Teenage girls see sex as "a bit of fun" that gives them the confidence to take control of other areas of their lives, new research has found.
Others talk about uncontrollable physical desire that makes them want to "jump on" boys they are attracted to.
Academics from the Thomas Coram Research Institute at the Institute of Education in London interviewed 54 sixth-form girls aged between 16 and 18. The girls spoke about their experiences of sex and intimate relationships.
Most girls described sex as "normal" or "a bit of fun". One said: "It's just natural, isn't it?" Many discussed the enjoyment they had experimenting sexually with their partners, and tended to assume that they would find the experience pleasurable and fulfilling.
Some described themselves as "sexual people". For example, Iona said: "I mean, we're both quite sexual people ... I think I just enjoy healthy sex."
They also talked about their physical responses to boys. One spoke about having butterflies in her stomach when she saw one boy.
For some, this physical attraction was almost uncontrollable and dictated their subsequent actions. They said that sexual attraction left them with little choice in a situation: they were propelled, almost unconsciously, to act.
Barbara said: "There'd be certain people who I'd look at and go, 'Oh, I really want to have sex with you.' I literally want to jump on them."
And Iona said: "It's like when you wake up in the morning ... and they're lying next to you. You're like, 'All right' - off you go and have sex."
But the girls also felt this physicality allowed them to develop as people, becoming more confident and knowledgeable. They told the researchers that increased sexual experience brought not only increased sexual confidence, but also confidence to take control of other aspects of their relationships.
Bella talked about her newfound ability to initiate sex. This, she said, led her to see that the man is not necessarily the dominant partner.
"It was nice for him to be sensitive about it, instead of being like, 'Oh, yeah,' all the time," she said.
The girls also learnt from each sexual encounter, increasing their confidence in new relationships. Letita talked about drunkenly sleeping with a friend of her brother. "The next day it was just so awkward, and I felt really dirty," she said. She resolved never to put herself in such a situation again.
But the study questioned how willing these girls really are to accept this equality within relationships.
"While some young women positioned themselves as powerful in their physical responses and reactions to people, sex and events, they were much more timid about discursively positioning themselves as powerful when narrating non-sexual experiences with their intimate partners," they said.
RISE IN PREGNANCIES
Figures released earlier this year show conception rates among under-16s and 16-18s are on the rise for the first time since 2002.
More than 8,000 under-16s became pregnant in 2007. Conceptions per 1,000 12- to 15-year-olds in England and Wales rose from 7.8 in 2006 to 8.1 in 2007. Rates among 15- to 17-year-olds rose from 40.9 per 1,000 in 2006 to 41.9 per 1,000 a year later.
Teenage pregnancy rates have fallen by 12.6 per cent among under-18s, and by 12.3 per cent among under-16s since 1998, when the Government declared its aim of halving teenage pregnancies in England by 2010.