Maltz2015 (which study does it quote?), Kegan2016
The common misconception is that man peaks mentally at 25 and then declines. Scientists used to think that way because the brain grows with the body/bones until 25 years and then there are no structural changes in the brain (therefore, they thought, the development stops). Since then, the scientists discovered neuroplasticity and other things (todo: which?) that shows that man continues to develop mentally (Kegan2016).