Introduction to Usability Engineering

1. Introduction to Usability Engineering Laura Leventhal and Julie Barnes

2. Sources • Chapter 1, Protobook

3. Motivation for this Unit • When you are finished with the introduction (lectures 1 - 3), you should be able to : • Look at an object or a system that you have in your home. Separate the functional components of that system from the interface. • View a technology in a magazine, in real life or in a museum. Reflect on where that technology fell in the historical development of similar technologies.

4. Everyday Things Have a User Interface • Ken Olsen, founded and CEO of Digital Equipment, confessed that he can't figure out how to heat coffee in the company’s microwave. • POET stands for Psychology of Everyday Things. This book is by Don Norman. • The book contains many different examples of poorly designed everyday objects. It also discusses how the design process could be altered to ensure better design.

5. Some everyday examples: • Figure 1.1 coffee pot overhead • "If I were placed in the cockpit of a modern day jet airliner my inability to perform gracefully and smoothly would neither surprise nor bother me. But I shouldn't have trouble with doors and switches, taps and cookers (Norman, 1988, p. 2).

6. More examples • A friend told me of the time he got trapped in the doorway of a post office in a European city. The entrance was an imposing row of perhaps six glass swinging doors, followed immediately by a second, identical row. That's a standard design - it helps reduce the airflow and maintain the indoor temperature of the building. • My friend pushed on the side of one of the leftmost pair of outer doors. It swung inward and he entered the building. Then before he could get to the next row of doors he was distracted and turned around for and instant. He didn't realize it at the time, but he had moved slightly to the right. So when he came to the next door and pushed it nothing happened. "Hmmm," he thought, "must be locked." So he pushed the side of the adjacent door. Nothing. Puzzled my friend decided to go outside again. He turned around and pushed the door. Nothing. He tried the adjacent door. Nothing. The door he had just come in through no longer worked. He turned around once more and tried the inside doors again. Nothing. Concern to mild panic.... he was trapped! Just then a group of people on the other side of the entrance way (far to the right) passed easily through both sets of doors. My friend hurried over and followed them through. • How could such a thing happen? A swinging door has two sides. One is pillar and hinge, the other moves. To open the door one must push the moveable side. Pushing on the hinges has no effect. In this case, the designed had aimed for beauty, not utility. No distracting lines, no visible pillars, no visible hinges. So how can you tell which side to push?

7. More examples • Computer Disks - old floppy can go in any way/ small floppy only one way. Why - it is not really square! It is slightly rectangular. • CS department, ergonomically correct chair. Can anyone adjust it?

8. Conclusions from these examples: • Everyday devices have an interface, or boundary between device and user, which can be good, ok or terrible. • As we will learn in this course, software interfaces, like everyday devices can be good, ok or terrible. • Principles that assist in the design of usable everyday objects are useful to consider when designing software interfaces. • Heightened awareness of good vs. poor design of everyday devices makes us better evaluators of software interfaces.

9. How are we able to use everyday objects like doors? • Objects and their user interfaces give us subtle clues as to how to operate the interface. • From experience, we recognize and interpret these clues. • For example, the location and shape of a door knob may give us clues as to whether to push the knob or to turn it • The location and shape of a door knob may give us clues as to whether to push the knob or to turn it. • If in public buildings and wish to get out; do doors swing in or out? Why? [Fire Codes].

10. Visibility • Norman (1988) recognized that our ability to perceive and interpret these subtle clues is key to our ability to operate a user interface. • He defines a property of the user interface called visibility to describe the how well the interface presents these cues. • To promote usability, the correct parts of the user interface must be visible, and they must convey the correct message. • To be visible, a user interface must provide the appropriate information for achieving relevant tasks.

11. Examples of visibility • The holes in salt and pepper shakers help us identify which shaker is which. • From Norman - I have a slide projector on which the slides are changed with a single button, yet I sometimes want to move the magazine backwards instead of forwards. To do so requires me to hold the button down for a longer press. This is invisible and makes for difficult use even when one knows how to do it and horrendous learning at first. (note many multifunction watches are similar)

12. Too much visibility can be a bad thing • Norman (1988) points out that if a user interface has too many cues, the user may become confused or overwhelmed • From Norman. In England, I visited a home with a fancy new Italian washer-drier combination, with super-duper multi-symbol controls, all to do everything you ever wanted to do with the washing and drying of clothes. The husband (an engineering psychologist) said he refused to go near the thing. The wife (a doctor) said she had memorized one setting and tried to ignore the rest.

13. Norman’s Too Much Visibility Example (cont.) • Someone went to a lot of trouble to create that design. I read the instruction manual. That machine took into account everything about today's wide variety of synthetic and natural fabrics. The designers worked hard. They really cared. But obviously they had never thought of trying it out or of watching someone try to use it. • If the design was so bad, if the controls were so unusable, why did the couple purchase it? If people keep buying poorly designed products, manufacturers and designers will think they are doing the right thing and continue as usual.

14. An important property of visibility • Visibility must be interpreted for the specific context in which users will be performing their tasks!

15. To summarize so far • A user interface provides information to the user. • Experience helps the user find these clues.I • f the clues are absent or confusing, the interface will likely be difficult to operate.

16. The user’s role in the process. • The user receives information from the environment. • This information, in concert with the user’s prior knowledge allows them to build mental models of the device, its functionality and operation.

17. User Models of Devices • We understand how things work come from a mental (internal) model of the device or interface. • We build mental models of how to operate a device based in part on what user interface tells you about how a system functions (what it does). • Your mental model of the bicycle in from Carelman tells you that the bike will not work.

18. User Models of Devices • Our mental model is based in part on clues for how things work, from the visible structure of the device. In particular, we perceive • What can you do with the interface (called “Affordances” by Norman) • How does the interface limit what you can do with it or how its usage is constrained (called “Constraints” by Norman) • What is the relationship of action at the user interface to action of the device (called “Mappings” by Norman)

19. -- Information from a User Interface - Consider scissors • What is the user interface - UI are the finger holes. • What can you do with the interface - UI affords (allows you to) put fingers through holes and grasp scissors. • How is the use of the interface constrained - Use of UI is constrained by size of holes in context of finger size. • What is the mapping between the operation of the interface and the resulting function - Mapping is between holes and blades. Move the holes in and out and the blades slice together and apart.

20. In-Class Exercise • Consider the everyday objects that your teacher brought to class. • Identify interface • How do you operate the device? • How is the operation constrained? • How is the input of the interface related to the expected function?

21. More about Mappings and how they can go wrong. Don Norman's Refrigerator • Don Norman's refrigerator has the controls that are shown in 1.8. Suppose the freezer is too cold but the fresh food is just right. How would you adjust the controls so that the freezer is warmer, and the fresh food stays the same?

22. Don Norman’s Refrigerator (2) • There are two possible models of the refrigerator's operation because there are two possible mappings of controls to function. (fig 1.9) • Which is right? Turns out that it is "B" and that the controls are not independent, even though they look as if they are.

23. Example - mappings. Don Norman's stove. 3.3 - 3.5 • - How well/ natural controls map to functions they control (including affordance and constraints)

24. Example mappings • Recall Mappings - relationships of interface to action. • Consider the relationship between a set of controls and the results in a device. • For example, with a steering wheel, turning the wheel to the right makes the tires turn right. The mapping is the relationship between steering wheel interface and the action of the tires.

25. User Models Conclusions • A device which leads to a good user mental model is likely to be more usable than one that does not lead to such a model. • For everyday things, the user models are not necessarily complex. • When our mental model is incorrect or inadequate, we may have problems using the device. • The closer the mapping between the control (user interface) and its function, the more accurate the user model

26. Feedback • Definition - sending back to the user information about what action has actually been done or what action has been accomplished. • Feedback is a mechanism by which users can adjust their mental models.

27. Feedback examples • Old style telephones provided tactile feedback ("feel" when you pushed a button), sound feedback (tone sound when you pushed a button), sounds from the connection. • Contemporary style phones have more functions but often less feedback. • Contemporary phones may be more difficult to learn and feel confident about using.

28. Conclusions • Everyday devices have an interface. The user interface is the boundary between the user and the function of the device. • Information perceived from the user interface in concert with the user’s knowledge are used to form a mental model of the device and its operation. • Some specific information from the user interface that is potentially incorporated into this mental model are how the device is to be used, how its use is constrained and how the operation of the interface maps to the functional outcome.

29. More Conclusions • Feedback from the user interface is a way that users can check and evolve their mental models. • Everyday devices can be designed well or poorly for the user and the task. We cannot evaluate their design independently of either the user’s background or the context of the task.

30. Overview of KEY issues for Chapter 1. • All objects have a user interface. The user interface is the boundary between the person and the functionality of the device. If the boundary is transparent or seamless, the UI is probably usable. If the boundary is a barrier, it is probably not very usable. • Most people experience the functionality of the device as it is presented in the UI. Designers must separate the functionality of the device from the UI. • Here is an example of how functionality and UI are different. Quote from CEO of DEC. He can't operate his microwave, but he probably understands the physics of how the microwave works. The failure of the device is not in the functionality, but in the UI. But, if people can't operate the UI, they are not likely to get to the functionality.

31. Overview of KEY issues for Chapter 1 • The UI is sort of like the "skin" of an object. The UI is where people often get information as to how to operate an object. • How do we get this information? We perceive information from the UI and build a mental model of the characteristics of the UI. This mental model may be more or less accurate. Norman discusses the idea of the UI presenting subtle clues.

32. Overview of KEY issues for Chapter 1 • Perceptual information from a UI can be more or less "visible" in Norman's terms or more or less "perceivable" in a more general sense. If information is not visible, it is not likely that we will be able to operate the UI. Norman's example of the European Post Office doors is a good example of a UI in which the subtle clues (where to push) was not visible because the door and its hardware were all transparent. Our ability to extract subtle cues may also be compromised if the visible information is misleading (eg, the word "Salt" on the pepper shaker) or if there is so much visible information that it is in conflict with what we think is the intended function of the device. Norman's example of the Italian washer/dryer is an example in which the UI seems more complex than the intended function.

33. Overview of KEY issues for Chapter 1 • So good visibility of vital cues is critical for us to know how to operate the UI. What are the nature of the cues or type of information that can be extracted from the UI. There are at least three types of information that are relevant. 1) Information about what we can do or how we are to interact with the UI. Norman calls these the affordances of the device. Examples for simple devices with simple UI's often involve pushing, pulling, grasping. 2) Information about how is our interaction constrained. For simple UI's we may be constrained by motor skill considerations. 3) Information about the mapping of the action at the UI to the function of the device. • If any of these types of information is missing, difficult to extract (perceive), or confusing, the UI will likely fail or at least be unusable. Norman's stove and refrigerators are examples in which the apparent mapping of UI actions to functions may be wrong.

34. Overview of KEY issues for Chapter 1 • Feedback from a UI can enhance usability and help users form more complete mental models of the operation of the device. • When designing the UI's for complex systems, such as software, it is instructive to think about how we form mental models and operate UI's for simple devices. Complex system UI's can also fail if the user cannot extract reliable information about the UI (poor visibility), if the information about how the user interacts is wrong, if information about the UI's constraints, relative to the user is wrong, if information about the relationship of UI actions to functionality is wrong, and/or if the UI does not provide feedback.