They can also understand some grammar in a gestural language researchers use to communicate with them.

它们也懂一些研究人员用来与之交流的语法。

There may have been a transition from gestural communication to gestural language— from pointing to objects and pantomiming actions— to more efficient, abstract signing.

可能已经从手势交流过渡到手势语言——从指向物体和哑剧动作——到更有效、更抽象的手势。