I'd have thought by now that most people would understand that you can grow your intelligence. But no, the notion is still a shock to the system. As one acquaintance put it succinctly: "That can't possibly be true." He got riled up about it, but I suspect that's merely a bit stronger than what 99% of the adult population believes. In fact, check it out (or check yourself out). Most people still believe that a person is born smart, average or dumb--and stays that way for life.
Research over the past twenty years has shown beyond a doubt that the brain is more like a muscle. It gets stronger, a lot stronger, when you learn--and keep learning. Use it or lose it.
David Brooks pulled all this together in a fascinating column on human nature in which he summarizes the developmental issues, pushing back on over-zealous evolutionary psychology and innate beliefs. I quote the article:
The first problem is that far from being preprogrammed with a series of hardwired mental modules, as the E.P. types assert, our brains are fluid and plastic. We’re learning that evolution can be a more rapid process than we thought. It doesn’t take hundreds of thousands of years to produce genetic alterations...