What is Cognitive load?
Cognitive load is the total amount of mental effort being used in working memory at any given time. When cognitive load is high, people make more errors, take shortcuts, default to habits, and have less capacity for deliberate decision-making.
How it works
Sweller’s cognitive load theory identifies three types: intrinsic (the inherent difficulty of the material), extraneous (unnecessary difficulty created by poor design), and germane (productive effort directed at learning). Only extraneous load can and should be reduced through better design. High cognitive load impairs not just task performance but also self-regulation, making people more susceptible to biases, impulse decisions, and default options.
Applied example
A government benefits form that uses legal jargon, requires information in a non-intuitive order, and provides no progress indicator creates high extraneous cognitive load. Applicants make more errors, abandon the form more often, and are more likely to accept whatever defaults are pre-selected.
Why it matters
Cognitive load explains why simplicity in design is not a luxury but a functional requirement: every unit of unnecessary mental effort reduces the quality of decisions and increases errors.
