My Schizophrenic friend tells me the difference between schizophrenics and normal people is that normal people can hear their own thoughts whilst schizophrenics can hear other peoples.

Serious point, maybe schizophrenic symptoms are cause by a disruption in REM sleep. As in the suffers are experiencing a waking dream. Some time back they did an experiement on students and kept them awake for days-and-nights on end. Eventually they couldn't tell the difference between the dreaming and the real world.