[jonahbenton]

Would be interested in studies- in cats and others- that attempt to differentiate the processing that occurs in response to human utterance, as "words" as we understand them are an abstraction that elide many subtle aspects of communication. Pitch, tone, vocalization duration and speed, mouth position, etc. So many signals there, some of which may be relevant for cats, some not.

Am sure cats are able to distinguish bird types by their voices, and other prey as well, to a much more sophisticated degree than we (our ears) can. Calling those vocalizations "words" almost certainly wrong.