Sometimes,people say something to a friend or family member that they later regret because it hurts that person's feelings.

VOA: special.2010.06.20

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。

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