THE PECULIAR characteristics of the radio medium--flexibility, intimacy and the tremendous importance of the spoken word--tend to be lost when radio plays are translated into theater. When Harold Pinter wrote A Slight Ache (1959) and The Dwarfs (1960), the two plays being staged by the Adams House Drama Society this weekend, he used the radio form to experiment with a dramatic structure he felt could be "more flexible and mobile than in any other medium." More than his works written for stage, the radio plays are characterized by lucid visual imagery. His language paints whole worlds in the mind of the listener, through the themes of perception and identity, by powerful use of silence, and by a type of mobility that becomes inevitably constrained by the boundaries of a stage set.

So when the Matchseller in A Slight Ache shuffles into the Adams House Upper Common Room like some Boston Common exhibitionist--wearing a Balaclava helmet, Wellington boots and a rumpled black raincoat--the menacing power of his silent radio presence is instantly precluded. The question of whether he really exists, or whether he lives only in the minds of the conventional middle class couple whose back gate he has been haunting for months, has been answered. Over the radio, the character is an intangible, but no less real, symbol of the couple's fears and desires. He is able simply by his presence to drive Edward to destroy himself and to bring Flora new life. But when awkwardly portrayed in concrete terms, the Matchseller appears to be little more than a speechless idiot who mystifyingly turns Edward into a raving maniac. The enigma of the Matchseller figure is lost and the play becomes a joke.

So Pinter's silences and manipulation of tempo are crucial--they illuminate the dark spaces behind his terse, economical language, convey the Matchseller's power over Edward, and express (in The Dwarfs) Len's isolation and the abyss into which his attempts at communication disappear. Edward and Flora's stream of consciousness babble must be broken by pauses if we are to understand how he comes to destroy himself and dies a symbolic death, while she rediscovers herself and finds a new life.

Sadly, in Jeff Rusten's production of A Slight Ache, Gregory Farrell's Edward--fists clenched, temper detonating predictably--is rarely more than a caricature, a man who lost his mind long before the late-summer afternoon when he decides to confront "the figure at the end of the garden." The audience is deprived of Pinter's fascinating study of the way the man's personality disintegrates when threatened by a powerful negative force in the Matchseller. Barbara Borzumato, on the other hand, plays a disarmingly uncomplicated Flora. Her real, repressed self surfaces in the course of her positive reaction to the forces that destroy her husband. Borzumato has caught Pinter's disturbing talent at making his audience feel acutely uncomfortable in the presence of his characters.

In The Dwarfs, Mark Creatura's hyperactive portrayal of Len makes a farce out of the man's search for identity, obscuring Pinter's statements on the problems of self-identification and the perception of external realities. Len's passage through mental collapse and into maturity often seems crazed and unreal. And although his two friends are effectively played by Steven Naifeli and Christopher Chase, the production fails to express the dynamically changing relationship between the three men. It also fails to illuminate Len's intriguing responses, emphasized at each turning point in the relationship by the invasion of the dwarfs into his imagination.

BOTH PLAYS are plagued by similar tendencies, the casts rushing headlong against Pinter's rigorously controlled pace. It is as though even the performers cannot bear the strain and tension that are essential to the drama. Moments of dramatic explosion are lost in the relentless hurry of these productions. Since the tempo remains unvaried, characters and relationships aren't allowed to develop and the evening tends towards monotony.

Fascinating as Pinter's radio plays are, the Adams House production suffers from the strains of translation into theater and fails to make up for it by exploiting the visual opportunities afforded by the stage. Ultimately, the internal turmoil of two unconvincing main characters simply loses its relevance. At first it's funny, then just plain dull. Either way, it's not what Pinter intended.