Before someone accuses me of saying that all Republicans are intellectually substandard, I do not think that is true at all. Nevertheless, we have an ongoing stream of psychological studies that link decreased mental capacity with Republican practices and policies. Personally, I think that the leadership, the Republican politicians and pundits, are quite bright, with a few obvious exceptions. The problem is that they are devious enough to take advantage of their base by promulgating policies, designed to pander to their mental dysfunction.

Self-deprecating, too liberal for their own good, today’s progressives stand back and watch, hands over their mouths, as the social vivisectionists of the right slice up a living society to see if its component parts can survive in isolation. Tied up in knots of reticence and self-doubt, they will not shout stop. Doing so requires an act of interruption, of presumption, for which they no longer possess a vocabulary.

Perhaps it is in the same spirit of liberal constipation that, with the exception of Charlie Brooker, we have been too polite to mention the Canadian study published last month in the journal Psychological Science, which revealed that people with conservative beliefs are likely to be of low intelligence. Paradoxically it was the Daily Mail that brought it to the attention of British readers last week. It feels crude, illiberal to point out that the other side is, on average, more stupid than our own. But this, the study suggests, is not unfounded generalisation but empirical fact.

It is by no means the first such paper. There is plenty of research showing that low general intelligence in childhood predicts greater prejudice towards people of different ethnicity or sexuality in adulthood. Open-mindedness, flexibility, trust in other people: all these require certain cognitive abilities. Understanding and accepting others – particularly "different" others – requires an enhanced capacity for abstract thinking.

But, drawing on a sample size of several thousand, correcting for both education and socioeconomic status, the new study looks embarrassingly robust. Importantly, it shows that prejudice tends not to arise directly from low intelligence but from the conservative ideologies to which people of low intelligence are drawn. Conservative ideology is the "critical pathway" from low intelligence to racism. Those with low cognitive abilities are attracted to "rightwing ideologies that promote coherence and order" and "emphasise the maintenance of the status quo". Even for someone not yet renowned for liberal reticence, this feels hard to write.

This is not to suggest that all conservatives are stupid. There are some very clever people in government, advising politicians, running thinktanks and writing for newspapers, who have acquired power and influence by promoting rightwing ideologies.

But what we now see among their parties – however intelligent their guiding spirits may be – is the abandonment of any pretence of high-minded conservatism. On both sides of the Atlantic, conservative strategists have discovered that there is no pool so shallow that several million people won’t drown in it. Whether they are promoting the idea that Barack Obama was not born in the US, that man-made climate change is an eco-fascist-communist-anarchist conspiracy, or that the deficit results from the greed of the poor, they now appeal to the basest, stupidest impulses, and find that it does them no harm in the polls… [emphasis added]