Rupert Sheldrake, PhD, British biologist and researcher at Cambridge University, explains the phenomenon:

Consciousness is not, of course, all there is to the mind. Most of your activities and most of mine are unconscious; they’re habitual. The vast majority of what we do is unconscious habit. So consciousness is concerned with only a tiny part of our psychic life. It’s largely concerned with making choices. It’s largely concerned with considering alternative possibilities.