I was referring to species in general, not specific humans. The encephalization quotient[1] doesn't work quite as well for comparing primates to other primates

I was referring to species in general, not specific humans. The encephalization quotient[1] doesn't work quite as well for comparing primates to other primates either. The encephalization quotient is a fairly reliable way predict general animal intelligence. It's not just some anecdotal evidence. It's obviously not a silver bullet, because there are edge cases it doesn't consider, but the numbers it gives do give a very basic way to tell if a species may have sophisticated cognitive abilities. [1] https://en.wikipedia.org/wiki/Encephalization_quotient https://en.wikipedia.org/wiki/Encephalization_quotient