[Dominus]

I think that Halfpint is probably on a right track there, it would be difficult to masturbate without thinking explicit things, and those explicit images then would just cause the images (be them real or created by your mind) to become more deeply entrenched in your mind, which in turn leads to an gradual alteration of your thought processes. Like my Granny used to say "Too much sex is bad for you... Share it!"