Textbook of Usability

Cognitive load is the amount of working memory resources required to perform a task. It is a central concept in cognitive psychology and educational design, formalised by John Sweller in the 1980s as Cognitive Load Theory.

There are three types of cognitive load:

• Intrinsic load: the inherent difficulty of the material itself
• Extraneous load: load imposed by the way the material is presented (poor design, irrelevant information, confusing layouts)
• Germane load: load that contributes to learning (mental effort spent constructing schemas)

Working memory is limited, typically to about 4±1 items for novel information. When total cognitive load exceeds this capacity, performance degrades and learning fails.

Good usability minimises extraneous cognitive load. Examples:

• Clear visual hierarchy so users don't have to search for information
• Recognition over recall (show options rather than requiring users to remember commands)
• Consistent layouts so users don't relearn each screen
• Progressive disclosure to avoid overwhelming users with everything at once