From Chapter One:

If I had not made eye contact with the Mastiff, if my eyes had moved some fraction of an inch over to the left or right, he wouldn't have lunged. All that ballistic power would've sat, quietly watching, if I had changed the path of my gaze a quarter of an inch. A barely perceptible change in my behavior would have resulted in the stunningly obvious difference between a 200-pound dog sitting quietly or launching toward my face.