There seems to be no interesting difference between how the brain comes to acquire and use the spoken language versus a sign language.

似乎大脑在如何获得和使用口语语言,与如何获得和使用手语之间,不存在任何的差别

耶鲁公开课 - 心理学导论课程节选

That sign languages may be full-blown languages but they just take--they're just harder to learn because the brain and the body have adapted for speech.

手语或许是成熟的语言,但它们更难学,因为大脑和身体已经适应了口语

耶鲁公开课 - 心理学导论课程节选