WordNet
conditioned stimulus
n. the stimulus that is the occasion for a conditioned response
Usage examples of "conditioned stimulus".
In fact, the connection between the conditioned stimulus or CS (tone or rat) and the unconditioned stimulus or UCS (food or loud noise) must make sense and be useful, otherwise an animal or human won't learn that connection.
But starched sheets were a luxury I had only enjoyed when staying with some of the more house-proud women in the valley and had become a conditioned stimulus.