How Do I turn off auto Merge of verts while in edit mode.

I turned the doubles threshold to 0 and blender still wants to merge my verts sometimes. I never had this problem before 2.7x.
I am creating shape keys for facial rig and I DO NOT want to change my topology.

How do I turn off auto merge???

Thanks

Talmore

http://wiki.blender.org/index.php/Doc:2.6/Manual/Modeling/Meshes/Editing/Vertices

Second section explains auto-merge editing.

http://i.imgur.com/D46ccUm.png

or just press that button. lol

Thanks guys!

I remember hitting that button a while back and not seeing what it did. I must have left it turned on.
Guess I have a bad habit of not reading the tool tips. You have saved me much future heartache