A Person Loopback Test is an observation about yourself that tells you things you wouldn't otherwise notice.
Two examples of tests that I do come to mind:
Should I have named this page PersonalUnitTests?? :) -- shae
I have a loopback test for too-tired-to-drive. I don't use cruise control on long drives, and I drive a manual, which makes it extremely easy to maintain exactly the speed I want. I make it a habit to stay within one mph of my desired speed - this is how the anal retentive have fun on the road.
My theory is that when I'm tired I lose the ability to rapidly scan the road, instruments, and mirrors, and start fixating on one thing. Hence the speedometer goes unobserved for too long and my speed drifts. Unconsciousness is not far behind once that happens.
This technique may not apply as well to cars with automatic transmissions. I find it much harder to maintain a constant speed in them. They do work differently, but it could also be that I'm just not used to them. -- WayneConrad
My mother was once pulled over late at night by the Florida state police. Her offense: she was slow to dim her headlights. The officer explained that that was a sign of fatigue and that she should consider stopping for the night. -- WardCunningham
I was driving home from my printing job on second shift one night when I noticed a trooper behind me. Concerned that I might exceed the speed limit, I kept checking the gauge frequently. Approaching my home, he pulled me over. My attention to the gauge led to an unnoticed inattention to the solid line down the middle of the road. He thought I might be intoxicated. I guess I was just tired. In any event, I was looping back too much. -- WaldenMathews
This is a very important thing to have a loopback test for... I have one: I play a 9x9 game of Go against the computer and look at the final score. Takes perhaps ten minutes, but quite accurate. Still need a good way to measure reflexes though - perhaps PacMan?
When I am drinking and the tip of my nose gets numb, I stop drinking and do not drive until I can feel all of my nose again. If my teeth go numb, I don't drive until the next day. -- KenMegill
I fire up Windows Minesweeper on "Expert", and see how far I get without pausing to think "too much". A couple of rounds is usually enough to confirm whether mental fatigue or short attention span has set in.
What's the difference between fatigue and a temporary short attention span in that case?
Sometimes when I can't quite make a decision between two things, I'll pull out a coin to flip, and assign a choice to each side. I'll give it a big flip, call it in the air, and ignore the result: I'll usually have a quick flash of hope that it comes up a certain way, and I go with that. -- SckotVokes