Thanks to Tyler Cowan for the link to this about the self-awareness on-off switch:
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.
The team conducted a series of experiments to pinpoint the brain activity associated with introspection and that linked to sensory function. They found that the brain assumes a robotic functionality when it has to concentrate all its efforts on a difficult, timed task – only becoming "human" again when it has the luxury of time.
....“The regions of the brain involved in introspection and sensory perception are completely segregated, although well connected,” says [Ilan] Goldberg, “and when the brain needs to divert all its resources to carry out a difficult task, the self-related cortex is inhibited.”
The brain’s ability to “switch off” the self may have evolved as a protective mechanism, he suggests. “If there is a sudden danger, such as the appearance of a snake, it is not helpful to stand around wondering how one feels about the situation,” Goldberg points out.