cognitive psychology
Cognitive load
What is cognitive load?
The mental effort required to complete a task. Too much and people slow down, make mistakes, or quit.
Also known as: mental workload
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The demo
Two quick rounds, same question both times: which plan is cheapest? First you read it from a cluttered blurb, then from a tidy table. We time each.
Click the cheapest plan.
What this demo shows (text version)
You answer the same question twice (find the cheapest of four plans), once from a rambling paragraph and once from a clean table of the same kind of data. Almost everyone is markedly faster with the table: the information was identical, but the cluttered layout forced extra work (extraneous cognitive load) that the table removed. It is the case for clear grouping, plain language, and whitespace: they cut the mental effort a task demands.
Every bit of clutter, jargon, or poor grouping adds to the mental effort needed - and people slow down, slip up, or give up. You can’t remove the task’s inherent difficulty, but you can strip out the load you added; that’s mostly the layout’s job, not the reader’s.
Same information, same question, but the tidy version let you answer in a fraction of the time. That saved effort is lower cognitive load, and it is mostly the layout's job, not the reader's.
The load you can actually cut is the extraneous kind: clutter, jargon, bad grouping, decorative noise. The task's own difficulty you mostly cannot, so spend your effort stripping out the load you added.
Whitespace is not wasted space; it is how you lower the cost of looking. A cramped screen is not efficient, it just bills the reader for the room you saved.