At least a couple of the summer's comedies have something besides low farce in mind. Between pratfalls, The Survivors and Trading Places take time to comment on fads and attitudes that deserve a bit of caustic observation - although they also trade in the rambunctious gags and hackneyed vulgarities that have become dubious fads themselves in recent years.
The serious undercurrents of ''The Survivors'' recall such earlier Michael Ritchie satires as ''The Bad News Bears'' and ''Smile.'' Again, the story is mostly an excuse for shooting well-sharpened barbs at a foible that irks the filmmaker. This time the plot centers on two likable losers being hunted by a killer after witnessing a crime. But the movie's main enthusiasm is for heaping scorn on the American weakness for weapons, macho posturing, and the cult of ''survival'' at any cost.
Ritchie approaches his target slyly. First he introduces his heroes (played by manic Robin Williams and shaggy Walter Matthau) and plunks them into a few rough situations, testing their personalities under fire. The real theme of the picture surfaces bit by bit, through absurd but unsettling details - beginning in the first scene, when Williams is fired from his job and a dignified secretary hauls out a pistol when he seems reluctant to leave the office.
The movie hits its stride when the men visit a gun shop - more like a supermarket, really - and Ritchie delares war on the fortress mentality behind such a place. It's a goofy scene, and more than a bit scary. It lets us know Ritchie means what he says, and prepares us for still more scathing attacks later, when the characters go to a ''survival camp'' whose graduates hope to outlive some ''disaster'' they think is lurking around the corner.
Ritchie is a specialist in this kind of galumphing parody: He even turned ''Semi-Tough,'' based on a second-rate novel about football, into a lampoon of cults and gurus. ''The Survivors'' has a lot of flaws. Too many laughs are based on nothing more clever than a cheap four-letter word, and Ritchie - indulging his weakness for comic ''shtick'' - lets Williams revel in obsessive monologues long after they've stopped being funny. But there are some biting jokes along the way, and the movie's targets couldn't be more appropriate. Or chilling.
''Trading Places'' begins when a pair of crusty old capitalists have an argument about how personalities are shaped. They settle their bet by manipulating two hapless pawns - reducing their own pampered protege to poverty and showering a panhandler with wealth, all to see whether ''heredity'' or ''environment'' carries the day.
Since this is a good-natured movie, both pawns turn out to be nice guys, and they wind up with the last laugh. The message seems to be that sincerity and generosity run deeper than anything the biologists or psychologists can pin down.
So far, so good. But another message also comes across: that money is the measure of goodness and success. The climax is a trite reversal of fortune, with the good guys scooping up the bad guys' loot, and ''Trading Places'' turns into just another celebration of the dollar.
As the protege turned poor, Dan Aykroyd gives his most modulated screen performance ever, and Eddie Murphy is all energy as his bewildered counterpart. The director, John Landis, unfolds the action more subtly and with more obvious care than in any of his earlier pictures, though he still peppers the action with bits of ''Animal House'' crassness. As a comedy specialist, he's not a Preston Sturges yet, but it's good to see him stretching his wings further than before.