The New York Times: One of the great contradictions of modern American life is that almost everyone watches television while almost no one agrees anymore about what it really means to watch television. True, we know that as spring gets under way, new episodes of ''Desperate Housewives'' and ''C.S.I.'' and ''American Idol'' will battle for prime-time supremacy in the overnight Nielsen ratings. We also know that local broadcast stations around the country will begin scheming -- just as they do every April -- to win the May sweeps, the tense weeks when rival stations pursue a fierce one-upmanship of flamboyance and hype and the Nielsen-measured audience sizes determine future advertising rates. But when it comes to figuring out how many of us are watching these shows, and whether we're paying attention while we're watching and even whether we're actually noticing the advertisements among the shows we may or may not be watching -- well, this is where things get tricky.

For the past decade or so, watching television in America has been defined by the families recruited by Nielsen Media Research who have agreed to have an electronic meter attached to their televisions or to record in a diary what shows they watch. This setup may not last much longer. Just as programmers and advertisers are clamoring for a better understanding of the television audience, a wave of new consumer products has made it increasingly difficult to satisfy them. One day this January I sat in a Greenwich Village workroom with Bob Luff, the chief technology officer at Nielsen, as he pulled out gadget after gadget to show me what he's up against. Luff seemed to view the modern American home as a digital zoo where the lion is about to lie down with the lamb: radio is going on the Web, TV is going on cellphones, the Web is going on TV and everything, it seems, is moving to video-on-demand (V.O.D.) and (quite possibly) the iPod and the PlayStation Portable. ''Television and media,'' Luff said over the noise of five sets tuned to five different channels, ''will change more in the next 3 or 5 years than it's changed in the past 50.''

Our Ratings, Ourselves [The New York Times]