unconditioned stimulus

noun

1. psychol any stimulus evoking an unlearnt response, esp in the context of classical conditioning, in which the conditioned stimulus is followed by the unconditioned one

Example Sentences

Scientifically, the unconditioned stimulus which is drugs brings an unconditioned response, which is being high.

From Salon

Note that most English-language textbooks use the terms “unconditioned stimulus,” “unconditioned response,” and so on.

From Scientific American