President Trump, center, gestures as former Boys Scouts, Interior Secretary Ryan Zinke, left, and Energy Secretary Rick Perry, watch at the 2017 National Boy Scout Jamboree at the Summit in Glen Jean, W.Va. The speech was criticized as inappropriate for the young audience. (Steve Helber/AP)

Since taking office, President Trump has all but dismissed the need for decorum and civility, saying he’s “modern day presidential.” However, 97 percent of Americans say it’s important for a president to be civil. Given this disconnect, perhaps it’s time to stop wishing Trump adopts a more dignified persona and instead ask if his presidency is affecting our character, collectively and individually.

Behaviors such aggression, anger, blaming, bullying, dishonesty, greed, narcissism, negativity, profanity and incivility are all social contagions.

A social contagion describes how others’ actions infect mood and behavior, just as you might catch someone’s flu. With prolonged exposure, you’re at greater risk, but even a brief event — reading one tweet or watching a video clip — can affect behavior.

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Think about when a baby cries, others soon wail. Or how you walk into a room and feel tension in the air. We don’t have the wherewithal to investigate every threat so, as social animals, we evolved to subconsciously pick up cues from others. An efficient early warning system, social contagions trigger fear and furor, and they can have a stronger effect when someone is in leadership.

Of course, we shouldn’t pin every current social pathogen on the president. Inhumanity contaminates the entire political spectrum, and we’ve all succumbed to a pointless argument on Facebook. But what’s remarkable about the recent venom, according to Texas A&M professor of political rhetoric Jennifer Mercieca is, historically, from the Boston Tea Party on, Americans without power resort to incivility in a last-ditch effort to be heard.

Now, says Mercieca, those in power are often the most uncivil. And rather than a last resort, it’s the first inclination.

“Modern day presidential” includes belittling and demeaning citizens (e.g., “dumb as a rock,” “wacky & totally unhinged,” “lost his mind”). Months before he talked about “s—hole countries,” the president used inappropriate innuendo in a speech to Boy Scouts.

Directly and indirectly, Trump has accused officials, reporters and a Gold Star widow of falsehoods, while The Washington Post Factchecker determined he made more than 2,000 false statements during his first year as president.

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Already, this may be changing the nation’s discourse. Analyzing 462 million comments in Reddit, from 2005 to the 100th day of Trump’s presidency, researchers determined the site’s political dialogue was the most offensive in its history. But the president’s impact may go beyond virulent speech.

For example, Trump blamed Republican senators for failure to pass health insurance reform and blames Democrats for the stalemate on immigration.

University of Southern California professor of management Nathanael Fast found that after people read about their governor blaming others for a legislative defeat, they were more likely to blame others for a failure in their own lives. As leaders regularly blame others, avoiding responsibility becomes ingrained in the culture, research shows. People band together to “blamestorm” — find scapegoats for mistakes.

When leaders brag about their superiority and achievements, it makes “narcissism seem normal and what winners do,” said Jean Twenge, San Diego State University psychology professor and co-author of “The Narcissism Epidemic.”

Dishonesty also is communicable. People lie and cheat more after they’ve seen someone get away with it. Negativity is more infectious than positivity. De-energizing colleagues have up to seven times more impact than an energized one. In social media, anger travels faster than joy, and you’re more effective at riling up people you hardly know, research shows. If you include profanity in a comment, someone’s twice as likely to swear in reply.

When political leaders are uncivil on social media, it catalyzes aggression in supporters and opponents alike, according to work by University of Texas at San Antonio political psychology professor Bryan Gervais. Yet opponents know they’re angry. Supporters don’t perceive their aggression. They just think they’re cheering their guy.

Aggression, bullying and incivility mutate into social super-viruses.

After experiencing incivility at work, 94 percent of us respond with incivility of our own — most commonly with anger and a desire to retaliate. We escalate. We become like the president of whom, as first lady Melania Trump said, “When you attack him, he will punch back 10 times harder.”

Business professors Georgetown University’s Christine Porath and University of Florida’s Amir Erez study incivility’s impact, and have concluded just a mild dose of incivility has an effect. During one experiment, Erez had an actress scold neonatal intensive care (NICU) physicians and nurses before a simulated procedure. Everyone went on the defensive. They wouldn’t offer an opinion or help each other. These teams were 40 percent less effective in diagnosis and treatment.

Rudeness could be more dangerous to an infant in NICU than a chronically sleep-deprived physician or receipt of wrong medication. Since there’s no good remedy for rudeness, incivility becomes a psychological open wound. Research shows that we get predisposed to recognize subsequent meanness and more eager to punish. Yet our aim is imperfect: We may act against anyone in our path — boss, spouse, co-worker or bystander.

Of course, not everyone fights fire with fire. Some withdraw, gossip or are less social. But passive-aggressiveness is also incivility, with unique consequences. “People who witness incivility are three times less likely to help,” Porath said. “Think about the ripple effects of this across an organization.” Or society.

Incivility leads to anger leads to incivility leads to ….

Incivility may cost companies an annual $14,000 per employee. According to Porath and Thunderbird School of Global Management’s Christine Pearson, Fortune 1000 managers spend seven weeks each year dealing with the fallout.

Things are even worse when leaders — role models — are involved. Twenty-five percent of the most uncivil employees act that way because their boss is uncivil, reported Porath.

In the military, leadership-by-example is paramount. “We Soldiers admire and aspire to be leaders who operate with dignity and respect …. We go to great lengths to instill these traits in our troops at an early age,” wrote U.S. Army Major General (Ret.) Paul Eaton in an email.

“The behaviors exhibited by Mr. Trump however — the consummate toxic leader who makes sport of chaos, bluster, bullying, character attack, stealing credit while blaming others — are anathema to Army leadership’s primary task: create leaders who will motivate the American Soldier to fight and win our Nation’s wars,” wrote Eaton.

In fact, since 2003, researchers have studied toxic leadership in the military. They’ve learned that bullying leaders impair unit performance and physical and psychological well-being of those under their command. Service members are less likely to remain in the military, don’t report misconduct, and act uncivilly themselves, explained U.S. Army Colonel (Ret.) George Reed, dean of the School of Public Affairs at University of Colorado at Colorado Springs.

While some believe the best way to fight incivility and aggression is to ignore it, Reed warned, “Just as harmful is the … laissez-faire leader who lets bad things happen on their watch.”

Not punishing can be perceived as rewarding toxicity. And when a toxic leader is promoted, “ … you have toxicity in the organization that spreads,” Reed said.

At enormous cost.

An analysis in Joint Force Quarterly concluded that, in FY2016, toxicity in the military may have cost U.S. taxpayers as much as $4.7 billion — 8 percent of the year’s defense budget.

Notwithstanding the negative outcomes, there are those arguing we should accept this hyper-destructive environment as the new normal. However, the science is not so fatalistic. Researchers say, yes, the dark side is quicker, easier and more seductive. But positive behaviors also are contagious.

Receiving generosity makes you more likely to donate. If others cooperate, so do we. Goal-setting is catching. A leader’s confidence makes teammates confident and successful. Civil comments elicit civil responses, and we see these exchanges as less biased, more informative and trustworthy. Companies with enforced civility policies do better.

Therefore, we can take steps to safeguard our collective psyche. Research shows clear codes of conduct help because we understand what is expected of ourselves and others.

A civility policy can be as simple as agreeing that civil discourse focuses on issues; respects others; and acknowledges strength in others’ arguments. Hallmarks of incivility include: advocacy of violence; profanity; personal attacks; dehumanization of others; caricatures and stereotypes; and false facts and conspiracies presented as truth.

With this standard, Twitter and Facebook could use a red check or box to flag accounts of the regularly uncivil. Television media could create an “I” rating for incivility, to go with ratings for TV violence.

There’s scientific and popular support for these actions: Warning bystanders lessens incivility’s effects, while many surveyed say they’re ready to cut off uncivil media.

In her book “Mastering Civility,” Porath offers ways to protect ourselves — first and foremost, by limiting exposure. Reduce time with social media and uncivil news programming, and if you get sucked in, decompress lest you spread hostility around.

That’s the real answer. We must refuse to engage. Civility itself is an antidote to incivility. And this, a societal wellness program, can save time and money, improve cognitive functioning, and spur creativity and innovation.

Being nicer could make America great again.

Ashley Merryman is co-author with Po Bronson of two New York Times bestsellers, “NurtureShock: New Thinking About Children and “Top Dog: The Science of Winning and Losing.”