Not all employees are enthusiastic about Pret’s career tracks. At one store, Mr. Schlee introduces himself to a tired-looking employee on her lunch break. He jovially asks if she is a T.M.S. She shrugs and gives him a look as if he’s a parent trying to be cool.

It takes about three months to become a hot chef. It might seem that the training would cover procedures like making soup or baking croissants. But Pret has standardized so much — soups, for example, are sent to the shops premade and in plastic bags, and ovens are preprogrammed for each baked item— that the training is largely about food safety and disposal. A hot chef relying only on Pret’s training could have a hard time as a restaurant line cook, or even cooking a meal at home. Yet during a training class in London, employees were taking notes and asking questions as the trainer went over things like why they shouldn’t dump old soup down the toilet.

Mr. Flynn, the Stanford professor, says that emphasizing small advancements makes sense.

“That’s actually a very reasonable way to approach motivation,” he says. “Having them make continual progress provides them with feedback that they are doing what they need to be doing.”

THE streets are still wet from an early-morning cleaning on Eastcastle Street, not far from Paddington Station. It’s not yet 6:45, but Petronela Roman, with a big brunette topknot and cat-eye eyeliner, is making coffee for co-workers at a Pret store. Upstairs, employees put on white coats with red Pret logos. A barista from Brazil sprays himself with cologne.

At 7 o’clock, as the store manager, Lenka Karlovic, wraps up the morning meeting and employees are still downing their coffee, the first customer walks in. Flicking crumbs from her fingers, a worker rushes over with a "hello." The scream of the latte machine follows, and it’s off to the races.

It’s giddy in the kitchen at the back of the shop. It smells of chutney and mayonnaise, and Lukasz Gorczynski, who is training to become a kitchen supervisor, has his iPod blaring the Black Eyed Peas. Eight or so workers are running into the giant refrigerator, placing tomatoes on sandwiches, scooping mayonnaise from buckets and slicing through sandwiches with an electric-powered knife.

“Lemon juice, guys!” someone shouts.

“Open bread, guys!” says another.

Mr. Gorczynski and Ms. Karlovic have determined what must be ready when, based on average sales and the weather. The clock is running: Mr. Gorczynski’s task list includes making six bowls of granola within 1 minute and 17 seconds; 24 edamame packs within 6 minutes and 2 seconds; 20 containers of honey-granola within 6 minutes and 17 seconds. Berry bowls, muesli bowls, porridge toppings — the list goes on. The food is taken to the shop floor as soon as it is finished, and hundreds of sandwiches, salads and other items must all be in the cases by 10:30 a.m.