In 2020, while many communities were under Covid lockdowns, protesters were flooding the streets and economic uncertainty and social isolation were deepening, Americans went on a shopping spree. For firearms.

Some 22 million guns were sold that year, 64 percent more than in 2019. More than eight million of them went to novices who had never owned a firearm, according to the firearm industry’s trade association, the National Shooting Sports Foundation.

Firearm homicides increased that year as well, to 19,350 from 14,392 in 2019. The death count from guns, including suicides, rose to 45,222 in 2020 from 39,702 in 2019. The number of lives lost to guns rose again in 2021, to 48,830.

After quashing research into gun violence for 25 years, Congress began funneling millions of dollars to federal agencies in 2021 to gather data.

Here is what social psychologists are finding about who purchased firearms, what motivated them and how owning, or even holding, a firearm can alter behavior.

Who started buying guns?

Millions of Americans who had never owned a gun purchased a firearm during a two-and-a-half-year period that began in January 2019, before the pandemic, and continued through April 2021.

Of the 7.5 million people who bought their first firearm during that period, 5.4 million had until then lived in homes without guns, researchers at Harvard and Northeastern University estimated.

The new buyers were different from the white men who have historically made up a majority of gun owners. Half were women, and nearly half were people of color (20 percent were Black, and 20 percent were Hispanic).

“The people who were always buying are still buying — they didn’t stop. But a whole other community of folks have come in,” said Michael Anestis, the executive director of the New Jersey Gun Violence Research Center, who was not involved in the survey.

Why did Americans decide to buy guns?

Self-defense is the top reason Americans purchase handguns. Gun ownership is not just a constitutional right but a necessary form of protection, according to organizations like the National Rifle Association and National Shooting Sports Foundation.

A study of individuals who said they were planning to purchase a first or second firearm during the early days of the pandemic found that would-be buyers were more likely to see the world as dangerous and threatening than individuals who were not planning to purchase a firearm.

Those planning to buy firearms were more likely to agree strongly with statements like “People can’t be trusted,” “People are not what they seem” and “You need to watch your back,” compared with those not planning a purchase, noted Dr. Anestis, an author of the study.

Buyers were also more fearful of uncertainty. They tended to strongly agree with statements such as “Unforeseen events upset me greatly” and “I don’t like not knowing what comes next.”

They were particularly frightened by Covid, according to the study, which was conducted in June and July 2020. They were more likely to be essential workers. Dr. Anestis, who studies suicide, said those planning to purchase a gun were also more likely to harbor suicidal thoughts.

More than half of all gun deaths in the United States are suicides. In 2021, for example, there were 48,830 gun deaths; 26,328 were suicides.

“Firearm owners are no more likely to have suicidal thoughts than non-owners,” Dr. Anestis said. “But if you look at who purchased a firearm during the surge, and if it was their first firearm, they were much more likely than others to have had suicidal thoughts in the last month, year or lifetime overall.”

The number of suicides did not increase during the pandemic, but the presence of a gun in the home increases the risk for as long as the family owns the gun. And while research shows that some people buy a gun while they are planning a suicide, most people who used a gun to kill themselves already owned the firearm — for 10 years, on average.

Families with teenagers who kept one firearm loaded and unlocked were more likely than those who kept guns stored to buy another firearm during the pandemic, other researchers have found. It’s possible the families were keeping guns easily accessible because they feared for their safety, and that this concern motivated the purchase of an additional firearm.

But these households are particularly vulnerable to gun injuries, said Rebeccah Sokol, a behavioral scientist at the University of Michigan and a co-author of the study. “Teens have some of the highest rates of firearm fatal and nonfatal injuries,” she added.

To some, guns bring comfort.

Experiments have shown that human touch can be remarkably soothing. In one study in 2006, for example, neuroscientists found that when married women were subjected to mild electric shocks as part of an experiment, reaching out to take their husband’s hand provided an immediate sense of relief.

Nick Buttrick, a psychologist at University of Wisconsin-Madison, wanted to know whether firearms provided similar comfort to gun owners, serving as a sort of psychological security blanket.

“The real question I wanted to answer was, What do people get out of having a gun?” he said. “Why would somebody want to take this really dangerous thing and bring it into their lives?”

He recruited college students, some of whom came from gun-owning households, to participate in a study in which they would be subjected to very mild electric shocks (he likened the sensation to static electricity).

While the shocks were administered, participants were given a friend’s hand, a metal object or a prop that looked and felt like a pistol but had no firing mechanism. For participants who grew up around guns, holding the prop that resembled a firearm provided the greatest comfort, Dr. Buttrick said.

“If you came from a gun-owning household, just having a gun present makes you feel more at ease,” said Dr. Buttrick, whose study has not yet been published.

For participants unfamiliar with guns, the opposite was true: They became more anxious when holding a replica of a firearm. “If you didn’t come from a gun-owning household, having a gun present made the shock worse,” he said. “You were more on edge.”

But safety may be an illusion.

Advocacy organizations like the N.R.A. emphasize the need for safe handling and storage of firearms and offer training programs intended to make ownership safer. But critics say public health officials have done a poor job of communicating the risks to Americans.

Many studies have found that easy access to firearms does not make the home safer. Instead, ownership raises the likelihood of both suicide and homicide, said Sarah Burd-Sharps, the senior director of research at Everytown for Gun Safety, a nonprofit that works to end gun violence.

One of the earliest studies to bring attention to the danger was a 1993 paper in The New England Journal of Medicine that found that keeping a gun in the home brought a 2.7-fold increase in the risk of homicide, with almost all of the shootings carried out by family members or intimate acquaintances. The findings have since been replicated in numerous studies.

“You are much more likely to be a victim of that gun than to successfully protect yourself,” Ms. Burd-Sharps said, adding that gun owners “are tragically not understanding the risks.”

Carrying a gun can change how a person perceives threats.

When Amadou Diallo was shot 41 times in the vestibule of his building in the Bronx more than two decades ago, police officers said they mistook the wallet he was holding for a weapon. In Cleveland in 2014, a police officer killed 12-year-old Tamir Rice because he thought the child’s “airsoft” replica pistol was a real gun.

Researchers are increasingly focusing on the idea that an armed person is more likely to perceive others as armed, and to respond as though he or she were threatened, a concept called gun embodiment.

“The idea behind embodiment is that your ability to act in the environment changes how you literally see the environment,” said Nathan Tenhundfeld, an associate professor of psychology at the University of Alabama in Huntsville and a co-author of one recent study. “Gun embodiment gets at the idea of the old colloquialism ‘When you’re holding a hammer, everything looks like a nail.’”

Stereotypes and emotions influence an observer’s ability to correctly identify a gun and, therefore, whether a particular individual is actually armed. One study found that participants were more likely to mistakenly think that a Black person was holding a gun than to mistakenly think that a white person was armed.

In research using computer simulations, participants are more likely to shoot at a target who appears to be wearing a turban.

In a recent effort to replicate older studies on gun embodiment, Dr. Tenhundfeld and his colleagues gave college students a fake gun or a neutral object — a spatula. They held the objects while watching images of guns and other ordinary items come up on a computer screen.

They were asked to quickly decide whether to “shoot” in response. When the participants were holding the gun, they took longer to respond, had a harder time rapidly distinguishing between weapons and nonthreatening objects, and made more mistakes.

“They weren’t biased — they were just getting it wrong more often, and were slower while holding a gun when the object they were looking at was a shoe,” Dr. Tenhundfeld said.

It may be that this is a form of gun embodiment, he said, adding that the participant’s “ability to act in the environment is affecting how they see the environment — that holding that gun is distorting how you’re seeing the world.”