"However: the human mind has the capacity to give less than full conscious attention to a given task. It is well within human capacity to give primary conscious attention to one task, secondary conscious attention levels to one or more other tasks, and subconscious attention to yet other tasks, simultaneously."
Which is why, when I have a problem, I drive my car. It seems concentrating on my driving gives my subconscious time and space to work things out.
Woo-Hoo!