13-1: Classical Conditioning & Therapy

Psychology of Learning

Module 13: Behavioral Therapy

Part 1: Classical Conditioning & Therapy

Looking Back

Modules 11 & 12 explored how observational learning enables the acquisition & transmission of behaviors across individuals & generations. Part 1 now returns to classical conditioning, examining how principles discovered in Pavlov’s laboratory have been applied therapeutically to treat anxiety disorders, phobias, & other clinical conditions. The journey from laboratory discovery to clinical application illustrates how basic research translates into effective treatments that alleviate human suffering.

From Laboratory to Clinic

The principles of classical conditioning discovered by Pavlov in the laboratory have profound implications for understanding & treating psychological disorders. If fears & anxieties can be learned through association, perhaps they can also be unlearned through carefully designed therapeutic procedures. This insight—that learning principles could be systematically applied to change maladaptive behaviors—launched the field of behavior therapy & revolutionized clinical psychology. The bridge between laboratory research & clinical application demonstrates how scientific understanding of basic learning processes can generate effective treatments for real-world problems.

Little Albert: Conditioning Fear in Humans

In 1920, John B. Watson & his graduate student Rosalie Rayner conducted one of psychology’s most famous—and controversial—experiments at Johns Hopkins University. Their goal was to demonstrate that emotional responses, specifically fear, could be conditioned in humans through the same classical conditioning principles Pavlov had discovered in dogs. The study, published in the Journal of Experimental Psychology, would become a cornerstone of behaviorism while raising profound ethical questions that continue to resonate today.

Before the experiment, Watson & Rayner established that Albert showed no fear of various stimuli: a white rat, a rabbit, a dog, a monkey, masks with & without hair, cotton wool, & burning newspapers. Albert was described as remarkably stable & unemotional—”stolid” in Watson’s terms. The experimenters also confirmed that Albert, like most infants, showed a strong fear response to loud, unexpected noises. When a steel bar was struck with a hammer behind Albert’s head, he startled, his lips trembled, & he began to cry. This innate fear response to loud noise would serve as the unconditioned stimulus (US) in their conditioning procedure.

The Conditioning Procedure

When Albert was eleven months old, the conditioning began. Albert was placed on a mattress on a table in the laboratory. A white laboratory rat was presented, & as Albert reached for it, the steel bar was struck loudly behind his head. Albert “jumped violently & fell forward, burying his face in the mattress.” The pairing was repeated, & Albert began whimpering. A week later, additional conditioning trials were conducted. The rat was presented, the bar struck. Albert “fell over immediately to the right side & began to whimper.” After more pairings, Albert “fell over to the left side, got up on all fours & began to crawl away so rapidly that he was caught with difficulty before he reached the edge of the mattress.”

After seven pairings of the rat with the loud noise over two sessions, Albert began crying & trying to crawl away at the mere sight of the rat—even without the noise. The rat had become a conditioned stimulus (CS) that now elicited a conditioned fear response (CR). Watson & Rayner had apparently demonstrated that human emotional responses could be created through classical conditioning, supporting Watson’s behaviorist claim that psychology should focus on observable, learnable behaviors rather than unobservable mental states.

Stimulus Generalization

Five days after conditioning, Watson & Rayner tested whether Albert’s fear would generalize to similar stimuli. Albert showed fear responses to a rabbit he had previously approached without hesitation. He also showed negative reactions to a dog, a fur coat, cotton wool, & Watson’s hair. When presented with a Santa Claus mask with a white beard, Albert cried. This stimulus generalization—the extension of conditioned responses to stimuli similar to the original CS—suggested that phobias acquired through conditioning might spread to related objects, potentially explaining how specific fears could develop into broader anxiety patterns.

Ethical & Methodological Concerns

The Little Albert experiment would be considered grossly unethical by modern standards. Watson deliberately induced fear in an infant without parental informed consent as we understand it today. No attempt was made to eliminate the conditioned fear before Albert left the hospital. Watson himself acknowledged this ethical lapse, writing that they had intended to remove the conditioned responses but Albert was “adopted by an out-of-town family” before they could do so—a claim that remains contested. Modern institutional review boards would never approve such a study, which violates principles of informed consent, protection from harm, & obligation to reverse experimental effects.

Recent scholarship has raised methodological concerns questioning the experiment’s scientific validity. Powell & Schmaltz (2021) analyzed Watson’s original film footage & notes, concluding that the conditioning procedure was “largely ineffective.” They note that Albert’s fear responses were inconsistent & often weak—when allowed to suck his thumb, Albert showed no fear at all, even during conditioning trials. Watson changed details of the experiment across various accounts, raising questions about reliability. The number of conditioning trials varied in different tellings; the degree of fear generalization was exaggerated in later accounts. These inconsistencies suggest the study may not demonstrate what generations of psychology textbooks have claimed.

The Identity Controversy

The mystery of Little Albert’s true identity has sparked a scholarly detective hunt spanning decades. In 2009, psychologists Hall Beck & Sharman Levinson proposed that Albert was Douglas Merritte, son of a wet nurse at Johns Hopkins’ Harriet Lane Home. Tragically, Merritte died at age six from hydrocephalus—fluid accumulation in the brain. Fridlund, Beck, and colleagues (2012) later suggested that the infant shown in Watson’s film displays neurological abnormalities consistent with congenital hydrocephalus, raising disturbing questions about whether Watson knowingly experimented on a sick child.

However, researchers Powell, Digdon, & Harris (2014) identified an alternative candidate: William Albert Barger, whose mother also worked at the hospital. Barger was born within a day of Little Albert’s documented birthdate, his weight matched the film records, & his middle name was Albert. Unlike Merritte, Barger lived to age 87. His family reported he had a lifelong aversion to dogs—though whether this resulted from Watson’s experiment cannot be determined. The debate between the “Merritte” & “Barger” camps continues in academic journals, with each side presenting evidence for their candidate. This controversy illustrates how even foundational studies in psychology may rest on uncertain ground.

Little Peter: The Birth of Behavior Therapy

If Watson demonstrated that fears could be conditioned, Mary Cover Jones demonstrated that fears could be deconditioned—setting the stage for modern behavior therapy. Working under Watson’s general supervision in the early 1920s, Jones systematically studied methods for eliminating children’s fears. Her most famous case was Peter, a two-year-old-and-ten-month-old boy with an intense fear of rabbits. Unlike Little Albert, Peter had apparently acquired his fear naturally, not through experimental conditioning.

Little Peter was a healthy, active, intelligent three-year-old boy (IQ 102) who had developed an intense fear of rabbits. His fear extended to other furry objects—white rats, fur coats, feathers, cotton wool—suggesting the same pattern of stimulus generalization observed in Albert. Peter’s case offered an opportunity to develop & test methods for fear elimination, potentially helping countless children with similar fears. Jones would later be recognized as the “mother of behavior therapy” for this pioneering work, though her contributions were largely overlooked for decades.

Jones’s Method: Direct Conditioning

Jones systematically tested various methods for eliminating Peter’s fear, eventually developing what she called direct conditioning—the gradual introduction of the feared object while the child engaged in a pleasurable activity. This technique would later become the foundation for systematic desensitization. Jones recognized that simply exposing Peter to rabbits was insufficient; the exposure had to be paired with positive experiences to counteract the fear association.

Peter was placed in a high chair & given his favorite food—candy & crackers. While Peter ate, a caged rabbit was placed at the far end of the room—twelve feet away. Peter tolerated this distance while eating. Over subsequent sessions, the rabbit was moved progressively closer as Peter continued eating. The pleasure of eating was intended to inhibit the fear response, gradually replacing fear with tolerance & eventually positive feelings. Jones carefully monitored Peter’s comfort level, never moving the rabbit so close as to disrupt eating or elicit strong fear.

The Tolerance Series

Jones carefully documented Peter’s progress through what she called a tolerance series—a hierarchy of increasingly close approaches to the feared object. This hierarchy anticipates the anxiety hierarchies later formalized by Joseph Wolpe in systematic desensitization:

1. Rabbit anywhere in the room produces fear. 2. Rabbit 12 feet away tolerated. 3. Rabbit 4 feet away tolerated. 4. Rabbit 3 feet away tolerated. 5. Rabbit close in cage tolerated. 6. Rabbit free in room tolerated. 7. Rabbit touched when experimenter holds it. 8. Rabbit touched without experimenter. 9. Rabbit allowed on high chair tray. 10. Rabbit fondled. 11. Rabbit allowed to nibble on fingers. 12. Rabbit held affectionately.

Through 40 sessions over several months, Peter progressed from terror at the sight of a distant rabbit to affectionately holding & playing with the animal. The careful documentation of this progression established that fear could be systematically eliminated through graduated exposure paired with positive experiences.

Setbacks & Recovery

Peter’s progress was not linear. After making substantial gains, Peter contracted scarlet fever & was hospitalized for two months. Upon returning, he encountered a large dog that knocked him down, causing his rabbit fear to return to near-original levels. This spontaneous recovery of the extinguished fear demonstrated that therapeutic gains could be fragile & that setbacks could occur. However, Jones was able to re-establish Peter’s progress relatively quickly using the same direct conditioning procedures, suggesting that some learning was retained despite the apparent relapse. Modern therapists recognize that relapse is common & plan for maintenance strategies accordingly.

Social Learning Enhancement

Jones incorporated social learning elements into Peter’s treatment, anticipating Bandura’s later work on observational learning. Peter had daily play sessions with children who showed no fear of rabbits. Watching other children handle rabbits without distress may have facilitated Peter’s progress through vicarious extinction—observing that feared consequences did not occur for models. This combination of direct conditioning & social modeling proved more effective than either approach alone, suggesting that multiple learning mechanisms could be harnessed therapeutically. Contemporary behavior therapy often combines exposure-based techniques with modeling & other social learning interventions.

Generalization of Extinction

Most importantly, Peter’s reduced fear generalized to other stimuli. His reactions to rats, fur rugs, feathers, & cotton wool all diminished as his rabbit fear decreased. This generalization of extinction was the therapeutic opposite of the generalization of fear observed in Little Albert—demonstrating that both the acquisition & elimination of fear could spread to related stimuli. For therapists, this meant that treating one specific fear might produce broader benefits, reducing fear across multiple related situations.

Counterconditioning: The Core Principle

Counterconditioning involves pairing a conditioned stimulus that elicits an undesirable response with a new unconditioned stimulus that elicits an incompatible, usually positive, response. In Peter’s case, the rabbit (CS for fear) was paired with food (US for pleasure). Through repeated pairings, the rabbit came to elicit pleasure rather than fear. The original CS-fear association was not erased but rather overlaid with a new CS-pleasure association that competed with & inhibited the fear response.

The principle underlying counterconditioning is reciprocal inhibition—the idea that two incompatible emotional responses cannot occur simultaneously. One cannot feel relaxed & anxious at the same time; one cannot feel pleasure & fear simultaneously. By eliciting a response incompatible with fear (eating, relaxation, pleasure) in the presence of the feared stimulus, the fear response is inhibited & a new, positive association can form. This principle became the theoretical foundation for systematic desensitization & remains central to modern exposure-based therapies.

Joseph Wolpe & Systematic Desensitization

Building on Jones’s pioneering work, South African psychiatrist Joseph Wolpe developed systematic desensitization in the 1950s, creating a structured therapeutic procedure that could be widely applied. Wolpe formalized the principles Jones had demonstrated intuitively, creating a replicable treatment protocol that launched behavior therapy as a major force in clinical psychology. His work demonstrated that scientifically-grounded procedures could effectively treat conditions that psychoanalysis had struggled with for decades.

Wolpe experimented with laboratory cats, inducing experimental neuroses & then eliminating them by having cats eat while gradually exposed to increasingly anxiety-provoking situations. He then systematically applied these principles to human patients, publishing his seminal work in 1958. Wolpe’s approach was revolutionary in its emphasis on scientific methodology—treatment was based on established learning principles, outcomes were measured, & procedures were specified clearly enough for replication & refinement.

The Three Components of Systematic Desensitization

Wolpe’s systematic desensitization involves three main components. First, the client learns progressive muscle relaxation—a technique involving systematic tensing & releasing of muscle groups throughout the body. Clients learn to identify tension & achieve deep relaxation on cue. This skill typically requires several sessions to master but provides a portable relaxation response that can be used throughout treatment & beyond. The relaxation serves as the reciprocal inhibitor of anxiety.

Second, the client & therapist collaboratively construct an anxiety hierarchy—a list of fear-inducing situations ranked from least to most threatening. A client with public speaking anxiety might rank situations from “thinking about giving a speech” (low anxiety) to “speaking before a large audience of critics” (maximum anxiety). Hierarchies typically contain 10-20 items spanning the full range of anxiety intensity. Creating an effective hierarchy requires careful assessment of the client’s specific fears & the situations that trigger them.

Third, the client practices relaxation while imagining scenes from the anxiety hierarchy, beginning with the least threatening item. When the client can imagine that scene while remaining relaxed, they progress to the next item. If anxiety occurs, the client signals & returns to relaxation before trying again. Progression through the hierarchy is gradual—clients never advance until they can face each scene without significant anxiety. This systematic approach ensures that clients experience success at each step, building confidence & self-efficacy.

Imaginal Versus In Vivo Exposure

Wolpe’s original technique used imaginal exposure—clients imagined fear-inducing scenarios rather than confronting them directly. This approach offered practical advantages: clients could safely confront scenarios that would be dangerous, expensive, or impossible to create in reality. However, research has generally found in vivo exposure—real-life confrontation with feared stimuli—to be more effective than imaginal exposure for many anxiety disorders. Contemporary treatment often combines both approaches, using imaginal exposure for inaccessible situations & in vivo exposure when feasible. The choice depends on the specific fear, available resources, & client preferences.

Flooding & Implosive Therapy

Not all exposure therapy is gradual. Flooding involves immediate, prolonged exposure to intensely feared stimuli without gradual progression through a hierarchy. A person with a spider phobia might spend an extended session with spiders rather than progressing gradually from pictures to distant spiders to close contact. The rationale is that anxiety cannot be maintained indefinitely—physiological arousal naturally decreases over time (habituation). By preventing escape or avoidance during prolonged exposure, the fear response extinguishes. While potentially more efficient than gradual desensitization, flooding is more aversive & may lead to treatment dropout.

Implosive therapy is a variant that uses imaginal flooding with exaggerated, even unrealistic scenarios. The therapist helps the client vividly imagine worst-case scenarios related to their fear—not just encountering a spider, but being covered in spiders, eaten by spiders, transformed into a spider. The exaggeration is intended to maximize anxiety activation while the imaginal nature keeps the client physically safe. As with flooding, the principle is that prolonged exposure without reinforcement of fear leads to extinction. Research support for implosive therapy is mixed, & the approach has become less common as other exposure methods have proven effective with less client distress.

The Inhibitory Learning Model

Contemporary understanding of exposure therapy has shifted from an emphasis on habituation (fear reduction within & between sessions) to an inhibitory learning model emphasizing the formation of new, competing associations. According to this model, exposure does not erase the original fear memory but creates a new “safety” memory that competes with & inhibits the fear response. Success depends on strengthening this inhibitory learning through various techniques: varying exposure contexts, occasionally including feared outcomes, deepening extinction through additional exposure after fear reduction, & using retrieval cues to enhance generalization.

This model explains why treated fears sometimes return—the original fear memory still exists & can be reactivated by particular contexts, stressors, or the passage of time. The inhibitory learning model has generated therapeutic innovations including exposure variability, occasional reinforced trials, affect labeling, & attention to context during treatment. Recent meta-analyses confirm that exposure-based therapies remain among the most effective treatments for anxiety disorders, with large effect sizes compared to waitlist controls & equivalent or superior outcomes compared to medication treatments.

Exposure & Response Prevention

Exposure & response prevention (ERP) extends exposure principles to obsessive-compulsive disorder. Clients are exposed to obsession-triggering situations while prevented from performing compulsive rituals. A person with contamination obsessions might touch “contaminated” surfaces while refraining from washing. The anxiety triggered by the exposure gradually decreases when the feared consequences (illness, contamination spreading) do not occur. ERP is considered the gold standard psychological treatment for OCD, with response rates of 60-70% for those who complete treatment. The treatment can be challenging, requiring clients to tolerate significant anxiety, but the results justify the temporary discomfort.

Virtual Reality Exposure

Virtual reality exposure therapy (VRET) uses computer-generated environments to simulate feared situations. Clients with fear of heights can experience virtual glass elevators or mountain ledges; those with flying phobia can sit in virtual airplane cabins; combat veterans can process traumatic memories in virtual combat environments. VRET offers controlled, repeatable, customizable exposure experiences without the practical limitations of in vivo exposure—no need to book flights, find tall buildings, or access spiders on demand. Recent meta-analyses (Carl et al., 2019; Shahid et al., 2024) confirm VRET’s effectiveness for anxiety disorders, with effect sizes comparable to in vivo exposure. The technology continues advancing, with 360° video & augmented reality expanding therapeutic possibilities.

Aversion Therapy

While most classical conditioning therapies aim to reduce unpleasant emotional responses, aversion therapy uses conditioning principles to create unpleasant associations with problematic stimuli or behaviors. Historically, aversion therapy paired alcoholic drinks with nausea-inducing drugs (chemical aversion) or paired images of unwanted behaviors with electric shock (electrical aversion). The goal is to replace positive associations (alcohol = pleasure) with negative associations (alcohol = nausea), reducing the behavior’s appeal. However, effectiveness has been limited & ethical concerns are substantial. Chemical aversion can produce medical complications; electric shock raises obvious ethical issues. The approach has largely fallen out of favor for most conditions as more effective & less aversive treatments have developed.

Covert sensitization is an imaginal form of aversion therapy in which clients vividly imagine engaging in the unwanted behavior followed immediately by imagined aversive consequences. A person trying to quit smoking might imagine lighting a cigarette, then imagine intense nausea, vomiting, & public embarrassment. This approach avoids the physical risks of chemical or electrical aversion while still creating negative associations. However, research support is modest, & covert sensitization is rarely used as a standalone treatment today.

Efficacy of Exposure-Based Therapies

Contemporary research continues to validate the effectiveness of exposure-based treatments derived from classical conditioning principles. Meta-analyses by McLean and colleagues (2022) found that exposure therapy for PTSD showed large effect sizes compared to waitlist & treatment-as-usual conditions. The VA/DoD (2023) clinical practice guidelines recommend exposure-based treatments as first-line interventions for PTSD. For anxiety disorders more broadly, systematic reviews consistently find exposure therapy among the most effective psychological treatments available—comparable or superior to medication in both short-term & long-term outcomes. The principles discovered by Pavlov & first applied therapeutically by Mary Cover Jones continue to inform evidence-based treatments helping millions of people overcome debilitating fears & anxieties.

Looking Forward

Part 2 examines applications of operant conditioning to therapy, including token economies, contingency management, & behavioral activation for depression. Where classical conditioning therapies focus primarily on emotional responses & associations, operant approaches address voluntary behaviors & their consequences. Together, classical & operant conditioning principles provide the foundation for a comprehensive behavioral approach to psychological treatment—an approach that continues evolving while remaining grounded in scientific principles of learning.