Going against the trend, the new Volvo S80 has reverted to genuinely soft seats
MAYBE JUST sitting on our butt does prevent us from thinking straight. How else can we explain that the single bit of a car we're closest to - the seat - is the very item on which car makers typically spend the least time?

A simple block of foam sculpted to look attractive and offer tolerable support, the seat is about the most low-tech (and one of the cheapest) components on a modern car. This is probably why many orthopaedic specialists say that the typical car seat offers an inadequate underpinning, especially on long runs.

Some car makers spend a bit more time on them, most notably Mercedes- Benz. Its seats usually have springs and fibres (they used to have horse hair). And its latest seat, to be found in the new and excellent S-class, must be about the most high-tech contraption on which mankind has ever rested its backside. Push a switch and the seat starts imperceptibly to massage your spine, reducing ache. In addition, little fans in the seat provide ventilation, reducing sweat and fatigue.

Volvo is another maker which seems to be showing more than a passing interest in the science of seats. Its new S80, a likeable if unwieldy big saloon, has many novelties. But one of the most appealing is that its seats are soft. Every other so-called "luxury" car has seats with as much give as a sheet of slate.

It was the Germans who popularised rock-hard chairs, kidding us into believing that only firm seats could be truly supportive. Italian, British or French luxury cars built before about 1970 (before they copied the Germans) had great squishy chairs into which one's backside sunk like a boot in mud.

They were modelled on old-fashioned lounge chairs, which derived their comfort from the softness and thickness of their cushions rather than the shape of the seat - although they were, in fact, superior to most lounge chairs. Sculpted, supportive seats were virtually invented by the car industry.

The great American designer Walter Dorwin Teague wrote in 1940 that: "The automobile manufacturers have made, in the past few years, a greater contribution to the art of comfortable seating than the chair manufacturers have made in all history." Many would argue - especially after a long run on the M1 - that that is more of an indictment of chair makers than it is praise for car makers. None the less, in the past year or so, real progress has been made.

I like the new Volvo chairs because, for me, comfort should equate to luxury, and luxury should always pamper. Seats with about as much give as a park bench may, because of their curvature and bolstering, be able to support our backs and minimise ache. But true comfort - even in these ascetic, Blairite times - should be about more than merely reducing discomfort.

I own a four-year old Mercedes E220 estate and its fibre-and-springs seat - as hard as a Kaiser's helmet - have never caused me grief on a long run. But they also have a spartan feel which is inimical to true luxury. It is one of the reasons why no Mercedes or BMW is truly a luxury car, not even the new vibro-massaging S-class.

Rather, they are superior executive cars, designed to do a job rather than to offer joy. They are sensible rather than sensual cars, and luxury is a very sensual thing.

That is what I like about the Volvo S80's seats. They support, and yet they are supple. You feel special every time you climb on board, and disappear into your own little hedonistic world before it is time to start the engine, get going, and join the rat race.