Ah yes, one must remember rats are omnivorous like us, so they have no problem eating human flesh. Although I guess those sold as pets might have been conditioned not to care about that food source, or are too small and too few to take advantage of it.
I've also never gotten along particularly well with most birds. All the parrots I've known have been ornery buggers. I've met a couple non-parrots, and they seemed fairly decent, including a parakeet that would run straight at you and then tuck its head in so it could have its neck scratched.
And if you didn't scratch it properly, or for long enough, or in the right spot, he'd bite you. Crazy little nutter.
Having experience with birds (barely any with falcons), I should note a few things.
1. It's odd a bird would consider any given person a flock mate, regardless of three.
2. They have much higher sensitivity to touch, and they expect you, as a "flock mate", to be able to recognize the difference between feathers about to come out, feathers you should ignore, feathers just finished growing (still covered in chaff), and pin feathers still filled with blood and tissue...by touch.
3. The pin feathers, those still growing and those emptied of bloody tissue, itch a great deal. The bird requires other birds (or people who can do it right) to preen the tops of their heads; removing old chaff, zipping up the quills and barbs back together, then finally something akin to rubbing.
African Grays are fantastic mimics, but from what I can recall they're not really that bright. There was Griffon who learned what all the words meant, but otherwise it's just mimicry.
How many more learned African Greys are there? I never heard of Griffon. What did he/she learn?
Another sign of intelligence is the [MEMORY_LOST] test, where you are offered a choice of 3 doors (or cups) and told (truthfully) that behind one of them is a prize, behind the others, nothing. When you make a decision, the teller opens one of the other doors (picks up one of the cups) and asks you if you want to stick with your decision or switch to the other remaining door (cup). Humans tend to fail this test about 70% time, while pigeons tend to succeed about 60%. (I found this puzzle on the xkcd forums, found the research on it afterwards.)
In the above, what answer would you pick?
I take issue with quantifying it at all.
Psychology will march on without you. The scale will inevitably be changed, likely revised many times, dividing into groups and who knows what else. But you aught to start with
some measure, and we do have methods of measure for single individuals of a species. Just like humans, scores will change with time and conditions.
Or DJ's mockery, whichever you prefer.
You see, a lot of this stuff relies on unspoken consensus. It's crazy.
Science does not rely on unspoken consensus. We have our technology explosion thanks to this.
If you're looking for culling people, there are certainly many candidates, but trying to identify them involves using human judgement, that always makes mistakes, is rather foolish. Especially considering the noticeable effects of
power corruption, and the fact you wont start perfectly either...you can't even be sure it will start better than slime mold.
So, how to choose who should choose? How should the chosen choose?
An arbitrary limit isn't going to work when there are immediate consequences, especially considering people can change when useless young and 80 year olds can stay healthy and productive. So many awesome old people...