性行為的發展

人的性行為發展不會隨著青春期的過去而結束，而會持續到成人期。恰恰是在成人期，大多數男女才開始成為父母，而作為父母本身會改變他們對生活和行為的看法。此外，他們的性別角色和性行動仍能夠發生改變：不同的女性氣質和男性氣概模式成為一種時尚，他們可能會嘗試和喜歡上從未有過的性行為方式，隨著時間的推移，甚至他們的性取向可能會自發地略為發生轉移。

無論如何，現今成人的性關係可以分成許多種類型：除了對另一個性別中同一個人有傳統的長期婚姻關係以外，人們現在還發現有多種現代的生活方式：“單身”、“同居”和與性夥伴“公社”的群居體驗。一些男女有“開放的婚姻”，其他的人過著“連續的一夫一妻生活”（即反復的結婚、離婚和再結婚）。此外，一些國家認可同性和不同性別結合的“註冊式伴侶關係”，少數國家允許同性婚姻。

毫不令人驚訝地說，相當多的男女在他們有生之年嘗試著數種形式的性生活，所以就當代性關係要下一個明確而普遍適用的結論確乎是困難的。儘管如此，我們可以以相對確實的口吻得出這個結論：幸福和持久的伴侶關係更大程度上依賴於相互尊重、相互信任和相互理解，而不是總依賴於性行為。“性生活”能夠扮演一個有特殊意義的次級角色，但是它的頻率和強度一定會隨著年齡的增長而下降。相應地，在表達親切和肉體親昵中，愛才是一個決定性的因素。

Stages of Development

Adulthood

Human sexual development does not end with adolescence, but continues in adulthood. It is in adulthood that most females and males become parents, and this, in itself, changes their outlook on life and their behavior. Apart from that, their gender roles and erotic preferences can also still change: Different models of femininity and masculinity may become fashionable, new sexual practices may be tried and preferred, and even sexual orientations may spontaneously shift somewhat over time.
In any case, adult sexual relationships today can take many different forms: In addition to the traditional life-long marriage to the same person of the other sex, we now find the modern lifestyles of “singles”, couples just “living together”, and groups experimenting with sexual “communes “. Some women and men have an “open marriage”, others practice “serial monogamy” (i.e repeated marriage, divorce, and remarriage). In addition, some countries recognize “registered partnerships” for couples of the same and of different sex, and a few countries allow same-sex marriages.
Not surprisingly, quite a number of women and men try several of these forms in the course of their lives, and it is therefore difficult to draw definite general conclusions about contemporary sexual relationships. Still, one can state with relative certainty that happy and enduring relationships depend more on mutual respect, trust, and understanding than on sexual activity. “Sex” may play an important secondary role, but its frequency and intensity are bound to diminish with advancing age. Instead, love, as expressed in tenderness and physical closeness, becomes the decisive factor.