[king07828]

Rights can already taken away from people who are declared legally incompetent [1]. Similar procedures could be used to give rights to monkeys that can prove mental competence (e.g., are able to meaningfully communicate and show an understanding of money and property).

[1] https://www.law.cornell.edu/wex/incompetence#content

[newsbinator]

The default is for humans to have rights, and in extreme cases those rights can be taken away.

It's very, very rare for a human to have to prove mental competence for any reason. We let mentally incompetent people grocery shop and drive cars and vote, knowing full well they're a danger (or at least not a net benefit). Every town in every country contains well-known incompetent citizens.

What's the default for intelligent non-humans?

Does each one have to prove mental competence? At what level: that of an average human, or that of the lowest competent human?

Is the default to assume they are competent, and have all the rights and privileges of a human, or is the default to assume they aren't competent and don't have those rights?

Personally, it makes sense to me to err on the side of "any being who tells me plainly that they want a vote gets to vote".