It predicts that the best timing is when the conditioned stimulus, which is the signal, comes before the unconditioned stimulus, which is what you have to prepare for.

它预测，最佳的时机,莫过于作为信号的条件刺激，出现在需要你做准备的，非条件刺激之前。

耶鲁公开课 - 心理学导论课程节选

And my purpose will be not to say something as a postulate, but to show you where everything comes from, and it's best for you if you try to follow the logic.

我的目的不是,简单地告诉你们一个假说,而是给你们讲清楚这个理论的来龙去脉,如果你们能理解推导过程那就再好不过

耶鲁公开课 - 基础物理课程节选