Well, when Pavlov, for instance, started before conditioning there was simply an unconditioned stimulus, the food in the mouth, and an unconditioned response, saliva.

比如，在条件作用形成之前,只是简单的存在着无条件刺激，即食物，以及无条件反应，即唾液。

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Well, that's classical conditioning.

这就是经典条件作用。

耶鲁公开课 - 心理学导论课程节选