For gays and their allies—who now make up a majority of Americans — the past year has been a time of heartening election results and Supreme Court victories. But for the substantial minority of Americans who continue to oppose gay marriage, a siege mentality has taken hold. Some go so far as to argue that if gays were ever the victims of prejudice, the tables have now turned.

That's the rationale behind a wave of new state bills. Last week Charles Macheers, a Republican state representative from Kansas, had these words to say in support of a bill he described as a “shield” against discrimination: “Discrimination is horrible. It's hurtful … It has no place in civilized society, and that's precisely why we're moving this bill.” That bill died in the Senate, and similar bills in Idaho, South Dakota, and Tennessee have also stalled. But on Wednesday, the Arizona Senate passed a bill allowing “any individual, association, partnership, corporation, church, religious assembly or institution or other business organization” to refuse to serve people if they feel it violates their “free exercise of religion.” The bill's sponsor, Republican Senator Steve Yarbrough, argued during a two-hour debate on the Senate floor that “this bill is not about allowing discrimination” but “about preventing discrimination against people who are clearly living out their faith.”

Ever since it became déclassé to be anti-gay—it's hard to put a date on it, but some time around the start of this century—those who oppose equal treatment for gay people have made similar efforts to avoid appearing homophobic. They've insisted that they're driven not by a prejudiced view of gay individuals, but by a larger concern about the negative impact gay equality could have on society. In Virginia, for example, the state banned gay marriage by arguing that allowing same-sex marriage would trigger “unforeseen legal and social consequences” and inflict “serious and harmful consequences to the social order.” (That ban was struck down last week.) It's the same claim that opponents of openly gay military service made in support of “don't ask, don't tell”: The policy wasn't about prejudice, but about concerns that gay troops would harm unit cohesion and the security of the nation. (Don't Ask Don't Tell ended without a hiccup in 2011.)

Meanwhile, opponents of gay marriage often cite (discredited) claims that same-sex parenthood harms children. Just this week, Mitt Romney struggled to explain why children of same-sex couples in Massachusetts, the state he governed, seem to be thriving. Ultimately, Romney said it would take “generations” for his doomsday predictions to come true.

A similar line of reasoning could be found after Missouri defensive lineman Michael Sam announced he was gay. The NFL hopeful earned a standing ovation at a Missouri basketball game, yet set off a tense debate among older NFL executives and coaches. In anonymous statements to the press, they predicted a chaotic reaction by others while disavowing prejudice themselves.

It's a reflection of great progress by LGBT groups that hardly anyone wants to be associated with the term “homophobic.” In fact, last year, the Associated Press revised its stylebook to discontinue use of that word, which connotes a visceral fear of homosexuality rather than rational disapproval of its effects on society. The AP's Deputy Standards Editor Dave Minthorn told Politico that the word “seems inaccurate. Instead, we would use something more neutral: anti-gay, or some such.” Even gay writers like Brandon Ambrosino—who recently published an Atlantic piece titled "Being Against Gay Marriage Doesn't Make You a Homophobe"—have argued that opposing equal rights does not belie inherent fear of homosexuality. 

The term “homophobia” was coined in the 1970s by George Weinberg, a clinical psychologist who noticed his colleagues' irrational and visceral feelings toward many gay people. “I realized this thing is deeply emotional and is based on fear,” he once told me, and went on to define “homophobia” as dread or fear around gay people. In order to be defined as homophobic, you don't have to want to bash a gay person's head in; it's enough to simply have some level of emotional discomfort around homosexuality.

It's a term that's still too useful to abandon. Social psychologists have mounds of research on the role that emotions like fear and repugnance play in distorting our assessments of reality—that is, in creating bias. For starters, they've found that conscious reasoning is a much newer human capacity—evolutionarily—than gut feeling, and that the brain often deploys reasoned thought to rationalize feelings we already have. Rather than justifying a position—like, say, opposing gay marriage—based on how we actually feel, we often dream up non-existent dangers. Indeed, scientists have shown that our brains developed fight-or-flight mechanisms to help us avoid danger before our rational, deliberative machinery even perceives the threat.

Interestingly, researchers at Cornell and Yale (including Atlantic contributor Paul Bloom) have also shown that conservatives, on average, experience stronger levels of disgust than liberals do, and that an overall sensitivity to disgust correlates with anti-gay sentiment. “Our data show that disgust and politics are linked most strongly for issues of purity, such as towards homosexuality,” the authors explain.

Even more strikingly, researchers have found that people with negative views of gay people are prone to overstate the risks that gay rights pose. In one study, psychologists at Berkeley and Carnegie Mellon University measured subjects' emotional dispositions and their risk preferences, giving them separate scores for each. When the two sets of variables were correlated, they found that “fearful people expressed pessimistic risk estimates and risk-averse choices.”

It's no surprise that fearful people would be risk-averse. But this research showed not just that such people avoid risk but that they exaggerate it—in consistent and predictable ways. Researchers concluded that certain emotions, such as fear, activate “a predisposition to appraise future events in line with” whatever the person dreaded to begin with. In other words, fear makes people lose perspective on what the odds of danger really are. These visceral feelings often bypass consciousness, so we're not even aware of what we're feeling.

The psychologist Jonathan Haidt describes the amusing rationalizations his research subjects often came up with to justify moralistic positions. For instance, Haidt asked subjects if it was morally wrong to shred a flag while in your home and flush the pieces down the toilet. Those who said it was wrong couldn't readily explain why. When pressed, one said the flag could clog the toilet.

To take a more common example, people generally disapprove of consensual sex between adult siblings but they can't say why it's wrong. Psychologists refer to such feelings as “moral intuitions”—unconscious judgments that stem from emotional responses or learned associations, and are often related to disgust. Haidt says people consult their feelings to help them decide what to believe. This sounds fair enough at first blush, but we're not just talking about values here. Moral intuitions change the way people see the world around them. When your perceptions of reality are refracted through strong feelings, that's a recipe for bias. It explains the “harms” arguments about gay rights, and why they persist even though there's no factual information to back them up.

Technology now allows scientists to actually look inside the brain to see how bias works. During the 2004 U.S. presidential campaign, researchers put subjects in MRI scanners and fed them quotes from their preferred candidates. When subjects heard quotes that contradicted their candidate's position, they gave often-exaggerated explanations for the contradictions. When researchers looked at which regions of the brain were activated by this rationalization process, they found that it had taken place in the zones that govern emotion, not deliberative reasoning.

Several scholars have applied this research specifically to gay rights. Using a process called Implicit Association Tests, Yale's Paul Bloom and his colleagues documented a gap between how people say they feel about gays and how they actually feel. Researchers at the Yale Cultural Cognition Project dug deeper, exploring the role of rationalizations against same-sex parenting. Most opponents of gay parenting claimed their position was based on concern for the well-being of children raised by gay couples. But when given convincing evidence that kids with gay parents fare as well as others, very few changed their minds. Their brains sought to avoid the cognitive dissonance of holding beliefs that conflicted with their emotions.

This research doesn't prove, indisputably, that all opponents of gay rights are actually harboring feelings of disgust toward gay people—human feelings are more complicated than that. But it strongly suggests it, especially when you consider the undeniable pattern of predicting harms that never happen as a justification for blocking equality.

In one of the few areas of life that allows for true, rational deliberation—the courtroom—this is exactly what's being found. Recent rulings striking down gay marriage bans have found that those laws were rooted in prejudice, making them impermissible under the U.S. Constitution. The Supreme Court reached the same conclusion last June when it struck down the federal Defense of Marriage Act. The law, said the Court, was “motivated by an improper animus” and its purpose was to impose “a disadvantage, a separate status, and so a stigma upon all who enter into same-sex marriages.”

For those who don't feel disgusted by homosexuality, it's not hard to see that often-cited fears—that it will trample religious freedom, cause distractions in the lockerroom, harm kids and families—have no empirical basis. But those who believe these things may not realize these arguments are smokescreens for irrational bias. “Prejudice,” wrote Justice Anthony Kennedy in a 2001 ruling, “rises not from malice or hostile animus alone. It may result as well from insensitivity caused by simple want of careful, rational reflection or from some instinctive mechanism to guard against people who appear to be different in some respects from ourselves.”

This profound insight echoes the research in reminding us how universal bias is. All humans suffer from it in one form or another, and recognizing this can help shed light on those who use it as a basis for anti-gay lawmaking. But understanding these rationalizations—both the predictions of harm, and the insistence that prejudice is not a factor—is different from accepting them at face value. In fact, as states like Arizona struggle to find logical explanations for anti-gay laws, it's clearer than ever that bias, and not reason, is the motivating force behind them.