What could you do with an extra $500 a month? Lorrine Paradela got a better night’s sleep.

The 45-year-old single mother is one of the 125 Stockton residents receiving monthly cash disbursements as part of an attention-grabbing experiment on guaranteed income.

Paradela has been able to pay for a new car after her old one was wrecked in a crash. She bought a video game console for her 16-year-old son as a thank-you gift for his help taking care of his 10-year-old sister.

But the biggest transformation has been her state of mind. Paradela said she used to lie awake at night, thoughts racing over how she would pay her expenses. She would get up in the morning exhausted.

“I’d be asleep and my mind would still be thinking about bills. I’d be dreaming about bills,” she said. “The extra money made it a little bit easier to sleep, to breathe better.”

For 18 months, the Stockton Economic Empowerment Demonstration is tracking how the $500 payments change recipients’ lives, a test to prove the viability of a concept known as universal basic income. Supporters argue that providing everyone with a baseline wage would remove financial stresses, improve people’s health and address economic inequality.

The concept has been around for centuries, even popping up in “Utopia,” Thomas More’s 1516 book about an ideal society. It got a trial run in the United States in 1969 under President Richard Nixon, before Congress ultimately rejected his plan to replace welfare with annual payments of up to $1,600 for every poor, working family.

The idea of a guaranteed income regained currency in recent years, particularly among tech industry leaders in Silicon Valley. Many believe it could be the solution to a future in which more workers lose their jobs to automation.

Democratic presidential candidate Andrew Yang, a former corporate attorney and entrepreneur, has boosted it on the campaign trail. His candidacy revolves around a proposal to give $1,000 a month to every U.S. citizen over age 18.

Although it officially launched in February, the program in Stockton precedes Yang’s political rise. In October 2017, Mayor Michael Tubbs announced the city of 310,000 would run a pilot program to demonstrate how the additional income could relieve hardship in a community where nearly a quarter of residents live in poverty.

The Economic Security Project, an advocacy group chaired by Facebook co-founder Chris Hughes, provided the first $1 million for the program. A dozen organizations and private donors funded the rest of its $3 million budget. Many have Silicon Valley connections, such as the Future Justice Fund, which is run by Instagram co-founder Mike Krieger and his wife, Kaitlyn Krieger.

The universal basic income experiment is both a political and a personal mission for those involved. Sukhi Samra, director of Stockton’s program, speaks of the opportunity to reimagine the social safety net and of rooting the demonstration in values of social justice.

Unlike Yang’s proposal, which would require poor people to choose between the guaranteed income and benefits such as food stamps, the Stockton demonstration is intended as a supplement to welfare. By providing an income floor for participants, Samra hopes they can reshape their lives in ways that carry on after the experiment ends in August, by starting to save money or looking for a higher-paying job, improving their health or spending more time with their families.

Samra grew up in poverty in Fresno, the daughter of Indian immigrants. Neither of her parents had a high school education or spoke fluent English, Samra said, and her mother supported the family by working as a gas station cashier in the morning and at a Subway shop in the afternoon.

“She was working as hard as she could and the economy wasn’t working for her,” Samra said.

She said the guaranteed income demonstration is an opportunity to uplift hard-working folks like her mother and to imagine an economy that is more fair, especially for people of color and women pushed to the margins of society. She said their struggles are not captured by economic statistics that show a strong stock market and low unemployment.

“People aren’t poor by choice. People aren’t poor because they don’t work. People aren’t poor because they’re lazy,” Samra said. “People are poor because our systems have been created this way.”

Stacia Martin-West, an assistant professor at the University of Tennessee’s College of Social Work, and Amy Castro Baker, an assistant professor at the University of Pennsylvania’s School of Social Policy & Practice, are conducting research about the Stockton experiment.

Castro Baker said they are less interested in how participants spend the money than whether providing greater financial stability to residents of a “city that was hit by the worst of what capitalism has to offer” during the foreclosure crisis encourages them to engage more in civic life.

“Do we increase people’s sense of mattering and hope?” she said.

The research team randomly selected 125 participants from neighborhoods where the median income was below the citywide figure of $46,000. Twenty-five of them, including Paradela, volunteered as a “storytelling cohort” to share their experiences publicly. About 200 other people are being monitored as a control group.

Residents started receiving the monthly payments via debit cards in February, and data for the first five months of spending were released in October. Of the money that could be tracked, nearly 40% went to food and almost a quarter was spent at clothing, home goods or discount stores. Utilities and car maintenance both made up about 10% of the spending, and the rest went to medical care, insurance, recreation and other miscellaneous services.

Martin-West said she was not surprised by the findings, since poorer people often run out of food benefits before the month is over.

“It highlights where the gaps are,” she said.

Critics argue that expanding universal basic income on a broad scale would be impossibly expensive and counterproductive.

Rob Lapsley, president of the California Business Roundtable, which represents the state’s largest employers, called it a “complete distraction” from finding solutions to lower California’s cost of living and training a workforce for jobs that will be available in the future. His group conducted focus groups on anti-poverty programs two years ago and found many potential recipients of a guaranteed income resisted the idea because working gave them a sense of purpose and self-worth.

Organized labor has been alarmed as tech executives embrace the concept. Steve Smith of the California Labor Federation said unions worry that the tech industry is using guaranteed income as a “Trojan horse” to accelerate a transition to automation that is not nearly as inevitable as it portrays.

Smith said the private funding for Stockton’s program insulated it from the welfare trade-offs in proposals like Yang’s.

“I guess if a group of billionaires wanted to come together to raise $3 trillion a year to fund this program on a national scale, we might rethink our position,” he said. “But that’s not what’s going to happen.”

When Paradela received an invitation in the mail to participate in the Stockton demonstration, she was skeptical that it was real, she said, because “you don’t get nothing for free.” But she decided she had nothing to lose.

At the time, Paradela was working two jobs, one with special needs students and the other in a home for autistic teenagers. She was still just scraping by. Costs were adding up, including the $1,250-per-month rent for their three-bedroom apartment, which she did not want to leave because it was near good schools for her kids.

Paradela said it was embarrassing to struggle with finances. She kept her daughter home from friends’ birthday parties when she couldn’t afford to buy a gift. The child support payments she was supposed to receive from her ex-boyfriend were like a game of roulette.

“Sometimes you get it, sometimes you don’t,” she said. “You can’t really afford kids, period.”

The extra $500 a month isn’t a lot, Paradela said, but it helps. Soon after the program began, her car battery died and she used the money to buy a new one — a crucial purchase, since she needed the car for work and to drive to Salinas nearly every week to take her sick mother to the doctor.

Then in June, Paradela got in a car crash. Insurance money covered the down payment for a new, more reliable car, and her extra income goes to the $406 monthly payments.

“The money came just in time,” she said.

The program has improved her whole outlook. With the monthly disbursement in her pocket, she was able to scale back to one job and spend more time with her children. She can take them out to eat on occasion.

That has motivated her to return to school and get her bachelor’s degree. With a higher-paying job, Paradela said, she could continue to work less after the payments stop in August.

“It’s giving me a little leeway in life,” she said. “I’m going to keep going to make our lives better.”

Alexei Koseff is a San Francisco Chronicle staff writer. Email: alexei.koseff@sfchronicle.com Twitter: @akoseff