A lot of what we hear during elections is propaganda. We could guess that defences against it increase throughout life until senility. 16 years olds in particular still tend to live in the small cults that are nuclear families and thus lack an independence of thought. I wasn't qualified to vote until I was 30, and that's a level unachieved by a lot of people I know.
On the other hand, 0-17 year olds are completely unrepresented, yet have longer to live in the world. There's no solution to that, so there's a compromise between representation vs political understanding.
Male adolescents develop emotional maturity much slower than females. If this affects political judgement, then it's rational to allow women to vote at a lower age. I doubt this will be a popular view amongst the oft-male and sometimes alt-right Slashdotters.
Studies show that 16-17 year olds vote more than 18-25 year olds. Likelihood of voting increases from 18 onwards, causing yet more disparate representation -- a problem of all voting systems. Intergenerational differences increasingly come into play. People 60 and over become a minority in the adult world and seemingly retreat from social consciousness or other newer ideas. However, they vote more.
The study doesn't mention lowering the voting age at all, by the way.