1. The Art and Science of Human-Computer Interaction (HCI)
Usability:
The Art and Science of Human-Computer Interaction (HCI)

2. Learning Objectives
Human-Computer Interaction is a very broad and deep subject area.
The learning objectives are to develop an understanding of:
Design specification and testing for:
positive user experiences
error reduction and error handling
An iterative cycle of specification and testing
Different priorities, requirements and error consequences for different types of business.
A Human Factors perspective on designing HCI systems which minimize the effects of human error
Arriving at an idea of Usability via Mental Models

3. Guidelines for making systems user-hostile
Make things invisible. Exploit the tyranny of the blank screen.
Be arbitrary. Use non-obvious command names or actions.
Use arbitrary mappings between the intended action and what must actually be done.
Make operations unintelligible. Use idiosyncratic languages or abbreviations.
Use uninformative error messages (like, for example, the classic Unix message: Internal error: delete non-existent child).
Be impolite. Treat user errors as breaches of contract.
Make operations dangerous. Allow a single mistake to destroy invaluable work.
Make it easy to do disastrous things. Put warnings in the manual. Then, when people complain, ask ‘But didn’t you read the manual?’
(from Donald A Norman, The Psychology of Everyday Things)

4. Factors which influence a positive user experience
The system provides the relevant information to allow you to perform the tasks that the system is designed for
Key aspects which contribute to this:
Intuitiveness
Help information
Error handling and error reduction

5. Aspects of HCI Accessibility User-centred design Use-Case analysis
Site design
Input design
Output design
Interfaces between systems
Security design
Error-handling and exemption
Help information and documentation
General Principles
Specifics

6. Different aspects of HCI are associated with different system purposes
Sales & Selling
Enterprise Resource Planning (ERP)
Specialist (e.g. flight systems or healthcare)
Education
Image/Brand Focus
Trained Users – integrating data from different parts of the organisation
Consequences of errors can be potentially fatal
Augmenting and in some cases replacing traditional methods

7. The data <-> information challenge
One of the key challenges within HCI is determining how to convert data into usable, not just useful, information.
The criteria for useful and usable information will depend on your users. What might seem like data to one group of users will be seen as usable and useful information to others.
One of the most important requirements of good system design is to know any distinctive features of your user group which might make information appear to them as data and therefore not be either useful or usable.

8. Interacting with complex systems…

9. A380 cockpit

10. Human Factors Approach
A human factors perspective seeks to generalise about the functioning of humans with regards to helping us understand;
what factors facilitate humans performing their roles successfully with the use of technology
the potential sources of human error related to our biological, psychological and social characteristics
It seeks to move away blaming individuals for mistakes
This perspective can lead to anticipation of errors and therefore error prevention through research informed design

11. Human Error
Beatty (1991), a Human Factor specialist in aircraft safety, stated that he wanted to identify and study the following factors which contributed to aircraft accidents aside from mechanical failures:
conformity
perception
decision making
He believes that these relate to human error rather than pilot error; in other words, mistakes that are the result of our human condition rather than the piloting skill of individuals.

12. For example: A320 maiden flight
Unfortunately, things go wrong…
Why?
Inquiry still inconclusive, but:
Wrong runway (short, not long)
Wrong height (30’, not 100’)
Aircrew couldn’t see the ground
Autopilot had different ideas to captain (i.e., was wanting to land the plane, but captain wasn’t)
Questions about the engine control software
The captain was convicted and imprisoned – some say wrongly.
Black box recordings may have been tampered with…

13. Is a Human Factors Approach appropriate for businesses?
What are some of the potential costs of human error to businesses?
If you are purchasing a software system – what aspects of the HCI could affect your business effectiveness (direct e.g. Increased sales – indirect e.g. reputation – Ryan Air)
Have a look at this paper by Nigel Bevan.

14. Testing – before software release
Testing is a critical part of the software design process
The quality of testing depends on the design specification and functional specifications given to the testers
It depends on the selection of appropriate tester groups (e.g. Beta Testing)
Testing involves both usability and breakability tests

15. Evaluating System Improvements
User Feedback - e.g Adobe, Microsoft
The following are interconnected
Removal of errors and improved error handling
Improved functionality
Improved user experience

16. Continuous System Improvement Strategies
Iterative testing (e.g. Draper cycle)
New specifications are designed based on feedback from testers and users related to the improvement of the system in terms of:
Improving the users experience
Error reduction and improved error handling
May also be necessary as new software platforms are released (Apple Mac)

17. The Draper Cycle

18. Four Aspects of Usability
Effectiveness: users’ performance in terms of speed and errors
Learnability: allowing for learning and support of users
Flexibility: adaptability beyond the defaults
Attitude: within acceptable levels of human cost (tiredness etc.)
(From: Brian Shackel)

19. IBM’s Common User Access (CUA) guidelines
Design Principles
Each principle has supporting implementation techniques. The two design principles are:
Users can develop a conceptual model of the interface.
Users can develop a conceptual model of how an application should work. The user interface should confirm the conceptual model by providing the outcome users expect for any action. This occurs only when the application model is the same as the users' conceptual model.
Users can be and should be in control of the dialogue.
Allow users to control the dialog. Traditional applications that are sequential in nature do not support this principle. Putting users in control means that users should be able to perform any action in any sequence they want to complete their tasks.

20. Nielsen’s Usability Heuristics 1-5
1. Visibility of system status
The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.
2. Match between system and the real world
The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.
3. User control and freedom
Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.
4. Consistency and standards
Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.
5. Error prevention
Even better than good error messages is a careful design which prevents a problem from occurring in the first place.

21. Nielsen’s Usability Heuristics 6-10
6. Recognition rather than recall
Make objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.
7. Flexibility and efficiency of use
Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.
8. Aesthetic and minimalist design
Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.
9. Help users recognize, diagnose, and recover from errors
Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.
10. Help and documentation
Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

22. Nielsen reported that users identified navigability as the most important quality of an interface…

23. Navigability: An Online Commerce example
Fred is ordering plants from an online nursery. (The arrow indicates clicking on a link and moving to the next page.)
Step (a) Fred collects the products that he wants to buy by clicking any of the Add Item links in the catalogue.
Step (b) Fred checks the order form for correctness and clicks on the Payment link when done with the form.
Step (c) Fred enters credit card information and clicks ‘Submit’ or ‘Buy’.
Step (d) Fred sees that his purchase was approved.

24. Before leaving the store, Fred realizes that he forgot to buy the dibble that he needs to plant the tulip bulbs, so he uses the Back button to return to the pages of the catalog. As he goes back from (d) to (c) to (b) to (a), he realizes that he’s backed up over all of the ordering information.
Now he wonders about the state of his purchase:
Will his credit card be charged?
Will he get the items he has ordered?
Does he have to reorder?
When he clicks on the Add item link again, will he get an empty order form, or the one he has been using?
It is difficult for users to answer these questions, especially when they first encounter the situation. Designers should encourage users to kick the back habit. Instead of encouraging or requiring the use of the Back button, applications should have navigation buttons to take users directly to where they need to go.

25. 10 basic principles of system modelling
Naturalness – The system behaves as you would expect
Learnability – The system is straightforward to learn
Simplicity – It is not unneccesarily complicated
Explorability – It allows for curiosity
Accomodative – Suits different types of user
Modifiable – User can customise it
Consistency – Behaves the same between functions
Compatibility – with the target domain
Visibility – Important things can be seen
Invisibility – Less important / frequent things don’t need to be seen

26. So, what does a bad user interface look like?
Bud Uglly Design
…and a good one?
National Geographic magazine

27. Some theory: Mental Models

28. A layered approach to HCI
Physical layer (fingers on buttons, eyes on screen)
Lexical layer (which button to click? Which word to type?)
Semantic layer (what am I doing now?)

29. Mental Models (1)

30. Mental Models (2)

31. Mental Models (3)

32. Modelling a GUI (1)
This statechart models a simple dialogue box…

33. Modelling a GUI (2)
…and this is a more complex interface (a content browser).

34. So, is it worth it?
Cost saving in the Nuclear industry: A .1% Usability improvement = £1m saving in a year.
Think about your own experiences ordering online – ever had a frustrating experience? How could it be improved? Could it save you money?

35. Further reading Don Norman: The Psychology Of Everyday Things
HCI books by Jenny Preece, Ben Shneiderman, Dix & Finlay
Jakob Nielsen’s Usability website at