It's a fairly well-established fact, in political psychology, that leftwingers report lower levels of happiness than rightwingers. (This fact, you may have noticed, is self-reinforcing: learning of it makes leftwingers even gloomier.) What's much less clear is why. Conservatives like to argue that it's because the things they value – traditional families, faith, free markets – make people happiest. Liberals prefer to think conservatives are blinkered, clinging to an ideology that lets them avoid confronting life's grim truths; it's even been proposed that conservatism might be a mental illness. And there's an added complication: the social psychologists who study such questions, as the American academic Jonathan Haidt has complained, tend to lean left. But does that mean they are biased – or that, when you closely study the real world, you usually end up liberal? ("Reality has a well-known liberal bias" – Stephen Colbert.) It's all very murky – though if you're a liberal, like me, that's less of a problem, as studies suggest we might have more capacity for tolerating uncertainty. So there's that.

Earlier this year, two American bloggers triggered a global media convulsion by embarking on what they called a "mirror fast": covering the mirrors in their homes, and shunning mirrors elsewhere, in an effort to reduce what one of them called "the overriding self-consciousness that's taken up residence in my psyche". Since the social pressure to conform to ideals of beauty falls mainly on women, I can only guess what it's like to be so aware of one's appearance: I assume it's related to what I feel whenever a badly-angled photo reminds me how astoundingly bald I am. But for the fasters, the experiment proved a liberation. "All the other interests in my life – my goals, passions, friends, family, favourite hobbies, etc – have attracted the energy and attention I used to give to my looks," wrote Kjerstin Gruys, while Autumn Whitefield-Madrano said she felt "calmer and more serene". They'd pulled off an ingenious psychological trick. In a world obsessed with appearances, it's impractical just to decide you're going to think differently. What they'd done, instead, was to deny themselves the feedback that fuelled the fixation.