Representative Anthony Weiner, the once cheered, now shamed New York congressman, made at least two mistakes in the past two weeks. First, he lied—and then he cried.

"I have exchanged messages and photos of an explicit nature with about six women over the last three years," he admitted, after denying three days earlier that he publicly posted an R-rated photograph of himself via Twitter. He punctuated his June 6 confession with frequent sniffling. Cameras caught him wiping away a tear at least once, and the New York Times referred to him as "weeping and stammering."

Tears can take on different meanings depending on who leaks them and when. Here is why Weiner's waters went awry.

"Crying evolved as a signal to others that we're vulnerable and in need, but we have to consider whether or not the situation is one where it is appropriate to show one's vulnerability," says Randolph R. Cornelius, a professor of psychology at Vassar College who has studied crying for decades. "There are lots of situations where we don't want to do that."

Weiner might have hoped that his crying—however genuine it may have been—would elicit sympathy, but research and history have shown that people do not universally respond kindly to tears. A seminal 1982 study on self-presentation suggested that whereas people tend to reveal their own weakness as a cry for help, an emotional display can easily backfire.

Most research shows that a typical response to crying is to offer emotional support, but that does not mean that our reaction to tears is uniformly positive.

A 2006 study in Cognition & Emotion found that although people feel connected to and supportive of a crying person, the crier's presence also makes them uncomfortable and tense. In a follow-up study in the Journal of Social Psychology in 2008, the inclination to offer support held true, but participants judged a crying person more negatively than a noncrying person, felt more negative emotions in their presence and associated more negative characteristics with a crier than a noncrier.

Ad Vingerhoets, a psychologist at Tilburg University in the Netherlands and co-author of the two recent studies, has been investigating human crying for 23 years. We evaluate tears contextually, Vingerhoets says, asking questions like, "Do we know the person as honest and reliable? Is the person maybe emotionally unstable or not fit for a certain job?"

Given the fraught context of Weiner's confession, the odds may be stacked against him.

A little crying might have fared better if Weiner had confessed earlier on, when the tweeted picture first surfaced. "Tears then may have been a bit more accepted as a sign of contrition," says Valerie Manusov, a professor of communication at the University of Washington who studied now Secretary of State Hillary Clinton's 2008 crying incident on the presidential campaign trail. "Now they are more likely seen as a manipulation."

Even if Weiner's misty eyes were sincere, crying out of grief is not the same as crying out of guilt and shame. "People are okay with tears about something important that is out of the individual's control," says Stephanie A. Shields, a professor at Pennsylvania State University and  author of Speaking from the Heart: Gender and the Social Meaning of Emotion (Cambridge University Press, 2010). "Since Weiner is perceived as having brought the problem on himself and lying about it, people will likely view the tears negatively."

Despite all the strikes against Weiner's tears, he still has at least one thing going for him: he is a man.

"There is research suggesting that, in particular for men, moist eyes is a powerful signal," Vingerhoets says. "It is interpreted as: this is a sensitive man, but in control."

Women's tears, by contrast, are generally seen as a sign of weakness or emotional instability. In a 2009 paper about crying on the campaign trail, Erika Falk of Johns Hopkins University wrote that whereas both Mitt Romney and Clinton welled up while campaigning, the Romney incident generated only 14 mentions in the press. The Clinton incident generated 500 articles and became a defining moment in her campaign.

"If Weiner were a woman, the tears would have been seen very differently," Cornelius says, of Vassar. "Women who cry tend to be denigrated, whereas men who cry are not."

This imbalance, which Shields calls the "Mr. Sensitive advantage," has not always existed.

In a famous incident during the 1972 presidential primaries, Democratic front-runner Edmund Muskie called an outdoor press conference in the middle of snowstorm to defend his wife against demeaning allegations. Muskie maintained that the water on his face that day was melted snow, but it was too late. Newspapers across the country reported that he wept, his popularity tanked, and a new slogan on bumper stickers sealed his fate: "Vote for Muskie or He'll Cry."

"When Muskie cried—or else just appeared to tear up—he was uniformly perceived as weak," says Manusov. "Now, men seem to be allowed to cry. Bill Clinton, George W. Bush, and Joe Biden all do or did regularly."

But not all male crying is the same.

"John Boehner cries at the drop of a hat, but ostensibly about his own humble beginnings or patriotic things, so his weeping is seen by some as an expression of deeply felt values and therefore okay," Shields says.

And then there are occasions when tears are effectively expected. "People said if Bush didn't tear up when giving his post-9/11 speech, he would have been seen to care too little," Manusov says. "But when tears seem to serve one's own self-interest, as in Weiner's case, they are usually seen as occurring only because the person regrets having been caught."

When tears do not elicit sympathy, Shields says, reactions can instead include "contempt, anger, pity, or hilarity." Reactions toward Weiner's tearful confession will probably lean toward this latter category.

"It's going to be very difficult for him because of the nature of what he did," Cornelius says. "I'm not sure people are going to feel sorry for him."