An irrelevant stimulus is a stimulus that does not naturally produce a specific response, but through classical conditioning, comes to trigger a conditioned response.
Related terms
Conditioned Response: A learned response to a previously neutral stimulus after it has been paired with an unconditioned stimulus.
Unconditioned Stimulus: A stimulus that naturally and automatically triggers an unconditioned response.
Neutral Stimulus: A stimulus that initially does not elicit any particular response before it becomes associated with an unconditioned stimulus.