In Marie Curie's biography, her daughter recalls how focused her mother could be. When she was a child, she would be so intent on her reading that her siblings could build stacks of chairs around her - all unnoticed.
After a rousing few rounds of Mau with Barnacle Boy and some of his friends, I retired to my study to read for a while. Fluffy came up, but for once did not want to sleep on whatever I was working with. I kept reading (William Barry's Letting God Come Close). Suddenly the Boy is at the door, camera in hand. "Is the cat in here?" he demanded. "She was." "Did she have the mouse with her?" "The mouse??"
I hadn't noticed. At all.