Disassociation is an art learned very early in the imaginative years of childhood. It is the knack for being elsewhere when there is nowhere else to be. Of escaping when there is no means of escape. And of peopling the vibrant air of our alone times with familiars and companions from worlds far beyond this one. I learned it when I was quite young. I remember a friend of my brother's questioning how I could play by myself for hours with my clay and action figures. It has carried over into my whole life, this Jedi mind trick of disappearing from the here and now into my own imagination.
Definitely handy for all categories of prisoners locked in bare cells with only the food and water deliveries as the sole recreational events of a day. Of course, in most crowded penal facilities there will actually be the one or two roommates who usually ruin introspective escape with their many annoying and interrupting restless habits.