The disordered thinking of schizophrenia invariably reflects the cultural biases of the individual. Pruning, if that is a cause, must affect the filter that allows most of us to reject the thousand crazy ideas that pop into our heads each day, while permitting the few reasonable ones.
This may be why there is an environmental component. If a potential schizophrenic with an overly-pruned filter is exposed to the idea that a magical god came to earth and sacrificed himself to give us eternal life, and if that idea is presented culturally as real, it may be impossible for the schizophrenic to filter that and place it in the DMZ of fantastical-but-culturally-prevalent notions that the rest of us use.
Imagine how disordered one's thinking might become if we had no ability to interpret the spew with "a grain of salt".
The odd thing is that 'disorder' might contribute to one's ability to think 'laterally'. Some schizophrenic tend to exhibit certain amounts of clanging. In extreme instances it turns into what's referred to as 'word salad' (presumably the desire to have the alliterative sounds overwhelms one to the point where one no longer cares about conveying meaning). At the same time, a 'normal' mind definitely appreciates clanging when used as a well executed literary component (say, exhibited by Larkin or Cummings).
Schizophrenia is a real interesting mental disorder because it touches on so many other disorders (e.g. speech impediments like echolalia often seen in those on the autistic spectrum) and it's tendency to exhibit itself relatively late in life (early to mid 20s is very late for on-set as I understand it re: mental disorders).
The Post did a pretty good job conveying a complicated concept in an approachable manner to those who aren't in the field, but as always the primary source is useful, so here's the pre-print: http://www.ncbi.nlm.nih.gov/pubmed/26814963
n.b. My father is in the field and I sent this to him when I saw the mention of Eric Lander (they worked together at Whitehead before Lander left to direct Broad). He regards Lander as highly as I regard DJB. Often the media blows things up, I'd imagine these findings are fairly major within their field, if only because it survived the peer-review process into Nature.
IMO, what is most interesting about schizophrenia is complex functions with direct feedback still work. People can still move, recognize objects that they see, understand language etc. It's a problem with internal highly abstract concepts which is a fraction of what the brain does. But, at the same time that internal world can get really messed up.
Yes people with schizophrenia do exhibit specific 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.
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.
The brain and nervous system is a mixture of excitatory and inhibitory subsystems. One hypothesis is for certain mental behaviors or dsyfunctions they can be out of balance.
What causes the imbalance- genetic, geometery, chemistry, development- is the 64 billion dollar question.
This may be why there is an environmental component. If a potential schizophrenic with an overly-pruned filter is exposed to the idea that a magical god came to earth and sacrificed himself to give us eternal life, and if that idea is presented culturally as real, it may be impossible for the schizophrenic to filter that and place it in the DMZ of fantastical-but-culturally-prevalent notions that the rest of us use.
Imagine how disordered one's thinking might become if we had no ability to interpret the spew with "a grain of salt".