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unconditioned stimulus

psychology
Also known as: US, unconditional stimulus

Quick Summary

In psychology, an unconditioned stimulus (US) is something that naturally and automatically triggers a response without any prior learning. This response is called an unconditioned response. For example, the smell of food is an unconditioned stimulus that naturally causes salivation, which is the unconditioned response. This is an inborn reflex, not something learned.12

In contrast, a conditioned stimulus (CS) is a previously neutral stimulus that, after being repeatedly paired with an unconditioned stimulus, comes to trigger a learned response, known as a conditioned response. This process is fundamental to classical conditioning, a type of associative learning.32

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