On the 3rd floor of a London terraced house, I have a double bed with a very ancient mattress that I have been thinking of replacing for years. What stops me? The obvious problem, as Rory Sutherland noted in his recent British Brands Group Lecture is how do I get rid of the old one? A New York company apparently has captured virtually the entire market by promising to dispose of the purchaser's previous mattress.

The last 10 years or so have brought a flood of books that in one way or another focus on how people behave. In fact, we have probably learned more in the last decade than in the previous 50 years. And while what people say can be apparently interesting, it is rarely a guide to what they will do. My early life was spent trawling the murky depths of motivation, assuming rather lazily, that the link between motivation and actual behaviour was a more or less direct one. With the mattress problem the focus would have been on the insomnia index of the sleeper along with particular benefits of one mattress over others - the springs, the duck down component, the back support etc. All no doubt important but fails to grasp the real barrier which is much more mundane.

The concept of the 'customer journey' is probably underused. Shining a spotlight on just exactly what is going on in the purchase process gets you to not only the problem but often more interestingly, to the opportunities. As Asian food has become more and more popular, supermarkets have recognized that the average English kitchen rarely has a fresh supply of lemon grass, coriander, ginger, galangal, red pepper, etc and so have grouped them handily together in packets. Waitrose now nestles samphire and herb butter next to raw fish in the fish counter should you be seized with the urge for something fancy. Another of Rory's examples was the 'cocktail pod'. Just as English kitchens don't carry a load of fresh Asian herbs, neither do they carry the whole kit for cocktails. So Sainsbury together with Diageo have produced a place in the booze section which groups the tonic, the lime and the gin together. The possibilities here are endless.

Tim Ambler always felt marketers didn't get out enough: too much time in meetings and presentations. But nothing beats accompanying an ethnologist on a shopping expedition or applying, as Rory suggests, the many and useful principles of Behavioural Economics and other perceptual tools: framing, loss aversion, dummy choices, etc.

And finally, as yet another caution about believing what people say, never underestimate the self-deluding power of prejudice. Many years ago a man in a focus group explained with an apparent belief in the rationality of his reason for not drinking Guinness: "I never tried it because I don't like it".