Actually, what you're reffering to is "thinking outside the box" — the concept which psychology and cognitive science calls "lateral thinking". This is what you are describing and it amounts to change your frame of mind and get a whole new perspective at things.
What you're calling "thinking inside the box" is what is usually reffered to as "vertical thinking".
To get a pretty good insight into these concepts and the underlying reasons/theories check
Edward de Bono's books on the subject.