While watching a play with the New England Patriots you often see the z receiver or slot receiver (correct me if they aren't equivalent terms) motion towards the quarterback but then moves back to his original position?
To me as a outsider, it seemed pointless that he moved to near the center position and then back to his original spot.
Wikipedia does discuss the purpose motioning but it speaks about changing formations. If the receiver moves to his original position the formation is the same.
Also, I could see motioning to the other side would make sense to provide extra protection for a screen to a running back play.
During the presnap is there a purpose for motioning the slot receiver toward the center and back to his original position? Is it to test the defensive positions?