The start of the article loses me immediately.
The voting age wasn’t lowered due to psychologists: it was lowered due to the draft. Asking people to fight at the age of 18, regardless, meant that they should have a vote in what they were fighting for.
Wireplay is correct. If you’re old enough to fight and die for your country you should be allowed to vote.
That's the way it was sold. But the fact is that while being 18 means you can hold a gun and shoot it where you are told, it does not follow that you have the capability to judge what should be shot at.
Btw, the draft ended about that same time, but the voting age was lowered anyway. Which tells me that this selling point was just that, and not the real reason.