>Conclusion: No Evidence

>So to sum up: people have claimed that hydrocephalus destroys most of the brain yet having only a fraction of the brain is consistent with normal or above-average intelligence, and may even increase it. This is extremely implausible based on everything we know about intelligence and evolution and population distributions and is a bad description of what hydrocephalus does (conflating distribution & volume with brain matter). On average, hydrocephalus and similar things like hemispherectomy do (as expected) induce many deficits ranging from mild to severe, which can be accommodated to some degree by neural plasticity, individual differences, extensive environmental interventions, and freedom from natural selection . Claims to the contrary, aside from failing to deal with the many objections that this is implausible, turn out to be based on undocumented, fraudulent, or misleadingly described cases, and primarily pushed by cranks. Ultimately, hydrocephalus does not appear to present any particular challenge to the standard understanding of intelligence as being caused by a material brain whose efficiency at cognitive tasks is driven by neuron count, wiring patterns, neural integrity, and general health: not only is the evidence extraordinarily inadequate to justify the extraordinary claims made by some authors, it is unclear how much, if any, evidence there at all.

The thing about this "counter-argument" is it's conflating a basic point - some people, maybe only a few, are able to exhibit normal human intelligence with a much reduced brain size - with a host of apparently idiotic position people have taken in response to this situation. But of course dismissing the basic on this basis is fallacious.