Graphic Design Ladder Model, Steven Skaggs

"...a theory of graphic design must really draw from the theoretical foundations of many fields: a ladder of theories. The first rung is occupied by the studies of the psychology of visual perception. The second rung is semiotics, the study of signs and signifying actions. The third is the study of visual rethoric, devices of persuasion. The fourth is occupied by demographics, anthropology, sociology, and other "human factors"-fields that concentrate on the behaviours and preferences of groups of people in varius situations, times and places."

1. Visual perception theory
2. Semiotics theory
3. Rhetoric.
4. Human Factors.