This article in the New Scientist finds self absorbtion disappears when concentrating on a task.

Everybody has experienced a sense of “losing oneself” in an activity – being totally absorbed in a task, a movie or sex. Now researchers have caught the brain in the act.

Self-awareness, regarded as a key element of being human, is switched off when the brain needs to concentrate hard on a tricky task, found the neurobiologists from the Weizmann Institute of Science in Rehovot, Israel.