What should the voting age be?

[Sasaki Kojiro]

Yes, I suppose that would be an option. Interestingly, Wikipedia shows that the age of the draft has shifted wildly over the years. The very first Selective Service Act (1917) set the age of the draft as 21 to 30, with the age shifted to 21 to 45 in 1918. In 1940, the new draft age was set at 18 to 65 (!!!), and it's wavered up and down on the lower end of the scale since 1948.

The 65 year olds must not have been for active duty...

I understand what you're saying, but I'd need to see evidence that people are more willing to change their minds as they get older. My instinct makes me think that it's the other way around. Personally, I've only voted Republican once in my entire life, and that was when I was exactly 18 years old.

Yes, the evidence part is the weak point, though it works both ways. I do recall studies showing that when people were instructed to write a short paper arguing a random point, follow up studies showed that something like 90% of them believed in the point they had defended. So it's less about minds changing as it is minds not being set. I think when people vote at 18 they have to justify that decision to themselves, and even though it is often based solely on their upbringing they will invent something and stick with that.

To expand, I think the psychological research (which is common sense really) on our reasoning ability shows that it evolved to produce arguments and to evaluate arguments of others. But often when we produce arguments we fit them to a conclusion we already have or want (confirmation bias) and when evaluating the arguments of others we refute them anyway we can. Unless we have an additional motivation for truthfulness or honesty, which is pretty scarce and weak. So fundamentally when you have people saying "I'm a republican/I'm a democrat" they will filter everything through that. And we should delay their identifying with a party until they have a better filter.