Unconditioned Stimulus (US)

Definition

An unconditioned stimulus is something that naturally and automatically triggers an unconditioned response without any learning needed.

Analogy

The US can be compared to the smell of your favorite food cooking. Without needing any prior training or conditioning, this smell will automatically make you feel hungry - an unconditionally triggered response!

Related terms

Neutral Stimulus: A stimulus which initially produces no specific response other than focusing attention. In classical conditioning, when used together with an unconditioned stimulus, it becomes a conditioned stimulus.

Primary Reinforcer: A reinforcer that satisfies a basic biological need such as hunger, thirst, or sleep.

Sensory Input: Information received by sensory receptors — this could include anything you see, hear, taste, touch or smell.