NEW YORK – While computers appear to be taking over for humans in many areas, the checkout line at the grocery store isn’t one of them. For years, supermarkets have added self-checkout lines, but that has begun to change, the Wall Street Journal reports.

When self-checkout lines were first introduced, some touted the machines as a quick way to pay for groceries. NCR, which supplies self-checkout lanes for retailers, conducted a survey that found shoppers viewed self-checkout systems as faster than lanes with cashiers. But that perception generally does not play out in reality. Studies have been done that show the opposite: At any grocery store, watch the self-checkout lanes and the cashier lanes, and you’ll see that the humans are faster.

The reality is more and more customers are eschewing those “fast” lines for ones with human cashiers. Checking out groceries yourself involves more complexity than using an ATM or the airport check-in machines. For example, identifying fruits and veggies are a pain for the self-checker.

Computers won’t be entirely replacing humans at the checkout counters because figuring out which is kale and which is green leaf lettuce is too nuanced for a machine, said Frank Levy, who co-wrote the research paper Dancing With Robots.

“In the '60s, people assumed you'd be reading X-rays and CT scans by computers within years,” said Levy. “But it's nowhere near anything like that. You have certain computerized enhancements for simple images, but nothing like a real CT scan can be read by a computer—and the same thing would be true trying to separate arugula from everything else.”