The first qualification in Burke's definition of a human--that is "the symbol-using animal"--reminds me of linguistics, in which human language in set apart from other forms of animal communication by two distinct features: "creativity and freedom from external stimuli" (the features are quoted from Victor Raskin). Creativity means that, unlike other animals, we can shape unique messages. The second feature calls to mind Behaviorist studies where an animal is conditioned to respond in a certain way to a given stimulus.