Cognition refers to the mental processes by which we perceive, understand, memorize, and make decisions. In design, it introduces a major constraint: our attention and working memory capacities are strictly limited.

George Miller quantified this back in 1956: our working memory holds only about seven items at a time, "the magical number seven, plus or minus two." John Sweller built upon this to develop the cognitive load theory (1988): any superfluous mental effort—such as obscure labeling, unnecessary steps, or poorly structured choices—consumes a scarce resource and degrades performance. Steve Krug summarized this beautifully for the web with a title that became a golden rule: "Don't Make Me Think."

The natural inclination of great design is therefore to offload: simplify, group, hide what is not currently needed, and make the obvious blatantly obvious. Yet, there is a nuance that apostles of simplicity often overlook: not all difficulty is bad. Learning research refers to "desirable difficulty"—the exact effort that fosters understanding and long-term retention. A tool that is too seamless can hinder learning, treat users like children, or conceal a complexity that should instead be elegantly revealed. Lightening the cognitive load? Absolutely. Switching off the mind? Never.

Our core principle is one of simplexity: eliminating superficial effort while preserving meaningful engagement. We ruthlessly hunt down parasitic cognitive load without ever confusing simplicity with impoverishment. Making things beautifully simple does not mean making people passive.

What is at play elsewhere: attention, usability, cognitive biases, information design, and affordance.

References: G. Miller, "the magical number seven" (1956); J. Sweller, cognitive load (1988); S. Krug, Don't Make Me Think (2000).