性行为的发展

人的性行为发展不会随着青春期的过去而结束，而会持续到成人期。恰恰是在成人期，大多数男女才开始成为父母，而作为父母本身会改变他们对生活和行为的看法。此外，他们的性别角色和性行动仍能够发生改变：不同的女性气质和男性气概模式成为一种时尚，他们可能会尝试和喜欢上从未有过的性行为方式，随着时间的推移，甚至他们的性取向可能会自发地略为发生转移。

无论如何，现今成人的性关系可以分成许多种类型：除了对另一个性别中同一个人有传统的长期婚姻关系以外，人们现在还发现有多种现代的生活方式：“单身”、“同居”和与性伙伴“公社”的群居体验。一些男女有“开放的婚姻”，其他的人过着“连续的一夫一妻生活”（即反复的结婚、离婚和再结婚）。此外，一些国家认可同性和不同性别结合的“注册式伴侣关系”，少数国家允许同性婚姻。

毫不令人惊讶地说，相当多的男女在他们有生之年尝试着数种形式的性生活，所以就当代性关系要下一个明确而普遍适用的结论确乎是困难的。尽管如此，我们可以以相对确实的口吻得出这个结论：幸福和持久的伴侣关系更大程度上依赖于相互尊重、相互信任和相互理解，而不是总依赖于性行为。“性生活”能够扮演一个有特殊意义的次级角色，但是它的频率和强度一定会随着年龄的增长而下降。相应地，在表达亲切和肉体亲昵中，爱才是一个决定性的因素。

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.