Your argument against killing animals fails on its own grounds. Animals kill other animals all the time, without regard to some "cognitive" scale. Is it immoral for a lion to kill a gazelle? Or a honey badger to kill a cobra? No, because honey badger don't give a fuck. Animals have no concept of morality or self-awareness nor any concept of what "intelligence" is, so therefor they do not possess even close to the same magnitude of intelligence as humans do. If there is some scale of significant intelligence that should dictate what is acceptable to kill, animals violate it all the time, and so your entire argument falls apart. If anything, a cognitive function scale would be an argument FOR humans to kill ANY other animal, because clearly any other animal is not even in the same league as humans are with regard to intelligence. In fact, I'm not so sure you can even say that animals have ANY intelligence in the same manner that humans do: I've killed a pig and had other pigs come in and happily lap up the warm blood pulsing out of the dead pig's neck, without any clue that I was going to kill him next.... that is to say, pigs are fucking stupid. When any other animal besides a human invents a cell phone or a space ship, then I might consider them to have similar cognitive abilities. Until then, I want to eat dolphin bacon at some point in my life.