Classical Conditioning
For many people, the name Ivan Pavlov (1849–1936) rings a bell. His early twentieth-century experiments—now psychology’s most famous research—are classics, and the phenomenon he explored we justly call classical conditioning.
Ivan Pavlov “Experimental investigation . . . should lay a solid foundation for a future true science of psychology” (1927).
Pavlov’s work laid the foundation for many of psychologist John B. Watson’s ideas. In searching for laws underlying learning, Watson (1913) urged his colleagues to discard reference to inner thoughts, feelings, and motives. The science of psychology should instead study how organisms respond to stimuli in their environments, said Watson: “Its theoretical goal is the prediction and control of behavior. Introspection forms no essential part of its methods.” Simply said, psychology should be an objective science based on observable behavior.
This view, which Watson called behaviorism, influenced North American psychology during the first half of the twentieth century. Pavlov and Watson both came to share a disdain for “mentalistic” concepts (such as consciousness) and a belief that the basic laws of learning were the same for all animals—whether sea slugs or dogs or humans. Few researchers today agree that psychology should ignore mental processes, but most do agree that classical conditioning is a basic form of learning by which all organisms adapt to their environment.
Pavlov’s Experiments
Flip It Video: Pavlov’s Experiments
Pavlov was driven by a lifelong passion for research. After setting aside his initial plan to follow his father into the Russian Orthodox priesthood, Pavlov earned a medical degree at age 33 and spent the next two decades studying dogs’ digestive system. This work earned him Russia’s first Nobel Prize. But it was his novel experiments on learning, which consumed the last three decades of his life, that earned this feisty, intense scientist his place in history (Todes, 2014).
Pavlov’s new direction came when his creative mind seized on an incidental observation. Without fail, putting food in a dog’s mouth caused the animal to salivate. Moreover, the dog began salivating not only to the taste of the food, but also to the mere sight of the food, or the food dish, or the person delivering the food, or even at the sound of that person’s approaching footsteps. At first, Pavlov considered these “psychic secretions” an annoyance—until he realized they pointed to a simple but fundamental form of learning.
Pavlov and his assistants tried to imagine what the dog was thinking and feeling as it drooled in anticipation of the food. This only led them into fruitless debates. So, to explore the phenomenon more objectively, they experimented. To eliminate other possible influences, they isolated the dog in a small room, secured it in a harness, and attached a device to divert its saliva to a measuring instrument (Figure 26.3). From the next room, they presented food—first by sliding in a food bowl, later by blowing meat powder into the dog’s mouth at a precise moment. They then paired various neutral stimuli (NS)—events the dog could see or hear but didn’t associate with food—with food in the dog’s mouth. If a sight or sound regularly signaled the arrival of food, would the dog learn the link? If so, would it begin salivating in anticipation of the food?
Figure 26.3 Pavlov’s device for recording salivation
A tube in the dog’s cheek collects saliva, which is measured in a cylinder outside the chamber.
The answers proved to be Yes and Yes. Just before placing food in the dog’s mouth to produce salivation, Pavlov sounded a tone. After several pairings of tone and food, the dog, now anticipating the meat powder, began salivating to the tone alone. In later experiments, a buzzer,1 a light, a touch on the leg, even the sight of a circle set off the drooling. (This procedure works with people, too. When hungry young Londoners viewed abstract figures before smelling peanut butter or vanilla, their brain soon responded in anticipation to the abstract images alone [Gottfried et al., 2003].)
Peanuts
A dog does not learn to salivate in response to food in its mouth. Rather, food in the mouth automatically, unconditionally, triggers a dog’s salivary reflex (Figure 26.4). Thus, Pavlov called this drooling an unconditioned response (UR). And he called the food an unconditioned stimulus (US).
Figure 26.4 Pavlov’s classic experiment
Pavlov presented a neutral stimulus (a tone) just before an unconditioned stimulus (food in mouth). The neutral stimulus then became a conditioned stimulus, producing a conditioned response.
Salivation in response to a tone, however, is learned. It is conditional upon the dog’s associating the tone with the food. Thus, we call this response the conditioned response (CR). The stimulus that used to be neutral (in this case, a previously meaningless tone that now triggers salivation) is the conditioned stimulus (CS). Distinguishing these two kinds of stimuli and responses is easy: Conditioned = learned; unconditioned = unlearned.
If Pavlov’s demonstration of associative learning was so simple, what did he do for the next three decades? What discoveries did his research factory publish in his 532 papers on salivary conditioning (Windholz, 1997)? He and his associates explored five major conditioning processes: acquisition, extinction, spontaneous recovery, generalization, and discrimination.
Acquisition
To understand the acquisition, or initial learning, of the stimulus-response relationship, Pavlov and his associates wondered: How much time should elapse between presenting the NS (the tone, the light, the touch) and the US (the food)? In most cases, not much—half a second usually works well.
What do you suppose would happen if the food (US) appeared before the tone (NS) rather than after? Would conditioning occur? Not likely. Conditioning usually won’t occur when the NS follows the US. Remember, classical conditioning is biologically adaptive because it helps humans and other animals prepare for good or bad events. To Pavlov’s dogs, the originally neutral tone became a CS after signaling an important biological event—the arrival of food (US). To deer in the forest, the snapping of a twig (CS) may signal a predator’s approach (US).
Research on male Japanese quail shows how a CS can signal another important biological event (Domjan, 1992, 1994, 2005). Just before presenting an approachable female quail, the researchers turned on a red light. Over time, as the red light continued to herald the female’s arrival, the light alone caused the male quail to become excited. They developed a preference for their cage’s red-light district, and when a female appeared, they mated with her more quickly and released more semen and sperm (Matthews et al., 2007). This capacity for classical conditioning supports reproduction.
Sexual conditioning also occurs in rats. When their early sexual experiences are with partners scented with a peculiar odor, rats later display a preference for similarly scented partners (Pfaus et al., 2012). In humans, too, objects, smells, and sights associated with sexual pleasure—even a geometric figure, in one experiment—can become conditioned stimuli for sexual arousal (Byrne, 1982; Hoffman, 2012). Onion breath does not usually produce sexual arousal. But when repeatedly paired with a passionate kiss, it can become a CS and do just that (Figure 26.5). The larger lesson: Conditioning helps an animal survive and reproduce—by responding to cues that help it gain food, avoid dangers, locate mates, and produce offspring (Hollis, 1997). Learning makes for yearning.
Figure 26.5 An unexpected CS
Psychologist Michael Tirrell (1990) recalled: “My first girlfriend loved onions, so I came to associate onion breath with kissing. Before long, onion breath sent tingles up and down my spine. Oh what a feeling!”
Through higher-order conditioning, a new NS can become a new CS without the presence of a US. All that’s required is for it to become associated with a previously conditioned stimulus. If a tone regularly signals food and produces salivation, then a light that becomes associated with the tone (light → tone → food) may also begin to trigger salivation. Although this higher-order conditioning (also called second-order conditioning) tends to be weaker than first-order conditioning, it influences our everyday lives. Imagine that something makes us very afraid (perhaps a guard dog associated with a previous dog bite). If something else, such as the sound of a barking dog, brings that guard dog to mind, the bark alone may make us feel a little afraid.
Extinction and Spontaneous Recovery
What would happen, Pavlov wondered, if, after conditioning, the CS occurred repeatedly without the US? If the tone sounded again and again, but no food appeared, would the tone still trigger salivation? The answer was mixed. The dogs salivated less and less, a reaction known as extinction. Extinction is the diminished response that occurs when the CS (tone) no longer signals an impending US (food). But a different picture emerged when Pavlov allowed several hours to elapse before sounding the tone again. After the delay, the dogs would again begin salivating to the tone (Figure 26.6). This spontaneous recovery—the reappearance of a (weakened) CR after a pause—suggested to Pavlov that extinction was suppressing the CR rather than eliminating it.
Figure 26.6 Idealized curve of acquisition, extinction, and spontaneous recovery
The rising curve shows the CR rapidly growing stronger as the NS becomes a CS due to repeated pairing with the US (acquisition). The CR then weakens rapidly as the CS is presented alone (extinction). After a pause, the (weakened) CR reappears (spontaneous recovery).
Generalization
Pavlov and his students noticed that a dog conditioned to the sound of one tone also responded somewhat to the sound of a new and different tone. Likewise, a dog conditioned to salivate when rubbed would also drool a bit when scratched (Windholz, 1989) or when touched on a different body part (Figure 26.7). This tendency to respond to stimuli similar to the CS is called generalization (or stimulus generalization).
Figure 26.7 Generalization
Pavlov demonstrated generalization by attaching miniature vibrators to various parts of a dog’s body. After conditioning salivation to stimulation of the thigh, he stimulated other areas. The closer a stimulated spot was to the dog’s thigh, the stronger the conditioned response.
Generalization can be adaptive, as when toddlers who learn to fear moving cars also become afraid of moving trucks and motorcycles. And generalized fears can linger. Years after being tortured, one Argentine writer reported still flinching with fear at the sight of black shoes—his first glimpse of his torturers as they approached his cell. Generalized anxiety reactions have been demonstrated in laboratory studies comparing abused with nonabused children (Figure 26.8). When an angry face appears on a computer screen, abused children’s brain-wave responses are dramatically stronger and longer lasting (Pollak et al., 1998). And when a face that we’ve been conditioned to like (or dislike) is morphed into another face, we also have some tendency to like (or dislike) the vaguely similar morphed face (Gawronski & Quinn, 2013).
Figure 26.8 Child abuse leaves tracks in the brain
Abused children’s sensitized brains react more strongly to angry faces (Pollak et al., 1998). This generalized anxiety response may help explain their greater risk of psychological disorder.
Stimuli similar to naturally disgusting objects will, by association, also evoke some disgust. Shape otherwise desirable fudge to resemble dog feces, and people will be repulsed (Rozin et al., 1986). Ditto when sewage gets recycled as pure drinking water (Rozin et al., 2015). Toilet → tap → yuck. In each of these human examples, people’s emotional reactions to one stimulus have generalized to similar stimuli.
Discrimination
Pavlov’s dogs also learned to respond to the sound of a particular tone and not to other tones. One stimulus (tone) predicted the US, and the others did not. This learned ability to distinguish between a conditioned stimulus (which predicts the US) and other, irrelevant stimuli is called discrimination. Being able to recognize differences is adaptive. Slightly different stimuli can be followed by vastly different consequences. Facing a guard dog, your heart may race; facing a guide dog, it probably will not.
Pavlov’s Legacy
What remains today of Pavlov’s ideas? A great deal. Most psychologists now agree that classical conditioning is a basic form of learning. Judged with today’s knowledge of the interplay of our biology, psychology, and social-cultural environment, Pavlov’s ideas were incomplete. But if we see further than Pavlov did, it is because we stand on his shoulders.
Why does Pavlov’s work remain so important? If he had merely taught us that old dogs can learn new tricks, his experiments would long ago have been forgotten. Why should we care that dogs can be conditioned to salivate to the sound of a tone? The importance lies, first, in the finding that many other responses to many other stimuli can be classically conditioned in many other organisms—in fact, in every species tested, from earthworms to fish to dogs to monkeys to people (Schwartz, 1984). Thus, classical conditioning is one way that virtually all organisms learn to adapt to their environment.
“I don’t care if she’s a tape dispenser. I love her.”
What conditioning principle is influencing the snail’s affections?2
Second, Pavlov showed us how a process such as learning can be studied objectively. He was proud that his methods involved virtually no subjective judgments or guesses about what went on in a dog’s mind. The salivary response is a behavior measurable in cubic centimeters of saliva. Pavlov’s success therefore suggested a scientific model for how the young discipline of psychology might proceed—by isolating the basic building blocks of complex behaviors and studying them with objective laboratory procedures.
Applications of Classical Conditioning
Other units in this text show how Pavlov’s principles can influence human health and well-being. Here are three examples:
- Drug cravings. Former drug users often feel a craving when they are again in the drug-using context—with people or in places they associate with previous highs. Thus, drug counselors advise their clients to steer clear of people and settings that may trigger these cravings (Siegel, 2005).
- Food cravings. Classical conditioning makes dieting difficult. We readily associate sugary substances with an enjoyable sweet sensation. Researchers have conditioned healthy volunteers to experience cravings after only one instance of eating a sweet food (Blechert et al., 2016). Eating one cookie can create hunger for another. People who struggle with their weight often have eaten unhealthy foods thousands of times, leaving them with strongly conditioned responses to eat the very foods that will keep them in poor health (Hill, 2007).
- Immune responses. Classical conditioning even works on the body’s disease-fighting immune system. When a particular taste accompanies a drug that influences immune responses, the taste by itself may come to produce an immune response (Ader & Cohen, 1985).
Pavlov’s work also provided a basis for Watson’s (1913) idea that human emotions and behaviors, though biologically influenced, are mainly a bundle of conditioned responses. Working with an 11-month-old, Watson and his graduate student Rosalie Rayner (1920; Harris, 1979) showed how specific fears might be conditioned. Like most infants, “Little Albert” feared loud noises but not white rats. Watson and Rayner presented a white rat and, as Little Albert reached to touch it, struck a hammer against a steel bar just behind his head. After seven repeats of seeing the rat and hearing the frightening noise, Albert burst into tears at the mere sight of the rat. Five days later, he had generalized this startled fear reaction to the sight of a rabbit, a dog, and a sealskin coat, but not to dissimilar objects, such as toys.
John B. Watson Watson (1924) admitted to “going beyond my facts” when offering his famous boast: “Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief, and, yes, even beggarman and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.”
Little Albert In Watson and Rayner’s experiments, “Little Albert” learned to fear a white rat after repeatedly experiencing a loud noise as the rat was presented. In these experiments, what was the US? The UR? The NS? The CS? The CR?3
For years, people wondered what became of Little Albert. Sleuthing by Russell Powell and his colleagues (2014) found a well-matched child of one of the hospital’s wet nurses. The child, William Albert Barger, went by Albert B.—precisely the name used by Watson and Rayner. This Albert, who died in 2007, was an easygoing person, though, perhaps coincidentally, he had an aversion to dogs. He died without ever knowing of his early life in a hospital residence or his role in psychology’s history.
People also wondered what became of Watson. After losing his Johns Hopkins professorship over an affair with Rayner (whom he later married), he joined an advertising agency as the company’s resident psychologist. There, he used his knowledge of associative learning to conceive many successful advertising campaigns, including one for Maxwell House that helped make the “coffee break” an American custom (Hunt, 1993).
The treatment of Little Albert would be unethical by today’s standards. Also, some psychologists had difficulty repeating Watson and Rayner’s findings with other children. Nevertheless, Little Albert’s learned fears led many psychologists to wonder whether each of us might be a walking warehouse of conditioned emotions. If so, might extinction procedures or new conditioning help us change our unwanted responses to emotion-arousing stimuli?
One patient, who for 30 years had feared entering an elevator alone, did just that. Following his therapist’s advice, he forced himself to enter 20 elevators a day. Within 10 days, his fear had nearly vanished (Ellis & Becker, 1982). With support from airline AirTran, comedian-writer Mark Malkoff likewise extinguished his fear of flying. He lived on an airplane for 30 days, taking 135 flights that had him in the air 14 hours a day (NPR, 2009). After a week and a half, his fears had faded and he began playing games with fellow passengers. (His favorite antic was the “toilet paper experiment”: He’d put one end of a roll in the toilet, unroll the rest down the aisle, and flush. The entire roll would be sucked down in three seconds.) In Unit XIII we will see more examples of how psychologists use behavioral techniques such as counterconditioning to treat emotional disorders and promote personal growth.