Acquisition in Classical Conditioning

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

Consider 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 It Works

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

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 your 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.

Once the association between the CS and UCS has been established, the response is said to have been acquired. At this point, the behavior is still often reinforced 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, and extinction may occur. If you continue reinforcing the association between the bell and the food, the response will become much stronger.

Factors That Influence Acquisition

A number of factors can affect how quickly acquisition occurs. First, the salience 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 faster 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.

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.

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