ROD CAIRD is doing battle with two assumptions about television: (1) that talking heads are always boring and (2) that documentaries can't appeal to wide audiences on major networks.Mr. Caird is head of factual programming for Granada Television in Britain, one of the largest and most respected makers of documentaries in the world. The company is better known in the United States for its dramatic series shown here on public television, such as "The Adventures of Sherlock Holmes,Brideshead Revisited," and "The Jewel in the Crown." Caird's "jewel" of the moment, at least as far as American audiences are concerned, is "Dinosaur! a look at the prehistoric giants narrated by former CBS News anchorman Walter Cronkite. Produced by an international consortium - Granada, Satel (Austria), and Primedia (Canada) Dinosaur!" will be shown in the US Sept. 8-11 on cable's Arts & Entertainment Network. The four hours of "Dinosaur!" will play in Germany, Austria, Spain, and Italy too, and will be dubbed or subtitled where needed. International coproductions are becoming more and more prevalent, said Caird in an interview at Granada's modest New York offices on Madison Avenue, just a stone's throw from NBC's corporate headquarters at Rockefeller Center. Because of the huge costs involved (including special effects to create "living," moving dinosaurs), Granada "couldn't have made 'Dinosaur! by itself, he says. Fortunately, the appeal of these extinct creatures crosses boundaries of culture and language. Finding projects that "each partner would want to do on its own but can't afford to" is becoming more common in an increasingly worldwide market for programming, Caird says. While US commercial networks have all but abandoned documentaries to public television and cable channels, Granada makes and airs them on its commercial network in Britain. The company's goal, says Caird, is to "try to make really great programs - that make money." Can a documentary really attract a prime-time audience? Caird answers with an example. Recently a Granada-produced documentary entitled "35 Up" played to 17 million viewers, one-third of the British population, the equivalent of some 80 million Americans tuned to a single program. "You can't do that with all documentaries; it's not going to work all the time," he concedes. But such successes allow Granada to produce other documentaries, which pull in smaller audiences, and still make an overall profit. He cites an expose of questionable salmon fish-farming techniques in Britain and the filming of a rare tribal ritual in remote Ethiopia as examples of important films that draw smaller audiences. But such subjects need not be boring in the hands of a skilled filmmaker, Caird says. Television, he says, should concentrate on what television does best: show people telling stories about people. "The television screen is made for the human face. It's the right shape," Caird says. "Issues don't work so well. Landscapes can look nice. But everybody has seen them. Nothing can beat a person telling their own story. [TV] is a people medium.... That's what makes me so irritated when people say, 'There are too many talking heads in this documentary. But they can be boring, too, he acknowledges. Thus the need for talented filmmakers and well-chosen topics. Even though he produces films with "a shelf life of years," Caird thinks of himself more as a journalist than, say, a book publisher. "The whole point about being a journalist is that you're curious, you're inquisitive. You want to know what's happening," says Caird, who spent several years as both a newspaper and television reporter before becoming an award-winning producer. Caird says he thinks people enjoy learning about even complex or scientific topics - if the documentary-maker does not use language that sounds stuffy or exclusive. In "Dinosaur!" for example, "We don't use the word 'paleontologist.' We talk about 'dinosaur detectives.' Because that's what they are." All this is part of fighting for his audience, and not only against completing TV shows. He tries to visualize what his program will look like on "a not very good television, on the other side of the room, with something else going on in the room - and somebody holding a [remote control] zapper in their hand ready to turn you off!"