In America, overt racism and discrimination are easy to spot: White supremacists marching in Charlottesville, Va.; fabricated claims of white people being attacked at Black Panther; hate crimes, like that of the Oklahoma man convicted earlier this month of murdering his Lebanese neighbor.

But there is another kind of discrimination that is quieter, harder to identify and to address: microaggressions. Harvard psychiatrist Chester Pierce coined the term in 1970 to describe racially charged "subtle blows ... delivered incessantly."

Some recent examples:

A Conservative Political Action Conference speaker saying last week that Michael Steele only became Republican National Committee chairman in 2009 "because he was a black guy."

A New York Times editor tweeting “Immigrants: they get the job done,” with a video of Olympic figure skater Mirai Nagasu, who was born in California.

A U.S. Air Force Academy officer sending an email to cadets about proper haircuts and also saying that Michael Jordan was never seen with "gaudy" jewelry or sagging pants. (A higher-ranking officer later apologized.)

Critics deride microaggressions as a buzzword that curtails free speech and promotes a liberal agenda of political correctness. Public health experts, however, point to a growing body of research that suggests the accumulated impact of these stressors affect long-term health and can contribute to higher rates of mortality and depression.

"A lot of people hear 'microaggressions' and they think, 'Oh, it’s just the little things that hurt people’s feelings,'" said Roberto Montenegro, a chief fellow in child and adolescent psychiatry at Seattle Children's Hospital. He studies the biological effects of discrimination. "It isn’t about having your feelings hurt. It’s about how being repeatedly dismissed and alienated and insulted and invalidated reinforces the differences in power and privilege, and how this perpetuates racism and discrimination."

A 2017 survey conducted by NPR, the Robert Wood Johnson Foundation and the Harvard T.H. Chan School of Public Health, found that 92% of African Americans believe they're discriminated against, and nearly half say individual prejudice is a bigger problem than discrimination rooted in government policies. A January 2018 study in the Journal of Multicultural Counseling and Development found that of counselors who had clients reporting race-based trauma, 89% identified "covert acts of racism" as a contributing factor.

Everyday insults

A little more than a decade ago, Columbia psychology professor Derald Wing Sue expanded the concept of microaggressions to include its affects on other marginalized groups, including other racial and religious minorities, women and the LGBTQ community.

Some commonplace examples:

A white woman clutching her purse when walking past a black man (signaling black men are dangerous criminals)

Asking someone who isn't white "Where are you really from?" (signaling they are not American)

"Complimenting" a gay person by saying "but you're not gay gay" (signaling stereotypically gay traits are bad)

Mistaking a female physician for a nurse (signaling women aren't as capable as men)

"Anytime you're put into a box, it's damaging because people ... are unable to perceive you in other ways," said Nantasha Williams, head of social impact and political engagement at the Women's March.

Montenegro remembers vividly one particular "dehumanizing" moment. He had completed his doctorate in sociology and was leaving an upscale restaurant with his wife, standing in line at the valet curb, when a white woman handed him her keys, mistaking him for an attendant. Minutes later, another white woman did the same. He has also been confused for a custodian at the hospital where he works.

Montenegro acknowledges such slights can be unintentional but said they not only take the wind out of someone's sails, they are frustrating and hurtful.

"Imagine feeling that over, and over and over," Montenegro said. "It can take its toll."

Death by a thousand cuts?

Each time Montenegro experiences one of these subtle slights, his body reacts. Anger and anxiety produce a stress response, and he argues that, over time, chronic exposure turns these microaggressions into "micro-traumas."

"Experiencing this kind of discrimination prematurely ages the body," he said. "And that’s a pretty scary concept."

Racial discrimination accelerates aging at the cellular level, according to a 2014 study in the American Journal of Preventive Medicine. Although the disparity in death rates between blacks and whites narrowed from 1999 to 2015, it still remains, according to the Centers for Disease Control and Prevention. Many African Americans in their 20s to 40s experience conditions that white people suffer from when they're older, such as heart disease and stroke.

Some experts point to lifestyle choices, income, education and geography as reasons behind the disparities.

However, Arline Geronimus, a professor of health behavior and health education at the University of Michigan, believes "people think we have much more choice over our health than we do." She pointed to late activist Erica Garner, whose father Eric Garner died on Staten Island in a police chokehold in 2014. Erica later died at 27 of a heart attack.

"She was an activist fighting what must of have been a very painful and enraging system," Geronimus said. "Erica Garner may have been 27, but chances are in a variety of ways — her cellular aging, the aging of her various body systems or organs — she was probably much older than that. That makes you more vulnerable and fragile and susceptible to all kinds of health problems and less able to fight them."

Geronimus uses the term "weathering" to describe the way chronic stressors — which can include interpersonal microaggressions and institutionalized racism — erode bodies. Humans have life-threatening stressors activate a physiological stress response, like seeing a tiger in the bushes; the problem is that people who experience discrimination are "endlessly seeing tigers," she said.

Guilty of microaggressions? How to change your behavior

Psychological research suggests the key to confronting biases is by exposing yourself to what makes you uncomfortable — "to different environments, different individuals, different settings, different ideas," Montenegro said.

To that end:

Drop the defensiveness

If someone says you offended them, listen

Think before you speak

Seek out books, podcasts and other media to learn about current and historical behavior and policy

"A lot of white individuals think the concept of being racist is a moral judgement. They feel that if they acknowledge that they’re racist they’re morally a bad person," Montenegro said. That fear, he explains, is part of "white fragility" — the defensiveness many whites experience when their understanding of race is challenged. "We have to acknowledge that we all discriminate," he said, otherwise "it's going to be difficult to be able to talk about it."