The next level would be to sync language. Which is by far more difficult.
Saying the same sounds at the same time then the same words then completing one anothers sentences.
Of course no planning the movements and stuff.
Try it out see what happens.
Funny enough my silly little 4 y/o niece was was mimicking me the other night. Everything I said and did, she said and did. I finally fooled her into thinking that she "lost the game" when I thought it was going on for too long and decided to mimick her also. Only I was saying what she was saying at the same time she was saying it... we were definitely in synch! Her mother was getting spooked out by me... lol. I have always thought we have a strong connection though. We have spent a lot of time together, especially in the first six months of her life.