Classical conditioning, also referred to as Pavlovian, is a fundamental form of associative learning in which an organism learns to connect or associate two stimuli that repeatedly occur together.
In this process, a previously neutral stimulus is paired with a stimulus that naturally elicits a specific response; eventually, the neutral stimulus comes to trigger that same response on its own
John B. Watson proposed that the process of classical conditioning (based on Pavlov’s observations) was able to explain all aspects of human psychology.
Everything from speech to emotional responses was simply patterns of stimulus and response. Watson completely denied the existence of the mind or consciousness.
Watson believed that all individual differences in behavior were due to different learning experiences.
Watson (1924, p. 104) famously said:
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 beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations and the race of his ancestors.
How Classical Conditioning Works
There are three stages of classical conditioning. At each stage, the stimuli and responses are given special scientific terms:
Stage 1: Before Conditioning:
In this stage, the unconditioned stimulus (UCS) produces an unconditioned response (UCR) in an organism.
In basic terms, this means that a stimulus in the environment has produced a behavior/response that is unlearned (i.e., unconditioned) and, therefore, is a natural response that has not been taught.
In this respect, no new behavior has been learned yet.
For example, a stomach virus (UCS) would produce a response of nausea (UCR). In another example, a perfume (UCS) could create a response of happiness or desire (UCR).
This stage also involves another stimulus that has no effect on a person and is called the neutral stimulus (NS). The NS could be a person, object, place, etc.
The neutral stimulus in classical conditioning does not produce a response until it is paired with the unconditioned stimulus.
Stage 2: During Conditioning:
During this stage, a stimulus which produces no response (i.e., neutral) is associated with the unconditioned stimulus, at which point it now becomes known as the conditioned stimulus (CS).
For example, a stomach virus (UCS) might be associated with eating a certain food such as chocolate (CS). Also, perfume (UCS) might be associated with a specific person (CS).
For classical conditioning to be effective, the conditioned stimulus should occur before the unconditioned stimulus, rather than after it, or during the same time.
Thus, the conditioned stimulus acts as a type of signal or cue for the unconditioned stimulus.
In some cases, conditioning may take place if the NS occurs after the UCS (backward conditioning), but this normally disappears quite quickly.
The most important aspect of the conditioning stimulus is the it helps the organism predict the coming of the unconditional stimulus.
Often during this stage, the UCS must be associated with the CS on a number of occasions, or trials, for learning to take place.
However, one trial learning can happen on certain occasions when it is not necessary for an association to be strengthened over time (such as being sick after food poisoning or drinking too much alcohol).
Stage 3: After Conditioning:
The conditioned stimulus (CS) has been associated with the unconditioned stimulus (UCS) to create a new conditioned response (CR).
For example, a person (CS) who has been associated with nice perfume (UCS) is now found attractive (CR). Also, chocolate (CS) which was eaten before a person was sick with a virus (UCS) now produces a response of nausea (CR).
Classical Conditioning Examples
Pavlov’s Dogs
The most famous demonstration of classical conditioning comes from Ivan Pavlov’s experiments with dogs.
Pavlov observed that dogs began salivating not just at the sight of food, but at stimuli that reliably preceded it, such as the sound of a bell.
In his procedure, he first presented a bell tone alone.
The dogs showed no salivation, making it a neutral stimulus.
When food was then presented, salivation occurred naturally: the food was the unconditioned stimulus (UCS) and salivation the unconditioned response (UCR).
After repeatedly pairing the bell with food, the bell alone was sufficient to trigger salivation.
The bell had become a conditioned stimulus (CS) and salivation a conditioned response (CR), a learned reaction to a previously neutral cue.
Fear Response
Watson and Rayner (1920) were the first researchers to apply classical conditioning principles to human emotional responses, investigating how the process might explain the development of phobias.
Their subject, known as Little Albert, was an infant described as healthy and generally unemotional.
At nine months old, his reactions to various stimuli were assessed, including a white rat, burning newspapers, and a loud noise produced by striking a steel bar.
Only the noise provoked fear, making it the UCS, with fear as the UCR. The other stimuli, including the rat, were neutral.
At eleven months, the rat was paired with the loud noise on seven occasions over seven weeks.
By the end of this period, the rat alone elicited fear: it had become the CS and fear the CR.
Notably, the conditioned fear transferred spontaneously to similar stimuli, including a rabbit and a dog, demonstrating stimulus generalisation.
The conditioned response persisted five days after conditioning ended, remained detectable after ten days, and was still present a month later, illustrating the durability of conditioned fear responses.
Panic Disorder
Classical conditioning is thought to play a central role in the development of panic disorder (Bouton et al., 2002).
The disorder often begins with an initial panic attack, which functions as a UCS, producing intense fear and physiological arousal as unconditioned responses.
During this first attack, neutral stimuli present in the environment, both external (a particular location, for example) and interoceptive (sensations such as an elevated heart rate), become associated with the panic response.
These become conditioned stimuli capable of triggering anxiety and panic in their own right.
Through this conditioning process, anxiety becomes focused on the prospect of future attacks.
This anticipatory anxiety, itself a conditioned response, leads to heightened vigilance toward bodily sensations, which in turn lowers the threshold for panic.
The result is a self-reinforcing cycle that can entrench the disorder after a single conditioning episode.
Consistent with this account, most patients with panic disorder report a distinct early episode that preceded the onset of the condition, and prospective research confirms that conditioned anxiety can develop in the aftermath of an initial panic attack (Bouton et al., 2002).
Importantly, these conditioning processes are thought to operate largely outside conscious awareness, driven by emotional learning systems that function independently of declarative memory.
Addiction
Classical conditioning also underpins cue reactivity theory, which holds that people learn to associate environments and situations (such as a particular pub, social group, or time of day) with the rewarding effects of a substance.
Once established, these cues alone can trigger craving.
In the case of nicotine, the drug itself is the UCS, and the dopamine-mediated pleasure it produces is the UCR. Stimuli consistently present during smoking, initially neutral, become conditioned stimuli through repeated pairings.
They then elicit a conditioned response: craving and physiological arousal, even before the substance is consumed.
When nicotine is absent, dopamine levels drop and withdrawal symptoms emerge, increasing the likelihood of smoking in the presence of those conditioned cues.
This cycle helps explain both the persistence of addiction and the difficulty of quitting in familiar environments.
Supporting evidence comes from Carter and Tiffany (1999), who conducted a meta-analysis of 41 cue-reactivity studies across alcohol, cigarette, cocaine, and heroin dependence.
Dependent individuals consistently showed stronger physiological arousal and reported higher craving in response to drug-related cues compared to neutral stimuli.
Classroom Learning
Classical conditioning has implications for the classroom, particularly in shaping students’ emotional associations with learning.
While operant conditioning tends to have more direct instructional applications, teachers should be mindful that repeated negative experiences can condition aversive responses to school itself.
A student who is bullied may learn to associate the school environment with fear and anxiety.
Similarly, a student who is humiliated in front of the class during a particular subject may develop a lasting aversion to that subject, one that persists long after the original incident.
In this way, what appears to be a fixed personal dislike may in fact reflect a conditioned emotional response established early in a student’s academic career.
The practical implication is straightforward: creating positive, low-anxiety learning environments is not merely good pastoral practice; it is a prerequisite for effective learning.
Principles of Classical Conditioning
Neutral Stimulus (NS)
A neutral stimulus is one that initially produces no conditioned response. It only begins to elicit a reaction after being repeatedly paired with an unconditioned stimulus.
In Pavlov’s experiment, the bell was the neutral stimulus: before conditioning, it produced no salivation. It acquired significance only through its association with food.
Unconditioned Stimulus (UCS)
An unconditioned stimulus is any feature of the environment that automatically and reliably produces a response without prior learning.
No conditioning is required; the response is innate.
In Pavlov’s study, food served as the unconditioned stimulus, reliably triggering salivation the moment it was presented.
Unconditioned Response (UCR)
An unconditioned response is the natural, automatic reaction produced by an unconditioned stimulus. Like the stimulus that triggers it, the response requires no prior learning.
Pavlov demonstrated this by presenting a dog with food and measuring salivation, a reflexive biological response that occurred without any training.
Conditioned Stimulus (CS)
A conditioned stimulus is a previously neutral stimulus that, after repeated pairing with an unconditioned stimulus, comes to elicit a response on its own.
In Pavlov’s experiment, the bell became the conditioned stimulus: through its association with food, it eventually triggered salivation independently.
In essence, the organism has learned to treat one stimulus as a reliable signal for another.
Acquisition
Acquisition is the initial phase of classical conditioning during which the association between a neutral stimulus and an unconditioned stimulus is established.
With each pairing, the neutral stimulus becomes increasingly effective at eliciting a response.
Acquisition is considered complete when the conditioned stimulus reliably produces the conditioned response.
Extinction
Extinction is the gradual weakening and eventual disappearance of a conditioned response when the conditioned stimulus is repeatedly presented without the unconditioned stimulus.
Once the predictive relationship between the two stimuli is broken, the conditioned response loses its functional basis.
In Pavlov’s experiments, when the bell was sounded repeatedly without food following, the dog’s salivation progressively diminished until it ceased altogether.
Importantly, extinction does not erase the original learning; it reflects new learning that overrides it.
Spontaneous Recovery
Spontaneous recovery is the reappearance of an extinguished conditioned response after a period of rest, when the conditioned stimulus is presented again.
The recovered response is typically weaker than the original conditioned response and will extinguish again more rapidly if the unconditioned stimulus is not reintroduced.
Pavlov observed this when, after allowing time to pass following extinction, he rang the bell again and found that his dogs resumed salivating, albeit less strongly than before.
Spontaneous recovery demonstrates that extinction suppresses rather than permanently eliminates conditioned associations.
Generalization
Generalisation occurs when an organism responds to stimuli that are similar, but not identical, to the original conditioned stimulus.
The greater the similarity, the stronger the generalised response tends to be.
In Pavlov’s experiments, a dog conditioned to salivate at one bell tone might also salivate in response to a bell of a different pitch.
This reflects the organism applying its learned association broadly across related stimuli.
Discrimination
Discrimination is the complementary process to generalisation: the organism learns to distinguish between similar stimuli and responds only to those specifically associated with the unconditioned stimulus.
Through repeated exposure, Pavlov’s dogs learned to differentiate between two bells, salivating only at the one that had been paired with food and ignoring the other.
Discrimination training produces more precise, selective conditioned responses.
Higher-Order Conditioning
Higher-order conditioning occurs when an established conditioned stimulus is used to condition a new neutral stimulus, without any further involvement of the original unconditioned stimulus.
For example, once a bell (CS1) has been conditioned to elicit salivation through pairing with food, a light (NS) can then be paired with the bell alone.
In time, the light elicits salivation by itself, even though it was never directly paired with food.
Here, the original conditioned stimulus effectively functions as an unconditioned stimulus in the second stage of learning.
Higher-order conditioning demonstrates how conditioned associations can extend beyond direct experience, creating chains of learned responding.
Blocking
Merely pairing two stimuli is not always sufficient.
If an animal has already learned to associate a bell with a shock, simultaneously adding a light alongside the bell will not cause the animal to learn to fear the light.
Because the bell already perfectly predicts the shock, conditioning to the new stimulus is “blocked
Critical Evaluation
Strengths
Scientific credibility and experimental rigour
A foundational strength of classical conditioning is its scientific basis.
By rejecting subjective introspection in favour of controlled laboratory experimentation and the direct measurement of observable behaviour, Pavlov’s work helped transition psychology from a philosophical discipline into an empirical science.
The classical conditioning framework breaks behaviour down into discrete stimulus-response units, providing the experimental control necessary to establish causal relationships with precision.
This reductionist approach, while not without its critics, has the practical advantage of making complex behaviours testable and reproducible.
Phenomena such as acquisition, extinction, generalisation, and discrimination have all been demonstrated repeatedly across a wide range of species and laboratory settings, including in human participants conditioning responses such as the eye-blink and galvanic skin response.
Supporters of reductionism argue that simplifying behaviour in this way is a prerequisite for rigorous science.
Critics, however, note that it can produce incomplete explanations when the full complexity of human behaviour is at stake.
Clinical Applications
One of the most significant strengths of classical conditioning is its translation into effective clinical therapies for mental health conditions.
Treating Phobias and Anxiety
Phobias and anxiety disorders are treated using the principle of extinction, extended into the technique of systematic desensitisation.
The patient is first taught deep relaxation, then constructs a hierarchy of feared stimuli from least to most threatening.
Working progressively through this hierarchy, the patient learns to associate each stimulus with relaxation rather than fear, a process known as counter-conditioning.
Because a person cannot be simultaneously relaxed and terrified (the principle of reciprocal inhibition), the conditioned fear response is effectively replaced.
Treating Addictions and Impulse Control Disorders
Addiction and impulse control disorders are addressed through aversion therapy, which pairs an addictive substance or behaviour with an unpleasant unconditioned stimulus, such as a drug that induces nausea or a mild electric shock.
Through repeated pairings, the previously rewarding stimulus becomes associated with discomfort, reducing the desire to engage with it.
A related technique, covert sensitisation, achieves a similar effect without physical intervention by asking patients to vividly imagine aversive imagery while thinking about the target behaviour.
Both approaches show increased effectiveness when combined with cognitive behavioural therapy or counselling.
Explaining involuntary behaviour
Classical conditioning provides a compelling account of how reflexive and involuntary responses, including phobias, emotional reactions, and physiological changes, are acquired through experience rather than being fixed biological givens.
This explanatory reach extends to clinical disorders.
In post-traumatic stress disorder (PTSD) sufferers frequently exhibit strong conditioned responses to stimuli that were present during the traumatic event, such as sounds, smells, or locations (Charney et al., 1993).
The conditioning framework accounts for why these responses are automatic and difficult to suppress voluntarily.
However, the model has limits here.
Since not everyone exposed to the same traumatic event develops PTSD, conditioning alone cannot be the full explanation.
Individual differences in how people appraise stressors, together with factors in the recovery environment such as social support and family stability, clearly moderate the outcome.
Broad explanatory power
Although classical conditioning was first identified through the study of animal digestion, its explanatory reach has proven remarkably wide.
It provides a principled account of how complex human emotions, including phobias, panic disorder, and everyday anxieties, are formed, and how they generalise beyond the original conditioned stimulus.
Its principles have been extended to shed light on language acquisition, moral and gender development, and the formation of interpersonal relationships, establishing it as one of the foundational theories of human behaviour.
Psychoneuroimmunology
Perhaps the most striking finding to emerge from classical conditioning research is that immune responses themselves can be conditioned.
In studies where a distinctively flavoured drink was repeatedly paired with an immunosuppressive drug, animals eventually showed measurable immunosuppression in response to the flavoured drink alone, without any drug being administered.
This demonstrates that classical conditioning is powerful enough to alter biological immune function, providing compelling evidence of a direct connection between psychological processes and physiological immunity.
Beyond its theoretical significance, this finding suggests genuine future potential for using conditioning-based protocols to modulate immune responses in medical treatment.
Weaknesses
Ignores biological predispositions
Classical conditioning traditionally assumed that any neutral stimulus could be paired with any unconditioned stimulus with equal ease, a principle sometimes called equipotentiality.
Research has shown this assumption to be false.
Seligman’s concept of biological preparedness holds that organisms are evolutionarily primed to acquire certain associations far more readily than others.
Humans and animals develop taste aversions.
For example, after a single pairing of a novel food with illness, even when several hours separate the two events, whereas comparable conditioning to visual or auditory cues is far weaker.
Similarly, humans acquire fears of evolutionarily relevant stimuli, such as snakes or heights, with far fewer pairings than fears of neutral objects.
Classical conditioning does not apply uniformly across all stimuli or all species. Conditioning is shaped and constrained by an organism’s evolutionary history, a dimension the original theory did not incorporate.
Ignorance of cognition
Critics accuse the behaviourist approach of being mechanistic and viewing humans merely as machines responding to stimuli.
Traditional conditioning posited that learning is an automatic, unthinking process resulting merely from the repeated pairing of a conditioned stimulus (CS) and an unconditioned stimulus (UCS).
However, cognitive psychologists argue that learning actually involves detecting and understanding the relationships between events.
This is supported by the blocking effect, which demonstrates that simply pairing a CS and a UCS is not sufficient for learning to occur.
For instance, if an animal has already learned that a light perfectly predicts an impending electric shock, subsequently adding a noise alongside the light will not cause the animal to condition a fear response to the noise.
Because the light already predicts the shock, there is no “prediction error” or surprise, making the new stimulus redundant.
Human Awareness and Rule-Based Learning
The limitations of classical conditioning become more pronounced when applied to human adults.
Research indicates that conscious awareness plays a decisive role in human conditioning.
Participants who are simply told that the unconditioned stimulus will no longer occur show an immediate loss of the conditioned response, bypassing the slow, gradual process of extinction that traditional theory predicts (Davey, 1983).
Conversely, participants who remain unaware of the relationship between stimuli frequently fail to show conditioning at all (Brewer, 1974).
This contradicts classical models that posit two separate learning systems, one conscious and one unconscious, with conditioning operating through the latter independently of awareness (Lovibond & Shanks, 2002).
There are also notable differences between young children or those with severe learning difficulties and older children and adults in conditioning and discrimination tasks, differences that appear largely attributable to language development (Dugdale & Lowe, 1990).
This suggests that humans have access to far more efficient, language-mediated, rule-based forms of learning than the slow, repetitive formation of stimulus-response associations can account for.
Ethical Concerns
The principles of classical conditioning raise ethical concerns about manipulating behavior without consent. This is especially true in advertising and politics.
- Manipulation of preferences – Classical conditioning can create positive associations with certain brands, products, or political candidates. This can manipulate preferences outside of a person’s rational thought process.
- Encouraging impulsive behaviors – Conditioning techniques may encourage behaviors like impulsive shopping, unhealthy eating, or risky financial choices by forging positive associations with these behaviors.
- Preying on vulnerabilities – Advertisers or political campaigns may exploit conditioning techniques to target and influence vulnerable demographic groups like youth, seniors, or those with mental health conditions.
- Reduction of human agency – At an extreme, the use of classical conditioning techniques reduces human beings to automata reacting predictably to stimuli. This is ethically problematic.
Deterministic theory
A final criticism of classical conditioning theory is that it is deterministic.
This means it does not allow the individual any degree of free will. Accordingly, a person has no control over the reactions they have learned from classical conditioning, such as a phobia.
The deterministic approach also has important implications for psychology as a science. Scientists are interested in discovering laws that can be used to predict events.
However, by creating general laws of behavior, deterministic psychology underestimates the uniqueness of human beings and their freedom to choose their destiny.
Limitations in explaining phobias
Although the Little Albert study demonstrated that fear responses can be classically conditioned, the model struggles to provide a complete account of clinical phobias.
Persistence is a particular problem.
If a person repeatedly encounters a feared stimulus without experiencing the original unconditioned stimulus, the conditioned fear should extinguish.
Yet real phobias often persist for years without any reinforcement.
Operant conditioning, specifically the negative reinforcement provided by avoidance behaviour, is needed to explain why the phobia is maintained long after the original conditioning episode.
Cognitive factors present a further difficulty.
Classical conditioning offers a purely behavioural account and cannot explain the irrational beliefs, catastrophic thinking, and anticipatory anxiety that characterise anxiety disorders.
Fear is not simply a reflexive response to a conditioned stimulus; it is bound up with how the person interprets and evaluates the threat.
The Role of Nature in Classical Conditioning
Behaviorists argue all learning is driven by experience, not nature. Classical conditioning exemplifies environmental influence.
However, our evolutionary history predisposes us to learn some associations more readily than others. So nature also plays a role.
Example 1
For example, PTSD develops in part due to strong conditioning during traumatic events.
The emotions experienced during trauma lead to neural activity in the amygdala, creating strong associative learning between conditioned and unconditioned stimuli (Milad et al., 2009).
Individuals with PTSD show enhanced fear conditioning, reflected in greater amygdala reactivity to conditioned threat cues compared to trauma-exposed controls.
In addition to strong initial conditioning, PTSD patients exhibit slower extinction to conditioned fear stimuli.
During extinction recall tests, PTSD patients fail to show differential skin conductance responses to extinguished versus non-extinguished cues, indicating impaired retention of fear extinction.
Deficient extinction retention corresponds to reduced activation in the ventromedial prefrontal cortex and hippocampus and heightened dorsal anterior cingulate cortex response during extinction recall in PTSD patients.
Example 2
In influential research on food conditioning, John Garcia found that rats easily learned to associate a taste with nausea from drugs, even if illness occurred hours later.
However, conditioning nausea to a sight or sound was much harder.
This showed that conditioning does not occur equally for any stimulus pairing.
Rather, evolution prepares organisms to learn some associations that aid survival more easily, like linking smells to illness.
Example 3
The evolutionary significance of taste and nutrition ensures robust and resilient classical conditioning of flavor preferences, making them difficult to reverse (Hall, 2002).
Forming strong and lasting associations between flavors and nutrition aids survival by promoting the consumption of calorie-rich foods. This makes flavor conditioning very robust.
Repeated flavor-nutrition pairings in these studies lead to overlearning of the association, making it more resistant to extinction.
The learning is overtrained, context-specific, and subject to recovery effects that maintain the conditioned behavior despite extinction training.
Classical vs. operant condioning
In summary, classical conditioning is about passive stimulus-response associations, while operant conditioning is about actively connecting behaviors to consequences. Classical works on reflexes and operant on voluntary actions.
- Stimuli vs consequences: Classical conditioning focuses on associating two stimuli together. For example, pairing a bell (neutral stimulus) with food (reflex-eliciting stimulus) creates a conditioned response of salivation to the bell. Operant conditioning is about connecting behaviors with the consequences that follow. If a behavior is reinforced, it will increase. If it’s punished, it will decrease.
- Passive vs. active: In classical conditioning, the organism is passive and automatically responds to the conditioned stimulus. Operant conditioning requires the organism to perform a behavior that then gets reinforced or punished actively. The organism operates on the environment.
- Involuntary vs. voluntary: Classical conditioning works with involuntary, reflexive responses like salivation, blinking, etc. Operant conditioning shapes voluntary behaviors that are controlled by the organism, like pressing a lever.
- Association vs. reinforcement: Classical conditioning relies on associating stimuli in order to create a conditioned response. Operant conditioning depends on using reinforcement and punishment to increase or decrease voluntary behaviors.
Learning Check
- In Ivan Pavlov’s famous experiment, he rang a bell before presenting food powder to dogs. Eventually, the dogs salivated at the mere sound of the bell. Identify the neutral stimulus, unconditioned stimulus, unconditioned response, conditioned stimulus, and conditioned response in Pavlov’s experiment.
- A student loves going out for pizza and beer with friends on Fridays after class. Whenever one friend texts the group about Friday plans, the student immediately feels happy and excited. The friend starts texting the group on Thursdays when she wants the student to feel happier. Explain how this is an example of classical conditioning. Identify the UCS, UCR, CS, and CR.
- A college student is traumatized after a car accident. She now feels fear every time she gets into a car. How could extinction be used to eliminate this acquired fear?
- A professor always slams their book on the lectern right before giving a pop quiz. Students now feel anxiety whenever they hear the book slam. Is this classical conditioning? If so, identify the NS, UCS, UCR, CS, and CR.
- Contrast classical conditioning and operant conditioning. How are they similar and different? Provide an original example of each type of conditioning.
- How could the principles of classical conditioning be applied to help students overcome test anxiety?
- Explain how taste aversion learning is an adaptive form of classical conditioning. Provide an original example.
- What is second-order conditioning? Give an example and identify the stimuli and responses.
- What is the role of extinction in classical conditioning? How could extinction be used in cognitive behavioral therapy for anxiety disorders?
References
Bouton, M. E., Mineka, S., & Barlow, D. H. (2001). A modern learning theory perspective on the etiology of panic disorder. Psychological Review, 108(1), 4.
Bremner, J. D., Southwick, S. M., Johnson, D. R., Yehuda, R., & Charney, D. S. (1993). Childhood physical abuse and combat-related posttraumatic stress disorder in Vietnam veterans. The American journal of psychiatry.
Brewer, W. F. (1974). There is no convincing evidence for operant or classical conditioning in adult humans.
Carter, B. L., & Tiffany, S. T. (1999). Meta‐analysis of cue‐reactivity in addiction research. Addiction, 94(3), 327-340.
Davey, B. (1983). Think aloud: Modeling the cognitive processes of reading comprehension. Journal of Reading, 27(1), 44-47.
Dugdale, N., & Lowe, C. F. (1990). Naming and stimulus equivalence.
Garcia, J., Ervin, F. R., & Koelling, R. A. (1966). Learning with prolonged delay of reinforcement. Psychonomic Science, 5(3), 121–122.
Garcia, J., Kimeldorf, D. J., & Koelling, R. A. (1955). Conditioned aversion to saccharin resulting from exposure to gamma radiation. Science, 122, 157–158.
Hall, G. (2022). Extinction of conditioned flavor preferences. Journal of Experimental Psychology: Animal Learning and Cognition.
Logan, C. A. (2002). When scientific knowledge becomes scientific discovery: The disappearance of classical conditioning before Pavlov. Journal of the History of the Behavioral Sciences, 38(4), 393-403.
Lovibond, P. F., & Shanks, D. R. (2002). The role of awareness in Pavlovian conditioning: empirical evidence and theoretical implications. Journal of Experimental Psychology: Animal Behavior Processes, 28(1), 3.
Milad, M. R., Pitman, R. K., Ellis, C. B., Gold, A. L., Shin, L. M., Lasko, N. B.,…Rauch, S. L. (2009). Neurobiological basis of failure to recall extinction memory in posttraumatic stress disorder. Biological Psychiatry, 66(12), 1075–82.
Pavlov, I. P. (1897/1902). The work of the digestive glands. London: Griffin.
Thanellou, A., & Green, J. T. (2011). Spontaneous recovery but not reinstatement of the extinguished conditioned eyeblink response in the rat. Behavioral Neuroscience, 125(4), 613.
Watson, J. B. (1913). Psychology as the behaviorist views it. Psychological Review, 20, 158–177.
Watson, J.B. (1913). Psychology as the behaviorist Views It. Psychological Review, 20, 158-177.
Watson, J. B. (1924). Behaviorism. New York: People’s Institute Publishing Company.
Watson, J. B., & Rayner, R. (1920). Conditioned emotional reactions. Journal of experimental psychology, 3(1), 1.
