You're weird.

I can't interpret what's behind me in a flash of movement. It's a glance back and between 3/4 of 1 second and 2 seconds. I often study my mirror and watch for movement in my peripheral vision before taking a quick glance back; the comparison when I know what to expect is MUCH faster than trying to analyze a completely new scene. It's just too hard. Often when I see a car, I can't tell if it's in the right lane or the next lane over unless it's RIGHT THERE behind me.

I'm going about 7m/s at 15mph. That's enough to pass a car or so in 1 second, which means that a small child or a person can get out into the street in the moment I glance away, or a car can pull out from behind a truck improperly parked at the corner. These are emergent conditions I've narrowly evaded from time to time. Once I completely lost it when I passed through a (green lighted) intersection at-speed (25mph) and immediately a woman un-parked her car directly in front of me; I skid around her car trying to not pull into oncoming traffic, then spun my bike in front of her car as she slammed her brakes. Could you imagine me taking a glance back just before that to see if it was safe to take the lane--a check I'd make, ironically, because I recognized that there was a person in the car and I wanted to move further out of the door zone. I wouldn't have made it; I'd have plowed into her car.

I bet you spend 4 minutes in the shower too. Everybody says they do... but a company in Britain hooked up sensors for all the people they surveyed (a group of some 3500) who attested to their typical 4 minute shower and found out they take an 8-10 minute shower. You should check your internal chronometer, it might be timing things a little quick.