An open-access textbook of usability — the science of designing things that people can actually use. From the cognitive psychology of perception, attention and memory, through the laws and heuristics of interface design, to the methods of usability testing, evaluation, and accessibility. For designers, software engineers, clinicians, researchers, and anyone who builds things that other humans must operate.
Chapters
Foundations
- 1 Introduction: What Is Usability?
- 2 Human Perception
- 3 Memory and Cognitive Load
- 4 Attention and Decision-Making
- 5 Motor Control and Fitts's Law
Laws and Models
- 6 The Model Human Processor
- 7 GOMS and the Keystroke-Level Model
- 8 Design Heuristics and Guidelines
- 9 Design Laws from Architecture
- 10 Design Laws from Aviation and Engineering
Domains of Application
- 11 Software Usability
- 12 Healthcare Software Usability
- 13 The Built Environment
- 14 Data Visualisation
Methods
- 15 Usability Testing
- 16 Heuristic Evaluation and Expert Review
- 17 Predictive Modelling
- 18 Experimental Design and Statistics for Usability
The Future
© 2026 Dr Chris Paton. All rights reserved.