Textbook of Usability

Bounded rationality, a concept introduced by Herbert Simon in 1956, describes the reality that human decision-making is rational but constrained — by limited time, incomplete information, and finite cognitive capacity. Rather than optimising over all possible options (which real decision-makers can never do), people apply heuristics and shortcuts that produce adequate decisions under constraints.

Simon contrasted bounded rationality with the "rational actor" of classical economics — an idealised agent with unlimited information and unlimited processing power. Real people don't work that way. They make decisions the best they can with what they have.

Key implications:

• Satisficing (choosing the first option meeting a threshold) rather than optimising
• Heuristics and biases that trade accuracy for efficiency
• Use of defaults to avoid decision effort
• Reliance on recognition over recall
• Attention to salient cues rather than comprehensive analysis

Bounded rationality is the theoretical foundation for much of usability research. Interfaces are designed for bounded agents, not idealised optimisers. The Model Human Processor, Hick's Law, cognitive load theory, and the heuristics-and-biases literature all build on the recognition that human cognition has real limits that good design must accommodate.

Herbert Simon received the Nobel Prize in Economics in 1978, partly for this work. The concept has influenced economics, psychology, computer science, and design — and remains one of the most important ideas underlying the scientific approach to usability.