蜥蜴脑（Lizard Brains）蜥蜴脑是人脑中掌管与理性思考无关的部分，也被科学研究证实是掌握本能的古老部分。（百度百科）

阅读外刊就是这样，需要不断查资料。以后遇到类似“本能反应”之类的词，或许可以根据语境使用 lizard brain.

还遇到一个非常有意思的词，其实一直知道这个词，但没有好好深究过，就是uncanny，以及看起来与之相反的canny。 Guess what？ They are not opposites.

同一篇文章：

Every position he takes is carefully calibrated to elicit a reflexive response from his supporters. His campaign is about fears that have existed since before we became sapiens （现代人） -- fear of the other, fear of going hungry, the joy of martial triumph. He has been brilliant at picking those primal scabs. He has an uncanny ability to find the perfect brickbat to throw at his opponents.

21世纪大英汉词典