As long as you make new neural connections your brain is going to grow[0]. An anecdotal fact which I heard many years ago was that adding a new perspective to look at something is like increasing your IQ by 10-20 points. Simply reading a lot of text within your comfort zone is not going to increase your mental capacity.
> An anecdotal fact which I heard many years ago was that adding a new perspective to look at something is like increasing your IQ by 10-20 points
I'd be skeptical about that. A few years ago there was this craze about increasing working memory and thus IQ using the dual-n-back game (advertised as the only game that has transference to unrelated tasks). Turned out to be a placebo. People have been dreaming about increasing their IQs and from time to time fall to various fads. Until there is strong scientific evidence, these 'IQ boosters' should not be taken seriously.
I wonder if learning to play music later in life has similar effects. I have read that music, if learned young in life — by age 12 or so, actually produces physical changes in the brain.
That's the first thing I wondered as well since I'm currently trying (and mostly failing) to learn how to play my guitar.
I also wonder what the limits to learning are. At some point, if I learn something new, does pushing that knowledge into my long-term store replace or weaken an existing memory?
I think of it as a time-decay function. There are only so many attentive, focused hours one can give during a day, and a memory only lasts so long before it decays from disuse. Some amount of area under this curve represents what a person can functionally retain. It isn't a fixed amount, as more connections between subjects tends to reinforce both, but there is a limit.
> 1) Neurogenesis halts in your early 20s. After that, no new neurons for you, sorry. Although the connections may change.
This statement as written is almost total nonsense. A cursory internet search yields abundant studies on adult neurogenesis. Even small amounts of cardiovascular exercise increase brain volume, stimulate neural growth, and create synaptic connections in adults well into old age.
At best, one could claim that neuron growth slows as we age, but it absolutely doesn't halt.
And yet when Arturo Alvarez-Buylla and his team of researchers actually searched for physical evidence of young neurons in adult brains, they found... nothing: https://www.nature.com/articles/nature25975
The studies which came before may be based on nonprimate animal models in which adult neurogenesis does occur. But the best evidence we have to date suggests that adult humans do not grow new neurons.
[0]https://www.ted.com/talks/sebastian_seung