Now, in Halliday’s model, the integration of these inner and outer domains, mode of consciousness and material experience, involves the cross-classification of the distinctions made in each, and this gives rise to the four microfunctions of protolanguage.
That is, the two central (projecting) types of sensing:
cognition and desideration
intersect with the two types of material experience:
objective and intersubjective.
yielding the four microfunctions of the socio-semiotic system that is protolanguage.
You can see from the table that
the interactional microfunction involves intersubjective cognition, (‘I think + me-&-you’)
the personal microfunction involves objective cognition, (‘I think + it’)
the regulatory microfunction involves intersubjective desideration (‘I want + me-&-you’) and
the instrumental microfunction involves objective desideration, (‘I want + it’).