It’s all about math. And you thought math wouldn’t serve you any practical use in your adult life.
According to mathematician Dan Meyer who spoke to Christopher Mele of the New York Times, “Every person requires a fixed amount of time to say hello, pay, say goodbye, and clear out of the lane.” This whole interaction takes about 41 seconds per person, and it only takes three seconds to ring up each item. The fixed 41 seconds will not change depending on the amount of people in line, so you have to calculate the three seconds per item instead.
Mele explains it like this, “One person with 100 items to be rung up will take an average of almost six minutes to process. If you get in a line with four people who each have 20 items, it will take an average of nearly seven minutes.”
If every line at the grocery store appears to have the same number of people and items, Mele suggests choosing the left lanes and avoiding talkative cashiers.