The voice scolds you like a disapproving mother: “Unexpected item in bagging area.” Then the traffic light of doom above your terminal starts blinking, letting the entire store know that you gambled in the self-checkout game and lost. What had seemed like a timesaver has turned into a lesson from the attendant you were hoping to avoid all along.

“Self-checkout lanes are like the left lane on the freeway and should be reserved for people who are fast and know what they’re doing,” said Sara Serie of Plymouth. “If you’re on the phone, have a cart full of large items, then don’t even think about using the self-checkout.”

Many shoppers say the automated process saves time and eliminates the burden of trying to make small talk with the cashier. But those same shoppers have plenty of gripes, as well: other customers taking too long, no help available and, of course, machines that are either too hard to figure out how to use or don’t work properly.

There’s even a support group on Facebook for people who hate self-checkouts and are “sick of merchants making us do the work for them.”

Obstacles aside, self-checkout machines are here to stay. There are more than 200,000 of them around the world, with that number forecast to reach 335,000 by the end of 2020, according to London-based research and consulting group RBR.

The DIY registers can be found everywhere from Walmart and McDonald’s to CVS and Urban Outfitters. Shopper satisfaction of the self-checkout process varies, but according to a recent consumer survey from the University of Chicago, only 25 percent of shoppers like automated grocery checkouts, whereas 50 percent strongly prefer interacting with a live clerk.

University of Minnesota student Courtney Nelson expressed frustration over the high number of self-checkout lanes at the Target in Dinkytown.

“Buying fresh produce in an automated lane is the worst,” she said. “I hate having to look up all the codes for everything, so I almost always go to the cashier.”

The love/hate relationship with self-checkouts spans generations. Retailers recognize that the technology is imperfect and upgrading the devices is essential to catering to the millennial shopper.

To improve its self-checkout process, Target developed new software for the system and a checkout computer that’s simpler and more intuitive for guests. Since the new system went live last August, Target says its self-checkout lanes are running smoother and faster, improving guest satisfaction.

But the retail chain also recognizes that not everyone likes self-checkouts and other customers, like Nelson, want options depending on what they’re buying, said Juan Galarraga, Target’s senior vice president of store operations.

“There are guests that love self-checkout and there are guests that love to talk and have a cashier ring you out,” Galarraga said.

Ginny Agresti is one of the latter. The Minneapolis woman does most of her shopping at her neighborhood Lunds & Byerlys, and she looks forward to chatting with the cashiers she has gotten to know over the years.

“Zipping through the self-checkout negates all of that,” Agresti said. “Whenever I have used the self-checkouts it feels like I’m trying to sneak through without interacting with people. How much in a rush do I have to be?”

Which raises another question: Are self-checkout lanes actually faster?

It depends.

During a recent trip to Target, Agresti used the self-checkout lane. Despite telling the machine that she brought her own bag, she kept getting an alert that she had an unidentified item in the bagging area.

“I removed the bag and kept trying to make the machine stop scolding me so I could pay and leave,” she said. “If I have to wait for someone to come rescue me, why didn’t I just go through the regular line?”

But for the most part, self-checkout is seen as being faster. A 2015 Consumer Reports survey of 63,000 shoppers found that three out of four shoppers who used the machines classified the experience as a timesaver.

“If you have just a few easy items, they are great,” said Peg Kaplan of Minnetonka. “If you have something odd that triggers the machine to require a human to come over and help, if you have some coupons that gum up the works ... then they are a pain and take longer than the regular human lines.”

The future is automated

Could we be headed to a time when all the cashiers have been supplanted by machines?

“I love them because they go quicker, but I hate that they are taking jobs away,” said Megan Ellingson of Bemidji, Minn.

Actually, the number of cashier jobs is climbing, according to the Bureau of Labor Statistics, but not nearly as fast as positions in other fields. Cashier jobs are expected to grow 2 percent by 2024, significantly slower than the 7 percent job growth overall, and technology is the main reason, according to the bureau.

While it’s difficult to predict just how much automation will affect cashier jobs, there is evidence that change is inevitable.

Amazon opened its first cashier-less store in Seattle earlier this year and recently announced plans to expand the concept to Chicago and San Francisco. Shoppers pick up their items and are charged as they go via an app on their smartphone. No human interaction is necessary.

A variation on this system is taking root in England, said Mary Johnson, a Minnesotan who has relocated to London. As they enter a store, shoppers are given a portable scan gun that they use to ring up items as they shop. “This is becoming more mainstream,” she said.

Walmart, on the other hand, ended its scan-and-go checkout service in April after it failed to become a hit with customers.

Local retailers who pride themselves on customer service say that human cashiers aren’t going away soon. At the 13 Lunds & Byerlys stores that have self-checkouts, nearly 30 percent of all transactions employ those lanes, a figure that’s up only slightly from 20 percent in 2013.

“While self-checkouts require less labor, we are a company that focuses heavily on providing high levels of service to our customers,” said Aaron Sorenson, spokesman for the stores. “We view the combination of self-checkouts and full-service checkout lanes as a nice blend of service and convenience to meet our customers’ needs.”

Staff writer Kavita Kumar contributed to this report.