Many dogs have an extensive vocabulary of words they seem to understand.
Eye contact has been long known to be one of the ways dogs communicate with each other and with mankind. Obedience people have known this for a long time. Often trainers start with vocal commands and later use only hand signals to evoke the same responses. How your puppies learn to communicate with other humans in the future may be conveyed by your hands today. For example, if you only pick up your puppies to put them into a crate or pen, they might come to associate hands coming towards them as an unpleasant experience.