Yes, this sounds more like a problem with textbooks than with science itself.
Textbooks are often censored for political reasons, such as Japanese textbooks’ treatment of Nanjing, or American textbooks’ treatment of the Japanese internment camps.
This is hard science though, so this won’t suffice as an explanation. I fear that people are attached to superstitions about how the brain works. Maybe people like an inaccurately simplified explanation of the brain that claims that specific, local parts of the brain perform specific functions.
We know that fMRI research is pretty sketchy, but even smart people like Sam Harris seem to rely on it too much.
I think the overjustification effect might be at play.
In this case, the reward is status. It’s important to note that the person must anticipate the reward, though. People might explicitly seek status, but subconsciously seeking status might provide enough anticipation to create the effect.
I am taking Eliezer’s definition of “stupidity” to mean increased incompetence in the field wherein the person gained status. In their field, we would expect high competence. Decreased competence in their field would come about from diminished interest in that field, from the overjustification effect.