When I was a little girl my mother would often say to me, "Edith, I know just who you've been playing with today." She knew because I had become something like the other little girl, whichever one it was, enough like her that the girl could be identified by my changed accent, my mannerisms, and other telltale changes. Children often copy other children quite unconsciously. So do adults. We are affected by the people we spend time with, in one way or another. God makes clear to us that not only is it sin to bow down to idols and worship or serve them, but that there is an effect which follows very definitely. People who worship idols become like them.