It's up with an individual! Yes actually...
In my case, I'm (Oriental) Asian and it has something to do with our culture. Most of us love (or, need) to be "alone" (Tradition), meditating for some thoughts that really bothers us. And know what? It won't get us go "crazy"... it keeps us "mentally well" instead....
I'm most of the time, "alone", watching "a castle in the air" (Daydreaming)...
Yet, haven't felt insane (I don't remember any instance).
But of course, we need to talk, to someone or even to something if we feel we've been so silent for almost all day... (to resist bad breath)
But not necessarily, we need to talk to someone (must be a human). We can talk to "trees", animals (pets) and even to ourselves alone. But if someone darts out from nowhere and caught you doing such a thing, He would definitely think you're crazy. Which maybe awful...
If you're unable to do anything when you're alone, somewhere, try meditating... just think of anything and focus on it... maybe to some small problems, you would eventually find solutions to it...
Coz the Brain, to extreme human understanding, "is an ultimate puzzle" which can't be figured out through any means "humanly". I don't know either... I sometimes meditate about it, but I haven't got any good clue yet.