ONLY IN AMERICA would you find (a) so many sentences that begin, "Only in America" and (b) a motorized bed adverised on televsion as providing "the most exciting way to relax."

Just what we needed - an exciting way to relax. The only thing better would be a mortuary advertising, "the most exciting way to rest in peace."

Television viewers, it might be assumed, have as much or more fun laughing at such ads as they have trying to laugh with TV shows like "Laverne and Shirley," where the comic aspects are more oblique. We have learned how to decipher ads, or so we may think, and even how to withstand them - except perhaps during those long holiday weekends when Joe Blow's Carpet Barn takes the trouble to tell us about its 18-hour sale approximately every 18 minutes. During these stretches of pure hell-on-earth, it's hard to keep from setting fire to one's own carpet out of a mad quest for revenge.

The fact of the matter is, however, that not all TV viewers are created equally impervious to the devious ploys of TV commercials. The younger a viewer is, the more vulnerable a viewer is. And this is one reason why the Federal Trade Commission's proposed inquiry into ads directed at children is not in any way out of order, as vociferous critics of it have claimed, nor somehow an act of sacrilege against the gods of capitalism.

After all, the FTC has only prposed hearings, not necessarily any new regulation. If Congress can permit the Pentagon to study the aerodynamics of the Frisbee, it can allow the FTC to study the effects of TV ads on children.

Why was there such fuss and dudgeon on the Hill over the FTC's plan to study this subject? The answer is painfully and rather shamefully obvious: The broadcasting industry maintains one of the strongest and most pervasive lobbies in town. Industry flacks went after public opinion while the lobbyists took care of Congress, denouncing even the thought of proposing such a study. Somehow this doesn't seem like a very enlightened atmosphere for debate on anything; the FTC study may have been justified how merely by the vehemence with which the forces of the status quo have attacked it.

The FTC has no ravenous desire to usurp parental roles in regulating children's eating habits as regards sugary snacks and sugar-soaked cereals sold on TV. There is considerable doubt, however, whether parents themselves very carefully regulate their children's viewing habits. For many hours of every week, televsion sets in effect become parents-in-absentia to millions of American tots. During these periods, ads for products which most children are not economically empowered to obtain on their own are pitched to them on TV by adult authority figures, peer group operatives, and an army of insidiously adorable cartoon creatures.

A cute, floppy-eared rabbit is currently engaged in a campaign to encourage the chug-a-lugging of cold chocolate milk by the young. The idea is to drink it all down in one fell slurp. The could give the little tykes headaches and stomachaches, of course, but the rabbit doesn't mention those. He's been hired to move that chocolate milk mix as fast as he can.

Children are not as equipped as adults to deal with the onslaught of commercial messages and yet they may be subjected to more commercials per program than adults are. A study released this week by Boston's Action for Children's Television (ACT) found that it is common for stations to exceed limits on commercial time, established by the industry's own National Association of Broadcasters (NAB), whcih call for not more than 9 1/2 minutes of commercials per hour on weekend childrens programs and 12 per hour on children's weekday programs.

Dr. F. Earle Barcus of Boston University, who conducted the study, found that some stations broadcast nearly 17 minutes per hour of commercials during children's time. He also found that during the 61 hours monitored, two-thirds of the foods advertised to kids were "highly sugared products." The study has been submitted to the Federal Communications Commission, where children's television is also an ongoing issue.

The nature of advertising has been changed tremendously by and through television. Advertising is no longer anything so simple as a statement of claims of superiority by one product over its competitors, though examples of this still exist. Not even kids would swallow the argument, after all, that a Snickers bar is nutritionally, chemically or morally superior to a Three Musketeers. Mention the word nutrition in an ad, anyway, and you risk terroizing the little darlings into doing something so rash as going outside to play.

Most TV commercials today try to associate products with varying states of emotional, physical and psychological well-being without actually claiming, in so many words, that the product will bring these states about. In so many pictures it can be done much more efficiently and without the risk of actually lying. Ads today tend to deal less in word associations than in image associations, something that may be very scientifically designed yet hard to analyze in concrete ways when seen on the air.

When you put marbles in a bowl of soup to make the vegetables rise to the top - as was done in one classic FTC false-ad-claims case - you are lying about the soup. This is clear enough. But if you show a man in a three-piece suit jumping for joy on the sidewalk after having consumed a bowl of said soup, you are not really claiming anything that can be disproved.

Thus the whole regulatory posture of the FTC regarding "truth in advertising" is becoming more and more out of date where TV commercials are concerned. This was spelled out eloquently for all the world to read five years ago in a landmark book on media manipulation, "The Responsive Chord," by Tony Schwartz, a veteran ad man who designed the legendary little-girl-with-daisy-and-H-bomb ad for Lyndon B. Johnson's 1964 presidential campaign against Barrry M. Golwater. Schwartz's fans include Marshall McLuhan.

Schwartz wrote in "Responsive Chord" that, "From the FTC point of view, 'telling the truth' should be the least important social concern. If electronic communication deals with effects, then government agencies responsible for safeguarding the public well-being should concern themselves with understanding the effects of a commercial, and preventing those effects that are not in the public interest.

"A recent television commercial for children's aspirin was 100 percent truthful by the most rigid FTC standards, but the effect of the commercial was to make children feel that aspirin is something to take when they want to have a good time. The commercial clearly demonstrates that truth is a print ethic, not a standard for ethical behavior in electonic communication."

There is evidence the FTC is getting hip to this distinction and the new audio-visual vocabulary of advertising. In a speech prepared last October for the Advertising Law Conference, Albert H. Kramer, director of the FTC's Bureau of Consumer Protection, called for a new look at standards by which ads are judged.

"If we are charged with determining whether an advertisement is false or deceptive, we must be able to make that evalution within the environment in which the ad is presented," Kramer said. "Our time-honored environment for resolving disputes is by the written word.

"Now, however, the media have changed. The media have left the written word behind in a cloud of dust and have created a new environment of multiple-sensory experience of which the written word is a minor part. A very serious problem arises when regulators evaluate the possible falsity, deception or unfairness of an ad without considering it in the same 'sensory experience' context that the ad sought to instill."

Advertising agencies have spent millions on behalf of their clients researching new avenues into the minds of the viewer, young as well as old. It only seems fair that the FTC spend some money to find out how children can be protected from these tactics and techniques, since they are our mst uninformed consumer group. Anyone who says that everything children see on TV will be helpfully interpreted for them by a handy adult is raving. And for Congress to set itself up as a roadblock in the pursuit of new knowldege about media responsiveness in children is a thoughtless sort of sabotage.

After much folderol, the FTC hearings are going ahead. The first will be held Nov. 6 in San Francisco, then move to Washington Nov. 20. Funding of this project has only been authorized through 1978, however, and in addition, the House Appropriations Committee slapped a rejoinder of sorts on the FTC by forbidding the commission is advance from limiting the advertising of "any food product which contains ingredients found to be safe for human consumption by the Food and Drug Administration" - in other words sugar.

An FTC spokesman says the rejoinder is "stupid" but that it can be worked around and may not be an obstacle. The committee's gesture on behalf of sugar and the TV lobby was hailed, however, by NAB President Vincent T. Wasilewski as verifying the fact that "Americans don't want the federal government dictating decisions that should be made by the family."

Children's advertising is "a commonsense issue," Wasilewski says, but the NAB has no monopoly on common sense, to put it midly. The FTC inquiry should be welcomed and its results heeded - unless, that is, we want to hand children over to television lock, stock and cookie jar.