"Observing the supermarket over the years, I’ve determined that there are three common checkout strategies. My local supermarket may be like yours—it usually has four or five checkouts open. If you watch carefully, you’ll see people adopting one of three strategies: The first is to pick the shortest line and get in it. Stick with it, no matter what. The second is to pick the shortest line and switch lines once (at a maximum) if something holds up your line—like the clueless person with a check but no check-cashing card. But that’s it, just one switch. The third is to pick the shortest line and keep scanning the other lines. Switch lines if a shorter one appears. Continue this process until you leave the store. The problem with the third strategy is obvious. Every time you switch lines, you’re starting over. In your search for a quick fix, you almost certainly waste time and you definitely waste energy jumping back and forth."
The Dip (Seth Godin)