Chapter 3 principles of hci

HCI Chapter 2

1. Introduction of HCI

2. How Human interacts with Computer? - Not primarily the study of Human - Not primarily the study of Computer - The study of bridge between them, which includes Observation of interactions between people & computers, e.g., Find examination papers via our library Web

3. Continuation: 􀂃 Analysis of the involved interactions, e.g., Are all the steps involved are necessary? 􀂃 Human consequences after interacting with computers, e.g., Can the user perform his task? Does he enjoy working with the computer?

4. What is HCI? Human: Individual user, a group of users working together, a sequence of users in an organization Computer: Desktop computer, large-scale computer system, Pocket PC, embedded system (e.g., photocopier, microwave oven), software (e.g., search engine, word processor)

5. Continuation: User interface: Parts of the computer that the user contacts with Interaction: Usually involve a dialog with feedback & control throughout performing a task (e.g., user invokes “print” command and then interface replies with a dialog box)

6. HCI SCOPE:

7. HCI SCOPE: Use & Context: Find application areas for computers Human: Study psychological & physiological aspects e.g., study how a user learns to use a new product, study human typing speed Computer: Hardware & software offered e.g., input & output devices, speed, interaction styles, computer graphics Development: Design, implementation & evaluation

8. HCI Goals: At physical level, HCI concerns the selection of the most appropriate input devices and output devices for a particular interface or task 􀂃 Determine the best style of interaction , such as direct manipulation, natural language (speech, written input), WIMP ( windows , icons , menus, pointers), etc.

9. HCI Goals: Develop or improve 􀂃 Safety 􀂃 Utility 􀂃 Effectiveness 􀂃 Efficiency 􀂃 Usability 􀂃 Appeal of systems that include computers

10. Safety: Safety: protecting the user from dangerous conditions and undesirable situations 􀂃 Users 􀂃 Nuclear energy plant or bomb-disposal – operators should interact with computer-based systems remotely 􀂃 Medical equipment in intensive care unit (ICU)

11. Continuation; Data 􀂃 Prevent user from making serious errors by reducing risk of wrong keys/buttons being mistakenly activated 􀂃 Provide user with means of recovering errors 􀂃 Ensure privacy (protect personal information such as habits and address) & security (protect sensitive information such as passwords, VISA card numbers)

12. Utility: Utility: extent of providing the right kind of functionality so that users can do what they need or want to do High utility 􀂃 Scientific calculator provides many mathematical operations, built-in formulae, and is programmable 􀂃 Low utility 􀂃 Software drawing tool does not allow free-hand drawing but supports polygon shape drawing 􀂃 Effectiveness: concern a user’s ability to accomplish a desired goal or to carry out work 􀂃 Find a master thesis in our library Web

13. Efficiency: Efficiency: a measure of how quickly users can accomplish their goals or finish their work using the system

14. Usability: Usability: ease of learning and ease of use 􀂃 Can I use the basic functions of a new digital camera without reading the manual? 􀂃 Does the software facilitate us to learn new functions easily?

15. Appeal: Appeal: how well the user likes the system 􀂃 First impression 􀂃 Long-term satisfaction

16. Example:

17. PRINCIPLES OF HCI

18. HERE ARE PRINCIPLES OF HCI Know your user Understand the task Reduce memory load Strive for Consistency Remind Users and Refresh Their Memory Prevent Errors/Reversal of Action Naturalness

19. Know your user This principle simply states that the interaction and interface should cater to the needs and capabilities of the target user of the system in design.

20. Understand the task Another almost-commonsensical principle is to base HCI design on the understanding of the task. The term task refers to the job to be accomplished by the user through the use of the interactive system. In fact, understanding the task at hand is closely related to the interaction modeling and user analysis. It really boils down to identifying the sequence and structure of subtasks at an abstraction level appropriate for the typical user within the larger application context.

21. Reduce memory load Designing interaction with as little memory load as possible is a principle that also has a theoretical basis. Humans are certainly more efficient in carrying out tasks that require less memory burden, long or short term. Keeping the user’s short-term memory load light is of particular importance with regard to the interface’s role as a quick and easy guidance to the completion of the task.

22. Strive for Consistency In the longer term, one way to unburden the memory load is to keep consistency . This applies to (a) both within an application and across different applications and (b) both the interaction model and interface implementation.

23. Remind Users and Refresh Their Memory Any significant task will involve the use of memory, so another good strategy is to employ interfaces that give continuous reminders of important information and thereby refresh the user’s memory.

24. Prevent Errors/Reversal of Action one effective technique is to present or solicit only the relevant information/action as required at a given time.

25. Naturalness Naturalness refers to a trait that is reflective of various operations in our everyday life. Affordance , a property (or additional cues) that appeals to our innate perception and cognition, thus making it so intuitive that the interface would require almost no learning.