[themitigating]

I'll bite

- the ability to explain why you think a certain way or did something (i.e. when you ask a child why they threw a glass they'll say "I don't know"

- the speed at which you learn/process new information

- the ability to understand your emotions and the level of control you have over them

- your willing to engage in debate

- how inquisitive you are

[fragmede]

In addition to "I don't know" is "I messed up". Everyone does stupid things occasionally. Stupid people double down on their stupidity once they realize what happened instead of owning up to it.

[brazzledazzle]

There's some nuance there though. Doubling down is (almost) always a stupid move but it isn't always stupid people that do it. It's rooted in insecurity which is independent of intelligence.