TRY an experiment: Next time you watch TV or go to a movie, pull away from the plot for a moment and see if you can imagine the story conference that lies behind the production. In your mind's eye picture a group sitting around a rosewood table in LA, some in Armani jeans and Zegna sweaters, some in designer sweats and Reeboks, jiggling knees impatiently as they put forward embellishments on the plot of the day. They are proposing, perhaps, Porsche (or pickup truck) chases, bikini beach games, apartment house stalkers, steamy bedroom or steamroom scenes, a sadistic crime boss, ''relevant'' cross-dressing. They are pushing ''hot'' casting, maybe a cameo appearance or two, frantic action (a helicopter chase here, a window-shattering explosion there). Overall they are weaving what they believe will sell in American cities, suburbs, and heartland - and then in Dusseldorf and Sao Paulo. We urge this mental game because so many Americans are disgusted over the direction of the main cultural influences on their families' lives but don't know whom or what to blame. Is it creators like the above, network bosses, studio heads, actor-directors, corporate conglomerates, lawmakers, courts, advertisers, the public? Who's responsible? A recent New York Times poll found what can only be described as overwhelming despair about the influence of popular culture. About 90 percent of those polled criticized some aspect of the pop culture scene, most often too much sex, violence, and vulgar language. TV was seen as the No. 1 culprit, with movies, recordings, and ''the media'' in general sharing blame. The most poignant quote came from a father of five surveyed in Cottage Grove, Tenn.: ''That's your future generation. It's what we've made them. Two parents are working all the time.... They don't know what's going on while they're not home.'' The old industry argument ''we only give 'em what they want'' won't wash. Nor will the psychologist/sociologist ''research'' claiming there's little or no connection between screen behavior and young viewers' actions. The Times poll showed half of respondents asserting that portrayals of sex and violence in the media affected the way young people behave in real life. Their instinct is right. It's true (give the psychologists a point) that horror movies and fairy tale violence usually don't rub off on viewers. But there is too much evidence of behavior and crime directly imitating the methodology and language on today's screens to be mere coincidence. Now return to the question of responsibility. Obviously blame rests on parents who don't teach by example or discussion; on top CEOs who turn a blind eye to how their film, TV, or record divisions act; on advertisers who chase ratings but don't encourage experiments to see if better fare will also rate well. But in the end change must come where content originates. V-chips, ratings, polls, and public protest may help to sway everyone involved in the industry. But it's ultimately the creators and embellishers - the folks around that LA or NY table - whose outlook needs to change. Perhaps because they see what's happening to their own children. Perhaps because they read the anguish in average Americans' reactions. Perhaps because of a memo from the boss. You can write to their CEOs and division bosses. Sway the plotters and you sway the future of our culture. About 90 percent of those polled criticized some aspect of the pop culture scene.