Neutral stimulus is part of the model of classical conditioning in the field of behavioral psychology that states a stimulus elicits a response, with neutral stimulus so named as it does not provide the desired response in a subject. This term is mainly used when a stimulus is designed to cause a reflexive response.
There are three other elements to the classical conditioning model, all of which are based on reflexive response to a stimulus.
Unconditioned stimulus is used to describe an event where a stimulus brings about a reflexive response without the need for learning or training.
The neutral stimulus, which does not generate any response, is then associated or paired with the unconditioned stimulus, in order to create a conditioned stimulus.
The conditioned stimulus arises as a result, meaning that when a conditional stimulus is presented, the conditioned response becomes the same as the unconditioned response to the unconditioned stimulus.
Pavlov's dogs are an excellent example of this process in practice. Initially, the food provides the unconditioned stimulus (with the unconditioned response being the dog salivating), while the bell fills the role of neutral stimulus, as it initially has no effect on the dogs reflexive reactions. Once the dogs are taught to associate the bell with food, the conditioned stimulus is created, causing the dogs to salivate at the sound of the bell, which they now associate with food.