That's the question at the heart of an interesting New Yorker article that focuses on the work of New York University social and moral psychologist Jonathan Haidt. The article opens with the now notorious occasion in which Haidt asked for a show of hands indicating political ideology during his presentation at the annual convention of the Society for Personality and Social Psychology. The New Yorker reports:
First came the liberals: a "sea of hands," comprising about eighty per cent of the room, Haidt later recalled. Next, the centrists or moderates. Twenty hands. Next, the libertarians. Twelve hands. And last, the conservatives. Three hands.
Social psychology, Haidt went on, had an obvious problem: a lack of political diversity that was every bit as dangerous as a lack of, say, racial or religious or gender diversity. It discouraged conservative students from joining the field, and it discouraged conservative members from pursuing certain lines of argument. It also introduced bias into research questions, methodology, and, ultimately, publications. The topics that social psychologists chose to study and how they chose to study them, he argued, suffered from homogeneity. The effect was limited, Haidt was quick to point out, to areas that concerned political ideology and politicized notions, like race, gender, stereotyping, and power and inequality. "It's not like the whole field is undercut, but when it comes to research on controversial topics, the effect is most pronounced," he later told me.
Haidt and his colleagues more formally lay out their concerns in a forthcoming article in Behavorial and Brain Sciences. From the abstract:
Psychologists have demonstrated the value of diversity—particularly diversity of viewpoints—for enhancing creativity, discovery, and problem solving. But one key type of viewpoint diversity is lacking in academic psychology in general and social psychology in particular: political diversity. This article reviews the available evidence and finds support for four claims: 1) Academic psychology once had considerable political diversity, but has lost nearly all of it in the last 50 years; 2) This lack of political diversity can undermine the validity of social psychological science via mechanisms such as the embedding of liberal values into research questions and methods, steering researchers away from important but politically unpalatable research topics, and producing conclusions that mischaracterize liberals and conservatives alike; 3) Increased political diversity would improve social psychological science by reducing the impact of bias mechanisms such as confirmation bias, and by empowering dissenting minorities to improve the quality of the majority's thinking; and 4) The underrepresentation of non-liberals in social psychology is most likely due to a combination of self-selection, hostile climate, and discrimination.
Of course, in their self-estimation liberals cannot be close-minded and discriminatory. The New Yorker notes that Harvard University psychologist Daniel Glibert explained:
"Liberals may be more interested in new ideas, more willing to work for peanuts, or just more intelligent."
Well, maybe. But some Dutch psychologists reporting the results of their survey of academic psychologists offered another reason: Overt professional discrimination against conservatives. From their study:
Hostility toward and willingness to discriminate against conservatives is widespread. One in six respondents said that she or he would be somewhat (or more) inclined to discriminate against conservatives in inviting them for symposia or reviewing their work. One in four would discriminate in reviewing their grant applications. More than one in three would discriminate against them when making hiring decisions. Thus, willingness to discriminate is not limited to small decisions. In fact, it is strongest when it comes to the most important decisions, such as grant applications and hiring.
The whole The New Yorker article is worth your attention.
For more background, see Haidt's Reason May 2012 cover article, "Born This Way?: Nature, nurture, narratives, and the making of our political personalities," and my article reporting on his research into the libertarian moral personality, "The Science of Libertarian Morality."