’re welcome at the dinner table after you get your room cleaned up”). 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, there’ll be no car” 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 while reinforcing more desirable alternatives. Remember: Punishment tells you what not to do; reinforcement tells you what to do. Thus, punishment trains a particular sort of morality—one focused on prohibition (what not to do) rather than positive obligations (Sheikh & Janoff-Bultman, 2013).

What punishment often teaches, said Skinner, is how to avoid it. Most psychologists now favor an emphasis on reinforcement: Notice people doing something right and affirm them for it.

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