The Psychology of Learning

Classical Conditioning

Pavlov's Discovery

In classical conditioning, a neutral stimulus is repeatedly paired with a stimulus that elicits a reflexive response, and then the neutral stimulus acquires the power to elicit the response on its own.
Ivan Pavlov was a Russian physiologist whose work laid the foundation for behavioral psychology. Pavlov's primary research focused on digestive processes. Digestion begins in the mouth when food cues (such as seeing, smelling, or tasting food) elicit salivation. Pavlov noticed that dogs in his laboratory salivated in response to nonfood cues, such as the sound of footsteps or the ringing of a bell that signaled feeding time. These otherwise neutral stimuli elicited what is normally an automatic, reflexive response to food. Pavlov referred to this as a learned reflex. Learning is the term used to describe a change in behavior as a result of experience. Classical conditioning involves learning an association between paired events. Specifically, a neutral stimulus is paired with a stimulus that normally elicits an involuntary, automatic response until the neutral stimulus elicits the response on its own. Acquisition is the stage of classical conditioning in which a conditioned response is trained. In this phase, a neutral stimulus is paired with a stimulus that normally elicits an involuntary, automatic response. Eventually, the neutral stimulus will trigger the same involuntary response on its own. The stimulus that normally elicits the involuntary response is called the unconditioned stimulus (US). The involuntary reaction that the US normally elicits is called the unconditioned response (UR). The neutral stimulus becomes a conditioned stimulus (CS) once it acquires the power to elicit an involuntary response by being repeatedly paired with the US. The response elicited by a CS is called the conditioned response (CR). For example, the loud noise of a firecracker (US) elicits an involuntary startle response. The shoulders rise, the mouth opens, the eyes close, and the body flinches (the UR). If a neutral stimulus, such as a flashing light, is repeatedly presented just before the firecracker explodes, the light alone (now a CS) will come to elicit the startle response (now a CR). In other words, the person will come to flinch at the flashing light because the brain has learned that it means an ear-splitting sound is imminent.

Classical Conditioning

In classical conditioning, repeatedly pairing two stimuli leads to a learned association. A loud noise naturally produces a startle response, but a flashing light does not. But if the light is repeatedly paired with the loud noise, eventually the light alone will produce a startle response.
In the real world, environments are complex. Many things may occur at about the same time. In overshadowing, organisms are more likely to form association with highly prominent neutral stimuli than with weaker neutral stimuli that may also be present. For example, if a soft tone and flashing blue light both precede the firecracker, organisms are more likely to learn an association between the light and firecracker than the soft tone and firecracker.

Higher-Order Conditioning and Blocking

Once an association between an unconditioned stimulus and a conditioned stimulus has been acquired, the conditioned stimulus can be used to elicit the conditioned response.
Higher-order conditioning (or second-order conditioning) occurs when a conditioned stimulus is used in place of an unconditioned stimulus to build an association between another neutral stimulus and the conditioned response. For example, once the flashing blue light acquires the power to elicit the startle response, it may be paired repeatedly with a flashing red light until the red light comes to elicit the startle response as well. In practice, higher-order conditioning typically elicits a weaker response that quickly goes away. In a process called blocking, once an association between an unconditioned stimulus and a conditioned stimulus has been acquired, that learning inhibits formation of new associations between an unconditioned stimulus and other stimuli. For example, if a startle response has been acquired to a flashing blue light that was paired with a firecracker exploding and a flashing red light is now paired with the flashing blue light just before the firecracker explodes, the blue light will still elicit the startle response when presented on its own, but the red light will not. The brain learns that the blue light is a sufficient predictor of what is to come.

Blocking in Classical Conditioning

Once an association between an unconditioned stimulus and a conditioned stimulus has been acquired, that learning will inhibit the formation of new associations. A person who has linked blue lights with loud sounds would have more difficulty learning an association between a red light and that sound. A person with no prior conditioning history would learn the new association easily.

Generalization, Discrimination, Extinction, and Spontaneous Recovery

Conditioned responses may occur only in response to specific stimuli (discrimination) or may generalize to similar stimuli. They may end after no longer being paired with the unconditioned stimuli (extinction) but return through spontaneous recovery.
In generalization, stimuli similar to a conditioned stimulus also elicit conditioned responses. For example, a person who learned an association between a flashing blue light and a firecracker may also begin to flinch at flashing lights of other colors. Or they may flinch in response to blue lights that do not flash. The learned response has generalized to other similar stimuli.

Conversely, through discrimination the brain learns to differentiate between stimuli that do and do not signal the onset of the unconditioned stimulus. For example, a firecracker may explode only after a blue light flashes but never after a white light flashes. The blue light will elicit the startle reflex, but the white light will not because the brain has learned to distinguish between events that follow the lights.

In the extinction phase, the conditioned stimulus is presented alone repeatedly—without the unconditioned stimulus—until the conditioned stimulus loses its power to elicit the conditioned response. In other words, the conditioned stimulus returns to a neutral stimulus. If the flashing blue light (conditioned stimulus) is presented repeatedly without the firecracker, eventually it will no longer trigger a startle response.

After the conditioned response has been extinguished, it sometimes spontaneously reoccurs. If a person does not see a flashing blue light for a period of time, they may flinch when they see it again. This happens because the original learned association between the light and firecracker never fully disappears.
Repeatedly pairing an unconditioned stimulus and neutral stimulus will lead to a learned association (acquisition). The neutral stimulus becomes a conditioned stimulus. Presenting the conditioned stimulus without the unconditioned stimulus will lead to extinction. Over time, the learned response may reemerge, a process called spontaneous recovery

Opponent Process Theory of Addiction

Classical conditioning underlies drug tolerance, overdose, and relapse.
Compulsive use of a substance despite harmful consequences is called addiction. According to the opponent process theory of drug addiction, classical conditioning influences drug tolerance and relapse. According to opponent process theory, environmental cues that signal drug intake is imminent lead the body to start the process of counteracting the drug. For example, if a drug lowers pain sensitivity, the body increases pain sensitivity in response to drug-related cues, such as a syringe. This is the brain's attempt to keep the body in balance. As the body becomes more skilled at counteracting the drug, people typically start increasing the dose taken. If a person takes this increased dose in an unfamiliar environment, the learned drug-related cues are not present. As a result, the brain does not trigger the protective response, and people may overdose. This explains why experienced drug users sometimes overdose after taking only their usual dose in an unfamiliar setting.

If an environment presents drug-related cues but the drug is not taken, people with addiction problems will experience withdrawal symptoms—for example, shaking, sweating, insomnia, and irritability. People can show physical signs of withdrawal years after kicking their habit when asked to perform their drug "cooking up" procedure. Watching a videotape of heroin preparation can have the same effect. Former alcoholics report intense cravings and evidence withdrawal symptoms when they enter bars. This is why it is much easier for people to overcome addiction in new environments, such as drug rehabilitation centers. The cues aren't there, so the cravings subside. But when they return to cue-rich environments, the cravings return, making relapse more likely.

Fetishes and Phobias to Neutral Stimuli

Classical conditioning can underlie the development of fetishes—the association of neutral stimuli with magical power or sexual arousal—and phobias—the association of neutral stimuli with fear-inducing stimuli.
The term fetish can refer to an object thought to have magical powers or to a sexual obsession with a usually nonsexual object. Both meanings are linked to classical conditioning. People can come to believe that ordinary objects have magical powers if they are present when an unusual event occurs. A baseball player may believe their lucky shoes help their team win if the team pulls off a surprise win the first time they wear the new shoes. Sexual fetishes can occur if the object becomes associated with sexual arousal. For example, a person may masturbate repeatedly to a video showing someone wearing high heels. Over time, they may learn an association between high heels and arousal. Eventually, high heels alone will produce arousal. Researchers have conditioned men to experience sexual arousal in response to neutral stimuli such as geometric shapes by pairing these cues with pornography.

People can develop phobias if an experience causes them to associate a neutral stimulus with a fear-inducing stimulus. For example, a person may develop a phobia of eating after a choking experience. The first scientific demonstration of acquired phobias was conducted by American psychologist John B. Watson and his assistant Rita Raynor. Watson and Raynor induced a phobia to a white rat in an 11-month-old infant (nicknamed Little Albert). They did this by striking a hammer on a steel bar whenever the rat was presented to the infant. Prior to this pairing, Albert showed that he liked playing with the rat. After the pairings, Albert cried and attempted to crawl away whenever the rat was presented. Albert's fear generalized to other similar stimuli, including the family dog, a fur coat, some cotton wool, and a Santa Claus mask.

Practical Applications of Classical Conditioning

Classical conditioning is used in aversion therapy, by pairing undesired behavior with an unpleasant stimulus, and in advertising, by repeatedly pairing desirable images with a company logo.
The goal of aversion therapy is to eliminate undesirable behaviors by pairing the behavior with an unpleasant stimulus. These pairings are continued until the undesirable behavior elicits an aversion (intense dislike or feelings of disgust) even when the unpleasant stimulus is no longer present.

Aversion therapy has been used to target drug and alcohol abuse, overeating, smoking, gambling, and compulsive nail biting. For example, a drug called Antabuse blocks the breakdown of alcohol. If people take this drug before drinking, consuming alcohol will lead to nausea. Eventually, even just smelling or tasting alcohol will make people feel nauseous. People who want to stop biting their nails may paint a spicy or foul-tasting substance on their nails. Other aversive stimuli used have included unpleasant odors or images and even mild electrical shock. While aversion therapy has proved successful in many cases, it remains controversial. By necessity, it involves inflicting some level of physical or emotional pain during the therapeutic process.

Classical conditioning often underlies advertisements used to increase sales. Ads often display products in ways that highlight features that naturally elicit feelings of desire. For example, a fast-food ad may show close-up, vivid pictures of appetizing food (US) that trigger feelings of hunger (UR). At the same time, viewers are repeatedly shown the company's logo (CS). Over time, simply seeing the logo (now a CR) may cause people to experience hunger and desire. The result is that the viewer is more likely to purchase the product.