I think the idea of a stock must have been invented independently at many times in history.

我认为股票这个概念,在历史上被反复提出过多次

耶鲁公开课 - 金融市场课程节选

When the conditioned stimulus and the unconditioned stimulus are brought together over and over and over again, pretty soon the conditioned stimulus gives rise to the response.

当条件刺激与非条件刺激,同时且多次反复出现，条件刺激很快也能引起条件反应。

耶鲁公开课 - 心理学导论课程节选