Functions of perception / irrational functions — generate knowledge about what happens in the environment over a certain interval of time.
The perception of invariants generates knowledge about what remains unchanged in objects and processes; the perception of changes generates knowledge about what changes in objects and processes.
By extrapolating perceived invariants and changes into the future, the psyche generates a possible or probable model of a world that does not yet exist. More details: Psychic Life as a Creative Process.
See also Invariant