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Branded Starbucks mugs line up on a shelf, before more than 8,000 branches nationwide will close this afternoon for anti-b...

Starbucks closed more than 8,000 stores for an afternoon of bias training. Will it work?

Starbucks closed more than 8,000 of its company-owned stores nationwide Tuesday afternoon to conduct unconscious bias training sessions with employees.

The decision was sparked by the arrest of two black men at one of the company’s stores in Philadelphia last month. The two men, Rashon Nelson and Donte Robinson, said they were at the store for a business meeting. But a Starbucks employee called police to say they were trespassing. Though Starbucks apologized and implemented new policies, the arrests set off dayslong protests at the store and accusations of racism.

The company said unconscious bias training is the first of many steps it will take to quell racial bias in the workplace and restore its reputation as a place where people feel welcome.

Here’s what we know about the company’s strategy — and whether these kinds of training are effective.

What’s the company’s plan?

Starbucks released details about the four-hour training curriculum last week, which suggested that employees would watch recorded footage and participate in self-guided group discussions.

The training sessions were expected to include videos by CEO Kevin Johnson and executive chairman Howard Schultz, both of whom spoke about making Starbucks a welcoming place. The company said it would also screen “You’re Welcome,” a documentary by Stanley Nelson related to racial discrimination.

READ MORE: Men arrested at Starbucks say they feared for their lives

Starbucks said in a news release that the training would also focus on understanding racial bias and the history of public accommodations in the nation. Moreover, the company said employees were to be given toolkits to go through group discussions about their own experiences with bias.

Starbucks declined the PBS NewsHour’s request for an interview.

Though Starbucks closed more than 8,000 company-owned stores Tuesday, more than 7,000 of its licensed stores — such as those operated by hotels, grocery stores and universities — remained open. The company said it would share its training content with employees at those locations, too, though it did not provide more detail on that rollout.

Does unconscious bias training work?

The short answer: It’s hard to say. One of the biggest problems with bias training is that so few people have evaluated whether it’s effective, said Patricia Devine, a professor of the University of Wisconsin-Madison who focuses on how to manage prejudice in society. Some studies have also found that, when done the wrong way, these kinds of trainings can actually make the problem worse.

Devine and researchers at the Prejudice and Intergroup Relations Lab have developed a new training approach to address biased behavior. The approach is different because it treats bias as a habit and comes up with strategies to break that habit. Devine said to do this, one must be aware of the problem, have a motivation to change it and come up with ways to replace it.

Even still, Rutgers University professor Chester Spell, who specializes in behavioral health in organizations, said diversity training programs rarely create changes on their own.

“What’s happening today at Starbucks is unlikely — in our opinion, from our research results — to do much by itself,” Spell said, adding that the success of Starbucks’ program will depend on how committed it is to sticking with the initiatives in the days, weeks and months after Tuesday’s training.

Katerina Bezrukova of the University at Buffalo, who co-authored a study on diversity training with Spell, said that diversity training can be more effective if it’s enhanced by follow-up practices that emphasize diversity on a day-to-day basis.

“It’s not really about the training itself; it’s about the training being complemented by other initiatives,” Bezrukova said. “We call it training that’s embedded in organizational structure and the way organizations run the business.”

Harvard University sociology professor Frank Dobbin said it’s important to remember that diversity and implicit bias trainings aren’t the only solution. Other solutions include: creating special recruitment programs where companies encourage minority groups to apply for jobs; establishing mentoring programs where managers interact with their employees, who are often minorities; and creating diversity task forces that identify problems within companies and find ways to solve them.

“Diversity training itself won’t produce any lasting changes even if you do it frequently,” Dobbin said. “You just can’t change people’s attitudes that easily.”

What’s next?

There’s a lot of pressure on Starbucks to “be one of the first to get antibias training right.”

Its success hinges in part on if and how the company is able to measure Tuesday’s trainings.

Devine told the NewsHour that a good way to measure whether diversity or implicit bias messaging sticks is through controlled experiments that allow organizations to analyze the impact training programs have on employees over time. The company also said it will conduct future training sessions that would address “all aspects of bias and experiences,” but didn’t offer further details.

Starbucks said it will make Tuesday’s curriculum available to the public and that it would also share it with partners, companies and other organizations interested in it. The company did not immediately provide a date for the release of those materials.

“The company’s founding values are based on humanity and inclusion,” chairman Howard Schultz said in a statement. “We will learn from our mistakes and reaffirm our commitment to creating a safe and welcoming environment for every customer.”