Midway through "Superior Attachments," a new play about adultery on the fringes of the college set, one of the characters proposes the game of "zipper mouth," which is not a bad idea at all, since it boils down to shutting up for a while.

If only someone had made a similar suggestion to playwright Carroll Carlson, who natters on interminably in what is easily the season's most banal drama. Presented with more good will and serious intentions than it merits by the Woolly Mammoth Theatre Co., "Superior Attachments" submits two couples to the agony of an extracurricular affair and lets them express every sentiment, fleeting or not, that ever popped into their heads.

The dialogue consists mostly of what is intended to be fast, brittle repartee, batted smartly back and forth. People don't talk like this in my experience. They play ping-pong this way. When the banter ceases, it is, unfortunately, to make way for bathetic wallowings that belong in a bedside diary, where they are unlikely to cause either harm or embarrassment. There is also a certain amount of bald talk about matters sexual, which is all that separates this play from the television soaps.

The title refers not only to the various relationships, but also to Lake Superior, which is just offstage. The chilly lake apparently serves as a metaphor for the opaqueness and flux in human intercourse, since one of the characters notes pointedly that "Superior doesn't give up its dead."

On another occasion, someone wonders, "How do you say what you want to say, when you don't know exactly what it is you want to say?" For once, no one has a quick retort.

In a nutshell,"Superior Attachments" revolves around Phil, a poet in residence at some university or another, and his wife, Barbara; plus Brad, the oafish assistant vice president for student affairs, and his wife, Wren, who was once fourth runner-up in the Miss Arizona contest. When Barbara decides to pursue her education at Ann Arbor, Mich., leaving Phil footloose during the week, Phil takes up with Wren, who happens to be pregnant. This gives them more than enough material to discuss. Each of two dozen or so scenes ends with a deeply knowing observation. One of the scenes features a slide show of vacation pictures, approximately as revealing as your Aunt Bea's snaps of Wichita.

The actors--Rodger Wilson Smith, Joann Robertson, Richard Bertone and Kirsten Vance--perform with all the sincerity they can muster. And Howard Shawlitz has directed the opus as if it were made of precious metal. Their collective faith is touching. Indeed, I believe theirs is the sort of faith that is said to move mountains. But it can't budge "Superior Attachments" one inch. SUPERIOR ATTACHMENTS. By Carroll Carlson. Directed by Howard Shawlitz; set, Steve Siegel; lighting, John Natali. With Rodger Wilson Smith, Joann Robertson, Richard Bertone, Kirsten Vance. At the Woolly Mammoth Theatre through May 14.