"Yes, for women who are honest about their responsive sexual behavior, the convulsing muscles of the vulva and the sphincter muscle of the anus is a convincing manifestation of orgasm...However, for women less honest and perhaps more self-conscious of their sexual behavior, those with a history of frequent masturbation gain the knowledge of genital and anal contractions during orgasm and can reasonably duplicate that response by conscious, voluntary control of their pelvic muscles."