  Such similarity arguments are, of course, inherently limited in that it is always open to critics to exploit some disanalogy between animals and humans to argue that the similarities don't entail the conclusion that both are sentient. Even when bolstered by evolutionary considerations of continuity between the species, the arguments are vulnerable, for the mere fact that humans have a trait does not entail that our closest relatives must have that trait too. There is no inconsistency with evolutionary continuity to maintain that only humans have the capacity to learn to play chess. Likewise for consciousness. Povinelli &amp; Giambrone (2000) also argue that the argument from analogy fails because superficial observation of quite similar behaviors even in closely related species does not guarantee that the underlying cognitive principles are the same, a point that Povinelli believes is demonstrated by his research into how chimpanzees use cues to track visual attention (Povinelli 1996). 