Diamond, which followed women identifying as lesbian, bisexual, or unlabeled, found that "more women adopted bisexual/unlabeled identities than relinquished these identities," over a ten-year period.
In a longitudinal study about sexual identity development among lesbian, gay, and bisexual (LGB) youths, Rosario et al.
"found evidence of both considerable consistency and change in LGB sexual identity over time".
From an anthropological perspective, there is large variation in the prevalence of bisexuality between different cultures.
Among some tribes, it appears to be non-existent while in others a universal, including the Sambia of New Guinea and similar Melanesian cultures.
and the concept is one of the three main classifications of sexual orientation along with heterosexuality and homosexuality, which are each parts of the heterosexual–homosexual continuum.
A bisexual identity does not necessarily equate to equal sexual attraction to both sexes; commonly, people who have a distinct but not exclusive sexual preference for one sex over the other also identify themselves as bisexual.
Kinsey studied human sexuality and argued that people have the capability of being hetero- or homosexual even if this trait does not present itself in the current circumstances.
Psychologist Jim Mc Knight writes that while the idea that bisexuality is a form of sexual orientation intermediate between homosexuality and heterosexuality is implicit in the Kinsey scale, that conception has been "severely challenged" since the publication of Homosexualities (1978), by Weinberg and Alan P. Kinsey's 1948 work Sexual Behavior in the Human Male found that "46% of the male population had engaged in both heterosexual and homosexual activities, or 'reacted to' persons of both sexes, in the course of their adult lives".
Youths who had identified as both gay/lesbian and bisexual prior to baseline were approximately three times more likely to identify as gay/lesbian than as bisexual at subsequent assessments.