NEW YORK >> Starbucks closed thousands of stores today and asked employees to talk about when they noticed their racial identity, discuss what unconscious bias is and watch videos in which people of color describe feeling unwelcome in stores.

Hawaii stores were scheduled to close at 2:30 p.m. today, although some locations would remain open throughout the afternoon.

It was all part of the coffee chain’s anti-bias training, created after the arrest of two black men in a Philadelphia Starbucks six weeks ago. But whether the training, developed with the NAACP Legal Defense and Education Fund and other groups, will prevent another embarrassing incident remains to be seen.

“This this is not science, this is human behavior,” said Starbucks Chairman Howard Schultz. “This is just the first step of many that we’re going to take.”

The training was personal, asking workers to break into groups of three to five people to talk about their experiences with race. According to training materials provided by the company, they were asked to pair up with a co-worker and list all the ways they “are different from each other.” A guidebook reminds people to “listen respectfully” and tells them to stop any conversations that get derailed.

“I found out things about people that I’ve worked with a lot that I didn’t know,” said Carla Ruffin, a New York regional director at Starbucks, who took the training earlier Tuesday and was made available by the company to comment on it.

Ruffin, who is black, said everyone in her group said they first experienced bias in middle school. “I just thought that was pretty impactful, that people from such diverse backgrounds, different ages, that it was all in middle school.”

She said the training and discussion is needed: “We’re never as human beings going to be perfect.”

Starbucks declined to specify how much the training is costing, but Schultz called it “quite expensive.”

“We’ve had certain shareholders call and say, ‘How much is this going to cost and how do you justify this?’ My answer to them was simply, we don’t view it as an expense. We view it as an investment in our people and the long-term cultural values of Starbucks.”

The company also lost sales from closing early, though the late-in-the-day training sessions meant no disruption to the busier morning hours.

At the company’s Pike Place Market location in Seattle, commonly referred to as the original Starbucks, the store stopped letting people in at 1 p.m.

Trina Mathis, who was visiting from Tampa, Florida, was frustrated that she couldn’t get in to take a photo but said the shutdown was necessary because what happened in Philadelphia was wrong.

“If they haven’t trained their employees to handle situations like that, they need to shut it down and try to do all they can to make sure their employees don’t make that same mistake again,” said Mathis, who is black.

Others visiting the store questioned whether the training would make a difference or suggested it was overkill.

Anna Teets, who lives in Washington state, said the problem has been fixed and the company has dealt with the situation. “It’s been addressed,” she said.

The training was not mandatory, but Starbucks said it expected almost all of the 175,000 employees to participate. It said they will be paid for the full four hours. Executives took the same training last week in Seattle.

Training in unconscious, or implicit, bias is used by many corporations, police departments and other organizations. It is typically designed to get people to open up about prejudices and stereotypes — for example, the tendency among some white people to see black people as potential criminals.

Many retailers, including Walmart and Target, say they offer some racial bias training. Nordstrom has said it plans to enhance its training after apologizing to three black teenagers in Missouri who were falsely accused by employees of shoplifting.

In the Philadelphia incident, Rashon Nelson and Donte Robinson were asked to leave after one was denied access to the bathroom. They were arrested by police minutes after they sat down to await a business meeting.

The arrest was recorded by cellphone and triggered protests, boycott threats and debate over racial profiling, or what has been dubbed “retail racism.” It proved a major embarrassment for Starbucks, which has long cast itself as a company with a social conscience and had even encouraged dialogue about race before — to some mockery.

Nelson and Robinson settled with Starbucks for an undisclosed sum and an offer of a free college education. They also reached a deal with the city of Philadelphia for a symbolic $1 each and a promise from officials to establish a $200,000 program for young entrepreneurs.

Starbucks said the arrests never should have occurred. It has since announced anyone can use its restrooms, even people not buying anything.

Some black coffee shop owners in Philadelphia suggested black customers instead make a habit of patronizing their businesses. Amalgam Comics and Coffeehouse owner Ariell Johnson said she has called the police just once in the two years she has been open. She said that should happen only when there is a provocation or danger.

Calvin Lai, an assistant professor of psychological and brain sciences at Washington University in St. Louis, said that diversity training can sometimes have mixed effects.

“In some cases it can even backfire and lead people who are kind of already reactive to these issues to become even more polarized,” Lai said.

One afternoon wouldn’t really be “moving the needle on the biases,” he said, especially since Starbucks has so many employees and they may not stay very long.

Starbucks has said the instruction will become part of how it trains all its workers.