When I read this story, it made me laugh because like the author, I masturbated when I was in pre-school too. I don't remember how I discovered it, however, I don't know how I learned how to walk, or talk, or many other things, so it must have been really early in life.
The way I remember masturbating all my life was also one of the ways the author in the above link did. I lay in bed and placed my hands between my legs and rubbed my lower body over them.
I never did this in front of anyone, I knew somehow that this should be done when I was alone, and I usually did this in my bed with a blanket over me as well. That way if someone did walk into my room, I could quickly jump off my hands and no one would know what I was doing.
But sometimes, I did this without a blanket over me, if I was sure no one was home. I must have made a mistake once. My older sister is three and a half years older than me. A few weeks ago, she asked me how I discovered masturbation, she said she knew I did it regularly. I asked her how? She confessed that when she was in grade seven she saw me through a window in the house masturbating on the floor, and that she knew I didn't see her. She told me that she didn't know what it was that I was doing, (I didn't know either, never had a name for the word of this personal habit) but when she was alone later, she tried the same thing and felt really wonderful.
Wow, I was probably only in grade three or four, and yet somehow I influenced my older sister to do this. Of course when she asked me how I discovered it, I couldn't help her because I didn't know. She can remember the first time she masturbated, but I cannot remember the first time I masturbated. Kind of makes me sad too, I wish I knew how I could have discovered it, but I have no idea.