Acquisition in Classical Conditioning

Training dog
sestovic / Getty Images

Acquisition refers to the first stages of learning, when a response is established. In classical conditioning, acquisition refers to the period when the stimulus comes to evoke the conditioned response.

Classical conditioning is a learning process that involves pairing a previously neutral stimulus with a stimulus that naturally evokes a response. After a response has been acquired, the previously neutral stimulus will then evoke the response all on its own.

Consider Ivan Pavlov's classic experiment with dogs. By associating the presentation of food with the sound of a tone, Pavlov was able to condition the dogs to salivate to the sound. The phase in which the dogs began to salivate to the sound is the acquisition period.

How Acquisition Works

How does acquisition occur? In classical conditioning, repeated pairings of the conditioned stimulus (CS) and the unconditioned stimulus (UCS) eventually lead to acquisition.

The unconditioned stimulus is one that naturally evokes the unconditioned response (UCR). After pairing the CS with the UCS repeatedly, the CS alone will come to elicit the response, which is then known as the conditioned response (CR).

Once the association between the CS and UCS has been established, the response is said to have been acquired.

Repeated Pairings Are Needed

During acquisition, the conditioned stimulus and unconditioned stimulus are repeatedly paired to create an association. Multiple pairings are required, but the number of trials needed can vary depending on what is being learned.

For example, imagine that you are teaching a dog to fear the sound of a rattlesnake. This type of learning will likely occur much more quickly since the animal may already be primed to form such an association. As a result, the acquisition will happen much faster than if you are teaching the dog to play dead.

The strength of the conditioned response will continue to increase up to a certain point before it begins to level off.

Reinforcement Can Strengthen the Response

Once the behavior has been acquired, it is still often reinforced in order to strengthen the association. For example, imagine that you are teaching a pigeon to peck a key whenever you ring a bell. Initially, you place some food on the key and sound a tone right before the pigeon pecks the key.

After several trials, the pigeon begins to peck the key whenever he hears the tone, meaning he has acquired the behavior. If you stop reinforcing the behavior at this point, the bird would quickly stop engaging in the action (this is known as extinction). If you continue reinforcing the association between the bell and the food, the response will become much stronger.

In order for acquisition to occur, the neutral stimulus and naturally occurring stimulus must be paired together multiple times in most cases. Once the response has been acquired, continuing to pair them can help strengthen the response.

Factors That Affect Acquisition

A number of factors can affect how quickly acquisition occurs. If you are trying to create a conditioned response, you may need to vary these.

Salience of the Stimulus

The salience (strength or novelty) of the conditioned stimulus can play an important role. If the CS is too subtle, the learner may not notice it enough for it to become associated with the unconditioned stimulus. Stimuli that are more noticeable usually lead to better acquisition.

For example, if you are training a dog to salivate to a sound, the acquisition will be more likely if the sound is noticeable and unexpected. The sound of a bell will produce a better result than a quiet tone or a neutral sound that the animal hears regularly.

Timing of the Association

Second, timing plays a critical role. If there is too much of a delay between the presentation of the conditioned stimulus and the unconditioned stimulus, the learner might not form an association between the two.

The most effective approach is to present the CS and then quickly introduce the UCS so that there is an overlap between the two. As a rule, the greater the delay between the UCS and the CS, the longer acquisition will take.

Acquisition Examples

It can be helpful to examine a few examples of how acquisition can occur in different settings.

Acquired Fear Responses

A classic example of acquisition is the famous Little Albert experiment conducted by John B. Watson and Rosalie Rayner. In the experiment, Watson and Rayner paired the sight of a white rate with a loud clanging sound that frightened their subject, a nine-month-old boy. 

While the child was initially unafraid of the white rat, repeatedly pairing the sight of the rat with the clanging sound eventually led to the child acquiring a fear response. Once acquired, the child displayed fear of the rat. Today, this type of experiment would be considered unethical, because the baby was harmed by it (he experienced a fear he did not previously have).

In Real-World Settings

Fear of school can be another example of an acquired response in children. While a child might have initially enjoyed school, repeated experiences with bullying or negative interactions with a teacher might cause a child to acquire a fear response. 

When it comes to the fear response, sometimes it only takes one pairing of the stimulus with the unconditioned stimulus. In such cases, this can lead to the development of a phobia.

In this case, classical conditioning could also be used to help a child acquire a more positive attitude toward school. If the child had a supportive, nurturing teacher, they may acquire a positive association that helps overcome their previous fear.


The conditioning of a fear response can help illustrate how acquisition works. By associating a stimulus with something that triggers fear, people may eventually acquire a fear of that previously neutral stimulus.

A Word From Verywell

Acquisition represents an important part of the learning process. By repeatedly pairing a neutral stimulus with something that naturally leads to a response, people are able to acquire new associations that can affect how they behave and respond in different settings.

Understanding how this process works can help you can gain insight into the learning process. This can be helpful if you are trying to teach or learn a new behavior

4 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Eelen P. Classical conditioning: Classical yet modernPsychol Belg. 2018;58(1):196–211. doi:10.5334/pb.451

  2. Learning. In: Walinga J, Stangor C, eds. Introduction to Psychology: 1st Canadian Edition. British Columbia Ministry of Advanced Education, Skills & Training.

  3. Huang J, Ruan X, Yu N, Fan Q, Li J, Cai J. A cognitive model based on neuromodulated plasticity. Comput Intell Neurosci. 2016;2016:4296356. doi:10.1155/2016/4296356

  4. Moustafa A, Wufong E, Servatius RJ, Pang KCH, Gluck MA, Myers CE. Why trace and delay conditioning are sometimes (but not always) hippocampal dependent: A computational model. Brain Research. 2012;1493. doi:10.1016%2Fj.brainres.2012.11.020

By Kendra Cherry, MSEd
Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."