If, like me, you've recently purchased a mattress, you'll know it's an astoundingly tedious and soul-depleting process – rendered only slightly less awful by the fact that when you do finally collapse, exhausted by indecision, in the middle of the beds department, there are plenty of places to lie down. Long ago, maybe mattress-shopping was a simple choice between "firm" and "soft", but these days it's a thicket of dilemmas. Memory foam, wool, gel, fibre? Solid-slatted or sprung-slatted? Lumbar zoning? Perhaps a pillow-top? This complexity at first seems hard to explain. Sure, it's nice to have options, but why deliberately aggravate customers, delaying the moment of purchase with so many extra decisions? Aren't mattress-makers aware of one of the best-known truths of consumer psychology: that too much choice makes people miserable?

Recently, as part of a personal experiment in the psychology of money, I spent almost a month trying to make every purchase I could in hard cash. So before I go further, I should apologise if you were one of the people who found themselves stuck behind me in supermarket queues while I fished through my rucksack for the little beige envelopes in which I'd stashed that week's notes and coins. (More on these shortly.) Some time ago, in the US, Visa ran a series of ads based on the premise that people who don't pay with plastic infuriate other customers; the slogan was, "because money shouldn't slow you down". I can report that this fury is real. Even checkout staff didn't seem grateful to receive the exact change, counted out in scores of tiny coins, even though this procedure almost always took me less than 15 minutes.