Sign languages vary from country to country,and many are not well known internationally.

VOA: standard.2009.09.10

It turns out that sign and--the developmental milestones of sign languages and the developmental milestones of spoken languages are precisely the same.

手语的发展阶段,和口语语言的发展阶段是完全相同的

耶鲁公开课 - 心理学导论课程节选

I'm going to put aside for the moment the question of sign languages and how they work.

我想暂时把手语,及其如何作用的问题先放到一边

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

One of the real surprising findings in my field over the last ten/twenty years has been that the acquisition of sign languages has turned out to be almost exactly the same; in fact, as far as we know, exactly the same as the acquisition of spoken languages.

过去的十到二十年间,在我的研究领域里最令人吃惊的发现之一就是,各种手语的获得过程,被证明几乎是完全相同的,实际上据我所知,和口语语言的获得过程是完全相同的

耶鲁公开课 - 心理学导论课程节选