The latest research about TV viewing indicates the audience is increasingly busy, fidgety and prone to multitask. Dramas have responded by becoming denser than ever, with many juggling more than a dozen regular characters, dispensing with the traditional A-B plot structure and moving toward something in the A-through-J range.How, then, do we align this shift with the “padding paradox,” where the most popular reality TV programs contain more padding than a room full of department-store Santas? Watch “American Idol” or “Dancing With the Stars” — especially when they expand into two-hour mode — and it’s remarkable how little occurs between the actual singing/dancing and the subsequent judging/analysis. With “Idol,” those who record the show in advance can excise much of this fat, including the idle chit-chat with contestants, the counseling sessions with better-known pop acts, and any time Ryan Seacrest or Paula Abdul’s lips begin to move. Throw in zipping through the commercials, Coke-sponsored moments and parts of classic songs butchered by the no-talent contingent among this season’s finalists, and an industrious viewer can strip a two-hour episode down to roughly 32 minutes without really missing a thing. Ditto for “Dancing,” which in its closing weeks — once most of the pairs are eliminated — should be called “Sitting Around and Talking About Dancing With the Stars, Periodically Interrupted by Dancing.” Nevertheless, millions of viewers eat up the fabricated drama and the slow building, building, building devoted to the competitions. Given how impatient the audience is perceived to be, this is amazing: Even at a sporting event — and based on these shows’ strong appeal among women, figure skating is the closest parallel — there isn’t this much dead time around the performances. This aspect of “reality” is all the more confounding surveying the elaborate narrative contortions implemented by high-profile dramas, which — perhaps fearing the accusation that “Lost” hasn’t moved fast enough in disgorging its secrets — have plowed through story at what would traditionally be viewed as a breakneck pace. Consider “Grey’s Anatomy,” where the principal characters have exhausted so many sexual combinations, the writing staff is almost beginning to start over. “Heroes” has killed off part of its cast while rapidly adding newcomers, set against fast-moving revelations about who’s related to whom and a time-traveling apocalyptic threat. Yet even those shows pale in complexity next to HBO dramas like “Deadwood” and “The Wire” — each incorporating roughly three dozen characters while layering every season upon the preceding one in a manner that will eventually prompt universities to devote graduate courses to them. The large casts and intricately woven plots not only elevate budgets, they also heighten risks that a series will strike a painfully false note and cause the entire house of cards to come crashing down. Public tastes, in fact, have never seemed more fickle or changed as quickly, as evidenced by the millions that have lost the “Lost” itch — or become less desperate for “Desperate Housewives” — in a relatively short time frame. By contrast, big reality franchises operate on an entirely different plane, ostensibly unfettered by the tyrannical demands that discerning viewers apply to many top dramas; rather, people sit and stare and sometimes entertain themselves, picking apart the participants’ clothes, hair and body language. At a recent presentation, NBC Universal president of Research and Media Development Alan Wurtzel cited studies showing that more than 30% of daily media usage is now multitasked, painting a portrait of active viewers who simultaneously chat online or play games, say, while watching television. In that respect, a check-your-brain-at-the-door experience like “Idol” or “Dancing” might be strangely in tune with a portion of today’s audience, facilitating their multitasking habit by providing ample time — beyond the commercial pods — to do homework, call mom, check email or cook dinner without missing anything of consequence. Nielsen has been under pressure to enhance its measurement system, providing additional data about ratings for individual ads and even attentiveness levels during particular programs. Until someone concocts a machine that can gauge the link between TV viewing and brain activity, however, dramas will likely remain on the short end of this equation — compelled to stay lean and mean in order to survive, while reality TV’s titans layer on the lard.