Yes people with schizophrenia do exhibit <i>specific</i> abnormalities that are a reflection of the culture, but the real environmental factors that lead to schizophrenia are things like stress, which incidentally lead to synaptic pruning.<p>I think it is better to think of this aggressive pruning idea as a general loss of computational ability. You are correct that a lot of the brain spends energy rejecting hypothesis about the world, so less computational ability would inevitably lead to less filtering and more suspect beliefs.