What is He Doing?

Last night I decided instead of taking the interstate home form work, I'd go the back way. Needless to say, I got stuck behind this slow ass van. As I am driving behind this guy I noticed the passenger appeared to be dancing. Only this was a strange dance if that's what it was. He would lean towards the dashboard and then lean back against his seat. He did this probably about 10 times and then he would turn halfway around in his seat and look in the back of the van. Then, like a strange ritual, he would go back to this "rocking" motion. He did this the whole time I was behind them. I kept expecting some sort of reaction from the driver. Nothing. He just kept his eyes focused on the road ahead of him, never looking over at the strange behavior of his passenger. I took this to mean this was a normal habit for this guy. I'm sorry, if someone was rocking in my car, I would have to acknowledge it. I heard one time that rocking is a sign of insanity. Maybe that's where the phrase "Off their rocker" came from. Either way, I sped up to pass the first chance I got. Not only because I was afraid this guy was going to totally freak out and grab the steering wheel, but I really had to pee and they were driving way too slow. Hey, I'm all about staring at crazy people, but when you gotta go, you gotta go.