Halliday & Matthiessen (1999: 189):
The most prominent reflex of the conscious/non-conscious distinction in English is that it is built into the system of pronouns:
This distinction is all-pervasive, since third-person pronouns provide one of the main resources for constructing discourse through anaphora. The boundary between conscious and non-conscious, of course, is fluid and negotiable: different systems, and different speakers (or the same speaker on different occasions), may draw it in different places. But the guiding principle is that 'conscious' means prototypically adult human and may be extended outwards (a) to babies, (b) to pets, and (c) to higher animals — as well as by rhetorical strategies of various kinds.
Blogger Comments:
To be clear, less anthropocentrically, the grammar construes anything with a nervous system and sense organs as the medium of a mental process of perception, and thus as conscious. That is, the clause the ant saw the worm construes the ant as conscious.