What Is an Unconditioned Response?

Mother and two daughters salivate looking at cupcakes

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An unconditioned response is an automatic reflex that occurs in response to an unconditioned stimulus. Unconditioned responses are natural and innate, and therefore, don’t have to be learned. The concept of unconditioned responses was first defined by Ivan Pavlov as part of his discovery of classical conditioning.

Key Takeaways: Unconditioned Response

  • An unconditioned response is a natural and automatic reaction to an unconditioned stimulus; it is present from the time we are born.
  • Ivan Pavlov defined unconditioned response as part of the process of classical conditioning, which posits that when a naturally occurring stimulus and an environmental stimulus are repeatedly paired, the environmental stimulus will eventually elicit a similar response to the natural stimulus.


Unconditioned responses are automatic and unlearned. They can be seen from the time we are born. Up until Ivan Pavlov’s experiments that led to the discovery of classical conditioning, however, these innate responses were not yet defined.

Pavlov, a Russian physiologist, set out to study dogs’ digestive systems. However, he noticed something else in the process. While it was natural for a dog to salivate when food was put in its mouth, if the food was paired with something else, like a light turning on or a bell ringing, the animal would soon associate the bell with the food as well. Once a connection between the food and the light or bell was made, even if food wasn’t present, the dog would salivate to the light or the bell by itself.

This process is called classical conditioning. It hinges on pairing an unconditioned stimulus with a neutral stimulus. The neutral stimulus could be anything, but the unconditioned stimulus must provoke a natural, reflexive response. Pairing the unconditional stimulus and neutral stimulus causes the neutral stimulus to become a conditioned stimulus. If these stimuli always occur together, the unconditioned stimulus will become associated with the conditioned stimulus. As a result, the unconditioned response that initially only happened in reaction to the unconditioned stimulus will also occur in response to the conditioned stimulus. The response elicited by the conditioned stimulus is called a conditioned response.

So in the scenario with Pavlov’s dogs, the food is the unconditioned stimulus, salivation is the unconditioned response, the light or bell is the conditioned stimulus, and salivation in response the light or bell is the conditioned response.


Anytime you have an involuntary, unlearned response to a stimulus, it is an unconditioned response. Some examples include:

  • Jumping when you hear a loud noise.
  • Puckering your mouth when you eat something sour.
  • Quickly pulling your hand away from a hot stove.
  • Gasping when you get a paper cut.
  • Getting goosebumps when you feel cold.
  • Jerking your leg when a doctor taps on your knee for a reflex test.
  • Feeling hungry when you smell food.
  • Blinking when a puff of air is blown in your eye.
  • Sneezing when a feather tickles your nose.
  • Flinching and perspiring when you receive an electric shock.
  • Having your heart rate and breathing slow down when your favorite relative hugs you.

These responses all happen automatically from birth. Any natural reaction is an unconditioned response and in many cases people are not aware of them. Often unconditioned responses are physiological, including salivation, nausea, pupil dilation, and increasing or decreasing heart rate. They also include involuntary motor responses, such as twitching or flinching.

Unconditioned Versus Conditioned Responses

There are key differences between conditioned and unconditioned responses.

  • An unconditioned response is innate and natural, it does not have to be learned.
  • A conditioned response is learned only when an unconditioned stimulus has become linked in an individual’s mind with a conditioned stimulus.

It’s important to remember that because classical conditioning depends on a set of unconditioned responses, it is restricted to this range of unlearned, automatic responses. For example, suppose that every time you go to a movie theater, the smell of popcorn wafting from the concession stand makes you feel hungry. Over time, if you experience the smell of popcorn with the experience of going to the movie theater enough, you will start to become hungry when you’re walking towards the movie theater or even when you’re making plans to go to the movie theater. In other words, your involuntary, natural response of hunger has become associated with the process of planning and going to a movie theater, even though the experience of going to a movie theater was initially neutral.

Thus, classical conditioning always starts with an unconditioned response to an unconditioned stimulus. And a conditioned response is limited by the range of natural, innate unconditioned responses that we can exhibit.


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Vinney, Cynthia. "What Is an Unconditioned Response?" ThoughtCo, Dec. 6, 2021, thoughtco.com/unconditioned-response-4590292. Vinney, Cynthia. (2021, December 6). What Is an Unconditioned Response? Retrieved from https://www.thoughtco.com/unconditioned-response-4590292 Vinney, Cynthia. "What Is an Unconditioned Response?" ThoughtCo. https://www.thoughtco.com/unconditioned-response-4590292 (accessed March 28, 2023).