If there's no spectrum of colours, is the result white noise?

The study of prejudice and discrimination has been one of the cornerstones of social psychology since the 1950s. But new research suggests that as well as studying discrimination, social psychologists may engage in it themselves. In a paper in the journal Perspectives on Psychological Science, Yoel Inbar and Joris Lammers from Tilburg University find a striking - and perhaps concerning - relationship between the political ideology of social psychologists (who are typically liberal or left wing) and a willingness to discriminate against their politically conservative (right-wing) colleagues.

In two surveys of members of the Society for Personality and Social Psychology - in the US, Canada and Europe - respondents who identified as strongly liberal were more likely to say they would vote against an openly conservative job candidate, or rate papers and grant proposals more negatively if they seemed to be promoting a conservative agenda.

So is social psychology a self-serving cabal of discriminatory lefties producing research that reinforces their own beliefs? Or is there something more subtle, more complicated, but no less comment-worthy going on?

The researchers' confirmation that people with conservative ideologies are uncommon in social psychology common rooms will surprise no one. Seeking to explain (or, from a conservative perspective, excuse) behaviour is a trait more commonly associated with the Left. Ask a group of social scientists to explain the rioting on the streets of Britain in 2011, and they will point to problems in the rioters' childhoods, or social and economic inequality, locked in over generations - not the "criminality, pure and simple" seen by Prime Minister David Cameron.

The very act of enquiring into the underlying reasons for particular attitudes and behaviours seems to slot much more neatly into a left-wing than a conservative ideology. To be clear, this does not excuse discrimination. But it might help to explain why social psychology is so heavily weighted towards those who self-identify as liberal, and even why research promoting a conservative agenda would be viewed less positively. If the goal of the discipline is to explain (rather than control or punish) socially embedded attitudes and behaviour, conservatively tinged research may not appeal to social psychologists.

Of course, it is not psychology but sociology that has historically had the closest associations with the politics of the Left. From Marxist theorists studying class politics, to trades union experts going into the field with their comrades, sociologists have tended to be much bolder in wearing their political affiliations on their sleeves. But if the politics of sociology is more open, it is also, in many ways, less problematic. A healthy dose of "reflexivity" (including consideration of the personal biases that researchers may bring to their work) is as much a part of the methodology of sociology as a literature review. Social psychologists, however - who have embraced empiricism so strongly - use "objective" methods and so are expected to be free from such biases. Perhaps, rather than wish for a "less biased" group of researchers, we should be more open to the idea that social psychology is not as "value free" as many of its practitioners assume.

It has long been known that even beyond the social sciences (where the ratio of liberal to conservative academics is the sharpest), academia is a less popular career choice for those on the Right. Even in economics, where groups such as the Chicago School have become infamous for their politically influential theories of free-market neoliberalism, research suggests that US scholars are three times more likely to be of the Left than the Right. In an article published recently in the journal PS: Political Science and Politics, Robert Maranto and Matthew Woessner (specialists in public policy and educational reform) even suggest that "conservatives should bypass impenetrable islands of leftism (eg, sociology, social work, women's studies, and ethnic studies) that may be impervious to outside perspectives. The natural sciences are certainly an inviting territory because their major controversies are less likely to involve the most ideologically divisive issues."

But the social sciences are never going to become more diverse if conservatives simply keep away. In fact, Inbar and Lammers' survey of psychologists found that people tended to overestimate the extent to which their colleagues were liberal, producing an even more polarised mental picture of the state of their discipline, and perhaps even a reason to play down any conservative leanings of their own.

Compared with any group of academics, social psychologists understand the importance of motivated reasoning - the process through which our ideological beliefs filter the facts in front of us. If researchers are to avoid falling victim to this trap themselves, a bit more political diversity is surely required.

Otherwise, when we pronounce on other people's beliefs, biases and prejudices, why should they take any notice?