Donald A. Norman
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Don Norman is the author of numerous books including "Emotional Design," and more recently, "Living with Complexity." He is co-founder of the Nielsen Norman group, a professor at KAIST (in Korea), and IDEO fellow, and a design theorist, studying the fundamentals of modern design.
Donald A. Norman has a Bachelor of Science in Electrical Engineering from MIT and a Doctor of Philosophy in Psychology from the University of Pennsylvania. He also holds a honorary degree from the University of Padua, Italy. He has been a professor of Computer Science (at Northwestern University), Psychology and Cognitive Science (at University of California, San Diego). He has also worked for Apple Computer at Apple's Advanced Technology Group and for Hewlett-Packard. He now collaborates with Jakob Nielsen and Bruce "Tog" Tognazzini in the Nielsen Norman Group
Recently Norman received the the 2006 recipient of the Benjamin Franklin Medal in Computer and Cognitive Science.
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Norman, Donald A. (2007): Gavriel Salvendy (Ed.): Handbook of human factors and ergonomics (3rd edn.). In Universal Access in the Information Society, 5 (4) pp. 421. http://dx.doi.org/10.1007/s10209-007-0068-x
Norman, Donald A. (2007): A Review of: \"Handbook of Human Factors and Ergonomics\" by Salvendy, G.. In International Journal of Human-Computer Interaction, 23 (1) pp. 189-190. http://www.leaonline.com/doi/abs/10.1080/10447310701360813
Norman, Donald A. (2006): Interaction design is still an art form.: ergonomics is real engineering. In Interactions, 13 (1) pp. 45-60.
Norman, Donald A. (2006): Emotionally centered design. In Interactions, 13 (3) pp. 53-ff.
Norman, Donald A. (2006): Logic versus usage: the case for activity-centered design. In Interactions, 13 (6) pp. 45-ff.
Norman, Donald A. (2006): Words matter. talk about people: not customers, not consumers, not users. In Interactions, 13 (5) pp. 49-63.
Norman, Donald A. (2006): Why doing user observations first is wrong. In Interactions, 13 (4) pp. 50-ff.
Norman, Donald A. (2006): Trapped in a Lufthansa airline seat. In Interactions, 13 (2) pp. 41-ff.
Norman, Donald A. (2005): Robots in the home: what might they do?. In Interactions, 12 (2) pp. 65.
Norman, Donald A. (2005): Whose profession is this?: everybody\'s, nobody\'s. In Interactions, 12 (3) pp. 51.
Norman, Donald A. (2005): Human-centered design considered harmful. In Interactions, 12 (4) pp. 14-19.
Norman, Donald A. (2005): Do companies fail because their technology is unusable?. In Interactions, 12 (4) pp. 69.
Norman, Donald A. (2005): To school or not to school?. In Interactions, 12 (5) pp. 51.
Norman, Donald A. (2005): There\'s an automobile in HCI\'s future. In Interactions, 12 (6) pp. 45-ff.
Norman, Donald A. (2004): Introduction to This Special Section on Beauty, Goodness, and Usability. In Human-Computer Interaction, 19 (4) pp. 311-318. http://www.leaonline.com/doi/abs/10.1207/s15327051hci1904_1
Norman, Donald A. (2002): Home Theater: Not Ready for Prime Time. In IEEE Computer, 35 (6) pp. 100-102. http://csdl.computer.org/comp/mags/co/2002/06/r6100abs.htm
Norman, Donald A. (2002): Complexity versus difficulty: where should the intelligence be?. In: Gil, Yolanda, Leake, David (eds.) International Conference on Intelligent User Interfaces 2002 January 13-16, 2002, San Francisco, California, USA. pp. 4. http://doi.acm.org/10.1145/502716.502720
Norman, Donald A. (2002): Emotion & design: attractive things work better. In Interactions, 9 (4) pp. 36-42.
Norman, Donald A. (1999): Affordances, Conventions, and Design. In Interactions, 6 (3) pp. 38-41.
Norman, Donald A. (1994): How Might People Interact with Agents. In Communications of the ACM, 37 (7) pp. 68-71.
Norman, Donald A. (1994): Trends in the Computer Industry: Life-Long Subscriptions, Magical Cures, and Profits Along. In: Szekely, Pedro (eds.) Proceedings of the 7th annual ACM symposium on User interface software and technology November 02 - 04, 1994, Marina del Rey, California, United States. pp. 193. http://www.acm.org/pubs/articles/proceedings/uist/192426/p193-norman/p193-norman.pdf
Norman, Donald A. (1993): Cognition in the Head and in the World: An Introduction to the Special Issue on Situated A. In Cognitive Science, 17 (1) pp. 1-6.
Marcus, Aaron, Norman, Donald A., Rucker, Rudy, Sterling, Bruce, Vinge, Vernor (1992): Sci-Fi at CHI: Cyberpunk Novelists Predict Future User Interfaces. In: Bauersfeld, Penny, Bennett, John, Lynch, Gene (eds.) Proceedings of the ACM CHI 92 Human Factors in Computing Systems Conference June 3-7, 1992, Monterey, California. pp. 435-437. http://www.acm.org/pubs/articles/proceedings/chi/142750/p435-marcus/p435-marcus.pdf
Norman, Donald A. (1992): Where Human Factors Fails: Ergonomics versus the World of Design and Manufacture. In: Proceedings of the Human Factors Society 36th Annual Meeting , 1992, .
Norman, Donald A. (1991): Collaborative Computing: Collaboration First, Computing Second. In Communications of the ACM, 34 (12) pp. 88-90.
Norman, Donald A. (1984): Stages and Levels in Human-Machine Interaction. In International Journal of Man-Machine Studies, 21 (4) pp. 365-375.
Draper, Steven, Norman, Donald A. (1984): Software engineering for user interfaces. In: Proceedings of the 7th International Conference on Software Engineering , 1984, Silver Spring, MD. pp. 214-220.
Norman, Donald A. (1984): Four Stages of User Activities. In: Shackel, Brian (eds.) INTERACT 84 - 1st IFIP International Conference on Human-Computer Interaction September 4-7, 1984, London, UK. pp. 507-511.
Norman, Donald A. (1983): Design Principles for Human-Computer Interfaces. In: Smith, Raoul N., Pew, Richard W., Janda, Ann (eds.) Proceedings of the ACM CHI 83 Human Factors in Computing Systems Conferenc December 12-15, 1983, Boston, Massachusetts, United States. pp. 1-10.
Norman, Donald A. (1983): Design Rules Based on Analyses of Human Error. In Communications of the ACM, 26 (4) pp. 254-258.
Norman, Donald A. (1982): Steps Toward a Cognitive Engineering: Design Rules Based on Analyses of Human Error. In: Nichols, Jean A., Schneider, Michael L. (eds.) Proceedings of the SIGCHI conference on Human factors in computing systems March 15-17, 1982, Gaithersburg, Maryland, United States. pp. 378-382.
Norman, Donald A., Shallice, Tim (1980). Attention to action: Willed and automatic control of behaviour. Centre for Human Informati. Centre for Human Information Processing, University of California, San Diego, CA, USA
Norman, Donald A. (1980): Twelve Issues for Cognitive Science. In Cognitive Science, 4 (0) pp. 1-32.
11.10 Commentary by Donald A. Norman
It is clear that our understanding of the nature of interaction has been evolving in a practical sense, in terms of our scientific understanding, and in terms of the underlying philosophy. Dag Svanaes has done an excellent job of describing the changes in philosophical approaches to the study of interaction that have occurred in the last few decades. But the review feels as if it stopped at the end of the 20th century, but today we are well into the 21st century. So the changes described in the article have continued: we are still evolving our understanding, still making progress.
From my point of view, the study of interaction is far ranging, including all the ways by which we interact with the environment. As Svanaes points out, interaction means the interplay between the state of the environment and the actions of agents (which are usually people), where the actions change the state of the world. Interaction can be accidental or purposeful, goal-directed or deliberately non-intentional.
Although the definition provided by Svanaes is appropriately broad, the chapter and its examples are surprisingly limited to discussions of the way by which individuals interact with information systems. The chapter primarily reflects single individuals interacting with computational systems. Pity: interaction is far broader. Interaction designers must deal with groups of people, sometimes separated by time and or distance, with non-computational objects and with the natural world. Designers who are designing services, rules, and procedures must be concerned with how systems and services interact with employees, technical staff, and of course customers and others who make use of the services. Some interaction designers have to be concerned with interactions among machines. The principles of interaction design are far more important to be limited to single individuals interacting with information systems and displays.
Interaction design is critically important for lots of non-computer systems. Thus, skis are a tool for interaction, as are baseball and cricket bats, the rules of engagement of soccer (football), and the way by which we steer and control our automobiles. Interaction designers must work with a wide variety of technologies, not just those of information and computer systems.
Our philosophical basis for the understanding of interaction has been evolving rather dramatically. As Svanaes points out, in the early days of personal computers, which is where interaction design started, we took a strict, internal-processing, information processing point of view to describe the system and to develop rules for designers. This approach has been seminal in teaching us about affordances (and what I now call “signifiers”), conceptual models, and the role of feedback, appropriate mapping, and all the many other formal, theoretical principles that have resulted from these studies. However, this approach is also very narrow, limiting, and now widely considered either to be too restrictive or, by some, simply wrong.
Today, our understanding of human cognition is undergoing major changes. We no longer look at pure information processing. Instead, we know that emotion and cognition interact in fundamental ways, that the entire human body interacts with the environment, and that as a result we must come to understand the whole system. It is not enough to use limited input and output mechanism. Hence, the development of mobile systems that are location, position, and orientation sensitive, where the entire body is involved, where the gestures, posture, and movements of the entire body are taken as inputs to our systems and where the results are not simply changes in some image on a screen, but changes that envelop the body, surrounding it with sights, sounds, and feelings, exciting the entire panoply of sensory systems. Haptics and gestures are missing from this article as are simulators that move in space to engage the proprioceptive systems. Three-dimensional sound is as important as three-dimensional sight. Haptics is increasingly important.
The review of affordances in the article needs to be expanded. Affordances are about possibilities: an affordance is a relationship between a person and the environment. But it is not affordances that are critical to interaction, it is our perception of those affordances. After all, an affordance that is not known about might as well not exist. To make this distinction more clear, in my recent work I call the perceptual signal of an affordance a “signifier.” (D. A. Norman, 2011: Living with Complexity. MIT Press.) Signifiers are the clues for people about possible actions, hence possible interactions.
I don’t know where Svanaes got the notion that the popular view of information processing in HCI is that it “sees perception as sense data being passively received by the brain.” (In his section on Merleau-Ponty). The notion that perception is an active, constructive process is an old one in psychological theories and it is certainly dominant today. We don’t follow Merleau-Ponty: we follow where the data have taken us. But Gibson, for example, was a strong advocate of the active nature of exception, and that was 50 years ago.
The view of HCI and of cognitive science held by Svanaes seems rooted in the last century.
Today, we study interaction as a fundamental property of human and social behavior, rooted in the entire body, where the person – or people – is inside a sensory field that is rich in information. All the senses are involved, not just the visual sense that is the focus of this chapter: haptics, proprioception, smell, sight, and sound. That is why the development of rich sensors and novel haptics are so encouraging. This is why we have surround sound, motor and solenoid-driven hairs and other objects to grasp, fondle, and manipulate. This is why medical simulators involve the entire body, allowing the novice surgeon to put the hand inside the simulated body, feeling the beating heart, the throbbing veins, and the different pressures and feelings associated with cutting through different layers of skin. Interaction today is a rich, vibrant filed.
Some of these topics are still in their infancy, so the definitive articles within this Encyclopaedia will have to wait a few years. I am disappointed, however, that these new developments and approaches are not discussed within the article – they aren’t even hinted at. So stay tuned for further news.
Norman, Donald A. (-0001). Human-Centred Design Considered Harmful. Retrieved 2014-01-19 00:00:00 from http://www.jnd.org/dn.mss/human-centered_desig.html
Norman, Donald A. (-0001). Logic Versus Usage: The Case for Activity-Centred Design. Retrieved 2014-01-19 00:00:00 from http://www.jnd.org/dn.mss/logic_versus_usage_.html
Ortony, Andrew, Norman, Donald A., Revelle, William (2005): The role of affect and proto-affect in effective functioning. In: "Who Needs Emotions?: The Brain Meets the Robot (Series in Affective Science)" Oxford University Press .
Norman, Donald A. (2004). Design as communication. Retrieved 2012-03-19 00:00:00 from http://jnd.org/dn.mss/design_as_communication.html
17.8 Commentary by Donald A. Norman
Anyone who cares about innovation must read Clay Christensen. Why? Let me start with some history.
I first encountered Christensen's works when I was at HP, in 1997. His first book was still in manuscript form and was widely circulated among a small group of enthusiastic managers. I got a copy and also fell in love. Most importantly, it precisely described the situation we were in at HP: we had several disruptive products in the pipeline, but the executives at HP were incredibly risk aversive, so they shunned them, or in some cases, required them to be so watered down and deprived of resources for proper development, that they became self-fulfilling prophecies for the executives: they were doomed to fail.
We even brought Christensen to HP. I remember well a talk he gave which covered our situation precisely. The reception by the audience was wonderful: the reception by HP executives was dismal. Afterwards a few of us gathered around him and told him that we were case studies of the kinds of failure he was describing.
When I wrote my book "The Invisible Computer," I used Christensen's work as a starting point for my discussion of the book's subtitle: "Why good products can fail." I modified his basic graph (see Figure 1 of Christensen's article) to reframe the point in design terms. The result, shown here, as my Figure 1, should be self-explanatory.
My book was about the way new products get adopted by the market. The standard view, that market acceptance starts with early adopters and then, slowly, brings in late adopters, was first formulated in 1962 by the Stanford professor Everett Rogers (1995) and then publicized in Geoffrey Moore's book "Crossing the Chasm" (Moore, 1995: alas, in this book Moore failed to give credit to Rogers, an omission he corrected in his next book). These two groups of adopters are very different. Indeed, Moore argued that they were separated by a chasm that could only be bridged by a better product and different marketing. I often describe the difference by stating that for early adopters, the technological promise suffices. For late adopters, human-centered design is essential, for these people don't want promises, they want easy to understand, effective, enjoyable products. I realized that this view of the product acceptance cycle could be combined with Christensen's insights of the relationship of technological capabilities to customer needs: Figure 2.
Since the publication of his first book, Christensen has continued to expand and elaborate upon his ideas of product disruption. In the original formulation of his model, including my adaption, the line that depicts "required performance" is horizontal. But as Christensen points out in his article for this encyclopedia, the level should differ for different people and different applications, and so in his later work he has reminded readers that the line is simply the average of the user base. More importantly, he points out that the line should not be horizontal. After all, with the passage of time and the acceptance of the technology, people's needs change, becoming more sophisticated and requiring more performance. At the least, therefore, the line must slope upwards, so that with the passage of time, more is required than in the early stages. Companies try to accommodate this changing need through the addition of extra features, more powerful processors, and more powerful everything, from processors, to motors, to whatever variables are of interest. These additions and minor modifications of Christensen's model do not change the basic thrust.
Christensen has also greatly strengthened this model by adding a new dimension: market. In the original model depicted by Figure 1, product performance is plotted against time. In this two-dimensional model, the only enhancements relevant are price and performance. Here, disruptive innovation always occurs at the low end of performance: new entrants to the market provide less performance, but a very low cost, thus satisfying the needs of people who do not require the ever-expanding capabilities of the main products.
The modified model recognizes that disruption can occur by changing the market population, serving people who would never would have even considered the product. Hence the third dimension: market. Want an example? Consider the first home computers, for example the Apple II. These were puny devices, no match in quality for the computers then in use in universities and companies. They offered no challenge to the makers of these machines, which meant their makers could safely ignore them. But individuals and students could never have purchased any of the large, complex, and expensive computers that were then being sold to industry. As a result, the Apple II opened up an entire new market of customers: individuals bought them and fell in love with their capabilities, even if they were very limited and of low quality. Eventually, these weak, puny home computers took over the home market while slowly expanding their capabilities. Eventually, they became today's powerful machines that now dominate in home, business, education, and entertainment.
I can attest to this issue, for when I first experienced the Apple II computer, I wondered why anyone would ever buy one. To me, it was a huge step backwards from the laboratory machine I was using all day at the University. A year or two later I surprised myself by buying one for my family, and years after that, I left the university and went to work for Apple. (A truly disruptive technology.) These early machines opened up an entire new marketplace for people who would never have thought of purchasing an IBM office computer or a DEC machine (Digital Equipment Corporation, later known as Digital), the two companies that then dominated the world of computers. Over time, of course, the home computer took over the world. DEC no longer exists. SUN no longer exists. Silicon Graphics no longer exists. And IBM has gotten out of the personal computer business.
So, the modified model has two ways by which disruptive influence can take place: low-end disruption or market disruption.
Note that it would be a mistake to equate these arguments with different kinds of innovative forces: these are not the same as incremental or radical disruption, as Christensen points out.
17.8.1 The theory is easy to understand: the practice is extremely difficult
It is really easy to understand the message that Christensen presents. It is really difficult to execute upon that message. Why?
Consider the story of Eastman Kodak. Long the world's leader in photography, it has faltered. What happened it was disrupted by the rise of digital photography. Why? Didn't they see it coming? No, they missed the early signs because their customers all wanted high quality films that delivered high quality images: digital could not even come close to competing.
Kodak made cameras, but its real income was derived from film and chemicals. Serious amateurs and professionals all preferred film. Radiologists explained at great length why only film X-Rays could deliver the depth of contrast and resolution they demanded. Professional photographers said the same thing. The customers drove the old industry.
Kodak knew about digital technology. Their researchers were working on it. They had produced one of the first digital cameras (a joint project with Apple). And they even hired as CEO someone from HP who was a champion of digital photography. But it was too late. Moreover the strength of the company was in analog technology, in imaging, in film, and in chemistry. Imaging was still relevant: the rest was much less relevant.
And the customers were correct. The early digital cameras were inferior. I am fond of giving talks about my failures. One of the first projects I watched when I joined Apple was a failure. It was an exciting, well-done product, but it failed in the marketplace. What was it? A digital camera (the joint project with Kodak). Why did it fail? See Figure 1. It was far to the left. Basically, products that are too early will fail. The customers aren't ready and the technology is not good enough. Our camera did not have a display screen (they were too expensive then), it took low-resolution photos, and it could only hold a few of them. It was difficult to transfer the photos to a PC and then difficult to work with them. Inexpensive ink-jet printers did not exist, so there was no way to print them in color.
Apple withdrew the camera from the market. Too bad: had Apple stuck to it, it would have been the leader in digital photography instead of the poor humble company that it is now. (Self protection: that last sentence is meant as a joke.)
When you are a historian looking back, it is easy to see the disruptive technology and wonder why the existing companies do not jump on them. When you are inside the companies, it is very difficult to see. Inside the company it looks like yet another one of those hair-brained research projects by those impractical researchers that is completely impractical.
I can give other examples from my own experience. I, and my co-workers at both Apple and HP, would sometimes identify new ideas and emerging products as disruptive forces that would change the industry, only to discover that they didn't, either because they were simply the wrong idea or, in the case of some things (such as the digital camera), it was simply premature. Another example would be or Apple's Newton, which, if you never heard of it, simply proves my point. Newton contained many of the innovations that today are commonplace in our smart phones, but it died after a very public, very humiliating life experience.
Similarly, my co-workers and I dismissed radical new products as irrelevant, such as my early dismissal of the personal computer or Apple's dismissal of the first browser (a long story, to be told some other time). The view of a company from the perspective of an academic scholar, looking back in time over the historical record is very different from the view of the company itself. For that matter, the view is from different from the executive suite than from that seen by the middle managers, or individual contributors. The view from the company's research laboratories is different once again. And finally, the view from the member of a small, just-funded startup company is yet again very different. The large company is biased not to see disruptions: the startup is biased not to see hurdles that might prevent them from causing an immense disruption.
Christensen's analyses are important and influential. I, myself, find them very compelling. But they are very difficult to apply. After reading Christensen's chapter I thought about each of the nine companies I am currently advising, attempting to see how the information in the chapter would be relevant. Some are small startups, but others are larger, including at least one of the largest companies in the world. In every single case I concluded that the company was different and didn't fit the mold. This was true even for the several companies that believe they are about to cause a major upheaval in product space. Yes, they might be disruptive, I concluded, but not in the sense described in these books for they were entering new territories where comparative products do not exist. Is my analysis correct? Only time will tell.
Although I use business cases in teaching students, these cases are written long after the event. They are written with the benefit of hindsight, for the writers know what actually happened. As a result, the case always depicts the events in a manner that is cleaner and more logical than the experience of those living the case. A case history invariably ends with a question: which option should the company select? Well, I have lived through the examples given in some of those cases. It didn't seem that clean and logical to us. At the time, we didn't recognize that we were at a decision point: we didn't recognize those nice, clearly stated options.
Analysis is easier than syntheses. Hindsight is easier than foresight. The view from inside the battle is different from that of the historian.
17.8.2 Comment on the Chapter
Note that the chapter presented here is an excerpt/adaptation from the Christensen's book "The Innovator's Solution," which was published in 2003. As a result, many of the examples are dated. This is especially the case for Table 17.2 of the Appendix, where the examples of companies are often quite radically out of date. I will leave the analysis of the today's relevance of the companies to the points of the article as an exercise for the reader. Just realize that the table was constructed over a decade ago, which in the case of some businesses is a lifetime. Indeed, given the rate at which technology businesses are absorbed by other companies or simply fail, it can be more than a lifetime.
About Don Norman
Don Norman wears many hats, including co-founder of the Nielsen Norman group, IDEO fellow, Visiting Professor at KAIST (South Korea), consultant, advisor, board member, and author. His latest book is Living with Complexity. He lives at jnd.org.
Norman, Donald A., Hutchins, Edwin, Hollan, James D., Lewis, Clayton H., Cypher, Allen, Hooper, Kristina, Laurel, Brenda K. (1986): User Centered System Design: New Perspectives on Human-Computer Interaction, Norman, Donald A., Draper, Stephen W. (eds.), ,
Norman, Donald A. (2004). Ad–Hoc personas & Empathic Focus. Retrieved 2004-01-01 00:00:00 from http://www.jnd.org/dn.mss/personas/empath.html
3.8 Commentary by Donald A. Norman
Technologies migrate as they mature. In early childhood, their very existence is a marvel, even as people wonder what can be made of it. In early adolescence, they become more and more able to perform useful functions for us, and for a while, they are judged primarily on their ability to do more and more, better and better. Finally, in maturity, it is the quality of the experience provided by these technologies that matter. Adolescents thrust their technological underpinnings into our consciousness, even as we resisted. But once the technology becomes mature, it recedes into the background, supportive of the total experience it provides.
Design, it has been said (Krippendorff, 1989) is the creation of meaning, and as Hassenzahl points out, the essence of meaning to us people is our experiences.
The chapter by Marc Hassenzahl ought to be required reading in courses of design, and perhaps even more importantly, in engineering and computer science. Do the devices we design and produce work well? Do they do marvelous, mysterious operations, working invisibly across space and time? Yes, they do, but doing that is a means, not the end. The end is the experiences they engender, the stories we tell, and the way that they enriched our lives.
But this creates a problem. We know how to design things that accomplish particular, concrete actions. But how can experiences be designed? As Hassenzahl points out they can’t be: they can only be supported. To use another design term: we can design in the affordances of experiences, but in the end it is up to the people who use our products to have the experiences.
The product provides the "How" part of an experience. It is up to people to provide the "What" and the "Why." But designers can help here as well, setting the framework, providing the initiative, providing examples.
Design has moved from its origins of making things look attractive (styling), to making things that fulfill true needs in an effective understandable way (design studies and interactive design) to the enabling of experiences (experience design). Each step is more difficult than the one before each requires and builds upon what was learned before.
The first step toward experiences was to learn about and embrace emotion and products that were pleasurable. This step has just been taken, with an increasing number of books, journal articles, and conferences attesting to the interest in this topic. But these steps too were in their infancy, addressing primarily the need and desirability along with the technical difficulties of measuring the resulting emotions or pleasure.
Marc Hassenzahl throws down the gauntlet for future designs: to produce products that deliver the Why, What, and How.
Krippendorff, Klaus (1989). On the Essential Contexts of Artifacts or on the Proposition That "Design Is Making Sense (Of Things)". Design Issues, 5(2), pp. 9-39.
About the Author
Don Norman is the author of numerous books including "Emotional Design," and more recently, "Living with Complexity." He is co-founder of the Nielsen Norman group, a professor at KAIST (in Korea), and IDEO fellow, and a design theorist, studying the fundamentals of modern design. Although he invented the term "User experience" while an executive at Apple, he is pleased that people like Marc Hassenzhal have moved beyond the phrase to deep substance. Although Norman travels an inordinate amount, he can always be found at www.jnd.org
Hutchins, Edwin, Hollan, James D., Norman, Donald A. (1986): Direct Manipulation Interfaces. In: Norman, Donald A., Draper, Stephen W. (eds). "User Centered System Design: New Perspectives on Human-Computer Interaction" .
Norman, Donald A., Shallice, Tim (1986): Attention to action: Willed and automatic control of behaviour (Revised reprint of Norman and Shallice (1980)). In: Davidson, Richard J., Schwartz, Gary E., Shapiro, David (eds). "Consciousness and Self-Regulation: Advances in Research and Theory" Plenum Press .