"Gunfighter Moment" from Soldier Systems...

You need to read this on Natural Instincts, by Aaron Barruga:

"The quality at which we perceive information determines whether we receive data that is actionable or just noise. Entering a crowded room, you can scan the environment by simply moving your eyes within their sockets. Moving your head left and right may be necessary to gather data at different angles, but if we jerk our heads too quickly, any information about our surroundings becomes a blur. Another gift passed on to us from our ancestors is our body’s preference for expending the least amount of effort possible to accomplish a task. Unnecessary movement expends precious energy, but can also signal to predators our location…"

BTW, read this, too, from ZeroGov, one of the most thoughtful training articles I've read in a while:

Lets cut to the chase. The Derp can be deafening at times. In an effort to help combat some of this and save a lot of folks a lot of heartache, I am tossing out a few tactical tidbits for those interested. (All while staying in my lane of course)