A Baby Mystery

For the past two weeks, there has been a little mystery. Every night I put Ian down in his crib. Sometimes I put him at one end, sometimes at the other end, sometimes in the middle, but always lengthwise. Every time I wake up to take him out of his crib, I find him turned 90 degrees, like this:



(In this photo, the front of the crib is at the bottom, the back of the crib is at the top, and the ends of the crib are out of the picture)
Why does he do this?? I can understand how he might be liable to turn himself -- I imagine that he rolls onto his side and kicks his legs, spinning himself in a circle. But why does he always stop in this direction? (It has nothing to do with the mirror, btw, because I just put that up yesterday). Maybe someday when he can talk (with all those words he's learning from reading with Daddy), he'll explain to me why he does this . . .