A stimulus is any object, event, or situation that elicits a response from an organism. It can be something we see, hear, touch, taste, or smell.
Unconditioned Stimulus (UCS): An unconditioned stimulus is one that naturally triggers a reflexive response without prior learning.
A conditioned stimulus is initially neutral but becomes associated with an unconditioned stimulus through repeated pairings and eventually elicits a conditioned response.
A neutral stimulus does not produce any specific response before being paired with an unconditioned stimulus.