oral sex as their main forms of sexual activity. Lesbians may categorize oral sex or fingering as sexual intercourse and subsequently an act of virginity loss, or tribadism as a primary form of sexual activity. Researchers commonly use sexual intercourse to denote penile–vaginal intercourse while using specific words, such as anal sex or oral sex, for other sexual behaviors. Scholars Richard M. Lerner and Laurence Steinberg state that researchers also "rarely disclose" how they conceptualize sex "or even whether they resolved potential discrepancies" in conceptualizations of sex. Lerner and Steinberg attribute researchers' focus on penile–vaginal sex to "the larger culture's preoccupation with this form of sexual activity," and have expressed concern that the "widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question [about sexual activity] matches what the researcher had in mind'". This focus can also relegate other forms of mutual sexual activity to foreplay or contribute to them not being regarded as "real sex", and limits the meaning of rape. It may also be that conceptually conflating sexual activity with vaginal intercourse and sexual function hinders and limits information about sexual behavior that non-heterosexual people may be engaging in, or information about heterosexuals who may be engaging in non–vaginal sexual activity. Studies regarding the meaning of sexual intercourse sometimes conflict. While most consider penile–vaginal intercourse to be sex, whether anal or oral intercourse are considered sex is more debatable, with oral sex ranking lowest. The Centers for Disease Control and Prevention (CDC) stated that "although there are only limited national data about how often adolescents engage in oral sex, some data suggest that many adolescents who engage in oral sex do not consider it to be 'sex'; therefore they may use oral sex as an option to experience sex while still, in their minds, remaining abstinent". Upton et al. stated, "It is possible that individuals who engage in oral sex, but do not consider it as 'sex', may not associate the acts with the potential health risks they can bring." In other cases, condom use is a factor, with some men stating that sexual activity involving the protection of a condom is not "real sex" or "the real thing". This view is common among men in Africa, where sexual activity involving the protection of a condom is often associated with emasculation because condoms prevent direct penile–to–skin genital