classical conditioning

Classical Conditioning

Behavioural Psychology Developmental Psychology

An Introduction to Classical Conditioning (Pavlovian Conditioning)

Like so many scientific developments, Classical Conditioning was discovered accidentally. Slightly more unusually, it was discovered twice - by a Russian Physiologist named Ivan Pavlov, and American Psychologist Edwin Twitmyer.

On this occasion, the Russian won the race to publish his findings and the credit was therefore Pavlov's for the taking (hence the alternative name for classical conditioning is Pavlovian conditioning).

Before we consider experimental evidence for classical conditioning, it will be helpful to understand exactly what this process of learning involves.

What is Classical Conditioning?

Classical conditioning is the process of learning by which a neutral stimulus is associated with a specific response simply by occurring at the same time as the 'actual', or natural, stimulus for a given response.

For example, if I offered you a biscuit you might smile. This is because biscuits make you smile.

Therefore: Biscuits are an unconditioned stimulus (often shortened to UCS). And smiling is an unconditioned response (UCR).

However, if every time I give you a biscuit I clap my hands, you might start to associate clapping (a neutral stimulus, or NS) with biscuits (the unconditioned stimulus).

Eventually the association will become so strong that just clapping will produce the same response as if I had given you a biscuit.

At the end of the process, therefore, clapping is a conditioned stimulus (CS) and smiling is a conditioned response (CR) to the stimulus.

Classical Conditioning is a direct method of learning, directly associating the outcome with the stimulus.

Click here to read our article on Operant Conditioning, another method of learning which uses reinforcement and punishment as instruments for learning.

There are many applications for Classical Conditioning, but first we shall consider some pivotal studies in the development of the theory.

Pavlov's Dogs - The Accidental Discovery

Ivan Pavlov wasn't a Psychologist. He was a Physiologist and used animals as his participants.

In the 1890s, Pavlov was studying the role of saliva in the gastric system.  Pavlov initially recorded that the dogs began to salivate, not when they began eating, but as soon as they heard or smelt food.1

This is a reflex response as salivation is an innate biological process, forming part of digestion.

However, in a series of environmental manipulations, Pavlov discovered that the dogs would also begin to salivate when events occurred that would otherwise be unrelated to feeding.

For example, by playing sounds to the dogs prior to feeding, Pavlov was able to demonstrate that the dogs could be conditioned to unconsciously associate neutral stimuli (the music) with being fed.

Pavlov made use of a device, which measured the rate at which the dogs' saliva glands made secretions, in order to record the dogs' behavioural responses to neutral stimuli.

Ivan Pavlov classical conditioning reflex

Pavlov conducted a series of variations on his initial study, which demonstrated that classical conditioning was not limited to musical sounds before feeding, but similar associations were demonstrated with doors opening, buzzers buzzing, metronomes ticking, and even electric shocks.

Types of Classical Conditioning

Are all methods of classical conditioning equal? No, they are not.

Pavlov played his musical tone to the dogs before providing their food, not after.

  • Forward Conditioning - the neutral stimulus is presented before the unconditioned stimulus (eg. Music then Food).
  • Backward Conditioning - the neutral stimulus is presented after the unconditioned stimulus (eg. Food then Music)

Forward conditioning is far more effective than backward conditioning. In fact, introducing the neutral stimulus after the unconditioned stimulus may not lead to an association at all.

Carr and Freeman (1919)2 compared forward and backward conditioning in rats, using a buzzer sound and closing doors in a maze environment. They found backward conditioning to be ineffective, whereas forward conditioning led to a successful association.

Two types of Forward Conditioning

What is the cut off for forming an association between a neutral stimulus and a response? Pavlov (1927)3 suggests that the longer the delay between the neutral stimulus and unconditioned stimulus, the more delayed the response would be.

There are two types of forward conditioning:

  • Delay Conditioning - this is where the neutral stimulus is provided immediately before and simultaneously with the unconditioned stimulus.
  • Trace Conditioning - this is where there is a delay after the neutral stimulus before the unconditioned stimulus is presented. The gap between the NS and UCS is referred to as the trace interval.

Generalising from the Rule

Whilst a specific neutral stimulus might be associated with a specific response, it is possible that a person (or animal) may generalise from the rule.

For example, if a dog builds an association between a buzzer tone (in B flat) and food it is possible that they may unconsciously generalise their association and also respond with the conditioned response when a buzzer tone in F sharp is presented.

The closer the stimulus is to the original conditioned stimulus, the clearer the response will be.

Watson's (1920) Little Albert Experiment (see below) is a good example of generalising in practice.

I Want To Break Free! Is it possible?

Once an animal or person has developed an unconscious association between a neutral stimulus and a response, can this association ever be broken?

Yes! There are multiple ways in which an association can be 'broken'. The main two are:

  • Memory - if the association isn't rehearsed for a long time, it is possible that it will be forgotten.
  • Extinction - this could be described as a process of 'unlearning'. By increasingly presenting the neutral stimulus without the initial unconditioned stimulus (eg. food), the association will be weakened as the person will no longer expect the neutral stimulus to be accompanied by the unconditioned stimulus.

Pavlov's research suggests that associations remain, even after extinction, and therefore can be re-activated by reintroducing the learned association. This process is known as spontaneous recovery.

The Little Albert Experiment (Watson, 1920)

Little Albert was the subject of an ethically dubious experiment conducted by the eminent behaviourist John Watson.4

Having read Pavlov's research, Watson wanted to replicate his findings with a human infant.

Watson may have seen classical conditioning as supporting evidence for his behaviourist assumption that all behaviours are learned and can be taught.

Little Albert was 9 months at the beginning of the experiment.

Method: To begin with, Watson introduced Albert to a series of white fluffy objects (a white rate, a white rabbit etc.) to check for any innate or pre-existing aversion. Albert did not demonstrate fear of any of these stimuli.

As with most infants (and adults!), Albert demonstrated an aversion to sudden loud noises. And so the experiment began.

Watson slammed a hammer against a steel bar when presenting the child with a white rat.

After repeated exposure to this scenario, Little Albert became distressed when he was introduced to the rat.

Results: Watson removed the loud noise, but Little Albert continued to demonstrate an aversion to the white rat and would wriggle away when the rat appeared.

Albert generalised his learned phobia of white rats to soft, white, fluffy objects. He was scared of white rabbits and even Santa Claus, for no reason other than he had associated a neutral stimulus (white and fluffy) with an unconditioned stimulus (unpleasant loud noise).

little Albert being experimented on.

Applications of Classical Conditioning

The obvious application of Classical Conditioning - given the roots of the theory - is for training animals, such as dogs, to perform certain desired behaviours. Combined with Operant Conditioning, animal owners are able to guide their pet's behaviour despite the obvious language barrier.

The advertising industry is also no stranger to the powers of association and often use classical conditioning techniques to intrigue and entice you to buy their products. This has led to a number of laws being passed in various countries limiting, for example, the ability of advertisers to market certain products (such as tobacco and alcohol) alongside certain other desirable stimuli.

For example, in the UK it is illegal to imply in an advert that alcohol makes you sexier. This is to protect against a learned association, via the process of classical conditioning, that one must purchase and consume alcoholic products in order to appear 'sexy'.



  1. Pavlov, I.P. (1927). Conditioned Reflexes: An investigation of the physiological activity of the cerebral cortex. Retrieved from
  2. Carr, H. and Freeman A. (1919). Time relationships in the formation of associations. Psychology Review. 26(6). 335-353.
  3. Pavlov, I.P. (1927). Conditioned Reflexes: An investigation of the physiological activity of the cerebral cortex. Retrieved from
  4. Watson, J.B. and Rayner, R. (1920). Conditioned Emotional Reactions. Journal of Experimental Psychology. 3(1). 1-14.