We've heard the stories: a child left mostly to himself at home because the parents are working and have practically no time to interact with him. Left by the babysitter to watch Nickelodeon the whole day while she does other household chores, the child grew up and learned to speak English as his first language, accent and all. Well and good.
Then there's the other one: a child left to himself in a household filled with dogs. The first sound that the child was able to make was a bark. Okay, this last story is anecdotal. I cannot deny nor confirm the veracity of it. But here's one story that I can.