"It is difficult to get a man to understand something, when his job depends upon not understanding it." The spectacle of rightist and centrist journalists trying to absolve the MSM of blame for the rise of Islamophobia reminds me of Upton Sinclair's famous quip.

They, of course, are by no means the only people at whom one might direct this accusation. Many of you us might also point it at: fund managers who deny the efficient market hypothesis; mainstream economists who reject some heterodox approaches; managerialists who stick to using crude targets; or centrist MPs who fail to see the need for new economic policies. And so on.

But I wonder: what exactly is the mechanism that Sinclair and those who quote him have in mind?

I doubt that many of us deliberately and consciously adapt our beliefs to our interests. We don't think "X is false but it serves my interests so I shall believe X". For example, a Tory government is probably more in my financial interest than a Labour one, but I struggle to find sympathy for the Tory party.

I suspect instead that other mechanisms are at work.

One is wishful thinking. This is not a deliberate process. Instead, as Jon Elster has said, it operates behind our backs, subconsciously. An experiment by Guy Mayraz has shown just how easy it is to induce this. He asked subjects to predict future moves in the price of wheat. Before doing so, he randomly divided them into two groups: "farmers" who would profit from a rising price, and "bakers" who would profit from a falling one. He found that farmers predicted higher prices than bakers. And they continued to do so even when they were given incentives for accurate predictions.

We all want to believe we are the good guys, and the wish is father to the belief; nobody really wants to believe they have contributed to mass murder. The joke in David Mitchell's famous question "are we the baddies?" is that he and his comrades had not asked that before.

A second mechanism is that we can distort our evidence-gathering. Jon Elster describes this:

Initially, let us assume, the evidence does not support the belief that I would like to be true. I then proceed to collect more evidence, adjusting and updating my beliefs as I go along. If at some point the sum total of the evidence collected so far supports my preferred belief, I stop. I can then truly tell myself and others that my belief is supported by the available evidence (Nuts and Bolts for the Social Sciences, p 37-38)

This is one reason why many clever people can (perhaps) be just as biased as stupider ones: they have more ways of gathering evidence and rationalizing it.

A third mechanism is professional deformation. This is the tendency for our training - into all professions, including economics - to inculcate not only techniques and knowledge but also biases, groupthink and blind spots.

Take, for example, Andrew Norfolk's reporting of the Rotherham child sex abuse scandal. Here, there was a trade-off, between a strong and important story on the one hand against the danger of stoking up Islamophobia on the other: Mr Norfolk saw at the time that his story was "a dream for the far-right" and the Christchurch murderer wrote "For Rotherham" on his ammunition. Journalists' professional upbringing is to favour publishing the story. And rightly so: it was true, and only a warped mind would see it as a reason to hate Muslims.

If that case is clear cut, though, what about Newsnight inviting Generation Identity onto their programme. Does the desire for "good debate" overcome the risk of publicizing fascism? And what about countless comment columns disparaging Muslims? Does the truth-value of these really outweigh the danger of encouraging the far-right.

In all these cases, journalists' professional presumption is to "publish and be damned." This is often a laudable instinct. But it is only a partial perspective, one which a journalist's training perhaps exaggerates*: journalists are often selected for and socialized into a strong belief in free speech. That biases them against seeing that such speech has a cost - and they are especially slow to see this if they don't want to.

My point here should be a trivial one, but I fear is overlooked in our histrionic environment. We are all prone to countless biases: yes, all, not least me. Sinclair's remark should be seen not as a description of a conspiracy, but of how these biases can operate together.

* The cost of trashy right-wing columns isn't just (or even perhaps mainly) the stoking of Islamophobia. It's the denial of space for discussion of other issues: if we're debating fascism we are not debating other things.