An awareness of performance loading is one element needed to be considered for good design. According to Lidwell, Holden and Butler (2003), Performance Load is defined as ‘the degree of mental and physical activity required to achieve a goal’. There are two types of performance load: cognitive load and kinematic load.
Cognitive load is the amount of mental activity required to perform a task (Wilbert, 2007, p. 85). Cognitive load theory suggests when users are bombarded with information, due to a shortage of working memory, overall usability is decreased. This results in lower than desired user performance. (Sweller, 1988). Errey, Ginns and Pitts (2006, pp. 5-6) also explain that there are two types of cognitive load: intrinsic cognitive load and extraneous cognitive load. The former is determined by the intrinsic nature of the to be learned content, while the latter is due to the instructional materials used in the presentation of information. It is optimal to minimize visual noise for reducing the cognitive load, to chunk information, to use memory aids, and to automate computation and memory intensive tasks.
Kinematic load is the degree of physical activity for achievement goal (Lidwell, Holden & Butler, 2003, p. 148). It is significant to decrease the degree of kinematic load by reducing steps needed for completion of tasks, minimizing motion and travel distances and automating repetitive tasks.
Errey, C., Gins, P., & Pitts, C. (2006). Cognitive load theory and user interface design: making software easy to use. Retrieved from http://www.ptgglobal.com/PDFArticles/Cognitive%20load%20theory%20and%20user%20interface%20design%20Part%201%20v1.0.pdf
Lidwell, W., Holden, K., & Butler, J. (2003). Aesthetic‐Usability Effect. In Universal Principles of Design (pp. 148- 149). Massachusetts: Rockport.
Seller, J. (1988). Cognitive Load Theory. Retrieved from http://www.instructionaldesign.org/theories/cognitive-load.html
Wilbert, O. G., (2007). The essential guide to user interface design: an introduction to GUI design principles and techniques. Retrieved from http://www.eblib.com.au