行为由当前刺激情境和过去的强化历史决定。

释义：勇敢的人敢闯天下，什么事情都能做成；过于谨慎的人却处处束手束脚，一步也难以前行。

I don't need a reason to believe in myself.

Every barrel of oil we produce must be the most responsibly produced barrel possible.

We are on the verge: Today our program proved Fermat's next-to-last theorem.