Why You're Drawn To Slower Checkout Lines

ReutersThere's reason why you rarely land in the fastest-moving checkout line at the grocery store.

According to queueing theory - which is the study of lines - the mathematical odds are stacked against you when you're trying to pick the fastest of more than two lines.

Wired's Adam Mann explains the theory in more detail.

"If there are three lines at the store... delays will happen randomly at different registers," Mann writes. "Think about the probability. The chances of your line being that fastest one are only one in three. Which means you have a two-thirds chance of not being in the fastest line. So it's not just in your mind: Another line is probably moving faster than yours."

There's a way to avoid this problem.

Queueing theorists have determined that forming one single line for several registers is the most efficient way to manage a queue, rather than maintaining several separate lines.

"With three registers, this method is about three times faster on average than the more traditional approach," Mann writes.

Trader Joe's and Chipotle are among the retailers that use this approach. But it can be risky because customers dislike the appearance of one long, snaking line, even if it moves faster than several shorter lines.

As Mann writes, "Researchers have noted that some customers balk at serpentine lines, which can stretch much longer than the more traditional approach, preferring their chances of winning the lottery with multiple lines."