Just last week, as I reach full draw on a relaxed, quartering away, upwind 8 pointer at 15 yds, he turned his head around and looked directly at me, I was in a deadfall wearing my ghillie, this deer never knew I was there and never moved till the arrow hit the ground on his other side,and then only went about 3 yds. seems I grazed a twig which sent my arrow about 1" over his back, I never made a sound and the bow is the quietest one I've ever shot, I have no doubt in my mind that this buck "felt" me there, I believe they have a sixth sense, but as with all creatures, they are sometimes pre-occupied with other things and just don't pay attention to everything around them, I learned a long time ago to never look a deer or other quarry in the eye, better safe than sorry.