This might concern competition pistol shooters only but I'm going to throw it out here anyways. Just as a preface, Ive been competing with my 1911 for the past 35 years in IPSC and USPSA style comps and have always shot one eye open for focus. Just last weekend I was doing some practice for an up coming 2 gun match using my rifle equipped with a dot sight that always shoot both eyes open. I then switched to my pistol and ran some bill drills using some smallish targets because I believe in the small target aim small theory. Ive run these same drills over and over again and am consistent. I then noticed that using my timer, my first shot on target has decreased by .2 seconds. My first shot on target is actually hitting the target instead of close enough for comp size targets. My total shot string time of 6 shots on individual targets has reduced by more then a second and half. I did this drill over and over again and that's when I realized that I was shooting with both eyes open. With both eyes open Im not focused on just that one target and then have to concentrate on the next. I see it, its right over there, that's the only way I can explain it. Give it a try. Yes you will see two guns in your sight picture, but your dom eye will chose the right one.