Classical Conditioning

What is Classical Conditioning?

Classical conditioning is a learning process in which a neutral stimulus (e.g., a ringing sound) is paired with a stimulus that elicits a natural response or reflex (e.g., food), creating an automatic, conditioned response to the neutral stimulus.

The Basic Idea

Why do we feel nauseated by the sight or smell of food that made us sick in the past? Why does the sound of a phone vibrating elicit automatic excitement or anxiety? Why do we feel comforted by the theme songs of our favorite TV shows? All these common experiences are fantastic examples of learned associations.

Over our lives, we learn to associate certain stimuli with specific responses. This occurs through an unconscious learning process called classical conditioning, in which our brains form connections between seemingly unrelated events, leading to automatic reactions.1 This means that a response typically evoked by one stimulus is now also evoked by another stimulus.

For example, research shows that people form associations between the smell of coffee and the energizing effect of consuming coffee.2 Initially, only the act of drinking coffee produces alertness. However, after repeatedly experiencing the scent of coffee alongside its natural stimulating effects, simply smelling coffee (without actually drinking it) can also produce alertness. Associations like these can be positive, negative, or neutral, but they all play a role in shaping our behaviors, preferences, habits, and fears.

Classical conditioning is a key area of study in behavioral psychology, as it’s primarily focused on how our environments shape our behavior. This unconscious learning process has several fascinating consequences, but can also be used to manipulate people’s emotions and behaviors (more on this later).

“No child is ever born afraid. Fear is a learned behavior.”

– Chérie​ Carter-Scott​, Ph.D., MCC, prominent behavioral scientist and bestselling author.

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Key Terms

The concept of classical conditioning is ripe with unique terminology. Understanding these terms is essential for interpreting academic research on the topic and grasping how this learning process really works. Let’s go over some of these key terms and concepts, using our coffee example from earlier to illustrate the classical conditioning process.

Neutral Stimulus: A stimulus that does not initially elicit a physiological response.3 This is the stimulus that is paired with the unconditioned stimulus to form an association between the two. In our example, the neutral stimulus is the smell of coffee before it’s associated with the effects of drinking coffee. 

Unconditioned Stimulus: A stimulus that elicits a natural response without prior learning. In our example, this is the coffee itself, which elicits an energy boost when consumed. 

Unconditioned Response: The natural, involuntary response to the unconditioned stimulus. In our example, the unconditioned response is the natural physiological effects of drinking coffee, such as alertness and increased energy.

Conditioned Stimulus: A stimulus that elicits a learned, conditioned response. The neutral stimulus (the smell of coffee) becomes the conditioned stimulus after repeated pairing with the unconditioned stimulus (the act of drinking coffee). As a result, the conditioned stimulus (the smell of coffee) now triggers a conditioned response (alertness) on its own.

Conditioned Response: The learned response to the conditioned stimulus. In our example, the conditioned response is the feeling of alertness to the smell of coffee alone, even before drinking it.

Extinction: The gradual weakening of the conditioned response when the conditioned stimulus is repeatedly presented without the unconditioned stimulus.4 The weakening association between the two stimuli causes the conditioned response to diminish or disappear completely. In our coffee example, extinction would occur if you repeatedly smelled coffee without actually drinking it. Over time, the association would become weaker and weaker.

Spontaneous Recovery: The reemergence of an extinguished conditioned response after a rest period, even when there are no further pairings of the conditioned stimulus and the unconditioned stimulus.1 For example, if you hadn’t smelled coffee for a while and then suddenly sat down with a cup, you might unexpectedly feel a surge in alertness, even if this response had previously disappeared.

Generalization: The tendency for a conditioned response to occur in response to stimuli that resemble the original conditioned stimulus. This might happen if you also start to feel alert when encountering the general scent of a coffee shop rather than solely the bold smell of a cup of coffee sitting right in front of you.

Discrimination: The ability to differentiate between similar stimuli and the conditioned stimulus, responding only to the conditioned stimulus. For example, this might mean you don’t feel the same alertness you get from smelling coffee when smelling a cup of tea or hot chocolate.

Operant Conditioning: A type of conditioning in which a behavior is associated with a specific outcome, such as a reward or punishment, that makes the behavior more or less likely to occur again.5 Unlike classical conditioning which focuses on unconscious behaviors and automated reflexes, operant conditioning is a conscious learning process involving voluntary actions and their results. For example, if you enjoy the taste and energy boost you get from drinking coffee, you’re more likely to drink coffee again in the future.


A Russian physiologist named Ivan Pavlov discovered classical conditioning accidentally. In the early 20th century, Pavlov was conducting research on the digestion of dogs, specifically studying how saliva aids the digestion process.1 This involved measuring the amount of saliva the dogs produced in response to food. In his research, Pavlov noticed that the dogs eventually began to salivate before the food arrived, in response to the arrival of the lab assistant who typically delivered the food.

Pavlov decided to examine this phenomenon more closely with a series of systematic experiments. For example, he tried ringing a bell shortly before presenting the dogs with food while measuring their saliva production. As expected, the dogs had no response to the bell initially, but naturally salivated in response to the food. After repeatedly pairing the bell with the food, Pavlov noticed that the dogs began salivating in response to the bell alone. Pavlov called this response a conditioned reflex.6

In his research, Pavlov also observed that the conditioned reflex was vulnerable to extinction, becoming weaker the more times the bell was presented without the food. At the same time, he observed that the conditioned reflex could spontaneously recover after some delay, even without subsequent pairings of the bell with the food. These discoveries were important as they revealed that learned behaviors can be unlearned or modified through experience.

Pavlov’s early experiments paved the way for further research as psychologists became interested in how classical conditioning influenced learning, particularly in humans. One of these researchers was John B. Watson. To explore classical conditioning in humans, Watson conducted the famous, and very unethical, “Little Albert” experiment, which involved conditioning a young child to fear a white rat.7 His experiment also involved exploring how this learned fear response could be generalized to similar objects, such as a rabbit, a dog, a fur coat, and even a Santa mask.

Together with the discovery of operant conditioning by B.F. Skinner a few decades later, classical conditioning contributed to the emergence of behaviorism in the mid-20th century. This marked a shift in the field of psychology as researchers began observing behaviors and how they related to environmental stimuli rather than studying internal mental processes.


Ivan Pavlov: A Russian physiologist who produced significant work on pancreatic nerves and stumbled upon classical conditioning in his research on the digestive system.8 Pavlov conducted further experiments on conditioned reflexes and found they originated in the cerebral cortex of the brain. His discoveries laid the foundation for behaviorism and earned him the Nobel Prize in 1904.

Edwin Twitmyer: A professor of psychology and director of the Psychological Laboratory and Clinic at the University of Pennsylvania who independently discovered classical conditioning around the same time as Pavlov.9 While working on his doctoral dissertation, Twitmyer found that a knee-jerk reflex could be triggered by a bell alone (without tapping the tendon), demonstrating a conditioned reflex. Despite presenting his findings to the American Psychological Association in 1904, he did not receive as much recognition as Pavlov for his discovery.

John B. Watson: An American psychologist who popularized behaviorism and established it as a psychological school in the early 20th century. Inspired by Pavlov’s work, Watson was interested in how humans could be conditioned to experience emotions like fear. He is well-known for his controversial “Little Albert” experiment conducted in 1920.7 This experiment, while ethically questionable by current standards, was highly influential in the development of behavioral psychology and our understanding of classical conditioning.


Clinical Applications

The discovery of classical conditioning gave psychologists a better idea of how we learn automatic responses or associations, providing valuable insight into learning and memory. As a result, classical conditioning principles are often used in therapy, especially when attempting to help people unlearn harmful habitual behavior. For example, people in addiction recovery are often advised to avoid environments they associate with substance use.1

Classical conditioning is also leveraged to help people overcome phobias. Through a process called counterconditioning, people can develop new conditional responses to stimuli that previously evoked fear, such as spiders or heights. Counterconditioning involves pairing the trigger stimulus with a response that is contrary to fear, such as relaxation or happiness. This is done through exposure therapy, or gradually exposing the person to the stimulus while they’re in a relaxed, non-fearful state.

Influencing Consumer Behavior

Classical conditioning is frequently used in advertising and marketing to influence consumers. Typically, the goal here is to create positive associations with the brand’s products. Marketers do this by pairing their products, logos, or other branding elements with unconditioned stimuli that naturally make us feel good, such as upbeat music, attractive models, humor, or positive imagery. Think about how Coca-Cola has associated the popular drink with moments of happiness and nostalgia, or how Apple has associated its products with a sense of innovation and modernity.10 These associations are key to the success of many major brands.


Ethical Concerns

Classical conditioning can be an effective marketing tactic for companies. It might even benefit the consumer by creating positive associations with healthy choices, encouraging people to exercise or choose healthy foods. However, leveraging classical conditioning can also be seen as manipulative and unethical, especially when it involves creating associations that could negatively impact people. For example, advertisements often attempt to associate addictive substances like alcohol with scenes depicting fun times, social acceptance, and popularity.

Classical conditioning also faces ethical issues when used in certain therapies. For example, therapists sometimes use aversion therapy to treat addictions. Aversion therapy involves pairing a negative stimulus with an undesirable behavior to evoke a negative response to that behavior. These negative stimuli might include medications that cause nausea, a bad taste or smell, or even an electric shock, though this last one is rarely used today.11 The use of aversion therapy is often criticized for causing psychological harm, possibly leading to the development of anxiety, fear, depression, and even PTSD. Aversion therapy is especially problematic when used nonconsensually, such as with children or people with intellectual disabilities.

The Role of Cognition in Learning

Another criticism of classical conditioning concerns its focus on automatic, unconscious processes. Critics of the behaviorist perspective argue that various other factors influence associations, including our complicated cognitive processes. Psychologist Robert A. Rescorla addressed this issue in an article published in 1988.12 He argues that classical conditioning occurs through conscious processes of prediction and expectation. For example, we know that the smell of coffee means that coffee is coming, and this tells us to expect the energizing effects of coffee in the near future. Rescorla states that the conditioned stimulus serves as a signal for the unconditioned stimulus, establishing a kind of expectation that triggers the response — kind of like the placebo effect, where expectation alone can trigger a physiological response.

Case Study

The use of classical conditioning in advertising is a fascinating topic. A business stands to gain a lot by having their audience form positive associations with their brand. Here’s an interesting case study of how a confectionary company, Kinder Joy, found success in the Indian market — a market that was already dominated by big brands like Cadbury and Nestle.13

Kinder Joy managed to carve out a niche for itself in the Indian market by using classical conditioning principles in its advertising. The company’s most well-known product, a chocolate egg with a toy surprise inside, was key to this process. Including the toy was a well-studied and intentional behavioral strategy. The goal? To associate the treat with the inherent joy and excitement children experience when receiving toys.

Beyond having children form this association while interacting with the product, Kinder Joy also focused on classical conditioning in advertisements, frequently featuring the toys that could be found inside the egg. This further strengthened the association between the product and feelings of joy.

This move helped Kinder Joy tap into a powerful emotional trigger and establish a unique brand identity that resonated with their young audience. The company was widely successful in its India launch, becoming one of the fastest-growing confectioneries in the country. This demonstrates how effective classical conditioning can be for driving sales and building a brand image.

Related TDL Content


Behaviorism emerged as a popular school of thought in the 20th century, led by notable behaviorists Watson and Skinner. This theory of learning focuses on observable behavior and how behavior is shaped by external stimuli. Classical conditioning is just one of these learning processes — check out this article to learn about other behaviorism concepts.


Learning processes like classical conditioning and operant conditioning play a crucial role in the development of habits by influencing how we respond to environmental cues. Check out this article to learn more about the psychological principles behind habits and the historical background of habits as a topic of study.


  1. Rehman, I., Mahabadi, N., Sanvictores, T., & Rehman, C. I. (2023, August 14). Classical Conditioning. In StatPearls [Internet]. StatPearls Publishing. 
  2. Fukuda, M. (2021) Habitual Coffee Drinkers May Present Conditioned Responses from Coffee-Cue. Curr Psychol 40, 5881-5887. 
  3. Rouleau, N., Karbowski, L. M., & Persinger, M. A. (2016). Experimental Evidence of Classical Conditioning and Microscopic Engrams in an Electroconductive Material. PLOS ONE, 11(10), e0165269. 
  4. Lattal, M. K. & Lattal, K. A. (2012) Facets of Pavlovian and operant extinction, Behavioural Processes, 90(1): 1-8. 
  5. Staddon, J. E., & Cerutti, D. T. (2003). Operant Conditioning. Annual Review of Psychology, 54, 115–144.
  6. Pavlov, I. P. (1927). Conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. Oxford Univ. Press. 
  7. Watson, J. B., & Watson, R. R. (1921). Studies in Infant Psychology. Scientific Monthly, New York, 13, 493–515.
  8. Nobel Prize Outreach AB. (2024). Ivan Pavlov – Biographical. Retrieved June 18, 2024, from
  9. Edward B. Twitmyer. (2007, August 12). UPenn Psychology. Retrieved June 18, 2024, from
  10. Marketing Examples of Classical Conditioning (2023, November 6). Primitive Agency. Retrieved June 18, 2024, from
  11. Sangu, M. (2017). Electrical aversion therapy. In Reference module in neuroscience and biobehavioral psychology. Elsevier. 
  12. Rescorla, R. A. (1988). Pavlovian conditioning: It's not what you think it is. American Psychologist, 43(3), 151–160. 
  13. Gauba, R. (2020) The Impact of Classical Conditioning on Consumer BehaviorThe Case of Kinder Joy. Pacific Business Review International 13(5): 103-114.

About the Author

Kira Warje

Kira Warje

Kira holds a degree in Psychology with an extended minor in Anthropology. Fascinated by all things human, she has written extensively on cognition and mental health, often leveraging insights about the human mind to craft actionable marketing content for brands. She loves talking about human quirks and motivations, driven by the belief that behavioural science can help us all lead healthier, happier, and more sustainable lives. Occasionally, Kira dabbles in web development and enjoys learning about the synergy between psychology and UX design.

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