The linguistic domain as a domain of orienting behavior requires at least two interacting organisms with comparable domains of interactions, so that a cooperative system of consensual interactions may be developed in which the emerging conduct of the two organisms is relevant for both. The specifiability through learning of the orienting interactions allows for a purely consensual (cultural) evolution in this domain, without it necessarily involving any further evolution of the nervous system; for this reason the linguistic domain in general, and the domain of self-consciousness in particular, are, in principle, independent of the biological substratum that generates them.

p. 43. - Biology of Cognition (1970)