As the clitoris is homologous to the penis, it is the equivalent in its capacity to receive sexual stimulation. One misconception, particularly in older research publications, is that the vagina is completely insensitive. However, there are areas in the anterior vaginal wall and between the top junction of the labia minora and the urethra that are especially sensitive. With regard to specific density of nerve endings, while the area commonly described as the G-spot may produce an orgasm, and the urethral sponge, an area in which the G-spot may be found, runs along the "roof" of the vagina and can create pleasurable sensations when stimulated, intense sexual pleasure (including orgasm) from vaginal stimulation is occasional or otherwise absent because the vagina has significantly fewer nerve endings than the clitoris. The greatest concentration of vaginal nerve endings are at the lower third (near the entrance) of the vagina.Sex educator Rebecca Chalker states that only one part of the clitoris, the urethral sponge, is in contact with the penis, fingers, or a dildo in the vagina. Hite and Chalker state that the tip of the clitoris and the inner lips, which are also very sensitive, are not receiving direct stimulation during penetrative intercourse. Because of this, some couples may engage in the woman on top position or the coital alignment technique to maximize clitoral stimulation.
In 1999, Whipple and Komisaruk proposed cervix stimulation as being able to cause a fourth type of female orgasm.Female orgasms by means other than clitoral or vaginal/G-spot stimulation are less prevalent in scientific literature and most scientists contend that no distinction should be made between "types" of female orgasm. This distinction began with Sigmund Freud, who postulated the concept of "vaginal orgasm" as separate from clitoral orgasm. In 1905, Freud stated that clitoral orgasms are purely an adolescent phenomenon and that upon reaching puberty, the proper response of mature women is a change-over to vaginal orgasms, meaning orgasms without any clitoral stimulation. While Freud provided no evidence for this basic assumption, the consequences of this theory were considerable. Many women felt inadequate when they could not achieve orgasm via vaginal intercourse alone, involving little or no clitoral stimulation, as Freuds theory made penile-vaginal intercourse the central component to womens sexual satisfaction.The first major national surveys of sexual behavior were the Kinsey Reports. Alfred Kinsey was the first researcher to harshly criticize Freuds ideas about female sexuality and orgasm when, through his interviews with thousands of women, Kinsey found that most of the women he surveyed could not have vaginal orgasms. He "criticized Freud and other theorists for projecting male constructs of sexuality onto women" and "viewed the clitoris as the main center of sexual response" and the vagina as "relatively unimportant" for sexual satisfaction, relaying that "few women inserted fingers or objects into their vaginas when they masturbated".