My favourite candidate in the American election of 2004 was Bob Graham, a Democratic senator from Florida whose policies were never very clear, but who had the endearing habit of logging every minute of his life in a series of colour-coded notebooks. "7-7.40am: kitchen, brew coffee, prepare and drink breakfast (soy, skim milk, OJ, peach, banana, blueberries)," read a typical entry. And another: "1.30-1.45pm rewind Ace Ventura." But this mild quirk counted against him - psychological quirks, or mild ones at least, apparently being a barrier to the presidency - and he soon dropped out of the race. This was a pity, since for anal retentives everywhere, Graham easily passed the legendary "barbecue test" of US politics: would you invite this candidate round for a burger? ("7-7.45pm: Attended barbecue.")

Graham's approach was overkill, to be sure. But logging certain aspects of your life can be a surprisingly powerful practice - not because there's much value in the record you create, but because the very act of recording exerts an interesting psychological effect. Spend a couple of days recording your time use in detail, several productivity experts advise, and you're likely to find yourself using it more efficiently. Record what you eat, and you'll find yourself eating more healthily, even without taking any other actions. (I tried both recently, for three days each. The time log alarmed me, by revealing how much time I'm capable of frittering away, but it helped, and the effects lasted beyond the three-day period. The food log turned me effortlessly into a health nut, but the effect was more short-lived.)

This is an individualised version of the Hawthorne effect, observed in the 1920s and 1930s at a Chicago factory. Experimenters from Harvard tried to boost employee productivity by adding rest breaks of different durations, and by changing the lighting, temperature and other factors. Many of the changes improved output - but so did changing things back. The mere fact of being observed, the study concluded, was what made people behave differently. Copious doubts have since been raised about the study, and besides, it's easy to see how it could be used as an excuse for keeping workers under close surveillance. But as a personal technique, it seems to work, helping us make unconscious behaviour conscious.

The idea of making the unconscious conscious chimes with the Buddhist concept of "mindfulness" - what the author and meditation teacher Sylvia Boorstein calls "the practice of paying attention in every moment of one's day". When I first encountered this notion, it was deeply unappealing: wouldn't it just mean becoming hyper-conscious of your every move, unable to relax because you were engaged in obsessive self-monitoring? The answer, I think, is that it could, if you did it in a judgmental way, relentlessly trying to analyse whether or not each action was the "right" one. But the lesson of the "personal Hawthorne effect" is that you don't need to make any such judgments. Merely observing your behaviour seems to make for better behaviour: just paying attention is enough.

oliver.burkeman@theguardian.com