Halliday & Matthiessen (1999: 608-9):
We prefer to conceptualise "reality construction" in terms of construing experience. This is not so much because it avoids metaphysical issues about the ultimate nature of reality — we are prepared to acknowledge a broadly materialist position; rather, we have three more specific considerations in mind.
(i) One is that what is being construed by the brain is not the environment as such, but the impact of that environment on the organism and the ongoing material and semiotic exchange between the two.
(ii) The second is that we want to emphasise the evolutionary perspective, since this allows us to start from what human beings have in common with other species rather than always insisting on our own uniqueness: when we talk of "construction of reality" it is almost impossible to avoid taking our own construction as the norm, whereas parakeets, pythons, and porpoises have very different experiences to construe — different both from each other's and from those of people.
(iii) The third point is that the concept of experience is, or can be, a collective one: experience is something that is shared by the members of the species — construed as a "collective consciousness", in Durkheim's classic formulation.