Since my time working in Muslim countries I've always suspected that endless brainwashing and indoctrination can actually alter the chemistry of the brain. The sensory stimuli (hearing, seeing etc.) generate electrical impulses which find their way to the brain. Here the millions of neural pathways (tracts) transport the data at the speed of light to the appropriate area(s) of the brain for processing. As I understand it these pathways are embedded early in life but can be modified later. For example the fear of dogs can become hard-wired in some people's brains from an early age but can subsequently be overcome.
I mentioned Muslims because it seemed to me that their brains quite literally would not process certain unpalatable inputs. And I'm not just talking about ignorant peasants here I'm thinking specifically about a number of highly qualified technologists with genuine PhDs from top Western universities. These were clever and able guys. But they proved incapable of handling a question such as 'do you really believe that Mohammed got onto his horse and flew up in the sky to negotiate with Allah?' I tell you that they went into melt-down. Not as in slitting my throat, more along the lines of a mental breakdown. It was an extraordinary experience.
What brings this to mind was a recent meeting with three Germans who were visiting my town. We got into discussion and I eventually brought the conversation around to Hitler, WW II and the Holocau$t™. I presented them with overwhelming evidence (if you're interested see The Holocau$t™ tag under 'Topics' on this blog's Home Page) of the mammoth fraud which had been perpetrated on the German people. Yet it was all for nought. Their brains simply could not process the data, the required neural tracts ossified and darkened as the tendentious ones bloomed and blossomed.
Hard to now what they said among themselves when we parted. But I'm not optimistic.