Performance load, the concept discussed in the document by Lidwell, Holden & Butler is the visual printable of balancing how much content there is with how complex the task is. Essentially designers have to ask how to create user friendly content that that is not performance exhaustive and ultimately ineffective for users.
There are two types of performance load. The first of these, Cognitive load is the amount of mental activity, i.e. the use of perception, memory and problem solving parts of the brain. Too much cognitive load and users become frustrated and tired and ultimately don’t want to continue using the product. An example of this is menus in websites. Smartly designed websites successfully guide users without dumbing it down, but engages enough cognitive functions to be effective (Mobley, 2014).
Kinematic load is how much physical effort is required to use a product. This could vary from pressing buttons, hauling gear and mechanical complexity. This type of load must be minimalized as much as possible, but enviable when it comes to using products (Lidwell, Holden & Butler, 2003). Smart design must recognise how much Kinematic load is necessary and when it is too much. If the products design is needlessly complex, or does it excite or emotionally connect with users, it will fail to manage kinematic load effectively.
At the end of the day, when your product and design is visually distracting, cognitively stressful and ultimately exhausting for the user, the design is a failure. Minimalizing performance load should and must be a staple of good product design (Weller, Ayres, Kalyuga, 2011).
To reduce performance load within the context of websites and digital, consider chunking text, minimal menus and other design decisions. Making your content/document accessible should be a considered a top priority (Brunken, Plass & Leutner, 2003).
Sources
Brunken, R., Plass J., L. & Leutner, D. (2003) Direct Measurement of Cognitive Load in Multimedia Learning, Educational Psychologist, 38:1, 53-61, DOI: 10.1207/ S15326985EP3801_7
Eric W. Mobley (2014) The Principles of Performance by Design. Retrieved from https://medium.com/@eric_mobley/the-principals-of-performance-by-design-32d0a5306bbe#.vxxe3o6ji
Greene, J. D., Morelli, S. A., Lowenberg, K., Nystrom, L. E., & Cohen, J. D. (2008). Cognitive load selectively interferes with utilitarian moral judgment. Cognition, 107(3), 1144-1154. doi:10.1016/j.cognition.2007.11.004
Lidwell, W., Holden, K., & Butler, J. (2003). Performance Load. In Universal Principles of Design (pp.148‐149). Massachusetts: Rockport.
Sweller, J., Ayres, P. L., Kalyuga, S. (2011). Cognitive load theory (1st ed.). New York: Springer.
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