Head position into impact ?

Now I think this might be nit-picking but I have been looking at some of the video's (and magazine sequences) of pro's like Tiger, Wie etc and it look's like as they are on the down-swing their head goes down too. In fact I've measured a down the line sequence and the head moves a few inches to as much as 6 inches downward towards the ball. Not all of the pro's do this but some do this at least during their driving the ball from the tee box. I also know that as you turn into the impact zone your head should look like it is resting on a pillow. Some say you should not pull your head up at all but just let it turn naturally around your spine as your right shoulder comes under it. As you continue to the follow through your head does not come up until near the end of the swing. Anyone have any thoughts on this?

Many good players lower into the downswing as they create a squat position with the legs, this creates balance and stability. It is not so much the head lowering, more a bending at the knees and a settling down through the hips.

Yes, I too have observed this in other players and have personally felt this dip or resting the head down on a pillow move in my own swing.

I think I do this because of the following sequence of events:
- from the top of my backswing, my first move is to transfer some weight from the back foot to the front foot. I do this with my shoulder still fully turned and with no head movement.
- since my spine angle is retained, this weight transfer causes my head to move left 1-2 inches.
- I then move my head back to the right to put it back to my original starting position (at least with regards to its vertical orientation with the ball).
- This creates a more layed back spine angle creating that 'resting on a pillow' position.

I've compared my swings where I just turn into the downswing (where my head stays in one spot up to impact) versus the one described above and I feel that more natural power is being generated by this 2nd downswing type. This type allows me to retain the lag a little more. Also, it feels that my moving of the head back to the original starting position somehow adds to the centripetal force.