Scientific meetings are not usually confrontational events, so it was notable when University of Virginia psychological scientist Jonathan Haidt roiled his colleagues at the 2011 gathering of the Society for Personality and Social Psychology. Addressing an audience of more than a thousand, the best-selling author of The Righteous Mind asked all of those who considered themselves politically conservative to raise their hands. Three hands went up. He then described two other attempts he had recently made to locate conservative social psychologists. He had searched the Internet for “conservative social psychologist,” and he had asked a small sample of social psychologists to name just one ideologically conservative colleague. These efforts together had turned up a single conservative social psychologist.

These small, informal efforts have big implications. They point to a “statistically impossible lack of diversity” in the field, Haidt has since argued, a worrisome situation that almost certainly fosters discrimination against both colleagues and students and, what’s more, may be skewing the entire research enterprise. Haidt is advocating remedies to reach a quota of 10 percent conservatives in social psychology by 2020.

Haidt’s message hit home with many of his colleagues, among them Yoel Inbar and Joris Lammers of Tilburg University, who describe the 2011 event in a new paper, to be published soon in Perspectives on Psychological Science. Inbar and Lammers decided to add some rigor to Haidt’s provocative but anecdotal findings, which they did in two anonymous, on-line surveys of personality and social psychologists. They wanted, first, to verify the widespread impression of a pervasive liberal bias in the field, but they wanted to drill down even further, asking: Are there really no conservative social psychologists, or are they just well hidden? Are some liberal on social issues, but perhaps more moderate—or even conservative—on economic questions, or foreign policy issues? And if they are deliberately hiding their politics and values, why?

Inbar and Lammers drew their sample from the membership of the Society for Personality and Social psychology, the same scientific group that Haidt addressed in 2011. They contacted all members on the mailing list, and got nearly 800 responses.

The findings clearly confirm the field’s liberal bias, but they hold some surprises as well. For example, although only 6 percent described themselves as conservative “overall,” there was much more diversity than anecdotal evidence suggests. Inbar and Lammers found an overwhelming liberal majority when it comes to social issues, but only when it comes to social issues. On economic issues, nearly one in five is a self-described moderate, and slightly fewer put themselves to the right of moderate. Similarly, on foreign policy questions, nearly a third of respondents called themselves either moderate or conservative. In short, there is much more ideological diversity among these scientists than generally thought.

So why are only three out of a thousand raising their hands when asked? Apparently, it’s because conservative social psychologists perceive the field as hostile to their values. And it’s not just perception. The more conservative respondents were, the more they had personally experienced an intellectually unfriendly climate. Importantly, self-defined liberals do not see this—or believe it. The hostility is invisible to those who don’t run into it themselves.

It gets worse. Inbar and Lammers also asked respondents to assess their willingness to discriminate against conservatives. Would they be more likely to reject a paper or a grant application that showed a politically conservative perspective? Would they be reluctant to invite a conservative colleague to a symposium? Would they favor a liberal job candidate over a conservative candidate? The disturbing answer to all these questions was yes, and the more liberal the respondents, the more likely they were to discriminate against conservatives in all these areas. So it appears that the well-hidden minority of conservatives have good reason to stay hidden.

The irony of these findings is not lost on Inbar and Lammers, nor on the several colleagues who have written commentaries to accompany the Perspectives article. If social tolerance and fairness are liberal values, most social psychologists would plead guilty to that bias—so it’s embarrassing to uncover intolerance of a different kind in one’s own back yard. What’s more, psychological scientists are supposedly the experts on cognitive biases, including harmful ones, yet here they are displaying just such skewed judgments and decisions. Several of the commentaries raise serious questions about how ideology might be shaping the issues and questions that social psychologists choose for exploration—and the ones they are blind to, or deliberately reject as uninteresting or taboo.

Why is social psychology so politically skewed, and what’s to be done about it. It may be true—as some of the commentaries state—that the field attracts a certain kind of inquiring and open mind that tends to embrace liberal values, and that conservative self-select out of the field. But this, most commentators agree, does not change the fact that pervasive liberal bias is unhealthy for the field—and for intellectual inquiry generally.

Perhaps even more alarming is what Richard Redding, of Chapman University’s School of Law, labels “prejudice and discrimination, straight up.” That is, the deliberate discrimination against conservative thinkers is not subtle, unconscious or inconsequential—but rather real and harmful and in need of remedy. That remedy may be the kind of affirmative action that Haidt and others are now endorsing, or it may be something more measured. In any case, the Perspectives article and commentaries suggest that the time may be right for some self-examination in the field.

Wray Herbert’s book, On Second Thought, is about cognitive biases and decision making. Excerpts from his two blogs—“We’re Only Human” and “Full Frontal Psychology”—appear regularly in Scientific American Mind and The Huffington Post.