About 6. I was the only boy on a childrens birthday party with 5 or 6 girls. It was summer, and we went to playground together with a mom of one of the girls. We played in the sand - but it was totally dry. No constructions possible... So without thinking about anything I peed in the sand - all the girls have watched (the mom read a book 20 meters away). Now we had a small amount of sand which can be used for constructions. We got more of such sand with every girl who peed in the sand, too (no female pee smily available...). I doesn't have any idea what "erotic" is at that age but I loved it a