Psychological research is necessary to good design because we process design mentally. Psychologists study learning and cognition processes, and designers can use that research in conjunction with design principles, to craft the most effective design. In Cognitive Load Theory, Sweller asserts that “Different categories of knowledge may be acquired, organised and stored in different ways and require different instructional procedures. Understanding how we deal with different categories of knowledge is a requirement in determining which aspects of human cognition are important from an instructional design perspective” (Sweller et al., 2011, p. 3). That is, if designers understand how people learn, they can choose the optimal design method to communicate information, so that consumers will learn effectively.
Sweller, J., Ayres, P. L., Kalyuga, S., & Ebook, L. (2011). Cognitive load theory (Vol. 1). New York: Springer.