Just as it is possible to break down a person in order to create someone you can control (by getting them to do anything you want them to do), so it is possible to program a part of a person's mind (a dissociated part that is split off, by trauma or other means, from connection with reality). You can «teach» that part of the mind to do what you want it to do without the part of the mind that is conscious and aware knowing what's going on. Hence, people with multiple personalities report that they "lose time," whereby they don't remember where they have been or what they have been doing. Here is how a patient, repeatedly sadistically sexually abused as a child, explains it:
"Dissociation is a way of escaping the intolerable. I'm sure it happened first during the trauma itself, and was a sanity-saving way of dealing with overwhelming physical pain as well as the psychological pain of betrayal. For me it took the form of physical numbness and cold, and to this day, when I dissociate, I most often go numb. First my hands and feet go; I can't feel them, and if my eyes are closed, I have no sense of where they are in space. Then the numbness in my face starts. I can't feel my lips or cheeks. When I dissociate badly, the whole body goes and I feel and move like a block of wood… Worse than the physical dissociation is what happens mentally while the physical numbness is in place.