About a month ago, my sister who is 10, started humping the couch. She developed a lot younger than me and she grew up really quickly, so I can imagine that feeling very horny hit her pretty suddenly. I remember that she was watching TV, just kind of moving her body back and fourth on the couch. She wasn't undressed or anything. She was going at it pretty hard and I don't think she really understood what she was doing, just that it felt good. I don't think she reached orgasm because she just kept doing it until our Mom called us to dinner.
She ate really fast and that night, she started humping the bed, although I doubt that she knew what she was doing. My friend had told me what humping was, so I guessed. I asked her what she was doing and she said, 'Nothing.' She just kept going and didn't really realize that she was jacking off. After a couple of minutes I heard her pull down her pants and keep going. She also pulled off her shirt and rubbed her grapefruit-sized breasts on the bed too. I asked her to stop and go into the bathroom, but she said that she wasn't doing anything. After a few more minutes she whispered, 'Oh my GOD!'
She asked me the next morning why it felt good to rock around on things and the next day she said she had an orgasm on the playground during school.