So, if somebody pokes you with a stick and you say, "Ouch," because it hurts, the poking and the "Ouch" is an unconditioned stimulus causing an unconditioned response.

如果有人用棍子戳你，你会因为疼而叫出来，戳的动作和你的喊叫“,这就是无条件刺激引起了无条件反射。

耶鲁公开课 - 心理学导论课程节选