To take an honest glance back through the history of human attitudes about masturbation is to be filled with sadness at all the guilt and pain we've needlessly inflicted upon ourselves. Because the bottom line on masturbation is this: Nobody has ever been able to show that it's harmful at all, whether physically or psychologically. The physical effects of self-stimulation aren't fundamentally different from those of any other kind of sexual activity, so how could it be harmful? In fact, today's sex therapists point to its many practical benefits.

• It can teach a woman how to reach orgasm - and in fact, many women first become orgasmic in this way. In Dr. sample, only 4 to 6 percent ofthe women who masturbated were unable to reach orgasm through self-stimulation (a much higher percentage than reach orgasm through intercourse).

• Rather than hindering a woman's ability to reach orgasm during intercourse, it can often help, by teaching her about her own sexual rhythms and preferences. ("Premarital experience in masturbation may actually contribute to the female's capacity to respond in her coital relations in marriage," Dr. Kinsey observed.)

• Older women who've passed menopause and don't have a sex partner often experience a gradual thinning and drying-Dut of vaginal tissues, which can make intercourse terribly painful once they do find a partner. One good way to keep the vaginal tissues soft, moist and pliable is to masturbate, preferably by lIsing something like a vibrator in the vagina, therapists say.

• Because it's often fevered, guilt-ridden and quick, masturbation may teach a young man to ejaculate all too fast. Yet, carefully practiced, it can also provide terrific training in ejaculatory control. In fact, the squeeze technique, a kind of stop- and-start masturbation, is a widely used and highly effective form oftherapy for men who ejaculate too rapidly to satisfy their lovers. (See "Premature Ejaculation.")

• Masturbation can also be used for mutual, rather than solitary, pleasure. It can be very instructive to watch your partner masturbate himself or herself to climax. It's one ofthe best ways for a woman to show her man precisely where her clitoris is and how she likes it to be stroked. Also, depressing as it is, mutual masturbation has gained a new kind of glamour in the age of AIDS. (See "Safer Sex.")