Traffic jam and bread
Not to brag, but I have a knack for choosing the slowest moving line in the grocery store. Same with TSA security lines and traffic lanes.
How and why does this happen? I spend at least a little time casually estimating which line will move fastest. When I observe other patrons, it seems I’m not the only one doing this. We’re all sizing up the cashiers, our fellow shoppers, and their purchases. But surprising no one, I probably overthink these things.

Chili out
Which are the best predictors of a speedy checkout? The efficiency of the cashier? Maybe at the margins.
I once saw a leaderboard at Costco that tracked the number of items each cashier scanned per minute. I was surprised both that they posted this kind of information where customers could see it and also that there was little difference between even the fastest and slowest cashiers. That is, this didn’t seem like a metric that would make a big difference to Costco’s bottom line.
After all, how many people have just abandoned their Costco carts because the cashier took too long to scan the items of the person in front of them? If anything, I’ve seen dozens of people use the waiting time to run and grab that huge bag of pistachios they can’t live without.
Okay, it’s me. I’ve done that, too.
If the cashier only minimally influences checkout time (except for extremely chatty employees, heaven help us), what about the cart of the shoppers in front of us? Undoubtedly. Uncommon items. Bulk produce without PLU code stickers. “Is that parsley or cilantro?” or “Um…what fruit is this?” Bad signs for quick checkouts.

Accept the unexpected
I’ve accounted for all the variables I can observe. A cashier who means business and a small cart of fully packaged and scannable foods. I’m in the clear. Except that I’ve forgotten one thing: the customer’s payment method.
A few weeks ago a woman in front of me paid with *gasp* a personal check. The cashier looked as though the customer had pulled a dead skunk out of her purse and offered it up as payment. She seemed nearly ready to call the Smithsonian with this historical artifact.
Naturally, everything ground to a halt as the cashier tried to figure out how to accept this form of legal tender. I watched helplessly as my produce lay strewn across the conveyor belt. I couldn’t possibly collect the scattered items and switch lanes now, could I? I settled in for the long process of finding someone who could accept this payment. I don’t remember how the situation resolved itself. It’s very possible ShopRite decided it was easier just to let the customer have the items for free rather than processing the check.
Sour grapes
It used to bother me that other lines moved faster than mine. I used to rue the wasted time and think how unobservant I had been to miss some small detail that should have made me choose another line.
This is one way in which I’ve become more curious and less judgmental. These few minutes don’t cost me anything. And, perhaps I shouldn’t admit this, but I enjoy observing what people buy and how they interact with one another. I’m always trying to recognize the limits of my awareness as an individual person, and the interactions between patron and cashier are surprisingly rich with detail.
Do they seem generally to care about how the other is doing, apart from the pleasantries? Do they seem tired, frazzled? Could they use a pick-me-up? What meals will the ingredients in their cart become? To whom will they serve them? How old is the cat that eats Fancy Feast? How long until the cashier’s shift ends, and what awaits them afterward?
Perhaps I am not extra bad at picking the optimal grocery store line. Maybe I only notice when my lane is the slowest. Or maybe it’s like the study that found that 80% of participants thought they were better than the median driver, a mathematical impossibility.
I guess someone has to be slower than average. Why not me?