"Gesticulation isn’t divorced from speech. It’s completely tied to your speech,” Goldin-Meadow tells Science of Us. “It’s part of your cognition. It’s not just mindless hand-waving.” Researchers haven’t yet pinned down exactly how this connection works, but Goldin-Meadow believes part of it is that gestures reduce what psychologists call “cognitive load,” or the amount of mental energy you’re expending to keep things in your working memory.

http://nymag.com/scienceofus/2016/07/talking-with-your-hands-makes-you-learn-things-faster.html