"The Horror of It All," a one-hour survey of movie thrillers at 8 tonight on Channel 26, cursorily traces horror films from the early German gothics of the '20s through the splatterama '80s. While the show's assembled clips are nothing to scream about, the casual observations of an odd lot of interviewees are diverting commentary on this nothing-if-not-durable genre. The motion picture gave human beings the means to duplicate nightmares and deepest fears as they had never been able to do before.

Veteran horror star John Carradine says, succinctly enough, "People love to be scared." Rouben Mamoulian, whose directorial credits include the 1931 Fredric March version of "Dr. Jekyll and Mr. Hyde," says he saw Robert Louis Stevenson's story as a parable about "the conflict between the high aspirations of every human being and his lower, baser instincts." Producer Roger Corman, who had a horror heyday at American-International Pictures (mainly with embellishments on old Poe stories), says, "Special effects are never an end unto themselves," suggesting that Roger hasn't been to too many horror movies lately.

Perhaps the most helpful commentator among those spliced into the hour (which is narrated by Jose' Ferrer) is Robert Bloch, who wrote "Psycho," one of the pivotal horror films of all time, but one given little notice by this program. (Other turning points given no notice whatever include "Night of the Living Dead," which changed the rules by breaking them, "Rosemary's Baby," which set off the demonology rage, and "The Exorcist," trailblazer among big-budget goremongers.)

Bloch, anyway, recalls seeing James Whale's "Frankenstein" as a youth and says the Frankenstein monster represents adolescence and adolescent sex drives. Of course, most movie monsters over the years have personified, in one form or another, lust amok; what was King Kong but a big hairy id? Ironically or not, considering the fact that people once thought "Psycho" had "gone too far," it is Bloch who, near the program's conclusion, suggests that horror movies today show too much explicit carnage and proposes Hollywood "call a halt somewhere along the line."

Among the rarer clips shown are a mesmerizing sequence depicting mesmerization in the 1931 "Svengali" with John Barrymore, and a brief peek at Francis Ford Coppola's first studio feature, "Dementia 13" (1963). Writer-director Gene Feldman is awfully squeamish about showing actual horrific moments from horror films, however, and much screen time is wasted with silly footage amateurishly shot at the Haunted Mansion in Long Branch, N.J.